Drought and salinity are severe environmental stresses and limit soybean growth. In this study, a comparative analysis of physiological and molecular responses of two soybean (Glycine max L.) genotypes to these stresses was carried out. Plants of drought-tolerant genotype RD (cv. FD92) and sensitive genotype SD (cv. Z1303) were exposed to 15 % (m/v) PEG 6000, which simulated drought stress, or 150 mM NaCl. The RD plants maintained larger leaf area and higher net photosynthetic rate, chlorophyll content, stomatal conductance, and relative water content compared with the SD plants. Leaf proline content increased under both stresses more in RD than in SD. The drought tolerance of RD plants was also correlated with greater antioxidant activity and lower content of hydrogen peroxide and malondialdehyde under stress conditions. Amounts of abscisic acid, jasmonic acid, and salicylic acid under stress increased to a greater extent in RD than in SD plants. At the molecular level, the effects of 20-d stress treatments were manifested by relatively higher expression of drought- or salt-related genes: GmP5CS, GmDREB1a, GmGOLS, GmBADH, and GmNCED1 in RD plants than in SD plants. These results form the basis for understanding the mechanisms of the drought- and salt-stress tolerance in soybean.

About 70 % of the total land area in the world are affected by soil freeze and thaw (FT) cycles. Root is the first organ of plant to sense soil environment and it is unclear how it copes with the soil FT. Based on the different functions of firstorder pioneer and fibrous roots in woody plants, we hypothesize that pioneer and fibrous roots respond differently. The experiment was conducted in a growth chamber using Picea asperata seedlings. We designed the FT based on field observation data. The physiological responses in fibrous and pioneer roots were examined. Fibrous roots had higher root vitality and N content, whereas pioneer roots exhibited higher total nonstructural saccharide content. The accumulation of O₂ ^- under FT treatment was similar in the two types of roots. Pioneer roots showed higher osmolyte (especially proline) content, whereas fibrous roots had higher peroxidase activity. The present study confirmed that fibrous roots have stronger metabolism ability, whereas pioneer roots are the key storage organs. FT in the temperature range from -5 to 5 °C are mild and do not cause serious injury to roots. Pioneer roots have higher tolerance to soil FT in spring than fibrous roots. The roots have different strategies to FT: fibrous roots increase the antioxidant system, whereas pioneer roots accumulate more osmolytes. Such knowledge can help us to understand how roots of woody plants cope with soil FT.

To determine the suitability of micropropagation techniques developed for conserving rare medicinal herb Ungernia victoris we estimated the genetic fidelity of plants produced through direct regeneration from the bulb scale segments and organogenesis from long-term callus culture. Average value of the Jaccard's distances between explant-derived regenerants and maternal plants calculated from RAPD data was 0.5 %, while that of estimated between callus-derived regenerants and maternal cell line was 4.2 %; average distances between the objects among the explant-derived and callus-derived regenerants were 0.7 % and 2.5 %, respectively. The data obtained suggest that conditions for in vitro culture applied in this work provide relatively high genetic stability of the species upon the direct regeneration in vitro and regeneration from the long-term cultured callus.

Abscisic acid (ABA) regulates various plant physiological processes, especially participates in the plant responses to harsh environments. The 9-cis-epoxycarotenoid dioxygenase (NCED) is a key enzyme in ABA biosynthesis pathway. Here, a TaNCED with an 1 887-bp open reading frame was cloned from wheat, which encodes a peptide of 628 amino acids. A chloroplast transit peptide sequence was found at the N-terminus of the TaNCED protein. Multiple sequence alignments indicate that the TaNCED protein shared high similarities with other NCEDs from different species. Real-time quantitative PCR analysis shows that expression of TaNCED was strongly up-regulated by treatments with ABA, polyethylene glycol, and drought stress, and it was down-regulated during germination of the wheat seeds. Ectopic overexpression of the TaNCED gene in Arabidopsis resulted in an increase of endogenous ABA and free proline content. A lower water loss rate and stomatal conductance of leaves were found in the transgenic plants in comparison with the wild type. Subsequently, the transgenic plants displayed an enhanced tolerance to drought stress but delayed seed germination. These data provide evidence that the TaNCED might play a primary role in regulation of ABA content during water stress and seed dormancy.

