Glandular trichomes, a specialized multicellular structure, are considered as biofactories due to their capability to synthesize and secrete a large amount of secondary metabolites. Tobacco leaves have a high density of glandular trichomes that produce huge amounts of secondary metabolites, which can be used as important industrial raw materials. However, molecular mechanism controling glandular trichome development in tobacco still remains largely unknown. In the present study, we found that NbGL3, an HD-Zip IV family gene from Nicotiana benthamiana, was highly expressed in mature leaves, and ethylene or auxin application could increase the expression of NbGL3. Virus induced gene silencing NbGL3 resulted in a decreased glandular trichome density on leaves. Putative downstream genes, such as micro trichome, cyclin B2, and wax inducer 1 like were down regulated in NbGL3 silenced plants. Our results demonstrate that NbGL3 could positively regulate initiation of glandular trichomes in tobacco.

Strelitzia reginae is a popular cut flower that has blue petals and orange sepals. Flower color is an important plant trait; however, little is known about its molecular mechanisms in S. reginae. In this study, cDNA libraries were constructed for blue petals and orange sepals of S. reginae. A total of 75 487 unigenes were obtained from transcriptome sequencing and de novo assembly, of which 41.86 % were annotated by public databases. Ultra-high performance liquid chromatography analysis revealed that anthocyanins were the main pigment in blue petals, and that carotenoids controled pigment formation in the orange sepals. Using a system analysis-based approach, 73 and 29 candidate genes related to anthocyanin and carotenoid biosyntheses were identified, respectively. Among these, chalcone synthase 2, chalcone isomerase 1, flavanone 3-hydroxylase 1, flavonoid 3',5'-hydroxylase 1, dihydroflavonol 4-reductase 1, anthocyanidin synthase 1, and anthocyanidin 3-O-glucosyltransferase 1 were considered to be important in regulating the formation of blue petals, and phytoene synthase 1, phytoene desaturaser 1, ζ-carotene desaturase 1, lycopene β-cyclase 3, and β-carotene hydroxylase 2 might play important roles in orange sepal formation. This study improves our understanding of flower color and provides evidence for future molecular breeding of ornamental plants based on flower color modifications.

In view of the ecological, social, and economic importance of Myracrodruon urundeuva Allemão, the objective of this study was to investigate the strategies of this species under drought during its initial phase of development. Two-month-old plants were cultivated under continuous irrigation or no irrigation for 20 d. After this period, the water-stressed plants were rehydrated for 20 d. Physiological, biochemical, and anatomical variables were evaluated on 20^th and 40^th day. Water deficit (25 and 85 % leaf relative content) caused senescence followed by leaf abscission. Growth in height was negatively affected by water deficit (37 % reduction). A decrease in the thickness of the mesophyll was accompanied by a decrease of the total chlorophyll content. Water deficit affected saccharide metabolism and altered cellular component dynamics. Enzyme activities were higher during the rehydration period than during the water stress. There was no increase in lipid peroxidation in plants subjected to water deficit. A reduction in the stomatal opening during water stress was a strategy of reducing water loss through transpiration.

Cytosine methylation plays an important role in plant development by regulating gene expressions. However, few studies have investigated methylation changes during the tissue differentiation and development of perennial plants. Here, the fluorescence-labeled methylation-sensitive amplified polymorphism method was used with eight primer combinations to detect methylation in leaves and xylem obtained at the stages of inflorescence emergence (IE), ovary start growth, and fruit maturity (FM) in two pecan (Carya illinoinensis) cvs. Pawnee and Stuart. The results show that the total methylation in the xylem was generally higher than in the leaves at each stage. Substantial methylation variations were observed at the amplified sites in pecan tissues at the various stages. The methylation patterns changed between the leaf and xylem, with frequencies from 44.97 to 67.01 % over the three stages in the two cultivars, among which the variation frequency between the tissues at the FM stage was the highest for each cultivar. The frequencies of methylation variation between the leaf samples at any two stages ranged from 31.86 to 45.88 %, with higher variation frequencies between the xylem samples (40.90 - 59.44 %) for each cultivar, which is consistent with the comparative results of polymorphism rates between the leaf and xylem over the three stages. Cluster analysis and principal coordinate analysis suggest that the xylem at the IE and FM stages had relatively distant epigenetic relationships with other tissue samples as a whole. This study reveals the patterns of methylation variation and methylation relationships among pecan tissues undergoing different developmental processes, implying the important roles of methylation in tissue differentiation and development of trees. These results lay a theoretical foundation for elucidating the regulatory mechanisms of methylation involved in tree development.

