Flood in rice fields at the time of seed sowing and early seedling establishment causes extensive crop loss due to the inability of the seeds to tolerate and overcome submergence. In the present study, rice genotypes from Assam, India tolerant to hypoxia during germination were identified through systematic screening of deep-water rice genotype collection from flood-prone ecosystem of Brahmaputra river valley. The difference in tolerance to hypoxia during germination within the species provides scope for identification of novel hypoxia-responsive factors involved in tolerance as mechanism of tolerance may not be conserved across tolerant germplasms. Tolerant genotypes were further subjected to physiological and molecular characterization. Growth rate kinetics in tolerant genotypes new Rangdhakekua bao (RKB) and cultivar Khao Hlan On (KHO) from International Rice Research Institute (IRRI) used as positive control exhibited stronger escape strategy under hypoxic condition compared to sensitive genotype IR-64 (negative control). Activities of α-amylase and pyruvate decarboxylase were significantly higher in RKB and KHO than in IR-64, while no significant difference was observed in the alcohol dehydrogenase activity. Reverse transcription quantitative PCR confirmed increased amounts of transcripts of sucrose nonfermenting 1 related protein kinase, myeloblastosis-related protein S1, rice amylase 3D, and trehalose phosphate phosphatase 7 genes, which are known to be involved in hypoxia signaling cascade. Besides, transcription factors (TFs) like ethylene responce factors 71 and 63, ethylene insensitive 3-like 1a and proteins like expansins A7 and A2, which are involved in cell elongation had also significantly higher amounts in RKB compared to IR-64. Additional factors that include TFs like ERF71 and ERF63 that shows perturbation at transcription even within tolerant genotypes might constitute the genotype-specific regulation, evolved as a part of its adaptive mechanism to survive under submerged conditions.

The aim of this study was to evaluate the tensile strength of the rachilla in spikelets of Polish cultivars of Festulolium braunii (K. Rich.) A. Camus during seed development and maturation. The investigations were carried out in 2009 - 2010 at the Plant Breeding, Szelejewo, Poland. The inflorescences were randomly harvested in June - July from plant collection in maintenance breeding of three Polish cultivars (Agula, Felopa, and Sulino). Using a specifically developed testing machine, tensile strength of the rachilla of individual spikelets were determined. Regardless of the F. braunii cultivar, the tensile strength of the rachilla decreased through consecutive growth stages. The highest tensile strength of the rachilla was observed during the phase of kernel watery ripe stage (BBCH 71) - it ranged from 510.1 mN in 'Agula' to 592.0 mN in 'Felopa'. At the fully ripe phase (BBCH 89), the value of this trait ranged from 19.2 mN in 'Agula' to 45.0 mN in 'Felopa'. It was also observed that in all tested cultivars of F. braunii, the spikelets located in the lower part of the spike were characterised by the highest tensile strength of the rachilla, whereas those in the upper part were characterised by the lowest values of this trait. This means that the caryopses in the spikelets located at the lower part of the inflorescence were less susceptible to shedding. Seed shedding the Polish F. braunii cultivars, especially 'Agula' and 'Sulino', may start as early dough and soft dough phases. By contrast, seed shedding 'Felopa' is moved to the later phases of seed maturation.

The reverse transcription quantitative real-time PCR (RT-qPCR) is becoming increasingly important for gene expression studies. However, the accuracy and reliability of RT-qPCR depend on normalizing expression to reference genes. In this study, ten candidate reference genes, including cyclophilin (CYP), elongation factor 1b (EF1b), α-tubulin (TUA5), β-tubulin (TUB4), ubiquitin10R (UBQ10R), 60S ribosomal RNA (60S), alcohol dehydrogenase (ADH3), metalloprotease (MTP), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and actin (ACT2) were evaluated for the stability of expression in three tissues of two peanut cultivars [Zhonghua 2(ZH₂) and 99-1507] under Al stress by four statistical algorithms (geNorm, NormFinder, BestKeeper, and RefFinder). The results suggested that the top-ranked reference genes under Al-induced programmed cell death (PCD) in peanut were UBQ10R, EF1b and CYP, with the most suitable combination of reference genes being [UBQ10R+ACT2]. The UBQ10R exhibited the most stable expression in all samples, while TUB4 was the least stable gene. The relative expression of AhMC1 (the caspase-like protease family gene, which played a significant role in Al-induced PCD) showed that there was no significant difference with the best reference gene and the best gene combination in RT-qPCR normalization, but there was significant difference with the least stable gene TUB4 as reference gene. This is the first study to evaluate the stability of reference genes in peanut under Al-induced PCD, and the results will provide guidance to identify appropriate reference genes for further RT-qPCR analyses under Al stress in peanut.