Protein phosphorylation/dephosphorylation is a major signalling event induced by abiotic stresses in plants. Sucrose nonfermenting 1-related protein kinase 2 (SnRK2) plays important roles in response to osmotic stress. In the present study, four SnRK2s, TpSnRK2.1/3/7/8, were cloned and characterized from Triticum polonicum L. (dwarf Polish wheat, DPW, AABB). All of these were individually located on 2AL, 1AL, 2AL, and 5BL. Two spliced isoforms of TpSnRK2.8 (TpSnRK2.8a and TpSnRK2.8b) were observed. TpSnRK2.1 and TpSnRK2.3 were classified into the group II; TpSnRK2.7 was classified into the group I; and TpSnRK2.8a/b were classified into the group III. Expression patterns revealed that TpSnRK2.1 responded to cold, NaCl, polyethylene glycol (PEG), and abscisic acid (ABA) in both roots and leaves; TpSnRK2.3 was strongly regulated by cold, NaCl, and ABA in both roots and leaves, and by PEG in roots; TpSnRK2.7 was induced by NaCl and PEG in roots, but was not activated by ABA; and TpSnRK2.8s were significantly activated by cold, NaCl, PEG, and ABA in both roots and leaves. From the above results, we inferred that TpSnRK2.1/3/8 may participate in the responses to environmental stresses in ABA-dependent signal transduction pathway but TpSnRK2.7 is possibly involved in responses to environmental stresses in a non-ABA-dependent manner. They play important roles in specific tissues under different stresses.

The interaction between phosphorus (P) and other media components alters root development and masks the plant response and thus limits the ability to correctly identify P-deficiency response (pdr) mutants. This study aims to assess changes in root development caused by different composition of growth media normally used in Arabidopsis research and to study their effects on pdr-mutant screening. Primary root growth of four genotypes was analyzed in media differing in P concentrations: half-strength Murashige and Skoog (1/2 MS) and Somerville and Ogren (SO). The effects of nitrogen source and Fe on root growth were investigated in each medium separately and in a mixture. We found that the primary root length of all genotypes grown on 1/2 MS was reduced in comparison with plants grown on SO medium. The mutant pdr9 was the most sensitive in 1/2 MS, This mutant was also hypersensitive to Fe that intensified its sensitivity to ammonium. Ammonium increased the root inhibition caused by Fe also in wild-type plants. In conclusion, on the basis of our study we recommend to use SO medium, which ensures an efficient selection to screen for pdr mutants through root growth. Moreover, nitrogen sources in the media other than nitrate should be taken carefully.

One of the largest families of transcriptional regulators contains WRKY proteins. They play important roles in plant defense responses. In this study, a novel WRKY gene, CsWRKY2, was isolated from the tea [Camellia sinensis (L.) O. Kuntze] plant. The full-length cDNA of CsWRKY2 was 2 050 bp in length and encoded a 522-amino acid peptide chain containing two typical WRKY domains and two zinc finger motifs, suggesting that CsWRKY2 was member of the WRKY group I family. A subcellular localization assay shows that CsWRKY2 was localized to the nucleus. Real time qPCR analysis shows that CsWRKY2 expression was higher in leaves than in other organs and was induced by cold (4 °C), drought stress, and exogenous abscisic acid (ABA). Additionally, ABA content was enhanced after the cold or drought stress and the effects were relieved by an ABA biosynthesis inhibitor. Furthermore, the expression of CsWRKY2 was up-regulated by exogenous ABA under the cold and drought stresses and down-regulated by an ABA biosynthesis inhibitor. Our findings indicate that CsWRKY2 played an important role in plant defense responses to the cold and drought stresses by participating in the ABA signaling pathway, downstream to ABA.

Plants respond differently to salinity stress due to their unique gene architectures. Among genes, transcription factors (TFs) regulate many physiological and biochemical processes by modulating the rate of transcription initiation of target genes. Modulation of TFs has been correlated to the salt adaptation of any given genotype. In order to identify the expression of eight TFs (belong to bHLH, CBF, MYB, WRKY, and Zpt2 families) in three annual Medicago genotypes (M. polymorpha cv. Ieze, M. laciniata cv. Shushtar, and M. laciniata cv. Gheshm) under salinity stress, the RT-qPCR analyses were performed. Attempts were also made to establish relationships between gene expression profiles and morpho-physiological traits in these genotypes. In response to salinity, cv. Ieze had minimal changes in biomass, the electrolyte leakage, H₂O₂ content, and the higher ratio of reduced to oxidized glutathione than the other genotypes. Furthermore, Ieze had lower accumulation of Na⁺ and less decrease in K⁺ content. Altogether, it is concluded that Ieze could be regarded as a salt tolerant genotype. Transcriptome profile showed considerable variation across Medicago genotypes and among plant tissues. Among five TFs, Zpt2-2 and CBF4 had higher expression in salt-tolerant genotypes suggesting these genes as good candidates in genetic improvement programs to produce stress-tolerant plants.