The responses of antioxidant enzymes (AOE) ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT) in soluble protein extracts from leaves and roots of tobacco (Nicotiana tabacum L. cv. Samsun NN) plants to the drought stress, salinity and enhanced zinc concentration were investigated. The studied tobacco included wild-type (WT) and transgenic plants (AtCKX2) harbouring the cytokinin oxidase/dehydrogenase gene under control of 35S promoter from Arabidopsis thaliana (AtCKX2). The transgenic plants exhibited highly enhanced CKX activity and decreased contents of cytokinins and abscisic acid in both leaves and roots, altered phenotype, retarded growth, and postponed senescence onset. Under control conditions, the AtCKX2 plants exhibited noticeably higher activity of GR in leaves and APX and SOD in roots. CAT activity in leaves always decreased upon stresses in WT while increased in AtCKX2 plants. On the contrary, the SOD activity was enhanced in WT but declined in AtCKX2 leaves. In roots, the APX activity prevailingly increased in WT while mainly decreased in AtCKX2 in response to the stresses. Both WT and AtCKX2 leaves as well as roots exhibited elevated abscisic acid content and increased CKX activity under all stresses while endogenous CKs and IAA contents were not much affected by stress treatments in either WT or transgenic plants.

A new member of the APETALA2/ethylene responsive element binding protein (AP2/EREBP) transcription factor family, HhDREB2, was isolated from Halimodendron halodendron. Based on the similarity of the AP2/ERF domain, HhDREB2 was classified into A-5 group of the DREB subfamily. The expression of HhDREB2 gene was induced by drought, high salinity, and low temperature, but not by exogenous plant hormones. Trans-activity assay demonstrated that HhDREB2 gene encodes a transcription activator. Furthermore, over-expression of HhDREB2 gene under the stress-inducible rd29A promotor in Arabidopsis resulted in enhanced tolerance to salt and drought stresses. The overall results reveal that HhDREB2 functioned as important transcription factor in regulation of stress-responsive signaling in plants and may be used for improving plant tolerance to abiotic stresses.

Germin and germin-like proteins (GLPs) are a broad and diverse family of developmentally regulated proteins widely distributed in plants. Oryza sativa L. harbours a large family of GLPs and serves as a good model for their study. In the present study, a germin-like protein gene (OsRGLP1) of rice origin was characterized by its heterologous expression in tobacco. The real-time PCR established almost a uniform expression of OsRGLP1 in leaves, stem, and roots of T₁ Nicotiana tabacum cv. Samsun. Although no morphological difference was apparent between T₀ transgenic and wild-type plants, leaves of mature transgenic plants showed necrotic lesions associated with an elevated content of H₂O₂, which was evidenced by in situ 3,3'-diaminobenzidine staining. A significantly higher activity of heat resistant superoxide dismutase (SOD) was observed in the transgenic plants as compared to the wild-type. The SOD activity in the transgenic plants was insensitive to potassium cyanide and sensitive to H₂O₂.

MAT (multi-auto-transformation) vector system has been one of the strategies to excise the selection marker gene from transgenic plants. Agrobacterium tumefaciens strain EHA105 harboring an ipt-type MAT vector, pNPI132, was used to produce morphologically normal transgenic Petunia hybrida 'Dainty Lady' employing isopentenyl transferase (ipt) gene as the selection marker gene. β-glucuronidase (GUS) gene was used as model gene of interest. Infected explants were cultured on Murashige and Skoog (MS) medium without plant growth regulators (PGR) and antibiotics. Shoots showing extreme shooty phenotype (ESP) were produced from the adventitious shoots separated from the explants. Visual selection was carried out until production of morphologically normal shoots (approximately 4 months after infection). Histochemical GUS assay detected GUS gene in both ESP and normal shoots. PCR analysis confirmed the presence of model gene (GUS gene) and excision of the selection marker (ipt) gene in the normal transgenic plants. The insertion sites (1-3 for ipt gene and 1-2 for GUS gene) were detected by Southern blot analysis using DIG-labeled probes of both genes. These results show that ipt-type MAT vector can be used successfully to produce marker-free transgenic Petunia hybrida plants on PGR- and antibiotic-free MS medium.

