Phosphorus is a key limiting factor for plant growth. Several approaches are developed to mitigate the impact of P shortage on plants and to the selection of crops with high P mobilizing capacity from P-deficient soils. In this work, four Medicago truncatula genotypes (A17, TN8.20, TN1.11, and TN6.18) were compared for their efficiency to cope with P limiting conditions using several criteria. Significant differences between genotypes, P deficiency treatments, and the interaction of genotypes with P deficiency treatments were found. P limitation resulted in an important decrease in shoot biomass, P content, P use efficiency, and photosynthetic parameters. A significant variability was found between the four genotypes, with A17 and TN8.20 being the most tolerant genotypes to P deficiency. This was consistent with the better ability of these genotypes to acidify rhizosphere and stimulate the activity of acid phosphatase and its relative gene (MtPAP1). The expression of P transporter genes (MtPT1, MtPT3, and MtPT5) was induced by P deficiency, however, the overexpression of those genes was more pronounced in tolerant genotypes. Overall, our data indicate that A17 and TN8.20 are more efficient in mobilizing P under limiting conditions and could be cultivated in P-deficient soils as forage crops.

Tomato is highly sensitive to chilling stress (0 - 12 °C) which severely affects plant growth and development. Transgenic tomato plants expressing the AtDREB1A gene under the control of the rd29A promoter were evaluated for its tolerance to chilling stress by exposing them to 4 °C for 5 d. The cold stress caused an increase in production of reactive oxygen species, however, transgenic plants had an effective antioxidant system due to an enhanced synthesis of catalase (CAT), superoxide dismutase (SOD), and ascorbate and so the reduced content of hydrogen peroxide and superoxide anions. Transgenic plants showed a slightly less reduction of chlorophyll and carotenoid content compared to wild-type plants. Similarly, a higher relative water content and a less electrolyte leakage were observed in transgenic plants. Accumulation of osmoprotectants, like proline and soluble sugars, helped transgenic plants to maintain a proper osmotic balance under the cold stress. Stress-responsive genes pyrroline-5-carboxylate synthase, CAT, SOD, and lipid peroxidase showed enhanced expressions under the cold stress in transgenic plants compared to wild-type plants. A recurrent exposure to the cold stress at the reproductive stage showed even higher expressions of these genes as compared to plants exposed to the cold stress for the first time. Thus, transgenic plants showed a better adaptation to the cold stress than non-transgenic plants by acquiring the stress memory of the stress experienced at the seedling stage.

Abiotic stress is one of the major challenges facing crop production globally. Abiotic stress resulting from low temperature is a major limitation to crop production, especially in the temperate regions of the world. Cold stress not only influence crop development and reduce yields, but also curtail the efficient distribution of agricultural products worldwide. An understanding of the molecular mechanisms underlying cold stress tolerance is important for the development of strategies to manage crop loss and improve yield. In this review, we explore the major molecular mechanisms involved in plant cold tolerance, including recent discoveries on interrelated gene networks and regulatory mechanisms for cold stress adaptation in crops. Further, we highlight the role of proteomics in the discovery of proteins involved in key signaling pathways, including late embryogenesis-abundant proteins, antifreeze proteins, cold-regulated proteins, heat shock proteins, and pathogenesis-related proteins. The role of these proteins, and their relative abundance in physiological-biochemical reactions, are discussed and key candidate proteins for plant genetic enhancement are suggested.

Histone variants can epigenetically regulate gene transcription through chromatin modulation. This regulation have been occasionally found in responses to abiotic stresses in plants, but their roles are not quite clear. Here, we describe 12 salt-responsive histone variant genes isolated from wheat. There was no sequence polymorphism in these 12 genes between the wheat cultivar 'JN177'and its salinity and drought tolerant derivative 'SR3' indicating that histone variant genes are highly conserved. However, these genes displayed differential patterns of transcription in 'JN177' and 'SR3'. When transformed into Arabidopsis thaliana, eight of the genes were silenced. The heterologous expression of the four active transgenes had no discernible effect on the Arabidopsis phenotype neither under control conditions nor under different abiotic stresses suggesting that histone variants could not be considered as candidate genes for molecular breeding by ectopic expression.