The present study aimed to investigate the effects of ethanolamine on glycine betaine and proline metabolism in Nicotiana rustica under salt stress. The in vitro grown tobacco (Nicotiana rustica) plants were pretreated with ethanolamine (at concentrations 70, 130, 270, and 530 μM for biochemical analysis and only at the concentration of 530 μM for molecular analysis) and then transferred to Murashige and Skoog medium containing 200 mM NaCl for 3 weeks. Our results showed that ethanolamine promoted glycine betaine biosynthesis by an increase in betaine aldehyde dehydrogenase (BADH) gene expression and BADH enzymatic activity. Moreover, ethanolamine pretreatment possibly reduced proline content in salt stressed plants via its negative effect on Δ-pyrroline-5-carboxylate synthase (P5CS) gene expression and P5CS enzymatic activity and its positive effect on proline dehydrogenase (PDH) gene expression and PDH activity.

Ultrastructure of leaf mesophyll and two-layer trap wall of Utricularia vulgaris L. was studied after 24-h and 48-h treatment with different concentrations of cadmium. The treatment of plants with 0.25 g(Cd²⁺) m^-3 caused different changes in the chloroplasts of the two organs. The thylakoids swelled in chloroplasts of leaf and the starch content increased in chloroplasts of traps. Higher concentrations of Cd (0.5 and 1.5 g m^-3) caused osmiophilisation of thylakoids in the chloroplasts of both studied organs. The secretory cells in the trap wall was resistant to Cd.

Proline is emerging as a critical component of drought tolerance and fine tuning of its metabolism under stress affects the plants sensitivity and response to stress. Thus the study was carried out to analyse the effect of water deficit on the proline content and principal enzymes involved in its synthesis (Δ¹-pyrolline-carboxylate synthetase) and catabolism (proline dehydrogenase) at different developmental stages and in different organs (roots, nodules, leaves, pod wall, and seeds) of two chickpea (Cicer arietinum L.) cultivars differing in drought tolerance (drought tolerant ICC4958 and drought sensitive ILC3279). It was observed that increased Δ¹-pyrolline-carboxylate synthetase activity under moderate stress in roots and nodules of ICC4958 caused an increase in proline content during initiation of reproductive development whereas increased proline dehydrogenase activity in nodules and leaves at this period helped to maintain reducing power and energy supply in tissues and proper seed development as seed biomass increased consistently up to maturity. On the other hand, roots and nodules of ILC3279 responded to stress by increasing proline content after the developmental phase of reproductive organs was over (near maturity) which negatively affected the response of pod wall to stress. Concurrent increase in activities of Δ¹-pyrolline-carboxylate synthetase and proline dehydrogenase in pod wall of ILC3279 aggravated the oxidative stress and affected seed development as seed biomass initially increased rapidly under stress but was unaffected near maturity.

Vriesea gigantea Gaudichaud is an epiphytic bromeliad with a high capacity to take up urea. In plants, urea is hydrolyzed by urease into ammonium and CO₂, providing nitrogen to the plant. Most studies of urea nutrition have focused only on nitrogen metabolism, whereas scarce attention has been given to CO₂ assimilation. Therefore, this study attempted to investigate whether urea could play an important role as a carbon source, which could be of a significant importance under water deficit conditions because of the limitation in atmospheric CO₂ influx into the leaves due to stomatal closure. In this study, detached leaves of V. gigantea were exposed to water deficit and supplied with urea. The most photosynthetic parts of the leaf (mainly the apical leaf portion) showed higher urease activities and CO₂ buildup near chloroplasts, particularly during the nighttime under water deficit conditions when compared to urea application without the water deficit. Moreover, part of the CO₂ generated from urea hydrolysis was fixed into malate, probably via phosphoenolpyruvate carboxylase. Therefore, urea may contribute to the carbon balance of plants under water deficit conditions. Our data suggest that, besides being a source of nitrogen, urea might also be an important carbon source during CO₂-limited conditions in leaves of epiphytic bromeliads.

