WRKY transcription factors (TF) family is involved in a huge variety of plant processes, including seed germination, plant development, phytohormone signalling, and defence against both biotic or abiotic stresses. In this work, WRKY TF family has been characterized in citrus. In a first experiment, the relative expression of CsWRKYs was analyzed in shoots and roots of plants treated with abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA) under in vitro conditions. Expression of CsWRKYs was also determined in roots of commercial citrus rootstocks subjected to osmotic and salt stresses. A total amount of 50 CsWRKYs has been found and devided into different groups of WRKY family according to the WRKY domain sequences. In response to the applications of phytohormones, the highest differences were observed in roots, and it was found that ABA and SA generally repressed CsWRKYs expressions, but MeJA induced their overexpression. Osmotic stress repressed the expression of most of the CsWRKYs, whereas salt stress induced their expression. Moreover, salt stress induced higher increase in CsWRKY expressions in the tolerant rootstock Citrus macrophylla than in the sensitive rootstock Carrizo citrange, suggesting that these TFs may play an important role in response to this stress.

This study investigated the role of hydrogen sulfide (H₂S) in the regulation of the ascorbate (AsA) and glutathione (GSH) metabolism by jasmonic acid (JA) in the leaves of Arabidopsis thaliana by using H₂S scavenger hypotaurine (HT) and H₂S synthetic mutant (SALK_041918, designated Atl-cdes). The results showed that JA significantly increased the H₂S content, the activities of L-cysteine desulfhydrase (L-CDes), D-cysteine desulfhydrase (D-CDes), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), L-galactono-1,4-lactone dehydrogenase (GalLDH) and γ-glutamylcysteine synthetase (γ-ECS), the ratio of AsA to dehydroascorbate (DHA), and decreased the content of malondialdehyde (MDA) and H₂O₂ in the wild type of A. thaliana, compared to control. The above effects of JA except the increased activities of L-CDes and D-CDes were suppressed by addition of HT. However, JA and HT+JA had no significant effects on the ratio of reduced GSH to oxidized GSH (GSSG) in the wild type of A. thaliana. Application of HT to the control decreased H₂S content, AsA/DHA ratio, and activities of APX, GR, DHAR, MDHAR, γ-ECS, and GalLDH, but had no effects on MDA content, activities of L-CDes and D-CDes, and GSH/GSSG ratio. In the H₂S synthetic mutant, JA had no obvious effects on above mentioned parameters except the D-CDes activity compared with the control. Our results suggest that JA-induced H₂S, which is a signal that leads to the up-regulation of the AsA and GSH metabolism.

Transcription factors are involved in lipid metabolism, and in present study, the transcription factor WRINKLED 1 (GhWRI1) was cloned from Gossypium hirsutum L. cv. Coker 201 by reverse transcription (RT)-PCR and rapid amplification of cDNA ends. The Pro35S:WRI1 vector was constructed and transformed into upland cotton cv. Sumian 20 using the pollen tube pathway method. After PCR and Southern blot verification of the positive transgenic plants, T₂ transgenic lines derived from T₁ individuals with the insertion gene in a single copy were chosen for further dissection. Semi-quantitative and quantitative RT-PCR analyses indicated that GhWRI1 gene expression increased in transgenic plants compared with that in the wild-type. Seed lipid content increased at most transgenic plants, and at the same time, protein content decreased. Compared to the control, major agronomical traits were not affected by overexpression of GhWRI1 in transgenic 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.

Ion transporters play an important role in ion homeostasis and control ion flow from its intrusion to exclusion in the entire plant system. Abiotic stress tolerance in plants depends immensely on the activity of these transporters. The transporter proteins are transcriptionally regulated by cis-elements present in their upstream region for specific activity. The presence of different cis-elements facilitates cross-talk between different signal transduction pathways. Depending on the cis-elements, a specific stress signalling pathway is activated, eliciting a physiological change towards maintaining ion homeostasis to alleviate stress. Beta-glucuronidase localization studies using various promoter regions indicated their expression specificity in organs/tissues. This review gives an overview about promoter activity of different transporters and its involvement under salinity stress.