Melatonin (N-acetyl-5-methoxytryptamine) is an essential molecule which regulates plant growth and development and alleviates the damaging effects of abiotic stresses. To evaluate the important functions of melatonin in response to salinity stress, the effects of exogenous melatonin on the antioxidant system and growth of tomato (Solanum lycopersicum L.) under 150 mM NaCl stress were investigated. The application of 100 μM melatonin compensated the growth inhibition caused by salt-stress. Melatonin treated seedlings had an increased fresh and dry masses of shoots and roots. The application of 1 - 200 µM melatonin notably enhanced the relative chlorophyll content (SPAD index), root characteristics, and gas exchange in tomato seedlings subjected to salt stress compared to seedlings treated with salt stress alone. Moreover, melatonin pretreatment minimized accumulation of reactive oxygen species and improved activities of antioxidative enzymes including catalase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase.

Cucumber (Cucumis sativus L.) is considered a model plant for the investigation of Fe deficiency responses, since it strongly exhibits typical strategy I, i.e. increased activities of Fe(III)-chelate reductase, H⁺-ATPase and iron regulated transporters. In this study, cDNA amplified fragment length polymorphism analysis was employed to identify genes differentially expressed in the root apex following Fe deficiency. The expression patterns of the most interesting transcript derived fragments were validated by semiquantitative reverse trascriptase - polymerase chain reaction. A set of new genes overexpressed under Fe deficiency, such as those coding for calmodulin, SNAP, TIM23 and V-PPase were identified. Furthermore, we also observed that calmodulin protein accumulated in Fe-deficient root apexes.

Circular RNAs (circRNAs), an emerging class of non-coding RNAs, are abundant in eukaryotic transcriptomes. Seed germination is one of the most important stages in the entire life cycle of plants that can be slowed down or totally restrained by high temperature. Our aim is to identify heat-responsive circRNAs and explore the potential function of circRNAs in tomato seeds at high temperature. Following high-throughput sequencing, 4 164 circRNAs were identified, and 980 circRNAs were shared in the control and high-temperature libraries. Among the 748 circRNAs with high expressions, 73 circRNAs were significantly up-/down- regulated in tomato seeds germinated at high temperature compared to the control. The parental genes of circRNAs existing in seeds only at high temperature were mainly involved in metabolic processes, cellular processes, catalytic activities, and binding based on Gene Ontology analysis. The results suggested that circRNAs were widespread in tomato and were generated from different chromosomes and diverse genomic regions. Some circRNAs in tomato seeds responded to high temperature during germination. This study provides the first genome-wide profile of circRNAs in response to high temperature during tomato seed germination and lays a foundation for studying the potential biological functions of circRNAs responding to heat stress.

In order to introduce drought tolerance and improved cell wall digestibility from fescue in fodder ryegrasses, we developed two amphiploid Festulolium synthetics. One is a synthetic composed of three selected drought tolerant F1 hybrid genotypes from a cross between tetraploid Lolium multiflorum and hexaploid Festuca arundinacea, further on called LMFA. The other is a synthetic composed of five selected genotypes with soft leaves from a cross between tetraploid Lolium perenne and tetraploid Festuca pratensis, further on called LPFP. We produced seeds in polycrosses of two generations of both amphiploids, i.e., syn1 and syn2, and tested them in plot trials to determine the yield and fodder quality. The syn1 of both Festulolium populations had a higher annual dry matter yield than the reference Lolium cultivars and Festulolium cultivars composed of the same parental species. However, the syn2 of LMFA did not show an improved drought tolerance during a dry growing season compared to other Festulolium cultivars, and the seed yield of LMFA syn1 was low and dropped extremely in syn2. The number of chromosomes of LMFA also decreased gradually from F1 to syn2, and there was a clear shift in chromosome composition towards the Lolium genome. The LPFP synthetic performed better. Although the sugar content was significantly lower than the sugar content of the perennial ryegrass cultivars, organic matter digestibility (OMD) of LPFP was as high as OMD of the tetraploid perennial ryegrass cultivars. The cell wall digestibility (NDFD) of LPFP was significantly higher than the NDFD of both parental species and higher than the NDFD of all tested Festulolium cultivars. The seed yield of LPFP was the same in syn1 and syn2. The chromosome number remained on average the same and no clear shift of the chromosome composition to one of the composing genomes was observed. Overall, chromosome analysis revealed a high number of aneuploidy in syn1 and syn2 generations of both LMFA and LPFP and a lot of variation in number of Lolium, Festuca and recombinant chromosomes, and in the Lolium:Festuca genome ratio was observed among different genotypes of the same population. Therefore, selection for genotypes with a more stable genome composition will be a prerequisite for a sufficient seed yield and a broader exploitation of these new Festulolium synthetics.