The responses of tobacco plants over-expressing trans-zeatin O-glucosyltransferase gene under constitutive or senescence-inducible promoter (35S:ZOG1 and SAG12:ZOG1) and of wild type (WT) plants to water stress and subsequent rehydration were compared. In plants sufficiently supplied with water, both transgenics have higher net photosynthetic rate (P_N) in upper and middle leaves and higher stomatal conductance (g_s) in middle leaves than WT. Water use efficiency (WUE = P_N/E) was higher in both transgenics than in WT. During prolonged water stress, both P_N and E declined to a similar extent in both transgenics and WT plants. However, 7 d after rehydration P_N in SAG:ZOG (upper and middle leaves) and 35S:ZOG (upper leaves) was higher than that in WT plants. Increased content of endogenous CKs in 35S:ZOG plants did not prevent their response to ABA application and the results obtained did not support concept of CK antagonism of ABA-induced stomatal closure. The chlorophyll (Chl) a+b content was mostly higher in both transgenics than in WT. During water stress and subsequent rehydration it remained unchanged in upper leaves, decreased slightly in middle leaves only of WT, while rapidly in lower leaves. Total degradation of Chl, carotenoids and xanthophyll cycle pigments (XCP) was found under severe water stress in lower leaves. Carotenoid and XCP contents in middle and upper leaves mostly increased during development of water stress and decreased after rehydration. While β-carotene content was mostly higher in WT, neoxanthin content was higher in transgenics especially in 35S:ZOG under severe stress and after rehydration. The higher content of XCP and degree of their deepoxidation were usually found in upper and middle leaves than in lower leaves with exception of SAG:ZOG plants during mild water stress.

During the normal developmental process, programmed gene expression is an essential phenomenon in all organisms. In eukaryotes, DNA methylation plays an important role in the regulation of gene expression. The extent of cytosine methylation polymorphism was evaluated in leaf tissues collected from the greenhouse grown plants and in in vitro-derived callus of three lowbush and one hybrid blueberry genotypes, using methylation-sensitive amplification polymorphism (MSAP) technique. Callus formation started from the leaf segments after 4 weeks of culture on a thidiazuron (TDZ) containing medium. Maximum callus formation (98 %) was observed in the hybrid blueberry at 1.0 mg dm^-3 TDZ. Although noticeable changes in cytosine methylation pattern were detected within the MSAP profiles of both leaf and callus tissues, methylation events were more polymorphic in calli than in leaf tissues. The number of methylated CCGG sites varied significantly within the genotypes ranging from 75 to 100 in leaf tissues and from 215 to 258 in callus tissues. Differences in the methylation pattern were observed not only in a tissue-specific manner but also within the genotype in a treatment specific manner. These results demonstrated the unique effect of TDZ and the tissue culture process on DNA methylation during callus development.

The response of higher plants to ionising radiation depends on factors related to both radiation properties and plant features including species, cultivar, age, and structural complexity of the target organ. Adult plants of dwarf tomato were irradiated with different doses of X-rays to investigate possible variations in leaf morpho-anatomical traits, photosynthetic efficiency, and genomic DNA. In order to assess if and how responses depend on leaf developmental stage, we analysed two types of leaves; nearly mature leaves (L1) and actively developing leaves (L2), whose lamina size corresponded to 70 and 25 %, respectively, of the lamina size of the fully expanded leaves. The results show that the X-rays prevented full lamina expansion of the L2 leaves at all doses and induced early death of tissue of plants irradiated with doses higher than 20 Gy. Most anatomical modifications were not clearly dose-dependent and the radiation-induced increase in phenolic compounds was irrespective of dose. At high doses of X-rays (50 and 100 Gy), photochemical efficiency decreased significantly in both leaf types, whereas total chlorophyll content significantly decreased only in the L2 leaves. The random amplification of polymorphic DNA data show that the X-rays induced mutagenic effects in the L2 leaves even at low doses despite the absence of severe phenotypic alterations. Genetic structure found in the population of samples corroborates the results of anatomical and eco-physiological analyses: the 20 Gy dose seems to mark the threshold dose above which genetic alterations, structural anomalies, and perturbations in the photosynthetic apparatus become significant, especially in the actively expanding leaves.