Rapid and non-destructive assessment of water status is essential to enhance crop performance. This study aimed to evaluate photosynthetic performance and to monitor water status in cotton under field conditions. A two-year experiment was conducted with three irrigation regimes to measure the following parameters: photochemical reflectance index (PRI), structural independent pigment index (SIPI), water index (WI), solar-induced fluorescence (SIF; retrieved from reflectance by using Fraunhofer line-depth method), gas exchange, and chlorophyll fluorescence (CF). The results showed that PRI decreased > 30 % in moderate drought (MD) and >50 % in severe drought (SD), compared with control. PRI was found to be positively correlated with net photosynthetic rate (P_N), stomatal conductance (g_s), transpiration rate (T_r), actual quantum yield of photosystem II photochemistry (Φ_PSII), but a negatively correlated with nonphotochemical quenching (NPQ). Solar-induced fluorescence around 761 nm (SIF₇₆₁) had significant correlations with P_N, Φ_PSII, and NPQ, but not with maximal quantum yield of PS II photochemistry (F_v/F_m). The relationship between PRI and PN was stronger at the beginning of water stress (R² = 0.86) than for the all stress stages (R² = 0.54), indicating that PRI could be more effective for assessing PN of cotton at early water stress. PRI was better correlated with relative water content and photosynthetic parameters than SIPI and WI and so it could also be a good indicator to evaluate cotton water status.

Leymus chinensis (Trin.) Tzvel is a rhizomatous grass species in the Eastern Eurasian steppe zone that is often limited by low soil nitrogen availability. Although a previous study showed that the rhizomes of L. chinensis have the capacity to take up nitrogen, the importance of such uptake for nitrogen nutrition is unclear. Moreover, little is known regarding the inorganic nitrogen uptake kinetics of roots and rhizomes in response to nitrogen status. Here, we first found that ammonium is preferred over nitrate and glycine for L. chinensis growth. Using the ¹⁵N-labelling method, we found that the rate of ion influx into roots was approximately five-fold higher than into rhizomes under the same nitrogen content, and the ion influxes into roots and rhizomes under 0.05 mM N were greater than in the presence of 3 mM N, especially in the form of NH₄⁺. Using a non-invasive micro-test technique, we characterised the patterns of NH₄⁺ and NO₃^- fluxes in the root mature zone, root tip, rhizome mature zone, and rhizome tip following incubation in the solution with different N compounds and different N concentrations. These results suggest a dynamic balance between the uptake, utilisation, and excretion of nitrogen in L. chinensis.

Ethylene response factor (ERF) is a key transcription factor of plant ethylene signaling pathway, which plays an important role in plant response to abiotic and biotic stresses by regulating the expression of downstream genes. However, little is known about the mechanisms of the regulation of gene expression by ERF proteins. Chloroplast is an essential organelle that is important for photosynthesis and biosynthesis of many essential metabolites. There exists an interaction between chloroplasts and the nucleus. Chloroplasts can send multiple kinds of signals to regulate the nuclear gene expression known as retrograde signaling. In our study, we have analyzed the expression of the components related to plastid retrograde signaling pathway to elucidate the mechanism of tomato ethylene responsive factor 1 (TERF1) in response to drought stress. Our results showed that TERF1 can regulate different biogenic and operational retrograde signals to regulate nuclear genes expression, which can improve plant tolerance to drought stress. We also propose a new potential of TERF1 in regulating nuclear gene expression, including regulation of different phytohormone signaling pathways and gene posttranscriptional modification triggered by different retrograde signals. Our results have enriched our knowledge about the function of ERF proteins and ethylene signaling pathway.

Growth responses of the moderately salt-tolerant velvet ash (Fraxinus velutina) and salt-sensitive poplar (Populus × euramericana) were investigated under heterogeneous root zone salinity. The salinity treatments imposed on the two root zones (lower-higher) were 137-137 (uniform), 103-171, 68-205, 34-239, and 0-273 mM NaCl for velvet ash, and 51-51 (uniform), 34-68, 17-85, and 0-103 mM NaCl for poplar. The leaf gas exchange of the plants was measured one month after these treatments were implemented, and the plants were sampled 75 d after treatment to measure other physiological parameters. Net photosynthetic rate, transpiration rate, total biomass, and fine root compensatory growth increased as the difference in salinity between the two root zones (i.e., salinity heterogeneity) increased in velvet ash. These parameters showed no significant difference among the treatments in poplar. The leaf Na⁺ content was lower under heterogeneous salinity than under uniform salinity in both tested species. The leaf proline content in velvet ash decreased under heterogeneous salinity compared to that under uniform salinity, whereas that of poplar increased. The soluble sugar content of velvet ash leaves increased under heterogeneous salinity, whereas no changes were observed in poplar. The increased fine root biomass in the lower salinity zone promoted velvet ash growth by decreasing the leaf Na⁺ and Cl^- content under heterogeneous salinity. The poplar's undifferentiated root distribution and gas exchange in response to the heterogeneous salinity were attributed to its salt sensitivity.