The halophyte Thellungiella salsuginea is a new model plants due to its small genome size, short life cycle, and copious seed production. Although T. salsuginea shares a high sequence identity with its close relative Arabidopsis thaliana, it shows a greater tolerance to salinity, drought, freezing, heat, and cold. To elucidate the mechanism of abiotic stress resistance in T. salsuginea, we characterized its cytosolic Apx1 gene (TsApx1) and established A. thaliana transgenic lines overexpressing TsApx1. Under 300 mM NaCl, the content of H₂O₂, malondialdehyde, and proline were lower and the activities of superoxide dismutase, catalase, glutathione peroxidase, and ascorbate peroxidase were all higher in the transgenic plants overexpressing TsApx1 (35S:TsApx1-GFP) than in the wild-type plants. The atapx1 mutant plants of A. thaliana had a NaCl/mannitol-sensitive phenotype. The ectopic expression of TsApx1 in the atapx1 mutant effectively remedied the phenotype. These results suggest that TsApx1 plays an important role in scavenging reactive oxygen species in the cytoplasm under salinity or drought. Although TsApx1 in T. salsuginea was constantly expressed at a high level, this gene was clearly inducible. In summary, the high constitutive expression and rapid induction of TsApx1 may contribute to the tolerance to abiotic stresses in T. salsuginea.

In plant cells, anion channels and transporters are essential for key functions. Members of the chloride channel (CLC) family located in intracellular organelles are required for anion accumulation, pH adjustment, and salt tolerance. Here, we cloned a maize (Zea mays L.) CLC gene, named ZmCLC-d, and found that its transcription was up-regulated under cold, drought, salt, and heat stresses, and after hydrogen peroxide (H₂O₂) and abscisic acid (ABA) treatments. The overexpression of ZmCLC-d in Arabidopsis conferred tolerance to cold, drought, and salt stresses; this tolerance was primarily displayed by an increased germination rate, root length, plant survival rate, antioxidant enzyme (catalase, peroxidase, and superoxide dismutase) activities, and a reduced accumulation of Cl^- in transgenic plants as compared with wild type (WT) plants. The accumulation of H₂O₂ and superoxide anion in leaves of the ZmCLC-d-overexpressing plants is much less than that of the WT plants. The expressions of some stress related genes, such as CBF1, CBF2, CBF3, DREB2A, and RCI2A, increased to a greater extent in the ZmCLC-d-overexpressing plants than in the WT. Our results strongly suggest that ZmCLC-d played an important role in stress tolerance.

Previously, the ascorbate peroxidase (APX1) activity and gene expression in Chinese cabbage (Brassica campestris, Bc) heat-tolerant cv. ASVEG2 were found to be significantly higher than in heat-sensitive cv. RN720 under a heat stress. Furthermore, BcAPX2 and BcAPX3, isoforms of BcAPX1, were cloned in this study. Our objective was to transfer BcAPX cDNA under the control of the ubiquitin promoter to Arabidopsis via Agrobacterium tumefaciens strain GV3101. We found that BcAPX genes were overexpressed in transgenic Arabidopsis, and the expression of APX, and the APX activity in transgenic lines were higher than in non-transgenic (NT) plants under high temperatures. The chlorophyll content and the germination rate were significantly higher, and the malondialdehyde content was lower in BcAPX1-3, 2-1, and 3-5 lines subjected to the heat-stress treatment than those in the NT plants. Compared to the NT plants, a lower heat-induced H₂O₂ accumulation was detected by diaminobenzidine staining in leaves of the transgenic lines with a high APX activity indicating that the overexpression of BcAPX in Arabidopsis could enhance heat tolerance by eliminating H₂O₂.

Saussurea involucrata Kar. et Kir. tolerates severe abiotic stresses including cold, and the level of membrane fatty acid desaturation is associated with its cold acclimation. We discovered and characterized a full-length cDNA of stearoyl acyl-carrier-protein desaturase (sikSACPD) which encodes a protein consisted of 396 amino acids. A sequence alignment of the SikSACPD protein showed that it shares 91 and 86 % identity with the SACPDs of Carthamus tinctorius and Helianthus annuus, respectively. Semi-quantitative RT-PCR showed that the expression of sikSACPD increased in S. involucrata leaves as the temperature decreased from 20 to -10 °C. Agrobacterium tumefaciens was used to transform fatty acid biosynthesis 2 (FAB2):SikSACPD and FAB2:FAB2 constructs into tobacco to investigate resistance to a freezing stress and fatty acid composition of the transgenic plants. The FAB2:SikSACPD transgenic plants showed a slightly more resistance to the freezing stress than the FAB2:FAB2 transgenic plants and the wild-type. The proportion of oleic acid (C18:1) in the leaves of SikSACPD transgenic tobacco increased from approximately 5 to 20 % compared with the leaves of non-transgenic tobacco when both were exposed to cold stress treatments. This study demonstrates that the SikSACPD transgene, when expressed in tobacco, conferred a higher cold tolerance in comparison with that observed in non-transgenic tobacco. Thus, this gene may be a candidate for enhancing cold tolerance in other crop plants.