Heat stress is one of the most crucial factors affecting crop growth and productivity worldwide. So, searching for a potent eco-friendly heat stress alleviator is the main issue nowadays. The current study was conducted to assess the ameliorative effects of 1.5 mM potassium silicate (K₂SiO₃, further only Si) or 1.66 mM silicon dioxide nanoparticles (SiNPs) on wheat (Triticum aestivum L.) seedlings exposed to heat stress (45 °C, 4 h). The observations show that Si or SiNPs treatments significantly restored the heat stress-provoked ultrastructural distortions of cellular organelles, particularly chloroplasts and the nucleus. Further, both Si and SiNPs enhanced the photosynthetic capacity as revealed by increments in the photochemical efficiency of photosystem II and the performance index as well as the content of photosynthetic pigments. A reduction in malondialdehyde accumulation in Si and SiNPs treated plants was positively related to their membrane stability index. The reverse transcription PCR analysis showed that Si treatment but not SiNP treatment stimulated the overexpressions of both Triticum aestivum plasma membrane intrinsic protein (TaPIP1) and Triticum aestivum nodulin 26-like intrinsic protein (TaNIP2) aquaporin genes parallelly with an improvement in the relative water content. This investigation reveals that Si was more effective than SiNPs in restoring the heat stress injuries. To the best of our knowledge, this is the first investigation exploring the effects of Si and SiNPs in improving thermotolerance of wheat seedlings.

Bamboo possesses many unique physiological characteristics, but the molecular understanding of many of these processes remains poorly understood till to date. One major reason is unavailability of sufficient sequence and expression data. Selection of suitable reference genes is pivotal to initiate any gene expression analyses. Although, suitable reference genes have been identified in the temperate bamboo Phyllostachys edulis, it has not been done for tropical bamboo. In this study, expression stability of 10 candidate reference genes were investigated in 4 widely grown tropical bamboo species (Bambusa tulda, B. balcooa, B. bambos, and B. vulgaris), different organs (young leaves from flowering and non flowering culms, flag leaf (leaf just below the mature inflorescence), possible flag leaf (leaf covering the immature inflorescence), culm sheath, internode, root, rhizome, and inflorescence bud), different parts (basal, middle, and tip regions of leaf; internodes located in the basal, middle, and tip region of the branch, and developmental stages early, middle, and late inflorescence buds) by using 3 reliable computational tools (geNorm, NormFinder, and RefFinder). A universal single reference gene for normalization of gene expression data was not identified. However, the eukaryotic initiation factor 4α (eIF4α), clathirin adaptor complexes medium subunit (CAC), and nucleotide tract-binding protein (NTB) were found stable in the selected organs across different bamboo species. On the other hand, eIF4α ranked top when different organs and peptidyl prolyl cis-trans isomerase/cyclophilin (CYP), eukaryotic elongation factor 1α (eEF1α) and ubiquitin 5 (UBQ5) ranked top when different developmental stages of B. tulda were analyzed. Taken together, this study not only identifies reference gene/s that are stable across species, organs, and developmental stages of bamboo, but it also assesses the impacts of major contributing factors regulating expression stability of the reference genes.

Stomatal guard cells are specialized epidermal cells regulating gas exchange. The ability to open or close in response to external and internal cues makes stomata a dynamic and fascinating system. Stomatal closure upon infection ensures restriction of pathogen entry into the plant and forms an essential component of innate immunity. The opening or closure of stomata is dependent on the turgidity or flaccidity of guard cells, respectively, facilitated by several signaling components, including reactive oxygen species, nitric oxide (NO) and Ca²⁺. Among these, NO is the most extensively studied gasotransmitter. Its pivotal role in stomatal closure by modulating various downstream components as well as regulation of crucial proteins by post-translational modifications makes NO an essential factor. Two more gasotransmitters, carbon monoxide and hydrogen sulfide, also trigger stomatal closure. Other gaseous molecules, like ethylene, methane, sulfur dioxide, ozone, and CO₂, can modulate stomatal closure, but they are not considered strictly as gasotransmitters due to specific criteria. We review the signaling events in guard cells triggered by these gasotransmitters leading to stomatal closure. We point out the dual role of NO to promote stomatal closure and stomatal opening. Both NO and H₂S help in reinforcing the innate immunity against pathogen attack. Although there is extensive information on the mechanism of NO action on stomata, the enzymatic source of NO or CO is still ambiguous. Similarly, research is warranted to establish the relative importance of and interactions among the three main gasotransmitters. Further studies on gasotransmitters would answer the ambiguity about their functions and confirm if they can act independently.