The present work aimed to investigate the mechanisms of nitric oxide (NO) and reactive oxygen species (ROS) generations and to explore their roles in the regulation of antioxidative responses in the wheat leaves under salinity. Except for an insignificant change of NO content and nitrate reductase (NR) activity due to 50 mM NaCl, NO, hydrogen peroxide, superoxide anion (O₂^*- ), hydroxyl radical (^*OH), chlorophyll and malondialdehyde content, as well as activities of nitric oxide synthase, NR, peroxidases (POD), catalase (CAT), and ascorbate peroxidase rose in response to different NaCl concentrations. Meanwhile, leaf superoxide dismutase activity lowered only at 50 mM NaCl. NaClstimulatory effects on NO content as well as POD and CAT activities could be partly alleviated by the application of 2-phenyl-4,4,5,5-tetrame-thylimidazoline-3-oxide-1-oxyl (PTIO, NO scavenger), exogenous CAT, or diphenylene iodonium (DPI, NADPH oxidase inhibitor). Native polyacrylamide gel electrophoresis (native-PAGE) also showed that the amount of POD (especially POD4, POD5, and POD7) and CAT (especially CAT1, CAT2, and CAT3) isozymes increased with increasing salinity but decreased by application of PTIO, CAT, or DPI. Furthermore, histochemical staining showed a similar change of O₂^*- generation. In addition, the inhibition of diamineoxidase (DAO), polyamine oxidase (PAO), and cell wall-bound POD (cw-POD) activities in NaCl-stressed seedlings seemed to be insensitive to the application of PTIO or DPI. Taken together, salinity-induced NO, H₂O₂, and O₂^*- generation influenced each other and played different roles in the regulation of antioxidant enzyme activities in the leaves of wheat seedlings under NaCl treatment.

Aluminum (Al) toxicity in acidic soils is a major factor restricting crop production. Although the molecular mechanisms of Al responses have been extensively investigated, microRNA (miRNA) mediated differential Al tolerance in different soybean genotypes remains largely unknown. In this study, two soybean [Glycine max (L.) Merr.] genotypes, Al-tolerant BX10 and Al-sensitive BD2, were treated with 0 and 50 μM AlCl3 and then used to construct the miRNA libraries for deep sequencing. Results revealed 453 miRNAs, whose expression patterns were affected by Al stress. We also identified 32 differentially expressed miRNAs: 19 in BX10, 7 in BD2, and 6 in both genotypes. The gene ontology analysis of their putative target genes indicated that stress-responsive genes and amino-acid-metabolism-related processes preferentially existed in BX10. Comprehensive analysis demonstrated that conserved miRNAs, such as gma-miR166k/o, gma-miR390g, and gma-miR396c/k, mediated root elongation in BX10, whereas gma-miR169r triggered oxidative stress in BD2. These processes could be regarded as important mechanisms conferring differential Al tolerance in BX10 and BD2. This study provided new insights into different Al response mechanisms in various soybean genotypes.