As key nuclear transcription factors, the ethylene-insensitive3/EIN3-like (EIN3/EIL) proteins play important roles in ethylene signal transduction pathway in various plants. In order to better understand the role of EIN3/EILs, one EIN3-like gene (designated ZmEIL1) was isolated from maize (Zea mays L.). The full-length cDNA of ZmEIL1 was 1 999 bp in length and encoded 647 amino acids. Sequence comparison of ZmEIL1 protein with other EIN3/EILs proteins revealed high conservation of five α-helices that could form a V-shaped cleft in a 3-D model, just like AtEIL3 in Arabidopsis thaliana. This protein showed transcriptional activation and activation domain located on the 507 - 647 amino acids in yeast. Furthermore, ZmEIL1 could interact with ZmERF1 in the yeast systems, which was downstream response factor in ethylene signal transduction pathway. Its mRNA could be highly induced in maize seedlings by ethephon and 1-methylcyclopropene treatments. Meanwhile, ZmEIL1 showed relatively high expression at 20 d after pollination in maize kernel. These results show that ZmEIL1 played an important role in the growth and development by participating in ethylene signalling pathway in maize.

Multiple allele-inherited male sterility has been widely used by breeders of Brassica rapa L. ssp. pekinensis, but the molecular mechanisms of male sterility are not yet clear. In this study, we isolated the full-length cDNA of a new gene (not included in the Brassica database). This gene, comprising 1 054 bp, encodes a 39.99 kDa protein with a Gly-Asp- Ser-Leu (GDSL)-lipase domain that is a member of the lipolytic protein GDSL family. The sequence of candidate gene is the most similar to extracellular lipase 6 (EXL6) of Arabidopsis and was therefore designated BrEXL6 and submitted to NCBI (accession No. JX131630.1). Reverse transcription semi-quantitative PCR and Western blot analysis showed that BrEXL6 and its encoded protein were significantly more expressed in fertile buds than in sterile buds. Quantitative PCR and in situ hybridization showed that BrEXL6 was highly expressed in the anthers of fertile buds, especially anthers at the pollen-development stages, but only weakly expressed in other tissues and floral organs of fertile plants and whole sterile plants. These results suggest that BrEXL6 is a pollen development-related gene. The results of this study provide clues for understanding the mechanisms underlying multiple allele-inherited male sterility.

The anatomic and functional leaf characteristics related to photosynthetic performance of Castanea sativa growing in vitro and in nursery were compared. The irradiance saturated photosynthesis in in vitro grown plantlets was significantly lower compared to nursery plants (65 vs. 722 μmol m^-2 s^-1). The maximum photosynthetic rate (P_Nmax) was 4.0 and 10.0 μmol(CO₂) m^-2 s^-1 in in vitro microshoots and nursery plant leaves, respectively. Carboxylation efficiency (C_E) and electron transport rate (ETR) were three-folds higher in nursery plants than in microshoots. The nonphotochemical quenching (NPQ) was saturated at 80 μmol m^-2 s^-1 in microshoots suggesting limited photoprotection by thermal dissipation. The microshoots had wide open, spherical stomata and higher stomatal density than nursery plants and they had almost no epicuticular wax. Consequently, the microshoots had high stomatal conductance and high transpiration rate. These anatomic and functional leaf characteristics are likely major causes of the low survival rates of plantlets after ex vitro transfer.

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.

Selenium (Se) is an essential trace element for humans and animals. A hydroponic experiment was performed to study the effects of sulphur (S) on Se uptake, translocation, and assimilation in wheat (Triticum aestivum L.) seedlings. Sulphur starvation had a positive effect on selenate uptake and the form of Se supplied greatly influenced Se speciation in plants. Compared with the control plants, Se uptake by the S-starved plants was enhanced by 4.81-fold in the selenate treatment, and selenate was readily transported from roots to shoots. By contrast, S starvation had no significant effect on selenite uptake, and selenite taken up by roots was rapidly converted to organic forms and tended to accumulate in roots. X-ray absorption near edge spectroscopy (XANES) analysis showed that organic forms of selenium, including selenocystine, Se-methyl-selenocysteine (MeSeCys), and selenomethionine-Se-oxide, were dominant in the plants exposed to selenite and accounted for approximately 90 % of the total Se. Whereas selenate remained as the dominant species in the roots and shoots exposed to selenate, with little selenate converted to selenite and MeSeCys. Besides, sulphur starvation increased the proportion of inorganic Se species in the selenate-supplied plants, but had no significant effects on Se speciation in plants exposed to selenite. The present study provides important knowledge to understand the associated mechanism of Se uptake and metabolism in plants.