Auxin signal transduction in plants depends on regulation by short-lived nuclear plant proteins called auxin/indole-3-acetic acid (Aux/IAA) proteins. The OsIAA9, which is highly and rapidly induced by auxin, encodes the entire Aux/IAA domain characteristic of the Aux/IAA family in rice. The promoter region of OsIAA9 contains several cis-elements. Analysis of P_OsIAA9:GUS transgenic plants indicates a specific expression of OsIAA9 in roots and seedling shoots, especially lateral roots and root tips. Based on real-time PCR, the expression of OsIAA9 was induced by multiple hormones and abiotic stresses. Furthermore, ectopic overexpression of OsIAA9 in rice led to fewer crown and lateral roots and reduced the inhibition of root elongation by auxin. These observations indicate that OsIAA9 was a negative regulator of auxin-regulated root growth.

Reverse genetics approaches in plants rely on post-transcriptional gene silencing to study the function of genes. In particular, virus-induced gene silencing (VIGS) has been successfully applied to identify gene function in some crops. To date, it is unclear whether phenylalanine ammonia-lyase (PAL) is involved in low temperature tolerance in the pepper. Here, we used an agroinfiltration protocol with tobacco rattle virus (TRV) constructs containing partial sequences from CaPAL for VIGS to test its role in anthocyanin biosynthesis and response to low temperature in the pepper (Capsicum annuum). We found that accumulation of anthocyanins in the leaves of pepper plants transformed with the TRV2:CaPAL vector was significantly reduced compared with peppers transformed with the empty TRV2 vector (TRV2:00). A significant reduction in expression of genes related to anthocyanins synthesis was also detected in peppers transformed with TRV2:CaPAL. When silenced pepper plants were exposed to a low temperature, we found decreased antioxidant system, PAL activity, and photosynthesis in plants transformed with TRV2:CaPAL compared with peppers transformed with TRV2:00. Low transcriptions of cold stress-response genes demonstrated that pepper tolerance to low temperature decreased. Future studies focused on the interaction between CaPAL and other abiotic and biotic stressors will shed further light into the role of CaPAL in stress response.

Arctium lappa and A. tomentosum are known medicinal plants in China. The complete chloroplast genomes from A. lappa and A. tomentosum were sequenced using Illumina sequencing technology. The total genome sizes of the complete chloroplast genomes of A. lappa and A. tomentosum were 152 767 bp and 152 688 bp, respectively, and contained a pair of inverted repeats of the same length (15,181 bp). The small single-copies were 18 584 bp and 18 582 bp, and the large single-copies were 83 821 bp and 83 744 bp, respectively. We identified and annotated 134 and 126 genes from A. lappa and A. tomentosum including, respectively, 90 and 89 protein-coding genes, 36 and 29 tRNAs, and eight rRNAs. A. lappa was found to have 10 tRNAs different from those in A. tomentosum, and A. tomentosum had three tRNAs different from those in A. lappa. There were only two types of simple sequence repeats of two species, mononucleotide and dinucleotide, and the sequences were A and T rich. In addition, the two ways of phylogenetic analysis show that the position of A. lappa and A. tomentosum is consistent within Asteraceae.

Plants exhibit morphological plasticity in response to changes in the proportion of far-red radiation (FR). However, little is known about the response to a sudden increase of FR component. Cucumber seedlings were acclimatized to radiation without FR (FR-) for 1 - 5 d after germination, and then transferred to radiation containing FR (FR+) at levels similar to those in natural sunlight. Other seedlings were acclimatized to FR- or FR+, which was maintained continuously. The sudden increase in FR damaged the cotyledons and the first true leaf, especially when radiation was changed from FR- to FR+ at days 3 or 4 after germination. Necrosis of the damaged leaves may have resulted from inhibition of water flow in leaf xylem, because wilting and decreased stomatal conductance were observed simultaneously with leaf necrosis. Plants in the treatment groups that showed the most frequent damage showed two peaks in cotyledon elongation. This suggests that the leaves that had been acclimatized to FR- were easily damaged by the sudden promotion of leaf expansion caused by FR+.

Lycium barbarum Thunb. and Lycium ruthenicum Murray (wolfberries) have been utilized as traditional medicinal and nutritional plants in China for centuries. Much research has been focused on their high quality, yet the molecular mechanisms underlying morphological differences remain unclear. In this study, a comparative analysis of morphological and cytological characteristics indicated that significant differences existed. Meanwhile, transcriptomic analyses of the flower and fruit were performed at different developmental stages, and a total of 54 795 differentially expressed genes (DEGs) were screened. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that these DEGs were significantly enriched in substance metabolism, catalytic activity, single organism process, starch and sucrose metabolism, carotenoid biosynthesis, amino sugar and nucleotide sugar metabolism, phenylpropanoid biosynthesis, and other pathways. Based on these significantly enriched pathways, the ratio between nonsynonymous and synonymous substitution rates (Ka/Ks), and numerous studies related to flower and fruit development, we preliminarily screened eight transcription factor families related to flower and fruit development and counted the number of potential transcription factor genes. These candidate genes could provide a basis for future functional verification, helping to further research on the molecular mechanism of morphological differences in the two Lycium species.