Structural alterations of chromosomes are often found in wheat-rye hybrids. In the majority of cases modifications are observed for rye chromosomes, yet chromosome aberration cases are described for wheat, including the progeny of Triticum aestivum disomic and monosomic addition lines. Since wheat-rye substitution and translocation lines are the source of rye chromatin in wheat breeding programs, the information on possible chromosome changes in the genomes of introgressive forms is important. Chromosome behavior in F₁ meiosis and chromosomal composition of F₂ karyotypes for double monosomics 1Rv-1A were studied by applying C-banding, genomic in situ hybridisation (GISH) using rye genomic DNA, and sequential in situ hybridization using repetitive sequences pAs1, pSc119.2 and centromere specific pAet-06 as probes. The double monosomics 1Rv-1A were obtained by crossing of disomic substitution line with chromosome 1A replaced by Secale cereale 1Rv in the bread wheat Saratovskaya 29 (S29) background with S29. The results indicated a high frequency of bipolar chromosome 1Rv orientation, as compared to 1A, at metaphase I (MI) (58.6 and 34.7 % of meiocytes, respectively), and, at anaphase I (AI), chromatid segregation of 1Rv compared to 1A (70.53 and 32.14 % of meiocytes, respectively). In few cases desynapsis of wheat homologues was observed, at AI, the chromosomes randomly distributed between the poles or underwent chromatid segregation. At AI, the two wheat homologues separated onto sister chromatids in 10.89 % of cells.The plants F2 karyotypes were marked with aneuploidy not only of chromosomes 1A and 1Rv, but also of 1D, 2D, 3D, 3B, 3A, 4A, 6D, 6B, 6A, and 7D. Structural changes were observed for the chromosomes of the first homoeologous group (1Rv, 1A, 1D, 1B), as well as for 2B, 5D, 6B, and 7B. The chromosomes 1Rv and 6B often demonstrated aberrations. The types of aberrations were centromeric break, deletions of various sizes, and a changed repeat pSc119.2 localization pattern.

Phosphites (Phis), inorganic salts of phosphorous acid, have shown to be effective in protection of plants against biotic stress. Recently, we have described that potassium phosphite (KPhi) induces tolerance to UV-B radiation in potato. To counteract the harmful effect of UV radiation, plants accumulate UV-screening compounds, such as flavonoids, sinapate ester, and lignin. In previous work, we have shown an increase in guaiacol peroxidase (POD) activity in plants pretreated with KPhi and further exposed to UV-B radiation. In order to continue with this study, the expression of different enzymes and components involved in cell wall reinforcement were analyzed. An isoform of POD induced by KPhi was analyzed by isoelectric focusing and further identified as suberization-associated anionic peroxidase (POPA) by mass spectrometry. In addition, other enzymes participating in lignin biosynthesis, like caffeoyl-CoA O-methyltransferase (CCoAOMT), determined by accumulation of transcripts, and laccase activity, visualized in zymogrames, were increased by KPhi treatment previous to UV-B exposure. Further, the accumulations of extensin (EXT) transcripts and of conjugated polyamines (PAs) were increased by KPhi treatment previous to UV-B exposure. All these results suggest cell wall reinforcement in leaves due to KPhi pretreatment followed by UV-B exposure.

Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECd^t (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECd^t/SGECd^t, SGE/SGECd^t, and SGECd^t/SGE. They were grown in hydroponics in the presence of 1 μM CdCl₂ for 30 d. The SGE and SGECd^t scions on the SGECd^t rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECd^t rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECd^t root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECd^t in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECd^t mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.

Candidate gene association studies implicate the detection of contributing single nucleotide polymorphism (SNP) for the target traits and have been recommended as a promising technique to anatomize the complex characters in plants. ERECTA gene in plants controls different physiological functions. In this study, we identified SNPs in 1.1 kb partial sequences of TaER-1 and TaER-2 of wheat (Triticum aestivum L.). Thirty-nine SNPs were identified in the coding regions of TaER-1 gene in 33 wheat genotypes, of which 20 SNPs caused non-synonymous mutations while 19 SNPs produced synonymous mutations; while 31 SNPs were located in the coding regions of TaER-2 gene in 26 genotypes, of which 18 SNPs caused non-synonymous mutations and 13 SNPs caused synonymous mutations. In addition, 32 SNPs in TaER-1 and 9 SNPs in TaER-2 were also identified in the non-coding regions. Moreover, the significant genetic associations of SNPs of TaER-1 and TaER-2 genes with carbon isotope discrimination, stomatal conductance, photosynthetic rate, transpiration rate, intrinsic water use efficiency (iWUE), leaf length, leaf width, stomatal density, epidermal cell density, and stomatal index were noted in wheat genotypes. This study confirms the importance of TaER-1 and TaER-2 genes which could improve iWUE of wheat by regulating leaf gas exchange and leaf structural traits. These identified SNPs may play a critical role in molecular breeding by means of marker-assisted selection.