Iron deficiency chlorosis occurs frequently in calcareous soils. The transformation of plants with ferric chelate reductase genes (FROs) provides a potential strategy to alleviate plant chlorosis under iron deficiency. A CjFRO2 gene isolated from Citrus junos Sieb. ex Tanaka was introduced into Poncirus trifoliata (L.) Raf via Agrobacterium-mediated transformation. The transgene integration and expression were confirmed by PCR, Southern blot, and real-time PCR analyses. Hydroponic- and soil-grown transgenic plants were tested for their tolerance to iron deficiency. Compared with nontransgenic (NT) P. trifoliata plants, a rhizosphere acidification capacity in the transgenic lines increased, and a ferric chelate reductase activity in roots was up to 3.39- and 2.93-fold higher in a hydroponic solution and soil, respectively. A transgenic line TO-8, which reacted similarly in hydroponics and soil, appeared tolerant to the iron deficiency. Its leaf chlorophyll and ferrous ion content was significantly higher than in NT. These results indicate that tolerance to the iron deficiency in P. trifoliata could be improved through the genetic engineering.

Plants face variable environmental stresses that negatively affect plant growth and productivity. The multiplicity of responses is an important aspect of the complexity of stress signalling. Abscisic acid (ABA) is a broad-spectrum phytohormone involved not only in regulating stomatal opening, growth and development but also in coordinating various stress signal transduction pathways in plants during abiotic stresses. The both ABA-dependent and ABA-independent signal transduction pathways from stress signal perception to gene expression involve different transcription factors such as DREB, MYC/MYB, AREB/ABF, NAM, ATAF1,2, CUC and their corresponding cis-acting elements DRE, MYCRS/MYBRS, ABRE, NACRS. Genetic analysis of ABA mutants has given insight that ABA-dependent and ABA-independent pathways for osmotic stress and cold stress interact and converge. This review focuses on ABA-dependent and ABA-independent transcriptional components and cascades, their specificity and crosstalk in stress gene regulation.

Tospoviruses are devastating plant viruses causing severe economic losses in a diverse range of crops worldwide. Here, we describe the development and evaluation of an RNA interference (RNAi) broad-spectrum virus resistance strategy based on a unique and short hairpin-RNA-generating construct (pNhpRNA). This construct was designed from a region of the nucleocapsid gene (N) of Tomato spotted wilt virus (TSWV) that showed a high sequence identity to the corresponding region in the related species Groundnut ringspot virus (GRSV) and Tomato chlorotic spot virus (TCSV). To test the effectiveness of the pNhpRNA construct, we developed a silencing reporter assay based on three fusion proteins in which the complete viral N gene sequence from each of the three tospoviruses was fused in frame to the green fluorescent protein (GFP) sequence. Co-agroinoculation of these constructs with pNhpRNA into leaves of Nicotiana benthamiana resulted in a strong silencing phenotype determined by GFP decay and suppression of the three N genes at the RNA and protein levels. To test the potential of the pNhpRNA construct to generate virus-resistant plants, we infiltrated the whole shoots of N. benthamiana with pNhpRNA. When these infiltrated plants were mechanically inoculated with the mentioned viruses 100, 70, and 60 % resistance phenotypes to TSWV, GRSV, and TCSV, respectively, were observed. The induction of a broad tospovirus resistance with a simple construct and a minimized off-target effect are the main contributions of pNhpRNA.

The metalloid arsenic (As) is highly phytotoxic, in part due to the similarity of the arsenates to phosphates, but also due to its ability to induce reactive oxygen species (ROS) formation, and in the form of arsenite directly interact with certain enzymes. Here we aimed to determine the effects of a short period of As exposure on Arabidopsis thaliana. Particular focus was given to shoot responses, which have received less attention in previous studies. A. thaliana (ecotype Col-0) plants (28-d-old) were cultivated hydroponically in the presence of 0, 27, 108, and 216 µM arsenic in the form of sodium arsenate for five days. Translocation of As from root to shoot increased with increasing As concentration in the medium and caused a reduction in growth. Photosynthesis was severely affected due to stomatal closure, increased ROS accumulation, and alterations in expression of genes involved in oxidative stress responses and As detoxification. Primary metabolism was also perturbed, suggesting both the direct inhibition of certain enzymes as well as active defensive responses. Overall the effects of As toxicity depended greatly on the degree of translocation from root to shoot and involved both direct effects on biological processes and secondary effects caused by the accumulation of ROS.

