Salt Stress Response In Plants Research Articles

TaUBA, a UBA domain-containing protein in wheat (Triticum aestivum L.), is a negative regulator of salt and drought stress response in transgenic Arabidopsis

TaUBA functions as a negative regulator of salt and drought stress response in transgenic Arabidopsis, either the UBA domain or the zinc finger domain is crucial for TaUBA's function. TaUBA (DQ211935), which is a UBA domain-containing protein in wheat, was cloned and functionally characterized. Southern blot suggested that TaUBA is a low copy gene in common wheat. qRT-PCR assay showed that the expression of TaUBA was strongly induced by salt and drought stress. When suffering from drought and salt stresses, lower proline content and much higher MDA content in the TaUBA overexpressors were observed than those of the wild-type control, suggesting TaUBA may function as a negative regulator of salt and drought stress response in plants. To study whether the UBA domain or the zinc finger domain affects the function of TaUBA, TaUBAΔUBA (deletion of UBA domain) and TaUBA-M (Cys464Gly and Cys467Gly) overexpression vectors were constructed and transformed into Arabidopsis. Upon drought and salt stresses, the TaUBAΔUBA-and TaUBA-M-overexpressed plants accumulated much more proline and lower MDA than the wild-type control, the TaUBA-overexpressors lost water more quickly than TaUBAΔUBA-and TaUBA-M-overexpressed plants as well as the wild-type control, suggesting that overexpression of TaUBAΔUBA or TaUBA-M improved the drought and salt tolerance of transgenic Arabidopsis plants and the possibility of ubiquitination role in the regulation of osmolyte synthesis and oxidative stress responses in mediating stress tolerance. qRT-PCR assay of stress-related genes in transgenic plants upon drought and salt stresses suggested that TaUBA may function through down-regulating some stress related-transcription factors and by regulating P5CSs to cope with osmotic stress.

Identification of a novel mitogen-activated protein kinase kinase gene (MKK2) in the oilseed rape Brassica campestris

Mitogen-activated protein kinase (MAPK) cascades participate in various processes, including plant growth and development as well as biotic and abiotic stress responses. MAPK kinases (MKKs), which link MPKs and MPKK kinases, are involved in MAPK cascades by mediating various plant stress responses. However, only a few MKKs from Brassica campestris (rape) have been functionally characterized. This study delivers the results from isolation and characterization of a novel gene, MKK2, from rape. Bioinformatics analysis revealed that the cDNA length of MKK2 is 1,344 bp with an open reading frame of 1,068 bp, which encodes a polypeptide containing 355 amino acids. The obtained MKK2 exhibited a predicted molecular mass of 39.3 kDa and an isoelectric point of 6.8. Quantitative real-time polymerase chain reaction analysis revealed that MKK2 expression can be induced by cold and salt. Western blot analysis revealed that MKK2 protein expression can be induced by cold, salt, and UV-B radiation. The MKK2 protein was localized in the nucleus. These results suggest that MKK2 is important for the regulation of cold- and salt-stress responses in plants.

A wheat aminocyclopropane-1-carboxylate oxidase gene, TaACO1, negatively regulates salinity stress in Arabidopsis thaliana.

TaACO1 could catalyze ACC into ethylene in vitro. Constitutive expression of TaACO1 in Arabidopsis conferred salt sensitivity, and TaACO1 regulates salt stress mainly via the DREB1/CBF signal transduction pathway. Ethylene signaling plays essential roles in mediating plant responses to biotic and abiotic stresses, besides regulating plant growth and development. The roles of ethylene biosynthesis in abiotic stress, however, remain elusive. In this study, an aminocyclopropane-1-carboxylate oxidase gene, TaACO1, affecting the terminal step in ethylene biosynthesis, was isolated from a salt-tolerant bread wheat introgression line Shanrong No. 3 (SR3) and its effect on salt-stress response was examined. Purified recombinant protein of TaACO1 heterogenously expressed in Escherchia coli could catalyze ACC into ethylene in vitro. TaACO1 transcripts were down-regulated by salt, drought, oxidative stress and ABA. TaACO1-transgenic plants conferred salt sensitivity as judged from the seed germination, cotyledon greening and the relative root growth under salt stress. Constitutive expression of TaACO1 in Arabidopsis increased AtMYB15 expression and suppressed the expression of stress-responsive genes AtRAB18, AtCBF1 and AtCBF3. These findings are helpful in understanding the roles of ethylene biosynthesis in plant salt-stress response.