Owing to cold resistance and a lack of heat resistance in spinach (Spinacea oleracea L.), heat is the primary constraint that limits its production in summer. This study examined the auxiliary effects of spinach rhizosphere microbes on improving the heat resistance of spinach. A strain isolated from the rhizosphere soil of heat-stressed spinach was identified as Bacillus subtilis and designated B. subtilis BE-L21. It produces indoleacetic acid, amylase, and protease and solubilizes phosphorus. Further research revealed that spinach seedlings inoculated with this strain of B. subtilis had increased content of soluble protein, soluble sugar, and proline that adjusted their osmotic potential. The reducing content of malondialdehyde showed alleviated irreversible damage of spinach plants under heat stress. Also the increased activities of antioxidant enzynes peroxidase, superoxide dismutase, and catalase enhanced the heat resistance of spinach. The results indicate that B. subtilis BE-L21 can contribute to tolerance of spinach seedlings to elevated temperatures by inducing physiological and biochemical changes in the plant.

To obtain immediate homozygosity by androgenesis, the doubled haploid method is often used. As a result, a mapping population was created utilizing rice (Oryza sativa L.) cvs. Mahulata and IR 20 as parents in order to find QTLs/genes for drought tolerance at the vegetative stage. The effectiveness of the doubled haploids (DHs) approach, on the other hand, is largely dependent on the ability to distinguish haploids from diploids among the green regenerants. Although flow cytometry and cytological screening for pollen sterility can be used to identify haploids, these methods are expensive, time-consuming, and need a sophisticated laboratory with highly trained workers. Plant height and other spikelet features have also been used to differentiate haploids from doubled haploids. However, no systematic analysis of several morphological features for distinguishing haploids in doubled haploids has been published to date. As a result, a cost-effective approach for distinguishing haploids from true DHs obtained from anther culture is required. The goal of this work was to identify haploids using morphological features and simple microscopic examinations without the use of chemicals or complex laboratory facilities. The cross between the IR20 and Mahulata yielded a total of 198 anther culture (AC) derived plants. A group of 41 plantlets was chosen as putative haploids based on their shorter height and Cq values using qPCR-based genotyping and finally validated that, in addition to plant height, other morphological traits such as total number of leaves/plant, total number of tillers/plant, and floral characters can be used to successfully identify haploids. We report a variety of morphological signs as indicators of haploid plants, including smaller plants, higher tiller density, narrower and shorter leaf length, and partial exertion of panicle from the flag leaf sheath. Other morphological markers for identifying haploids from DHs include smaller florets and anthers, and small desiccated microspores.

Brassinosteroids (BRs) are plant hormones that were isolated for the first time in the 1970s. This group currently includes more than 70 compounds that differ in their structure and physiological activity. BRs are present in plants in a free form or in the form of conjugates. BRs are known as plant growth regulators, but they also play a role in the plant response to environmental stresses. In the case of plants that are exposed to low/high temperature, exogenous BRs can counteract growth inhibition and reduce biomass losses as well as increase plant survival. BRs show a multidirectional activity in regulating the metabolism of plants exposed to extreme temperatures. The following BRs actions can be distinguished: changes in membrane physicochemical properties, regulation of the expression of selected genes (including stress-responsive genes), as well as indirect effects on metabolism through other hormones or signalling molecules (such as hydrogen peroxide). This review summarizes the current knowledge about the effects of BRs on the physiological and biochemical processes that occur in plants during exposure to low or high temperatures.