Small RNAs (sRNAs) are essential components of gene-regulatory networks, which guide plant development and tune it to environmental challenges. Though the past years have witnessed evidences on sRNA importance for stress response, there is scarce data on their involvement in resurrection plant survival under severe drought. Haberlea rhodopensis (hrh) is an angiosperm resurrection species, whose vegetative tissues can tolerate desiccation and recover upon rehydration. In this study, high-throughput sequencing sRNAs indicated a higher complexity of the sRNA population, especially of a 24 nt sRNA category, in the desiccated vegetative tissue of H. rhodopensis compared to unstressed tissues. The cross-species discovery was performed to predict 77 mature microRNAs (miRNAs), most of which were assigned to 23 high-confidence conserved miRNA families in the leaf tissue. Several members of the miR156/157, miR166, and miR399 families were found to be desiccation-responsive. The miR156/157 family members were found up-regulated upon dehydration and down-regulated upon rehydration, while the miR166 and miR399 family members followed an opposite trend of expression. A probable miR156/157 target, orthologous to the SQUAMOSA promoter binding protein-like, was reconstructed in H. rhodopensis based on genomic data available for this species and the closely related Boea hygrometrica. Reverse transcription quantittative PCR analysis confirmed the expression profile of hrh-miR156a-5p and hrh-miR157-5p established by sRNA sequencing and revealed an inverse expression pattern between these miRNAs and their targets in the desiccated tissue. Our study suggests that the miR156/157 and miR399 families are essential for plant survival under severe drought due to their ability to control plant development and growth by modulating transcription factor expression.

Real time quantitative PCR (qPCR) is a powerful tool for studying the expression of specific genes. The accuracy and reliability of qPCR analysis data require the selection of reference genes with stable expression. However, the reference genes that can be used for qPCR of Rehmannia chingii and R. henryi have not yet been identified. In this study, based on the transcriptome data of R. chingii and R. henryi, we initially selected genes with relatively stable expression in different samples. We screened six candidate reference genes in R. chingii and R. henryi and calculated their expression abundance by real time qPCR. Their expression stability was evaluated by three algorithms geNorm, NormFinder, and BestKeeper. Although the results obtained by different algorithms were not completely consistent, R. chingii type 2A phosphatase activator TIP41 and R. chingii 18S ribosomal RNA had the highest expression stability in six different samples of R. chingii, and R. henryi 18S ribosomal RNA and R. henryi actin showed the most stable expression in different samples of R. henryi. In addition, based on transcriptome data, four genes were screened in R. chingii and R. henryi, and the expression stability of the selected reference genes was further verified. This study laid the foundation for further analysis and verification of the functions of important genes in R. chingii and R. henryi.

Bupleurum chinense DC., a source of the traditional Chinese medicine Bupleuri Radix, is rich in triterpenoid saikosaponins with high pharmacological activities. The enzyme β-amyrin synthase (BAS), which converts the precursor 2,3-oxidosqualene to produce the triterpene skeleton, is crucial for the biosynthesis of triterpenoid saponins. In this study, we cloned the full-length sequence of the BAS gene from B. chinense, conducted a bioinformatics analysis, and expressed it in Saccharomyces cerevisiae to investigate its function. The cDNA of β-amyrin synthase (BcBAS, GenBank accession number: MN186093) cloned from aseptic seedlings of B. chinense was 2 307 bp with a 2 286 bp open reading frame coding for 761 amino acids. Phylogenetic analysis suggests that the BcBAS protein was closely related to the BAS proteins from Panax ginseng and Betula platyphylla. as chromatography mass spectrometry analysis showed that the enzymatic product was indeed β-amyrin, the precursor of oleanane type triterpenes. Overall, our findings lay the foundation for in-depth analysis of the biosynthesis pathway of saikosaponins.

Soybean is one of the most important economic crops in the world. However, the salinization of soil results in the decrease of soybean yield as it is only a moderately salt-tolerant crop. We treated three soybean cultivars with low and high concentrations of NaCl. The differentially expressed genes between the control group and the salt treatment group were identified by mRNA sequencing and analyzed by gene ontology and Kyoto encyclopedia of genes and genomes annotations. We performed weighted gene co-expression network analysis on all samples and found genes most related to the phenotype. After verifying the results of differentially expressed genes by quantitative PCR, we finally identified Glyma06G01990, Glyma08G22730, Glyma019G05140, and Glyma06G20160 as key genes affecting the soybean growth under salt stress.