Genes encoding plant WRKY transcription factors are important for stress response. In the current study, two WRKY transcription factor genes (JrWRKY6 and JrWRKY53) were identified from walnut (Juglans regia L.), and their function and involvement in stress responses were characterized. Under NaCl stress, JrWRKY6 and JrWRKY53 were upregulated in a short time (within 6 h of seedling exposure to salt) except in roots, in which the highest induction occurred at 24 and 48 h of salt exposure. The gene expression patterns under polyethylene glycol stress were similar to those under NaCl stress. Under heat stress, both genes were induced in all tissues, except for JrWRKY6 in leaf tissue of seedlings treated for 24 and 48 h. Both genes were also induced in all plants exposed to cold stress, except for JrWRKY6 in root tissue of seedlings exposed for 6 h and JrWRKY53 in root tissue exposed for 48 h. JrWRKY6 and JrWRKY53 also showed varied responses to abscisic acid (ABA), with the maximum expression being for JrWRKY6 in the roots of plants treated for 1 h, and JrWRKY53 in the leaves of plants treated for 3 h. Furthermore, under NaCl, sorbitol, heat, cold, and ABA treatments, yeast cells transformed with JrWRKY6 and JrWRKY53 showed an improved growth activity and density relative to the empty-vector-containing control yeast. Moreover, JrWRKY6 or JrWRKY53 could bind to the W-box motif. These results suggest that JrWRKY6 and JrWRKY53 can response positively to abiotic stressors and improve the plant tolerance to salinity, osmotic stress, and abnormal temperatures in a mechanism that likely involves the ABA signalling pathway and W-box binding activity.

Both lignin and silicon (Si) are major players in the resistance of plants to mechanical stress (MS). Focusing on the phenolic metabolism, here we studied the short-term effects of a local MS on tobacco (Nicotiana rustica L. cv. Basmas) plants with Si (+Si, 1 mM Na₂SiO₃) and without Si (‒Si) treatments in order to see how Si may modify local and systemic responses. One week after starting the Si treatment, a half of the plants were exposed to a mechanical pressure applying 980 Pa for 24 h on the upper side of the 3^rd leaf of each plant (+MS). The rest of the plants remained unstressed (‒MS). Plants were harvested 24 h and 72 h after starting the MS and the leaves directly exposed to the mechanical stress (DMS) and those indirectly exposed to the mechanical stress (IMS) from below and above the DMS leaf were analyzed for phenolic metabolism along with the corresponding leaves from‒MS plants. In the DMS leaf, the activities of polyphenol oxidase, phenylalanine ammonia lyase, and cytosolic and covalently-bound peroxidases increased by the MS, while decreased by Si. In accordance with this in the DMS leaf, the content of soluble and cell wall-bound phenolics and lignin were enhanced by the MS but decreased by Si. Interestingly, Si influenced the pattern of response to the MS depending on whether the leaves were directly treated by the MS or not. Silicon treatment augmented MS-induced lignin accumulation in the DMS leaf while rather inhibited lignin formation in the IMS leaves. These data show that Si modified MS-mediated changes in the phenolic metabolism differently in local and systemic leaves.

The present study was conducted to examine differential responses of roots and leaves of Artemisia annua to different arsenic concentrations (50, 100, and 150 μΜ) and treatment durations (1, 3, 5, or 7 d). The values of bioconcentration factor and translocation factor calculated on the basis of total As-accumulation in roots and shoots suggested that A. annua is a good As-accumulator. Above and below ground plant biomass was enhanced at 100 μΜ As but at 150 μΜ As was significantly reduced. As-treatment caused membrane damage more in the roots than in the leaves as reflected by higher degree of lipid peroxidation in the roots than in the leaves. In response to As stress, plants activated antioxidative defense for detoxification of induced reactive oxygen species (ROS), As sequestration via phytochelatins (PCS) as well as production of a wide range of secondary metabolites. All of them were activated differently in roots and leaves. Among enzymatic antioxidants, leaves significantly elevated superoxide dismutase (SOD), ascorbate peroxidase, and glutathione reductase, whereas in roots SOD, catalase, and peroxidase played significant role in ROS detoxification. Plants activated As-sequestration pathway through thiols, glutathione, and PCS and their respective genes were more induced in leaves than in roots. Further gas chromatography in tandem with mass spectroscopy analysis revealed differential modulation of secondary metabolites in leaves and roots to sustain As-stress. For example, roots synthesized linoleic acid (4.85 %) under As-treatment that probably stimulated stress-signalling pathways and in turn activated differential defense mechanisms in roots to cope up with the adverse effects of As.