Multidrug and toxic compound extrusion (MATE) proteins is a newly characterized transporter family in plants. However, knowledge of this family in systematic classification, molecular evolution, and expression patterns in plants is limited. In this study, MATE gene sequence, structure, and names as well as MATE protein size and subcellular localization in rice were analyzed using bioinformatics tools, chromosome localizations, and gene clusters. The function of MATE proteins was further elucidated on a basis of phylogenetic relationships. Using available transcriptomic data, the expression pattern and function of MATE were different in the selected organs and developments stages of rice. In addition, the relative abundance of OsMATE1 transcripts increased 3 h after copper treatment and so it was identified as a candidate gene for Cu tolerance in rice. This research provided basic data for further studies on MATE genes in rice and theoretical information about the biological function of MATE proteins.

Interaction between aluminum (Al) and boron (B) in Al accumulator species has not been characterized so far. In this work, tea [Camellia sinensis (L.) O. Kuntze] plants were cultivated hydroponically and treated with adequate (control) or low B supply (-B) without or with 300 μM Al (-B+Al) for 14 weeks. Growth of B-deficient plants was completely resumed by Al supplementation or even surpassed control plants regarding shoot biomass. Net photosynthetic rate was negatively influenced by the low B supply, and the Al treatment increased it up to the level of the control plants that was reflected in the higher content of saccharides. The activity of ascorbate peroxidase (APX) in the younger leaves decreased at the low B supply accompanied with an increased H₂O₂ content. The Al treatment increased the APX activity up to the level of the control plants simultaneously with the reduction of H₂O₂. Activities of superoxide dismutase (SOD) and peroxidase (POD) increased in the low B plants and the Al treatment augmented this effect. The content of malondialdehyde (MDA) in the leaves increased by low B but declined upon the Al treatment. In the Al-treated plants, the activity of nitrate reductase (NR) and the content of free α-amino acids exceeded those of the control plants, and nitrite concentration diminished. The shoot and root B content of the B-deficient plants supplemented with Al was similar with the B-sufficient ones. The results demonstrate that the up-regulation of C and N metabolism, the activation of antioxidative defense, and the enhancement of B uptake and transport were mechanisms for growth amelioration of the B-deficient plants by Al supplementation in tea.

Glycine-rich RNA-binding proteins (GR-RBPs) are involved in RNA processing and also some of them are output signals of the circadian clock. In tomato, one GR-RBP gene family (LeGRP1) is composed by three highly homologous genes (LeGRP1a-c); each one rendering three transcriptional products: the un-spliced pre-RNA (preLegrp1a-c), the mature mRNA (mLegrp1a-c) and the alternatively spliced mRNA (asLegrp1a-c). To get insight into their regulation and impact on RNA metabolism in fruits, Solanum lycopersicum cv. Micro-Tom was transformed with preLeGRP1a fused to the polygalacturonase promoter, which drives expression to fruits from the mature green stage. Our results demonstrated a complex positive regulation of LeGRPs, in which LeGRP1a overexpression led to the induction of the others LeGRP1 members. Even though the LeGRP1 transcription and the content of three LeGRPs proteins were affected, the overall LeGRP protein circadian rhythm profile was similar in transgenic and wild type (WT) fruits. However, when the fruits were kept at a chilling temperature after harvest, total protein content was significantly higher in transgenic than in WT fruits, and the content of some free amino acids was modified. The results obtained suggest a probable role of LeGRP1s: structural rearrangements and/or stabilization of mRNA to allow efficient processing of fruits under cold conditions.

The role of mitochondria and peroxisomes in the tolerance of the halophyte Cakile martima to salt stress was studied. The plants were subjected to 0, 100, and 200 mM NaCl for 5 weeks. The evaluation of oxidative stress according to the content of malondialdehyde (MDA), carbonyl (CO-) proteins, O2-, and H2O2, and the activities of several antioxidant enzymes, such as superoxide dismutase, peroxidase, and enzymes of the ascorbate-glutathione cycle were determined in two purified organelles, mitochondria and peroxisomes. The intact organelles were purified by centrifugation in Percoll density gradients. Results show that the content of MDA and CO- proteins was higher in mitochondria than in peroxisomes under the salt stress. The antioxidant enzymes showed higher activities in peroxisomes than in mitochondria under different NaCl concentrations. These activities were highest at 100 mM NaCl. Our results suggest that the ascorbate glutathione cycle in peroxisomes plays a key role in the tolerance of Cakile maritima to salinity.