Columnar apple is a valuable resource for genetic improvement of cultivated apples due to its special tree architecture. Strigolactones (SLs) are a novel class of plant hormones controlling shoot branching. The content of SLs is higher in columnar apple than in standard apples. In this study, the members of major gene families involved in SLs biosynthesis and signaling were identified from apple genomic sequences and their expression profiles were characterized in columnar and standard apples using reverse transcription quantitative polymerase chain reactions. In comparison with standard apple, the higher expressions of MORE AXILLARY GROWTH genes MdMAX3-1 and MdMAX4-4 were detected in both buds and shoots of columnar apple but the expression of DWARF gene MdD53-4 showed a lower expression in columnar apple. Overexpression of Columnar gene MdCo31 in tobacco increased SLs content and weakened the inhibition of SLs signal transduction by increasing expression of MAX3 and down-regulating the transcription of D53. Thus MdCo31 could be a strong candidate gene for the control of columnar habit.

Leaf venation and coupled physiological function of wild plants co-evolve during the natural selection. How artificial selection affects leaf vein traits and coordinated physiological functions of main crops are largely unknown. This study examined the changes of leaf vein traits and their correlation with gas exchange of flag leaves and yield in eight wheat genotypes of differing ploidy under the same growing conditions. The results indicate that flag leaf vein density (VLA), major-vein density (VLA_major), and minor-vein density (VLA_minor) decreased whereas the proportion of minor-vein length and interveinal distance between small longitudinal veins (IVD) increased during the polyploidization process, and the major advance occurred from the period from diploids to tetraploids. The VLA, VLA_major, and VLA_minor were closely coordinated with maximum net photosynthetic rate (P_N) and photosynthetic N use efficiency (PNUE), but not with stomatal conductance. The proportion of minor-vein length and IVD were negatively related with P_N and PNUE but positively related with N content per area (N_area) during wheat evolution. A higher proportion of minor-vein length and IVD, and a lower VLA_major in flag leaves along with a larger N_area were largely responsible for the increased yield in modern cultivars. The decreased redundancy of leaf vein density and increased minor-vein proportion in modern cultivars can confer a yield advantage during wheat evolution.

Plasmodiophora brassicae is a biotrophic pathogen causing clubroots of cruciferous crops. The Brassica rapa accession T1-145 has an ability to produce small spheroid galls (SSGs), which represent neither a fully compatible interaction nor a complete resistance. To explore the defense response in SSGs induced by P. brassicae infection, global transcriptome profiling SSGs was performed at different time points. By comparing gene expression patterns, we identified many defense related genes. The first group included genes encoding receptor-like protein/kinases, such as cysteine-rich receptor-like protein kinases, receptor-like proteins, phloem intercalated with xylem/tracheary element differentiation inhibitory factor receptor (PXY/TDR), PXY-correlated 1, wall-associated kinases, nuclear shuttle protein-interacting kinase, lectin receptor-like kinases, and flagelin-sensitive 2, which might activate a basal defense. The second group involved robust effector-triggered immunity response genes such as resistance to leptosphaeria maculans 1B, constitutive shade-avoidance 1, target of avirulence B operation 1, ribosomal protein of the small subunit 6, resistance to Pseudomonas maculicola 1-interacting protein 4, enhanced disease resistance 2L, and recognition of Peronospora parasitica 13-like protein 4. The third group included genes encoding secondary cell wall formation related protein/s, a nodulin-like protein, a germin-like protein, a jacalin-related lectin, a defensin-like protein, tumor inhibitors, and sugars will eventually be exported transporter, which might contribute to quantitative resistance against P. brassicae. The gene expressions were the highest at the late stage of infection. To our knowledge, it is the first report on exploring defense response genes during SSG occurrence by a transcriptome analysis. Our data would provide useful information to further explore molecular mechanisms of the incomplete resistance.

Ferredoxin-thioredoxin reductase (FTR) is an iron-sulfur protein that supplies electrons from photochemically reduced ferredoxin (Fd) to thioredoxin (Trx) in the ferredoxin/thioredoxin system in chloroplasts. The FTR is a heterodimer with a variable subunit (FTRv) and a catalytic subunit (FTRc). The function of FTRv is not well known. In petunia (Petunia hybrida), FTRv is a single-copy gene, which is named PhFTRv. In this study, the spatio-temporal expression of PhFTRv in petunia was analyzed, and PhFTRv transcription was found to be high in leaves and stems. A tobacco rattle virus gene silencing was used in this study. Virus induced gene silencing-mediated PhFTRv silencing resulted in large yellow-green leaves, delayed flowering, and reduced cold tolerance in petunia plants.