Phytocyanins (PCs) are ancient blue copper-binding proteins in plants that bind to single type I copper atoms and function as electron transporters. PCs play an important role in plant development and stress resistance. Many PCs are considered to be chimeric arabinogalactan proteins (AGPs). Previously, 38, 62, and 84 PC genes were identified in Arabidopsis thaliana, Oryza sativa, and Brassica rapa, respectively. In this study, we identified 30 putative PC genes in the orchid Phalaenopsis equestris through comprehensive bioinformatics analysis. Based on phylogeny and motif constitution, the P. equestris phytocyanins (PePCs) were divided into five subclasses: 10 early nodulin-like proteins, 10 uclacyanin-like proteins, five stellacyanin-like proteins, four plantacyanin-like proteins, and one unknown protein. Structural and glycosylation predictions suggested that 16 PePCs were glycosylphosphatidylinositol-anchored proteins localized to the plasma membrane, 22 PePCs contain N-glycosylation sites, and 14 are chimeric AGPs. Phylogenetic analysis indicated that each subfamily was derived from a common ancestor before the divergence of monocot and dicot lineages and that the expansion of the PC subfamilies occurred after the divergence of orchids and Arabidopsis. The number of exons in PC genes was conserved. Expression analysis in four tissues revealed that nine PC genes were highly expressed in flowers, stems, and roots, suggesting that these genes play important roles in growth and development in P. equestris. The results of this study lay the foundation for further analysis of the functions of this gene family in plants.

Real time quantitative PCR (qPCR) is widely used in gene expression analysis for its accuracy and sensitivity. Reference genes serving as endogenous controls are necessary for gene normalization. In order to select an appropriate reference gene to normalize gene expression in Casuarina equisetifolia under salt stress, 10 potential reference genes were evaluated using real time qPCR in the leaves and roots of plants grown under different NaCl concentrations and treatment durations. GeNorm, NormFinder, and BestKeeper analyses reveal that elongation factor 1-alpha (EF1α) and ubiquitin-conjugating enzyme E2 (UBC) were the most appropriate reference genes for real time qPCR under salt stress. However, β-tubulin (βTUB) and actin 7, which were widely used as reference genes in other plant species, were not always stably expressed. The combination of EF1α, UBC, uncharacterized protein 2, DNAJ homolog subfamily A member 2, and glyceraldehyde-3-phosphate dehydrogenase should be ideal reference genes for normalizing gene expression data in all samples under salt stress. It indicates the need for reference gene selection for normalizing gene expression in C. equisetifolia. In addition, the suitability of reference genes selected was confirmed by validating the expression of WRKY29-like and expansin-like B1. The results enable analysis of salt response mechanism and gene expression in C. equisetifolia.

Brassinolide (BL) alleviates salt injury in cotton seedlings; however, little is known about the molecular mechanisms of this response. In this study, digital gene expression analysis was performed to better understand the regulatory pathways of BL in NaCl-stressed cotton (Gossypium hirsutum L.). Compared with control plants (CK), a total of 1 162 and 7 659 differentially expressed genes (DEGs) were detected in the leaves and roots of NaCl-treated plants, respectively. Most of the DEGs in NaCl-treated plants, compared to CK, were regulated by BL. Moreover, expression patterns of DEGs in BL+NaCl treated plants were similar to those in CK plants; however, the responses of DEGs in the leaves and roots of NaCl-treated plants to BL differed. In the roots, BL-regulated DEGs were involved in protein biosynthesis, whereas in the leaves, BL promoted photosynthesis in NaCl-stressed cotton. BL treatment also significantly increased the overall biomass, chlorophyll a + b content in leaves, and the protein content in roots in NaCl-stressed cotton. The downregulation of stress-responsive genes in BL+NaCl-stressed leaves was also found. These results suggest that BL can alleviate NaCl injury in cotton plants.