Nitrogen and sulfur are major elements influencing plant growth and production of secondary metabolites. They interact to each other, but little is known about it in Isatis indigotica Fort. plants. In this study, 15 different treatments representing all possible combinations of 3 N treatments (N1, N2, and N3, corresponding to 5, 15, and 25 mM N, respectively) and five S treatments (S0, S1, S2, S3, and S4, corresponding to 0.00, 1.25, 2.50, 5.00 and 7.50 mM S, respectively) were used, and plant growth, indigo and indirubin yields, and expressions of genes encoding enzymes involved in N and S metabolisms were measured. The results show that the highest dry biomass was observed in N2S2 treatment. Moreover, net photosynthetic rate in the N2S2 treatment was significantly higher than under other treatments (except for N3S2 treatment). A low nitrogen concentration (5 mM) was beneficial to the accumulation of alkaloids, and the N1S1 and N2S2 treatments resulted in the highest yields of indigo and indirubin, respectively. Additionally, the yields of indigo and indirubin were positively correlated with the expression of APS reductase and glutamine synthetase genes, respectively.

Cell walls play an important role in the structure and morphology of plants as well as in responses to various biotic and abiotic stresses. Although the comprehensive analysis of genes involved in cellulose synthase has been performed in model plants, such as Arabidopsis thaliana and rice, information regarding cellulose synthase-like (Csl) genes in maize is limited. In this study, a total of 56 members of Csl gene family were identified in maize genome and classified into six subfamilies. Analysis of gene structure and conserved motif indicated functional similarities among the ZmCsl proteins within the same subfamily. Additionally, the 56 ZmCsl genes were dispersed on 10 chromosomes. The expression patterns of ZmCsl genes in different tissues using the transcriptome data revealed that most of ZmCsl genes had a relatively high expression in root and tassel tissues. Moreover, the expression profiles of ZmCsl genes under drought and re-watering indicated that the expression of ZmCsl genes were mainly responsive to early stage of drought stress. The protein-protein interaction network of ZmCsl proposed some potentially interacting proteins. The data presented a comprehensive survey of Csl gene family in maize. The detailed description of maize Csl genes will be beneficial to understand their structural, functional, and evolutionary features and provide an important foundation for studying the roles of ZmCsl genes in response to biotic and abiotic stresses.

A unique structural feature of plant sterols is the presence of a 24-alkyl group in the sterol side chain, which is synthesized by C24-sterol methyltransferase (SMT). Here we report for the first time that the bread wheat genome (AABBDD) contains at least three homoeologous genes encoding C24-sterol methyltransferase 1. While these copies have similar coding regions, they differ markedly in the nucleotide sequences of their non-coding regions. Sequencing de novo of the promoter regions of the TaSMT1 homoeologs demonstrated the occurrence of common and specific stress-sensitive cis-elements such as LTR, the cis-element involved in low temperature response. These cis-elements, along with other factors, determine the differences in the effects of stress on the expression of homoeologous TaSMT1 genes. For example, TaSMT1-5A is constitutively expressed in the roots and leaves, while TaSMT1-4D gene is highly stress-responsive. Another important enzyme involved in sterol biosynthesis is C22-sterol desaturase, which converts β-sitosterol into stigmasterol. This enzyme is encoded by homoeologous TaCYP710A8 genes, which, in contrast to TaSMT1, are all up-regulated in response to stress. Cold-induced expression of TaCYP710A8 is greater in roots than in leaves. This may be due to the higher cold sensitivity of the roots and the necessity to increase the amount of stigmasterol known as a “stress sterol”. Our findings suggest that the existence of homoeologous genes of sterol biosynthesis in polyploid plants supports the diversity of genetic mechanisms of sterol-mediated response of plants to stresses.