Solanum nigrum L. is an annual undomesticated berry plant of Solanaceae. The fruits of S. nigrum are tiny, but there are about 25 seeds in a single fruit. The total number of seeds produced in one plant can reach more than 3 000. The height is about 30 - 40 cm, and the whole growth cycle is two months when S. nigrum was cultivated in the light incubator of the laboratory. The Agrobacterium tumefaciens-mediated transformation has been established in S. nigrum. So S. nigrum has the characteristics of model plants. AcMYB110, an R2R3-MYB transcription factor from kiwi (Actinidia spp.), was transformed into S. nigrum mediated by A. tumefaciens. The results indicated that the petals of 35S:AcMYB110 S. nigrum plants are pink compared with white petals in wild-type plants, and content of anthocyanins was significantly increased in the pericarp from young fruit to its maturity, especially in the central part of the fruit flesh. The results showed that the ectopic expression of AcMYB110 in S. nigrum is consistent with the expression of AcMYB110 in kiwi. This suggests that AcMYB110 plays a conserved role in regulating anthocyanins synthesis in fruits and can be potentially applied for improvement of the anthocyanins content in horticulture fruits breeding.

Garlic mustard (Alliaria petiolata) is an herbaceous biennial plant native to Europe. In Ukraine, in addition to becoming a serious invader, garlic mustard can serve as a host to several viruses, which may affect agricultural crops. In view of this, the purpose of the study was to identify the virome of garlic mustard growing in Ukraine. Plant samples collected in Kyiv regions were tested for the presence of cucumber mosaic virus (CMV), turnip mosaic virus (TuMV), turnip yellow mosaic virus (TYMV), watermelon mosaic virus II (WMV), and turnip crinkle virus (TCV) by serological and/or molecular methods. According to the results found in the present study, symptomatic A. petiolata obtained in 2021 were infected with CMV (60%), TuMV (20%), or co-infected with CMV + TuMV (20%). TYMV, WMV II, and TCV were not detected in any of the collected samples. The cDNA fragments encoded the coat protein (CP) gene of CMV and TuMV were sequenced and named as CMV-Ap and TuMV-Ap, respectively. In phylogenetic analysis, the CMV-Ap closely resembled the German isolate MW582807 (Sarracenia sp.), with 99.8% nucleotide identity and belongs to subgroup II of CMV. In the phylogenetic tree, TuMV-Ap clustered with isolates AP017803, AP017764, AP017791, and JQ073722, and represented the highest identity (98.6%) to Iranian isolate IRNTRa9 (AP017803) from Rapistrum rugosum and Turkish isolate TUR49 (AP017872) from Raphanus raphanistrum. The sequences of CMV-Ap and TuMV-Ap were deposited in the GenBank under Accession Numbers MZ540213 and OM799323, respectively. The results obtained in the study indicate the important role of infected garlic mustard as alternative host and natural reservoir of CMV and TuMV from which these economically important viruses can spread to other wild and cultivated plants. This is the first molecular evidence of TuMV infection in A. petiolata from Ukraine.

The climate shift has resulted in frequent heat waves, which cause damaging effects on plant growth and development at different life stages. All cellular processes in plants are highly sensitive to a high temperature. The plasma membrane heat receptors usually sense temperature variations directly or via a change in membrane fluidity. The accumulation of damaged proteins and reactive oxygen species also aid in heat perception. Calcium ions and heat sensors transfer signals to transcription factors through a series of signaling cascades. The heat stress transcription factors (HSFs) effectively regulate expression of heat induced genes. The members of the heat shock transcription factor A1 (HsfA1s) family are master regulators of a heat stress response. Different HSFs interact with each other at different levels and simultaneously operate heat induced gene expression. Interaction of HSFs with each other on multiple levels provides chances for manipulation to improve plant heat stress tolerance.

The present work aimed to evaluate the effect of heat stress on common bean (Phaseolus vulgaris L.) genotypes during the reproductive phase as a function of the inoculation of plants with Bacillus subtilis. The treatments were established by inoculating two strains of B. subtilis (AP-3 and AP-12) and a control. The plants were subjected to heat stress when they reached the reproductive stage, with an increase in temperature to 28/33°C. The duration of the stress period was ten days. Flowering, biochemical, and gene expression evaluations were performed. There was the interaction of B. subtilis AP-3 with the bean cultivar IAC-Imperador, reducing flower abortion, promoting the formation of new flower buds, and increasing the content of proline and guaiacol peroxidase activity in plant tissues. However, there was a reduction of transcription of genes encoding the 1-carboxylic acid-1aminocyclopropane oxidase and ethylene response factors and an increase of the Δ¹-pyrroline-5-carboxylate synthetase1 gene. These results suggest that B. subtilis may modulate some metabolic pathways in response to high-temperature stress during the reproductive phase of the common bean. This also confirms that Bacillus strains represent a useful option to moderate abiotic stresses.