Phalaenopsis species are among the most popular potted flowers for their fascinating flowers. When their whole-genome sequencing was completed, they have become useful for studying the molecular mechanism of anthocyanin biosynthesis. Here, we identified 49 candidate anthocyanin synthetic genes in the Phalaenopsis genome. Our results showed that duplication events might contribute to the expansion of some gene families, such as the genes encoding chalcone synthase (PeCHS), flavonoid 3'-hydroxylase (PeF3'H), and myeloblastosis (PeMYB). To elucidate their functions in anthocyanin biosynthesis, we conducted a global expression analysis. We found that anthocyanin synthesis occurred during the very early flower development stage and that the flavanone 3-hydroxylase (F3H), F3'H, and dihydroflavonol 4-reductase (DFR) genes played key roles in this process. Over-expression of Phalaenopsis flavonoid 3',5'-hydroxylase (F3'5'H) in petunia showed that it had no function in anthocyanin production. Furthermore, global analysis of sequences and expression patterns show that the regulatory genes are relatively conserved and might be important in regulating anthocyanin synthesis through different combined expression patterns. To determine the functions of MYB2, 11, and 12, we over-expressed them in petunia and performed yeast two-hybrid analysis with anthocyanin (AN)1 and AN11. The MYB2 protein had strong activity in regulating anthocyanin biosynthesis and induced significant pigment accumulation in transgenic plant petals, whereas MYB11 and MYB12 had lower activities. Our work provided important improvement in the understanding of anthocyanin biosynthesis and established a foundation for floral colour breeding in Phalaenopsis through genetic engineering.

Ent-kaurene oxidase (EKO) catalyze three sequential oxidations in the early steps of gibberellin biosynthesis pathway. In this research, a cDNA sequence of InEKO1 gene in the model short-day plant Ipomoea nil was identified. Our studies revealed that inductive conditions for flowering caused an increase in the transcriptional activity of the examined gene in the cotyledons-the main organs for the perception of the photoperiodic stimulus. In contrast, in the second half of the 16 h long inductive night and after that, a decreased amount of InEKO1 mRNA in the apexes was detected. What is more, ethylene, the key inhibitor of flower induction in I. nil, elevated the InEKO1 expression exclusively in the cotyledons between 10 and 14 h of the inductive night.

Senescence is the last developmental stage in plants during which recycling of nutrients takes place from senescing organs to newly formed organs such as young leaves and developing seeds. In the present work, senescence induced alterations in mineral ions, chlorophylls, carotenoids, betacyanin, betaxanthin, proteins, amino acids, sugars, starch, and polyphenols were monitored in shoots of an extreme halophyte Salicornia brachiata. A sharp decline in the content of chlorophylls, carotenoids, and proteins in the shoot was noticed at middle and late stages of senescence in comparison with early stage. However, the content of betacyanin, betaxanthin, total soluble sugars, reducing sugars, and starch increased significantly in senescing shoots. The total free amino acid content decreased gradually with the progress of senescence. The content of major minerals did not change significantly with the progress of senescence, whereas marked changes in content of minor minerals were observed. From this study, it was concluded that the sugars and starch accumulating in senescing shoots might be transported into developing seeds to serve as storage nutrients. The accumulation of betacyanin and betaxanthin in senescing shoots suggests that these pigments may act as scavengers of reactive oxygen species during senescence. This study provides comprehensive information on the variations in the utilization of mineral nutrients and organic metabolites with progressing senescence in the halophyte S. brachiata.

Casuarina equisetifolia is widely planted in coastal areas of tropical and subtropical regions as windbreaks or to stabilize dunes against wind erosion due to its high salt tolerance and nitrogen-fixing ability. To investigate the mechanisms responsible for its salt tolerance, we examined growth, mineral composition, expression of genes for sodium (Na⁺) and potassium (K⁺) transport proteins, and antioxidant responses under NaCl treatments. Increasing NaCl concentrations inhibited lateral root elongation and decreased plant height, length of internodes, and numbers of branches and twigs. The Na⁺ content significantly increased whereas the K⁺ content significantly decreased in both shoots and roots with increasing external NaCl concentration, resulting in a significant increase in Na⁺/K⁺ ratio. Most of the Na⁺/H⁺ antiporter genes (NHXs) were obviously upregulated in roots after 24 and 168 h of salt stress, and NHX7 was especially induced after 168 h. Almost all salt overly sensitive (SOS) genes were induced after 168-h treatment. Additionally, activities of superoxide dismutase, glutathione peroxidase, and catalase were significantly changed in shoots and roots under salt stress. Hence, we conclude that salinity tolerance of C. equisetifolia mainly relied on sequestering excess Na⁺ into vacuoles and on induced expression of NHX and SOS genes in roots and thus the maintenance of sufficient K⁺ content in shoots.