Sri Lankan cassava mosaic virus (SLCMV) is the principal causal agent of cassava mosaic disease in the Indian subcontinent. To gain resistance against the virus, the coat protein (CP) gene, namely the AV1 of SLCMV-Adivaram isolate, was cloned in either sense or antisense orientation under the Cauliflower mosaic virus 35S promoter, and transgenic Nicotiana benthamiana plants were obtained through Agrobacterium-mediated transformation. A total of eight T1 transgenic lines, four harboring the CP-sense construct and four harboring the CP-antisense construct were challenged with agro-infectious clones of SLCMV DNA-A and DNA-B. Based on symptom exhibition at 20 days post inoculation, 3 out of the 4 CP-sense transgenic lines and all 4 CP-antisense transgenic lines showed a high level of resistance against SLCMV. In addition, a delay in symptom initiation was observed in all the transgenic lines inoculated with a high viral load at agro-dilution 1:625 from an absorbance (A₆₀₀) of 1. However, the resistance was more prominent at a lower viral load of 1:1000 agro-dilution. The viral titer was lower in the SLCMV-challenged transgenic lines compared to the non-transgenic N. benthamiana plants as confirmed by quantitative PCR and dot blot analysis. Furthermore, small RNA Northern blot analysis revealed lowered amounts of virus-specific small interfering RNAs in the resistant transgenic lines as compared to the non-transgenic plants upon SLCMV infection, which correlates to lower virus titers due to resistance against the virus.

Salt stress is one of the most critical environmental factors limiting plant growth, and hydrogen sulfide (H2S) can play a role in plant responses to this stress. To investigate the effects of H2S on mitochondrial functions under salt stress, we treated Malus hupehensis Rehd. var. pingyiensis germinating seeds with an 85 mM NaCl solution with or without an H2S donor sodium hydrosulfide (NaHS) and H2S scavenger hypotaurine (HT). Then, hydrogen peroxide (H2O2) content and antioxidant enzyme activities were measured in mitochondria of seedling roots. Our results show that the application of 0.05 mM NaHS rescued an NaCl-induced inhibition of root elongation, decreased H2O2 content, and enhanced superoxide dismutase (SOD), guaiacol peroxidase (POD), and catalase (CAT) activities in the mitochondria compared to NaCl treatment alone. It was also found that 0.05 mM NaHS significantly decreased the mitochondrial permeability transition pore and increased mitochondrial membrane fluidity, mitochondrial membrane potential, and cytochrome c/a ratio under NaCl stress. However, 0.02 mM NaHS did not affect root growth, antioxidant enzyme activities, and mitochondrial function under NaCl stress, whereas high concentrations of NaHS (more than 0.2 mM) had a weaker or negative effects. Moreover, 15 µM HT eliminated the beneficial effects of NaHS under NaCl stress. Our results suggest that H2S protected plants against salt stress by decreasing H2O2 accumulation and by regulating membrane stability and antioxidant system in mitochondria.

Triploid plants of ornamental Phlox drummondii Hook. were raised from cultures of endosperm excised from immature fruits having zygotic embryo at early dicotyledonous stage. Endosperm tissue was firstly cultured with the embryo on the Murashige and Skoog's (MS) medium supplemented with 5 μM 6-benzylaminopurine (BAP) + 10 μM α-napthaleneacetic acid (NAA) for 7 d and recultured after the embryo was removed. A friable callus appeared two weeks after removal of the embryo and it became compact callus mass in another three weeks. Upon transfer of this 5-week-old callus to the MS medium with 10 μM BAP + 2.5 μM indole-3-acetic acid (IAA), maximum percentage of green nodular shoot buds appeared from which regenerated dwarf shoots. Elongation of the dwarf shoots, however, required transfer of the individual dwarf shoots excised from the callus on the fresh medium and best results achieved on medium with low concentration of IAA (0.5 μM) in presence of 10 μM BAP. The shoots were then rooted in vitro and plants subsequently established in pots containing soil. Over 70 % of plants were triploid with a chromosome number of 2n=3x=21. Size of stem, leaves, flowers, pollen, and stomata of these triploid plants were higher and the plants were more vigorous as compared to naturally occurring diploid plants. In particular, flowers showed bright colour with enlarged central eye adding to their ornamental value.