Soil salinity leads to a reduction in plant growth, germination, relative water content, and production of wheat plants worldwide. Chitosan showed a positive effect on plant growth and development and improved plant stress tolerance. The current study aimed to examine the effect of different chitosan concentrations on the gamma-aminobutyric acid (GABA) shunt pathway in germinating seeds of wheat (Triticum durum L.) under salt stress (25 - 200 mM NaCl). We determined the seed germination pattern, seed moisture content, GABA shunt metabolites (GABA, glutamate, and alanine), oxidative damage in terms of malondialdehyde (MDA) accumulation, and the glutamate decarboxylase (GAD) mRNA transcription. Pre-treatment of wheat seeds with chitosan improved germination by enhancing germination percentage, seedling length, and seedling fresh and dry masses under salt stress. Data showed an increase in GABA shunt and their metabolites (alanine and glutamate), MDA content, and GAD mRNA transcription, and a decrease in germination percentage, seedling length, seedling fresh and dry masses for both untreated and chitosan-treated seeds under salt stress. Our results suggest that the elevation of GABA in chitosan-treated seeds was able to maintain metabolic stability under salt stress. The MDA content increased in chitosan-treated seeds as NaCl concentration increased, however, the increase was slightly lower than the MDA content in untreated seeds which confirmed that chitosan activates GAD mRNA expression that leads to activate GABA shunt to involve in the reduction of membrane damage and activation of reactive oxygen species scavenging systems under salt stress. Consequently, this study demonstrated that chitosan significantly enhanced the accumulation of GABA and amino acids metabolism to maintain the C:N balance and improved salt tolerance in wheat seeds during seed germination.

The “Centre for Experimental Plant Biology”, a joint project of the Institute of Experimental Botany of the Czech Academy of Sciences and CEITEC (represented by Mendel and Masaryk Universities), focused on elucidating  the mechanisms of plant responses to abiotic and biotic stresses and their combinations at the cellular level, in intact plants during vegetative and reproductive stages, and fruit development. The consortium demonstrated the importance of shared research facilities, complementary approaches, and knowledge exchange, addressing demanding questions  in plant biology. The consortium made breakthrough in plant-pathogen interactions, including identification of  exocyst-syntaxin cooperation in non-host resistance. The results confirmed the fundamental role of phytohormones in stress responses, including negative correlation of leaf bioactive gibberellins with drought stress, and the role of cytokinins in ROS homeostasis, sulphur metabolism, and heat stress responses, including volatile emission. Molecular analyses revealed expansin-mediated cell wall remodelling, brassinosteroid-mediated regulation of root growth through PIN2, the role of ALBA and LARP6C proteins in pollen development under abiotic stress, and heat stress impact on fertilization rate, embryo and seed development. Gene Set Enrichment and RNA-Seq analyses allowed to identify crucial genes involved in the apple scab resistance network. The main results obtained during the five-year project are summarised here.

Heat shock transcription factors (Hsfs) participate in a variety of plant physiological processes including the regulation of transcription factors associated with thermotolerance. Here, a Hsf gene DcHsfA1d was identified from carnation (Dianthus caryophyllus L.). The open reading frame (ORF) of DcHsfA1d was 1 368 bp and encoded a protein of 455 amino acids with a molecular mass of 51.039 kDa and an isoelectric point of 4.94. Sequence domain prediction revealed that DcHsfA1d protein exhibited five typical functional features and motifs. The transcription of DcHsfA1d was significantly up-regulated under heat stress or ABA treatment. Yeast two-hybrid experiment indicated that DcHsfA1d and DcHsp70 physically interact with each other. Overexpression of DcHsfA1d in Arabidopsis ecotype Columbia enhanced seedling thermotolerance by increasing the activities of catalase, peroxidase, and superoxide dismutase while reducing relative electrolyte leakage, malondialdehyde content, accumulation of O₂^- and H₂O₂ and by initiating transcriptional regulation of thermal protective gene expression under heat stress. Furthermore, under salt stress, the root length and fresh mass of Arabidopsis ectopically expressing DcHsfA1d were significantly higher than those of wild type, which indicated that the salt tolerance of transgenic Arabidopsis was improved to a certain extent. In summary, DcHsfA1d was demonstrated to play a positive regulatory role in heat stress response and it might be a candidate gene for salt tolerance using genetic modification.