The root specificity and phosphate (Pi) deficiency responsiveness of high-affinity phosphate transporter (PHT1) genes point to their promoters as a sustainable system to drive Pi acquisition-related transgenes in plants. In this study, a 3-kb promoter of the AtPHT1;4 gene from Arabidopsis thaliana fused to the β-glucuronidase (GUS) reporter gene was biolistically introduced into wheat (Triticum aestivum L.) and functionally characterized in transgenic plants grown in hydroponics and in pots with soil under various Pi supply rates. From among 27 T₁ progeny derived from 250 T₀, four transgenic lines reached T₃, with two of them showing detectable GUS activity in the roots of T₄ plants. An unusually high number of transgene insertions characterized these transgenic lines, along with an irregular pattern of histochemical GUS staining and weak GUS activity. GUS expression driven by AtPHT1;4 was consistently higher under most assay conditions, as it was unaffected by 0 to 0.5 mM Pi in hydroponically grown plants, as well as by 16 to 20 mg(P) kg^-1(soil) in potted plants. Raising the soil P up to or above 40 mg kg^-1 significantly down-regulated the quantity of GUS transcripts. These results show that the responsiveness of the AtPHT1;4 promoter to Pi availability in transgenic wheat was restricted to soil-grown plants, which highlighted the relevance of the substrate and Pi supply rates in assessing molecular responses to Pi deficiency.

This work studied the six β-galactosidases (BGALs) of the subfamily a1 of Arabidopsis, that have been proposed to play important roles in the cell wall remodelling during plant development, although their precise functions are still unknown. Knockout mutants bgal1, bgal2, bgal3, bgal4, bgal5, and bgal12 of Arabidopsis and their wild type (WT) plants were analysed to determine their morphology and composition of their cell walls. The gas chromatography and the Fourier transform infrared spectroscopy revealed differences between the mutants and their WT such as in the proportions of glucose, galactose, or xylose in bgal2 and bgal4 and in cell walls polysaccharides in bgal1, bgal3, and bgal5. However, these slight changes did not result in morphological variations during plant development. None of the mutant seedlings displayed a clear reduction in β(1,4)-galactan content, analysed by immunolocalization. The absence of significant phenotypic changes in the β-galactosidase subfamily a1 mutants could indicate possible β-galactosidases functional redundancy. Future studies will focus on the construction of multiple mutants that help to establish the precise function of each member of the β-galactosidase subfamily a1.

Tricyrtis spp., which belong to the family Liliaceae, produce unique flowers, whose tepals have many reddish-purple spots. Although elucidation of a molecular mechanism of tepal spot formation and molecular breeding for flower colour alteration are desired for Tricyrtis spp., only one flavonoid biosynthesis-related gene, TrCHS encoding chalcone synthase (CHS), has been isolated so far. In the present study, comprehensive isolation and expression analysis of the other flavonoid biosynthesis-related genes were carried out in Tricyrtis sp. Six genes (TrCHI, TrF3H, TrF3'H, TrFLS, TrDFR, and TrANS) encoding biosynthetic enzymes chalcone isomerase (CHI), flavanone-3-hydroxylase (F3H); flavonoid 3'-hydroxylase (F3'H), flavonol synthase (FLS), dihydroflavonol 4-reductase (DFR), and anthocyanin synthase (ANS) as well as three genes (TrMYB1, TrbHLH2 and TrWDR) encoding transcription factors myeloblastosis 1 (MYB1), basic helix-loop-helix (bHLH), and WD40 repeats (WDRs) were newly isolated. Phylogenetic analysis showed that each isolated gene was classified into the monocotyledonous clade. Deduced amino acid sequences of DFRs showed that TrDFR has no substrate specificity. "Early" genes in the flavonoid biosynthetic pathway (TrCHS, TrCHI, and TrF3H) were constantly expressed in tepals during flower development, whereas expression of "late" genes (TrF3'H, TrFLS, TrDFR, and TrANS) varied with the flower developmental stage. Expression patterns of the late genes were mostly correlated with those of transcriptional factor genes, indicating that the late genes may be under the control of a transcription factor complex consisted of TrMYB1, TrbHLH2, and TrWDR. Accumulation of anthocyanins in tepals occurred slightly after transcriptional upregulation of the late genes. Results obtained in the present study may be valuable for further studies on flower colour and flower colour pattern in Tricyrtis spp.

Zea mays L. is less tolerant to drought than Sorghum bicolor L. In the present study, we investigated the response of both plants to drought stress applied under field conditions by withholding water for 10 d. The plant growth in terms of shoot fresh and dry masses was more severely reduced in maize than in sorghum, consistently with reduction of leaf relative water content. Gas exchange was also more inhibited by drought in maize than in sorghum. The water use efficiency (WUE) of maize fluctuated during the day and in response to the drought stress. In contrast, sorghum was able to maintain a largely constant WUE during the day in the well-watered plants as well as in the stressed ones. Studying the expression of four aquaporin genes (PIP1;5, PIP1;6, PIP2;3, and TIP1;2) revealed that PIP1;5 in leaves and PIP2;3 in roots were highly responsive to drought in sorghum but not in maize, where they might have supported a greater water transport. The expression pattern of PIP1;6 suggests its possible role in CO₂ transport in control but not droughty leaves of both the plants. TIP1;2 seemed to contribute to water transport in leaves of the control but not droughty plants. We conclude that PIP1;5 and PIP2;3 may have a prominent role in drought tolerance and maintenance of WUE in sorghum plants.