Glutathione transferases (GSTs) mainly catalyze the nucleophilic addition of glutathione to a large variety of hydrophobic molecules participating to the vacuole compartmentalization of many toxic compounds. In this work, the putative tolerance of transgenic tobacco plants over-expressing CsGSTU genes towards the chloroacetanilide herbicide alachlor was investigated. Our results show that the treatment with 0.0075 mg cm^-3 of alachlor strongly affects the growth of both wild type and transformed tobacco seedlings with the sole exception of the transgenic lines overexpressing CsGSTU2 isoform that are barely influenced by herbicide treatment. In order to correlate the in planta studies with enzyme properties, recombinant CsGSTs were in vitro expressed and tested for GST activity using alachlor as substrate. The recombinant GSTU2 enzyme was twice more active than GSTU1 in conjugating alachlor to GSH thus indicating that CsGSTU2 might play a crucial role in the plant defense against the herbicide. Moreover, as a consequence of the infiltration with a bacterial suspension of the P. syringae pv. tabaci, transgenic tobacco plants but not wild type plants bestowed the capability to limit toxic metabolite diffusion through plant tissues as indicated by the absence of chlorotic halos formation. Consequently, the transgenic tobacco plants described in the present study might be utilized for phytoremediation of residual xenobiotics in the environment and might represent a model for engineering plants that resist to pathogen attack.

The current research was carried out to reveal the possible impacts of cold plasma on growth and physiology of wheat, as a new approach in plant science. Short and long-term impacts of different types of plasma (nitrogen and helium) with surface power density of 0.4 W cm^-2, exposure times (15, 30, 60, and 120 s), and repetitions (1, 2, and 4 times with 24 h intervals) were evaluated. Single-time applied helium or nitrogen derived plasma significantly promoted total root and shoot lengths, in contrast to four times application, and the root system was more sensitive than the shoot one. In addition, seedlings were more sensitive to nitrogen derived plasma, compared with helium. The physiological responses to plasma treatment were analyzed via protein assay and peroxidase or phenylalanine ammonia lyase (PAL) activities measurements. Plasma generated signaling molecules, especially ozone, nitric oxide, and/or UV radiation induced promotions in the peroxidase and PAL activities as well as increase in protein content in leaves, especially when times and/or repetitions increased. Plants were perished by the nitrogen derived plasma at the highest exposure time and number of repetitions. However, the seedlings with inhibited growth not only caught up control one month after, but even the growth rate and biomass accumulation in the shoot and leaves were accelerated. Increased leaf soluble phenol content was recorded in plasma treated seedlings, especially at longer times and more repetitions.

MADS-box genes encode a family of transcription factors that regulate diverse growth and developmental processes in plants, including flowering. In this study, comprehensive characterization and expression profiling analyses of seven sugar apple (Annona squamosa L.) MADS-box genes were performed using rapid amplification of cDNA ends method. Domain and phylogenetic analyses grouped these seven MADS-box genes into six different clades and they showed high similarity with orthologs in Arabidopsis. Expression patterns of these MADS-box genes were investigated during different flower developmental stages and in various reproductive organs, including petal, stamen, sepal, and pistil. Most of the MADS-box genes studied were least expressed in the sepal and AsAGL67 and AsAGL80 expression was weak in all tissues. AsSEP1 and AsAGAMOUS showed highest expressions in the stamen and pistil, and AsAGL12 showed stamen-specific expression. Dynamic expression patterns of MADS-box genes in different reproductive stages suggest involvement in flower development. Interestingly, a number of these MADS-box genes showed responses to gibberellin, abscisic acid, and salicylic acid treatments, suggesting control of their expression by phytohormones.

Melatonin (MT), a tryptophan derivative, plays an important role in the function and survival of organisms. To better understand the role of MT in cold tolerance, the melon (Cucumis melo L.) were sprayed with various concentrations of MT (0, 50, 100, 200 or 400 μM), exposed to cold stress (day/night temperature of 12/6 °C) for 7 d, and then returned to optimal conditions (28/18 °C) for 7-d recovery. The foliar application of MT (especially 200 μM) significantly alleviated cold-induced growth suppression, and MT-treated plants recovered more quickly than untreated plants. Further, MT-treated plants had higher chlorophyll content, photosynthetic rate, stomatal conductance, as well as maximal quantum yield of photosystem (PS) II photochemistry, and efficiency of excitation energy capture of open PS II centres under cold stress than untreated plants. Furthermore, exogenous MT significantly reduced malondialdehyde content and markedly increased the activities of antioxidant enzymes superoxide dismutase (SOD), guaiacol peroxidase (POD), and catalase (CAT) under cold stress. MT also increased expression of antioxidant genes CmSOD, CmPOD, and CmCAT under cold stress. The results indicate that MT pretreatment alleviated the detrimental effects of cold stress and accelerateds the recovery mainly by enhancing photosynthesis and antioxidant capacity in melon leaves.