Bacterial leaf blight (BLB) is a common disease that affects rice development and yield. The effects of major nutrients, especially nitrogen, on rice BLB susceptibility have been considered when devising rational fertilization strategies. However, the defense mechanism of rice against BLB under phosphate (Pi)-deficient conditions remains uncertain. Jasmonic acid (JA) is a phytohormone produced by rice plants to respond to abiotic and biotic stresses. Here, the involvement of the JA pathway in rice response to Xanthomonas oryzae pv. oryzae (Xoo) under low Pi was investigated in two contrasting rice cultivars G299 and G22. Expressions of JA-related genes under low Pi and Pi-related genes under JA treatment were assessed. The resistant capacity of G299 and G22 against Xoo infection was also investigated. In the JA-sensitive and Pi-sensitive cv. G299, JA-related genes were highly expressed under low Pi, and low Pi-responsive genes were strongly upregulated under JA treatment. Neither JA nor Pi pathways were activated in the JA-tolerant and low Pi-tolerant cv. G22. Low Pi strongly enhanced rice resistance to Xoo in cv. G299. Our study demonstrated that Pi deficiency confers rice resistance to Xoo. The JA pathway modulates the response to low Pi, depending on the cultivar. Pi-response genes are involved in Pi stress and may participate in the regulation of overall plant growth under various abiotic stresses. These findings provide new insights into the interaction between phosphate deficiency and the JA pathway and the subsequent effect on plant disease resistance.

With the dramatic increase in nanotechnologies, it has become probable that biological systems will be exposed to excess of nanoparticles (NPs). However, the impact of NPs on plants, remains to be explored. The aim of this research was to determine the effects of ZnO NPs on tomato (Solanum lycopersicum L.) plants. Plant growth, photosynthetic characteristics, chlorophyll fluorescence parameters, and activities of antioxidative enzymes were measured in 35-d-old plants. The ZnO NP treatments significantly inhibited tomato root and shoot growth, decreased the content of chlorophylls a and b, and reduced photosynthetic efficiency and some other chlorophyll fluorescence parameters in a concentration-dependent manner. However, the supernatant of ZnO NP suspensions did not affect growth of tomato, despite the presence of small amounts of Zn²⁺. Taken together, these results suggest that toxic effects on tomato plants were from ZnO NPs, not from Zn²⁺ released into the solution; toxicity was likely caused by reduced chlorophyll content and damaged photochemical system, which in turn limited photosynthesis and led to the reduction in biomass accumulation. Also, ZnO NPs enhanced the transcription of genes related to antioxidant capacity, suggesting that ZnO NPs could enhance the defence response by increasing activities of antioxidant enzymes.

Gibberellin 2-oxidases (GA2oxs) irreversibly convert bioactive gibberellins (GAs) and their immediate precursors into inactive GAs via 2-β hydroxylation and so regulate gibberellin content in plants. However, to the best of our knowledge, little has been known about the GA2oxs and its function in cool season turfgrass Poa pratensis. In this study, rapid amplification of cDNA end (RACE) was employed to isolate PpGA2ox from P. pratensis. The open reading frame of PpGA2ox was 1 047 bp in length, corresponding to 348 amino acids. PpGA2ox was localized in both nucleus and cytoplasm. The expression of PpGA2ox could be up-regulated by 10 μM gibberellic acid, 5 μM methyl jasmonate, or 10 μM indole-3-acetic acid. In addition, its native promoter could drive GUS expression in both leaf apex and shoot apical region. Moreover, overexpression of PpGA2ox in Arabidopsis led to GA-deficiency leading to dwarf phenotype, delayed flowering time, and increased chlorophyll content. Our study suggests that PpGA2ox could be a candidate gene for breeding new cultivars of P. pratensis.

WHIRLY transcription factors play critical roles in responses to biotic and abiotic stresses, but their other biological functions remain unclear. In this study, SlWHY2, a member of the WHIRLY family, was isolated from Solanum lycopersicum. The role of SlWHY2 was studied using transgenic tobacco plants. Real-time quantitative polymerase chain reaction analysis showed that SlWHY2 expression was induced by polyethylene glycol, NaCl, salicylic acid, hydrogen peroxide, and bacterial pathogens. SlWHY2 overexpression in tobacco caused enhanced tolerance to drought stress, as indicated by lower accumulation of malondialdehyde and relative electrolyte leakage, as well as higher relative water content and activities of superoxide dismutase and ascorbate peroxidase. Moreover, higher expression of cytochrome oxidase 1 (NtCOX1) and open reading frame 1 (NtORF1) were observed under drought in the transgenic lines. This suggested that overexpression of SlWHY2 enhanced tolerance to drought stress by regulating the transcription of mitochondrial genes and stabilizing mitochondrial function. Transgenic tobacco also displayed greater resistance to Pseudomonas solanacearum infection as evidenced by lower reactive oxygen species content and higher expression of defence-related genes. Overall, these findings suggest that SlWHY2 acts as a positive regulator in response to biotic and abiotic stresses.