The chlorophyll a fluorescence parameters of four Phaseolus vulgaris L. genotypes were evaluated under drought in two greenhouse experiments. Under severe water stress, the thermotolerant genotype 'Diplomata' maintained significantly higher values of predawn leaf water potential (Ψ_w), maximum F_v/F_m and effective (Φ_PSII) quantum yield of photosystem II , and non-photochemical quenching than 'Ouro Negro', in the first experiment, and 'A 285' and 'A 222', in the second one. Among these parameters, F_v/F_m showed more differences that discriminated between the genotype responses even when measured at night. Next, a difference between F_v/F_m after sundown and F_v/F_m at dawn on the same day (day ∆F_v/F_m), i.e., the intensity of photoinhibition, and a difference between F_v/F_m at dawn and F_v/F_m after sundown on the day before (night ∆F_v/F_m), i.e. the photoinhibition recovery, were evaluated. Day ∆F_v/F_m and night ∆F_v/F_m were significantly higher for 'Diplomata' under severe water stress in both experiments. In addition, 'Ouro Negro' in the first experiment and all the genotypes in the second showed negative values of night ∆F_v/F_m on the last day of drought when their Ψ_w were also minimal indicating no recovery from photoinhibition and the need for rehydration. At maturation, stressed plants of 'Diplomata' showed a significantly higher yield than 'Ouro Negro' in the first experiment and the same as 'A 285' in the second. Therefore, the thermotolerant genotype 'Diplomata' also showed drought tolerance, and the use of day ∆F_v/F_m and night ∆F_v/F_m fluorescence analysis was able to discriminate between the tolerances of these genotypes and to indicate the need for rehydration.

Fructose-1,6-bisphosphate aldolase (FBA), an essential enzyme involved in the glycolytic pathway, gluconeogenesis, and the Calvin cycle, plays significant roles in the regulation of plant growth, development, and stress responses. In this study, a novel gene, AhFBA (GenBank accession number KF470788), containing a 1077-bp open reading frame and encoding a protein of 358 amino acids, was isolated from Arachis hypogaea L. Bioinformatic analysis revealed that AhFBA belonged to class-I aldolases and preferentially localized in the cytoplasm. Real-time quantitative PCR analysis indicated that AhFBA had a higher expression in young fruits than in leaves and stems, and NaCl could trigger the highest expression of AhFBA in roots and leaves after 3-h and 6-h treatments. The salinity tolerance and survival of Escherichia coli transformed with AhFBA were notably enhanced compared with the control. Transgenic tobacco (Nicotiana tabacum L.) overexpressing the AhFBA gene exhibited a lower hydrogen peroxide content, electrolyte leakage, and malondialdehyde content and a higher photosynthetic efficiency, net photosynthetic rate, relative water content, and sucrose and proline content compared with control plants. Taken together, the results demonstrate that AhFBA functioned as a positive factor enhancing the tolerance of E. coli and N. tabacum to salinity stress, possibly by maintaining the osmotic balance and scavenging hydrogen peroxide.

Aims of the present two-year study were to evaluate the feasibility and identify potential drawbacks of the greenhouse/outdoors parallel plant growth methods for investigation of the effects of various winter chilling regimes on flowering quality indicators of four Greek olive cultivars, namely Mastoidis, Amfissis, and Lefkolia Serron (originating from mountainous and colder areas) compared to cv. Koroneiki (grown mainly in plain warm areas). Groups of potted olive plants were either grown outdoors under ambient temperature or transferred into a greenhouse for one, two, or three months during winter in Crete, Greece. During the first year, chilling accumulation deficit caused a marked decrease in the number of inflorescences per plant in all four olive cultivars. In the second year, chilling accumulation deficit had a negative effect on the number of inflorescences per plant in 'Mastoidis' at 3-month greenhouse treatment but not at all in 'Koroneiki'. Chilling deficit caused an overall decrease in the number of flowers per inflorescence in both 'Koroneiki' and 'Mastoidis' as well as in the percentage of morphologically perfect flowers. The width and length of inflorescences were not affected by chilling deficit in both the cultivars. In vitro pollen germination was reduced in all greenhouse treatments in 'Koroneiki'; however, this effect was significant only after 3 month, whereas no effect was observed in 'Mastoidis'. The results of the present study may contribute to understanding olive flowering biology and selecting appropriate cultivars for new plantations according to historical meteorological data and predicted climate change scenarios.

Various physiological and biochemical parameters associated with improved salinity tolerance in the transgenic rice lines overexpressing OsCaM1-1 gene and wild-type KDML105 were compared 3 d after exposure to 150 mM NaCl. The results showed higher relative water content, relative growth rate, content of photosynthetic pigments (chlorophylls a, b, and carotenoids), DPPH scavenging activity, and activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase in the transgenic plants when compared with the wild-type and control, KDML105 transformed with blank vector, whereas H₂O₂ content, Na/K and Na/Ca ratio, lipid peroxidation, and electrolytic leakage were lower. Taken together, the OsCaM1-1 gene overexpression probably reduced salt-induced oxidative damage in the transgenic plants by enhancing the activities of antioxidant enzymes.