Sugars are important molecules that function not only as primary metabolites, but also as nutrients and signal molecules in plants. The sugar transport protein genes family SWEET has been recently identified. The availability of the Dendrobium officinale and Phalaenopsis equestris genome sequences offered the opportunity to study the SWEET gene family in this two orchid species. We identified 22 and 16 putative SWEET genes, respectively, in the genomes of D. officinale and P. equestris using comprehensive bioinformatics analysis. Based on phylogenetic comparisons with SWEET proteins from Arabidopsis and rice, the DoSWEET and PeSWEET proteins could be divided into four clades; among these, clade II specifically lacked PeSWEETs and clade IV specifically lacked DoSWEETs, and there were orthologs present between D. officinale and P. equestris. Protein sequence alignments suggest that there is a predicted serine phosphorylation site in each of the highly conserved MtN3/saliva domain regions. Gene expression analysis in four tissues showed that three PeSWEET genes were most highly expressed in the flower, leaf, stem, and root, suggesting that these genes might play important roles in growth and development in P. equestris. Analysis of gene expression in different floral organs showed that five PeSWEET genes were highly expressed in the column (gynostemium), implying their possible involvement in reproductive development in this species. The expression patterns of seven PeSWEETs in response to different abiotic stresses showed that three genes were upregulated significantly in response to high temperature and two genes were differently expressed at low temperature. The results of this study lay the foundation for further functional analysis of SWEET genes in orchids.

Excess radiation is one of frequent natural environmental stresses that plants have to cope with on a daily basis. Therefore, plants have evolved many short- and long-term mechanisms to acclimate to high irradiance and tolerate it. Ureides, generated from purine degradation, have been proposed as compounds involved in environmental stress responses, including altered irradiance. In the present study, high irradiance was used to investigate ureide content and gene expression in Arabidopsis thaliana. Arabidopsis plants shifted to high irradiance showed high content of a specific ureide compound, allantoin. The accumulation of allantoin was associated with increased expression of uricase, an enzyme involved in its production. When an Arabidopsis mutant (aln-3), which constitutively accumulates elevated amounts of allantoin, was exposed to high irradiance, mutant plants demonstrated enhanced tolerance to the stress conditions compared to the wild-type plants. Our results provide evidence that accumulation of the allantoin might contribute in plants response to increased growth irradiance.

DNA methylation is one of the epigenetic mechanisms regulating gene expression in plants in response to environmental conditions. In this study, analysis of methylation patterns was carried out in order to assess the effect of water stress in two contrasting wheat genotypes using methylation-sensitive amplified polymorphism (MSAP). The results revealed that demethylation was higher in drought-tolerant genotype (C306) as compared to drought-sensitive genotype (HUW468) after experiencing drought stress. Comparisons of different MSAP patterns showed a high percentage of polymorphic bands between tolerant and susceptible wheat genotypes (from 74.79 % at anthesis to 88.89 % at tillering). Furthermore, differential DNA methylation in roots and leaves also revealed tissue-specific methylation of genomic DNA. Interestingly, 54 developmental stage-specific bands and 23 bands that were found contrasting between these two wheat genotypes were detected. Furthermore, a few sites with stable DNA methylation differences were identified between drought-tolerant and drought-sensitive cultivars, thus providing genotype-specific epigenetic markers. These results not only provide data on differences in DNA methylation changes but also contribute to dissection of molecular mechanisms of drought response and tolerance in wheat.

Sulfur dioxide is a widespread air pollutant and it also acts as a signaling molecule in various processes in mammals. However, the role of SO₂ in programmed cell death (PCD) in plants is unclear. Here we studied the role of SO₂ in gibberellin (GA)-treated wheat aleurone layers. The results showed that 100 μM SO₂ donor (NaHSO₃/Na₂SO₃) could effectively delay PCD and inhibit the coalescence of small protein storage vacuoles (PSVs) in aleurone cells treated with GA. Also, SO₂ could reduce the accumulation of hydrogen peroxide and superoxide anion in GA-treated aleurone layers. In this process, SO₂ could sustain higher activities of catalase, guaiacol peroxidase, ascorbate peroxidase, and superoxide dismutase and lower activities of lipoxygenase and polyphenol oxidase by comparing with GA alone. In addition, an induction of endogenous H₂S and NO was observed in SO₂-treated aleurone layers. The application of NO scavenger cPTIO could accelerate PCD in SO₂ or H₂S treated aleurone cells, suggesting that NO alleviated PCD by acting downstream of SO₂ and H₂S. In conclusion, these results imply that SO₂ could delay PCD in GA-treated wheat aleurone layers by enhancing cellular antioxidative capacity and H₂S/NO signals act downstream of SO₂.