The miR171 is a conserved microRNA (miRNA) family and has been shown to participate in plant growth and development. However, the precise function of miR171 in Pinus densata remains largely unclear. Mature miR171 sequence comparison reveals high similarity between Arabidopsis thaliana and P. densata and the pre-miR171 could fold into a characteristic stem-loop hairpin structure. Genes encoding GRAS (GAI-RGA-SCR) family transcription factors and actin binding protein were identified as targets of pde-miR171 using a modified RNA ligase mediated 5' rapid amplification of cDNA ends (RLM-RACE). Furthermore, the interaction between pde-miR171 and Arabidopsis SCL6 (SCARECROW-LIKE6) was further validated through transient co-expression of both genes in Nicotiana benthamiana leaves. Next, results of real-time quantitative PCR demonstrated that the expression of pde-miR171 was significantly up-regulated in miR171-overexpressing plants than in wild-type plants, which was inversely correlated with the expression of Arabidopsis SCL6 genes. In addition, overexpression of pde-miR171 in Arabidopsis induced larger leaves and earlier flowering under long-day conditions compared with the wild type. The findings presented here suggest that miR171 derived from a P. densata precursor together with its target gene SCL6 may play important roles in the regulation of primary root growth, leaf shape, and flowering time in plants.

The NAC (NAM, ATAF1/2, and CUC2) transcription factor family participates in responses to various kinds of environmental stimuli in plants. However, the roles of NAC protein in cold resistance, especially in the cold resistance of tomatoes, are not completely understood. This study examined the roles of a tomato (Solanum lycopersicum) NAC transcription factor (SlNAC35) in resisting chilling using transgenic tomatoes. GUS staining and expression analysis revealed that SlNAC35 expression was induced at 4 °C, thereby suggesting its involvement in plant responses to chilling stress. Moreover, transgenic lines over-expressing SlNAC35 exhibited high chlorophyll content, fresh mass, and low accumulation of reactive oxygen species and membrane damage under chilling stress. These results indicated that SlNAC35 overexpression enhanced the chilling tolerance of transgenic tomatoes. High expressions of cold tolerance markers SlCOR518 and SlCOR413IM1 were observed under chilling stress in transgenic lines. This observation suggested that SlNAC35 overexpression enhanced the chilling tolerance of transgenic lines by involving the c-repeat binding factor-cold stress response (CBF-COR) signaling pathway and by regulating SlCOR expression.

Various ecophysiological investigations on carnivorous plants in wet soils are presented. Radial oxygen loss from roots of Droseraceae to an anoxic medium was relatively low 0.02 - 0.07 μmol(O₂) m^{- 2} s^-1 in the apical zone, while values of about one order of magnitude greater were found in both Sarracenia rubra roots and Genlisea violacea traps. Aerobic respiration rates were in the range of 1.6 - 5.6 μmol kg^-1 (f.m.) s^-1 for apical root segments of seven carnivorous plant species and 0.4 - 1.1 μmol kg^-1 (f.m.) s^-1 for Genlisea traps. The rate of anaerobic fermentation in roots of two Drosera species was only 5 - 14 % of the aerobic respiration. Neither 0.2 mM NaN₃ nor 0.5 mM KCN influenced respiration rate of roots and traps. In all species, the proportion of cyanide-resistant respiration was high and amounted to 65 - 89 % of the total value. Mean rates of water exudation from excised roots of 12 species ranged between 0.4 - 336 mm 3 kg^-1 (f.m.) s^-1 with the highest values being found in the Droseraceae. Exudation from roots was insensitive to respiration inhibitors. No significant difference was found between exudation rates from roots growing in situ in anoxic soil and those kept in an aerated aquatic medium. Carnivorous plant roots appear to be physiologically very active and well adapted to endure permanent soil anoxia.