The present work examines global transcriptional and limited metabolic profiling to dissect the signalling pathways associated with gibberellin A₃ (GA₃) induced alterations in tobacco (Nicotiana tabacum L.) under field conditions. Our microarray analysis revealed that GA3 foliar application elicited 7 032 differentially expressed genes (DEGs) with 3 507 and 3 525 genes displaying up- and down-regulation, respectively. These DEGs broadly belong to diverse metabolic pathways: GA signalling and homeostasis, ethylene and auxin biosyntheses, saccharide metabolism, glycolysistricarboxylic acid cycle, terpenoid biosynthesis, shikimate-phenylpropanoid pathway, S-adenosyl methionine cycle, fatty acid biosynthesis, cell wall metabolism, oxidative stress, DNA repair, and stress responses. Transcription validation of representative DEGs was confirmed by real-time quantitative PCR. A relative enhancement in cellular acetyl-CoA pool corroborated with a concomitant increase and decrease in transcriptions as well as activities of histone acetyltransferases and histone deacetylases, respectively. Phytochemical analysis shows an enhanced content of total sugars, reducing sugars, total flavonoids, and phenolics with a concomitant decrease of the content of starch, chlorophylls a and b, and carotenoids. Gas chromatography with mass spectrometry analysis revealed the presence of 30 differential metabolites, mostly belonging to terpenoid biosynthesis pathway.

The seasonal course of xylem sap parameters (electrical conductivity EC, potassium concentration [K⁺], and pH) of three conifers (Pinus cembra, Picea abies, and Larix decidua) growing at the alpine timberline was monitored. We also looked into possible effects of [K⁺] and pH on the difference in hydraulic conductivity (Δk_s). In all studied species, EC, [K⁺], and pH varied considerably over the year, with pH ranging between 7.3 (February) and 5.8 (June) and [K⁺] changing between 0.4 (January) and 2.5 mM (June). The Δk_s was overall low with positive values during winter (up to +20 %) and negative values in summer (-15 % in August). Samples perfused with alkaline solutions showed higher Δk_s. Xylem sap parameters in all conifers under study were surprisingly variable over the year thus indicating either effects upon seasonal changes in environmental factors or active adjustments, or both. Although Δk_s values over the year were minor, observed induction of Δk_s by high pH might indicate a role for hydraulic adjustment in harsh winter periods.

Mapping of quantitative trait genes (QTGs) associated with drought related traits is essential for improving drought tolerance in crop species. In silico identification of candidate genes relies on annotation of critical QTGs to a variety of web resource-based datasets. The barley reference sequence was employed to map QTGs significantly associated with the proline accumulation and osmotic potential. Annotation of the critical QTGs contigs to the NCBI protein database identified 72 gene orthologs located on chromosomes 1H, 2H, and 7H, from which seven genes were identified as candidates. Expression analysis of all seven candidate genes revealed differential expression pattern between plants grown under well-watered conditions and drought-stress. The results represent a successful and highly powerful implementation of genome-wide scanning approach based on in silico mapping of QTGs to identify gene clusters having a common transcript pattern with similar function.