The aim of this study was to find a correlation between the freezing tolerance of three chickpea (Cicer arietinum L.) cultivars (İnci, Işik-05, and Sari-98) and their wild relative C. echinospermum and physiological responses. Chickpea plants (15-d-old) were subjected to cold acclimation (CA) (10 °C for 7 d), freezing (-3 or -5 °C for 2 h), and subsequent rewarming (25 °C for 7 d). In two separate experiments with three replications, we determined growth, water status, photosystem 2 photochemical activity, photosynthetic pigments, H₂O₂, malondialdehyde, and proline content, relative leakage ratio, antioxidant enzyme activities, and gene expressions in cultivars different in freezing tolerance. Freezing temperatures adversely affected all the physiological parameters of all cultivars. Rewarming did not lead to complete recovery. The cultivar İnci was more tolerant to the freezing temperatures than others.

Heterotrimeric guanine-nucleotide-binding proteins (G-proteins) play important roles in signal transduction and regulate responses to various stresses. Although G-protein signaling pathways have been extensively identified and characterized in model plants, there is little knowledge in non-model and especially in woody plants. Mulberry is an economically and ecologically important perennial tree, which is adaptable to many environmental stresses. In this study, we identified and cloned six G-protein genes including one Gα, one Gβ, two Gγ, one RGS (regulator of G-protein signaling protein) and one RACK1 (receptor for activated C kinase 1) involved in G-protein signaling. Sequence and phylogenetic analysis revealed that Morus G-proteins are evolutionarily conserved compared with those of other plants. A real-time quantitative reverse transcription polymerase chain reaction analysis showed that Morus G-protein signaling genes were ubiquitously but differentially expressed in various tissues. The expression of all of these genes was affected by abiotic stresses and signal molecules, which indicated that Morus G-protein signaling may be involved in environmental stress and defense responses.

The cation/H⁺ exchange is a basic process in transmembrane transport. The acquisition of genome sequences has now established that plants possess genes encoding a large number of cation/proton antiporter 1 (CPA1) proteins, few of which have been characterized with respect to their contribution to ion homeostasis. The CPA1s comprise plasma membrane, vacuolar, and endosomal forms, and they have been identified as important for a salinity tolerance. They are, however, also involved in both the control of cellular pH and K⁺ homeostasis, and regulate processes over a wide range of physiological events, from vesicle trafficking to development.

We compared C₃ and CAM (crassulacean acid metabolism) states in Mesembryanthemum crystallinum, a facultative CAM species, with respect to the involvement of phosphoenolpyruvate carboxylase (PEPC) and nitrogen metabolismrelated enzymes in plant response to Botrytis cinerea infection. The enzyme activities were monitored both in pathogeninoculated 2^nd leaf pair and non-inoculated 3^rd leaf pair. The control activities of most studied enzymes were dependent on the mode of photosynthesis. Compared to C₃ plants, those performing CAM exhibited higher PEPC, nitrate reductase (NR), and deaminating glutamate dehydrogenase (NAD-GDH) activities but lower glutamine synthetase (GS) and alanine aminotransferase (ALT) activities. Regardless of the mode of photosynthetic carbon assimilation, the plants responded to infection with enhancement of PEPC and inhibition of NR activities in the inoculated leaves. Whereas the activity of GS remained unaffected, those of all glutamate-yielding enzymes, namely ferredoxin-dependent glutamate synthase (Fd-GOGAT), aspartate aminotransferase (AST), ALT, and aminating glutamate dehydrogenase (NADHGDH) were altered after infection. However, the time-course and extent of the observed changes differed in C₃ and CAM plants. In general, CAM plants responded to infection with an earlier increase in PEPC and Fd-GOGAT activities as well as later inhibition of NR activity. Contrary to C₃ plants, in those performing CAM the activities of PEPC, Fd-GOGAT, NADH-GDH, and AST in the non-inoculated 3^rd leaf pair were similarly influenced by infection as in leaves directly inoculated with the pathogen. This implies that the local infection induced an alteration of carbon/nitrogen status in healthy upper leaves. This reprogramming resulting from changes in PEPC and nitrogen metabolism-related enzymes was C₃- and CAM-specific.