In order to produce human lactoferrin (Lf) in alfalfa (Medicago sativa L.), a construct containing human Lf cDNA under the control of cauliflower mosaic virus 35S promoter was engineered. As selectable marker bar gene, whose expression in plant cells confers tolerance to L-phosphinothricin (ppt) was used. Plants from a highly embryogenic alfalfa clone from the Bulgarian cultivar Obnova 10 were transformed using Agrobacterium tumefaciens mediated leaf disc method. Transgenic alfalfa plants were established from ppt-resistant calli via indirect somatic embryogenesis. The presence of human Lf cDNA in the genome of the selected regenerants was confirmed by polymerase chain reaction (PCR). Reverse transcriptase (RT)-PCR and Western blot showed expression of human Lf in leaf tissue. Studies on antibacterial effect of the recombinant glycoprotein were conducted and resistance of the transgenic alfalfa plants to two phytopathogens, Pseudomonas syringae pv. syringae and Clavibacter michiganensis, was demonstrated. The obtained results suggest that the expression of human Lf in alfalfa could be beneficial not only for producing recombinant protein for clinical application but also for crop quality improvement.

It has been hypothesized that xylanase inhibitors play important roles in plant defense against microbial pathogens. Currently, there is little information available about xylanase inhibitor OsXIP in rice and its gene expression. We cloned a xylanase inhibitor gene OsXIP from rice (Oryza sativa L. cv. Nipponbare) genomic DNA. To determine the function of OsXIP, we generated OsXIP-overexpressing transgenic rice plants. The transgenic plants had significantly higher OsXIP expression and showed enhanced defense response to Magnaporthe oryzae compared to the wild-type plants. The results also showed that the increased OsXIP expression was accompanied by the up-regulation of pathogenesisrelated genes. To clarify the OsXIP expression pattern, a ProOsXIP::GUS vector was constructed and transgenic plants were obtained. GUS staining results revealed that OsXIP showed organ-specific expressions in rice plants. OsXIP was primarily expressed in the roots and in the veins, but it was weakly expressed in the leaves. Analyses of the OsXIP expression in response to biotic and abiotic stresses indicated that it was drastically induced by biotic stresses and methyl jasmonate treatment. OsXIP, a member of a new class of antifungal proteins, may function as a barrier that prevents the cell wall degradation by xylanases excreted by fungal pathogens. The OsXIP was found to be a stressresponsive gene and it could take part in plant defense via a JA-mediated signaling pathway.

The MYB transcription factor superfamily is a large gene family that plays central roles in developmental processes and defence responses in plants. Unlike in Arabidopsis, only few members of the R2R3-MYB gene family have been functionally well characterized in maize, especially in abiotic stress-response pathways. Subgroup-specific conserved motifs outside the MYB domain may reflect functional conservation. A comparative genomics study using Arabidopsis abiotic stress-responsive MYB protein sequences identified 46 ZmMYB genes that may be involve in abiotic stress responses of Zea mays. An expression pattern analysis of the 46 ZmMYB genes under abiotic stress treatments was used to identify 22 MYB genes that were induced by one or more of the stress treatments. ZmMYB30 was highly upregulated under the four stress treatments. The ectopic expression of ZmMYB30 in transgenic Arabidopsis plants promoted salt-stress tolerance and also increased the expression of a number of abiotic stress-related genes, allowing the plants to overcome adverse conditions.

Woody plants faced multiple abiotic stresses in forest plantation that can influence their growth and development. Dalbergia odorifera T. Chen is a vulnerably endangered tree species, and references about its responses to abiotic stresses are very rare in literature. Furthermore, the mechanisms underlying the abiotic stress tolerance in plants induced by exogenous glycine betaine (GB) remains unclear. Indeed, the alternative oxidase (AOX) is one of the major components of antioxidant enzymatic machinery, and there are no studies that focused on the effects of GB on the amount of AOX protein in plants under drought or cold stresses. Thus, the aim of this study was to investigate the effect of exogenous GB on the phenotype, osmoprotectants, photosynthetic pigments, and antioxidant systems in D. odorifera under cold and drought stresses. The layout of the trial was a factorial experiment in a completely randomized design using two factors including abiotic stress (drought and cold) and GB. Moreover, the principal component analysis based on the measured parameters manifested how the selected ROS scavengers were dispersed throughout the treatments. The results showed huge beneficial impacts of GB on the phenotypic traits of D. odorifera; GB also influences positively the antioxidant machinery, photosynthetic pigments, redox-homeostasis, and water status in D. odorifera seedlings under both stresses. Moreover, exogenous GB affects more the AOX pathway in D. odorifera under cold stress than under drought stress.