An efficient in vitro regeneration protocol through somatic embryogenesis was established from stem transverse thin cell layers (tTCLs) of Dendrobium aqueum Lindley, an imperiled orchid. This study outlines the induction and successive maturation stages of D. aqueum somatic embryos (SEs). The tTCLs (~ 0.5 mm thick) cultured on halfstrength Murashige and Skoog (MS) medium containing cytokinins and auxins, either individually or in combination, produced embryogenic callus (EC). Treatment with 0.5 mg dm^-3 zeatin induced EC in 41.42 % of tTCLs. As many as 42.66 globular SEs per tTCL were formed in the presence of 1.5 mg dm^-3N⁶-(2-isopentyl) adenine (2iP) but only on 10.33 % of explants. The combined treatment of 2iP (1.5 mg dm^-3) and 0.5 mg dm^-3 6-benzyladenine resulted in 34 globular SEs on 14.7 % of tTCLs whereas the combination of 2iP and 1.0 mg dm^-3 indole-3-butyric acid (IBA) induced 7.4 globular SEs on 52.33 % of tTCLs. Supplementation of activated charcoal, amino acids, and antioxidants alleviated browning at all the concentrations tested, but the EC response declined. The addition of 0.5 mg dm^-3 polyvinylpyrrolidone to 1.5 mg dm^-3 2iP and 1.0 mg dm^-3 IBA produced 24 SEs on 19.89 % of tTCLs suggesting that the EC and SEs can be effectively induced by individual cytokinins whereas the synergistic treatments with other compounds can only enhance the induction of EC. Histological observations of EC showed the formation of globular SEs from sub-epidermal regions. Successive developmental stages of globular SEs and the intermediate stage of protocorm like bodies until the formation of plantlets were observed. The plantlets obtained through SEs showed no morphological variations, and inter simple sequence repeat profiles also confirmed the genetic fidelity of in vitro-derived progeny with high monomorphism (97.78 %). In conclusion, the use of stem tTCLs is an effective method to produce SEs through indirect somatic embryogenesis in D. aqueum.

Sucrose is a dominant sugar transported to the sink organs of a plant where it is metabolized to other compounds or stored. Here, the importance of sucrose metabolism in a drought-tolerant wheat cultivar was compared to a drought-sensitive one. The 4-d-old Triticum aestivum L. seedlings were exposed to drought induced by water cessation for 7 d and recovery after re-watering for further 7 d. Under control conditions, constitutive expression of genes encoding vacuolar invertase (VI) and sucrose synthase (SuS) and activity of sucrose phosphate synthase (SPS) were significantly higher in the tolerant cultivar than in the sensitive one. Drought promoted the expressions of SPS and VI genes in the tolerant cultivar and increased their activities to 175 and 132 %, respectively, of those under control conditions. The activity of SuS and expression of its gene, however, were identical in both cultivars under drought stress. These changes resulted in more remarkable accumulation of sucrose in tolerant than in sensitive cultivar under water stress.

An efficient plant regeneration protocol has been established for two commercial Populus hybrid clones, MC (Populus × euramericana) and UNAL (Populus × interamericana). The culture of internode segments on Murashige and Skoog (MS) medium with 0.5 μM α-naphthalene acetic acid (NAA) and 4 μM N⁶-benzyladenine for 7 weeks (2 weeks in absence of activated charcoal and 5 weeks in its presence) resulted in the highest frequency of shoot regeneration (100 % for MC and 82 % for UNAL). All regenerated shoots longer than 2 cm rooted on half-strength MS medium, independent of the addition of 0.1 μM NAA. Nevertheless, shoots developed better-formed roots in NAA-free medium, which had a positive effect on the acclimatization of plants. In order to know the cellular processes underlying in vitro shoot organogenesis, a histological study was made in UNAL internode-explants. Results revealed that in vitro culture caused swelling around the cut-off zones in all explants, but only those undergoing organogenesis formed proliferation centers under subepidermal cells, which led to formation of bud primordia. Moreover, in vivo tissues and explants with different in vitro response showed different immunolabelling patterns when they were treated with fluorescentmonoclonal antibodies directed to several pectin-polysaccharides of the cell wall. Results allow us to assign a predominant role of homogalacturonan with a low degree of methyl-esterification in the initiation of bud primordia, role of β-1,4-D-galactan side chains of rhamnogalacturonan-I in the cellular differentiation, role of α-1,5-L-arabinan side chains of rhamnogalacturonan-I and of homogalacturonan with a high degree of methyl-esterification in cell division and growth.

Aluminum (Al) is the main limiting factor for crop production in acidic soils. Efflux of organic acids is one of the mechanisms that determine Al-tolerance, and an Al-activated citrate transporter (multidrug and toxic compound extrusion) MATE1 gene is involved in different species. The contribution of the rye MATE1 gene (ScMATE1) depends on the rye (Secale cereale L.) cultivars and the crosses analyzed; there is no information about different rye species. The cDNA sequences, phylogenetic relationships, Al-tolerance, citrate exudation, and expression of the ScMATE1 gene were analyzed in several cultivars and wild species/subspecies of the Secale genus. Genotypes highly tolerant to Al were found within this genus. For the first time, sequences of the cDNA of the ScMATE1 gene were isolated and characterized in wild ryes. At least two copies of this gene were found likely to be related to Al-tolerance. The sequence comparison of 13 exons of ScMATE1 revealed variability between species, but also inter- and intra-cultivars. Variations were found in the Al-induced expression of ScMATE1 gene, as well as its contribution to Al-tolerance. The pattern of citrate exudation was inducible in most of the species/subspecies studied and constitutive in few. The phylogenetic analysis indicated that ScMATE1 is orthologue of two genes (HvMATE1 and TaMATE1) involved in the Al stress response in barley and wheat, respectively, but not orthologue of SbMATE, implicated in Al-tolerance in sorghum. ScMATE1 is involved in the response to Al stress in ryes, but its contribution to Al-tolerance is complex, and like in other species, there are tolerant and sensitive alleles in the different cultivars and species studied.

Zinc nutrition of tea (Camelia sinensis) have a great impact on acclimation to dehydration stress and on improvement of stress recovery. Dehydration stress induced by withholding water for 7 d decreased relative water content, dry mass of leaf, and content of antioxidants like ascorbate and glutathione and increased H₂O₂ content and lipid peroxidation and changed activities of superoxide dismutase, catalase, peroxidase, and glutathione reductase. A pre-treatment with 0.1 and 0.5 mM ZnSO₄ minimized these effects and increased Zn uptake. Further, foliar spray with 0.1 and 0.5 mM ZnSO₄ before rehydration lowered H₂O₂ generation, increased content of antioxidants and activities of antioxidative enzymes, and decreased lipid peroxidation. The present findings suggest that zinc regulates water stress responses and recovery after rehydration in tea.

Responses of rice to submergence have been extensively studied, but the molecular network behind the tolerance to this stress is still incomplete. Transcription factors (TFs) are important players in gene transcription regulation during stresses. Here, we analyzed expression of WRKY genes and morphological and anatomical changes in different rice cultivars under submergence. When they were submerged for 48 h, changes in root number, fresh and dry masses, and aerenchyma development were observed. Although accumulations of WRKY transcripts were observed in both shoots and roots, root tissues showed higher accumulation with a peak already after 6 h under submergence. Especially transcriptions of OsWRKY11 and OsWRKY56 were high, more than 100-fold in comparison with controls. The WRKY promoter analysis showed that some cis-regulatory elements could be characterized as stress-responsive elements and linked to oxygen depletion. In the promoter of OsWRKY62, two cis-regulatory elements were found: ARE and GC-motif. These elements are known to be involved in oxygen deficiency responses. In addition, the W-box cis-regulatory element, the target of WRKY transcription factors, was found in OsWRKY11, OsWRKY56, and OsWRKY62, suggesting a feedback control acting on the upregulation of WRKY transcription factors. Genes involved in the submergence stress and resulting aerenchyma development had a W-box in their promoter regions, which also suggested regulation by WRKYs. Overall, the results support the role of WRKY transcription factors in rice submergence tolerance and unveil their action in other tolerance mechanisms.

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 presence of solar radiation is one of the most important environmental factors, which is required for the optimal growth and development of plants. The absence of it (e.g. in the night period or artificially prolonged darkness) can alter the light-dependent signalling and regulation pathways and may induce new defence responses. Antioxidant enzymes as components of the plant defence system play a crucial role in the detoxification of reactive oxygen species (ROS) induced by several stressors; however, their regulation can be different in the light or in the dark. In this review we summarize the current knowledge about the physiological and molecular aspects of dark-modulated key antioxidant enzymes (superoxide dismutase, catalase, and ascorbate peroxidase) in different plant species and discuss their roles in different developmental processes (seedling growth and development or senescence) and in responses to environmental stresses (cold, chilling, heat, and biotic stress). Moreover, the hormonal regulation of respective gene transcription and the changes in activity of various isoenzymes at subcellular level are also summarized. Based on this knowledge, modification of these antioxidant enzymes may be used to increase the yield and stress tolerance of cultivated plants in the changing environment.