Maintenance of Chloroplast Structure and Function by Overexpression of the RiceMONOGALACTOSYLDIACYLGLYCEROL SYNTHASEGene Leads to Enhanced Salt Tolerance in Tobacco

In plants, the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactodiacylglycerol (DGDG) are major constituents of photosynthetic membranes in chloroplasts. One of the key enzymes for the biosynthesis of these galactolipids is MGDG synthase (MGD). To investigate the role of MGD in the plant's response to salt stress, we cloned an MGD gene from rice (Oryza sativa) and generated tobacco (Nicotiana tabacum) plants overexpressing OsMGD. The MGD activity in OsMGD transgenic plants was confirmed to be higher than that in the wild-type tobacco cultivar SR1. Immunoblot analysis indicated that OsMGD was enriched in the outer envelope membrane of the tobacco chloroplast. Under salt stress, the transgenic plants exhibited rapid shoot growth and high photosynthetic rate as compared with the wild type. Transmission electron microscopy observation showed that the chloroplasts from salt-stressed transgenic plants had well-developed thylakoid membranes and properly stacked grana lamellae, whereas the chloroplasts from salt-stressed wild-type plants were fairly disorganized and had large membrane-free areas. Under salt stress, the transgenic plants also maintained higher chlorophyll levels. Lipid composition analysis showed that leaves of transgenic plants consistently contained significantly higher MGDG (including 18:3-16:3 and 18:3-18:3 species) and DGDG (including 18:3-16:3, 18:3-16:0, and 18:3-18:3 species) contents and higher DGDG-MGDG ratios than the wild type did under both control and salt stress conditions. These results show that overexpression of OsMGD improves salt tolerance in tobacco and that the galactolipids MGDG and DGDG play an important role in the regulation of chloroplast structure and function in the plant salt stress response.

Comparative physiological analysis of lotus (Nelumbo nucifera) cultivars in response to salt stress and cloning of NnCIPK genes

Saline or salt water in the ocean accounts for 96.5% of total fresh water resource in the planet. Salinity is a global social and economic problem which severely inhibited plant growth and development. Utilization of marginal salt affected land and/or water resource becomes increasingly important because of the explosion of world population and climate change. In this study, salt stress resistance of fifteen N. nucifera cultivars was firstly evaluated. The results showed that Welcoming Guests was the most resistant cultivar, while Hunan Lotus was the most sensitive one. Resistant cultivar Welcoming Guests accumulated significant higher amount MDA and proline than Hunan Lotus prior to salt stress treatment, indicating Welcoming Guests was pre-conditioned to salt stress. Salt sensitive lotus cultivar exhibited relative lower antioxidant enzyme activities and higher reactive oxygen species accumulation than resistant one after salt treatment. Since calcineurin B-like protein interaction protein kinase (CIPK)/SALT OVERLY SENSITIVE2 gene family played essential roles during plant salt stress response, three NnCIPK genes were successfully cloned in this study. Phylogenetic analysis showed that these genes were high homologous to Arabidopsis and grape CIPK genes. Expression level analysis indicated that NnCIPK6 was highly induced by NaCl treatment in resistant cultivar, while expression levels of NnCIPK14s showed fluctuation in susceptible cultivar after salt treatment. These results partially characterized mechanisms of lotus salt stress resistance and provided useful information for utilization of lotus cultivars in salt water.

Cloning and Characterization of a Novel Vacuolar Na+/H+ Antiporter Gene (Dgnhx1) from Chrysanthemum

Plant vacuolar Na+/H+ antiporter genes play significant roles in salt tolerance. However, the roles of the chrysanthemum vacuolar Na+/H+ antiporter genes in salt stress response remain obscure. In this study, we isolated and characterized a novel vacuolar Na+/H+ antiporter gene DgNHX1 from chrysanthemum. The DgNHX1 sequence contained 1920 bp with a complete open reading frame of 1533 bp encoding a putative protein of 510 amino acids with a predicted protein molecular weight of 56.3 kDa. DgNHX1 was predicted containing nine transmembrane domains. Its expression in the chrysanthemum was up-regulated by salt stress, but not by abscisic acid (ABA). To assess roles of DgNHX1 in plant salt stress responses, we performed gain-of-function experiment. The DgNHX1-overexpression tobacco plants showed significant salt tolerance than the wild type (WT). The transgenic lines exhibited more accumulation of Na+ and K+ under salt stress. These findings suggest that DgNHX1 plays a positive regulatory role in salt stress response.

Molecular cloning and characterization of the mitogen-activated protein kinase kinase gene (MKK4) and its promoter sequence from oilseed rape (Brassica campestris L.)

Mitogen-activated protein kinase (MAPK) cascades are involved in various processes, including plant growth and development as well as biotic and abiotic stress responses. MAPK kinases (MKKs), which link MPKs and MAPKK kinases (MKKKs), are crucial in MAPK cascades because these kinases mediate various stress responses in plants. However, only few MKKs in Brassica campestris (rape) have been functionally characterized. In this study, a novel gene, MKK4 that belongs to a C MKK group, was isolated and characterized from rape. Bioinformatics analysis revealed that the length of cDNA was 1,317 bp with an open reading frame of 993 bp, which encodes a polypeptide containing 330 amino acids, including a putative signal peptide with 27 amino acid residues and a mature protein with 303 amino acids. The obtained MKK4 exhibited a predicted molecular mass of 36.5 kDa and an isoelectric point of 9.01. Quantitative real-time polymerase chain reaction analysis revealed that MKK4 expression could be induced by cold and salt. We also found that the MKK4 protein is localized in the nucleus. In addition, a 999 bp promoter fragment of MKK4 was cloned. Sequence analysis revealed that several putative regulatory elements were found in the MKK4 promoter. Transient expression assay showed that the MKK4 promoter fragments exhibited promoter activity and stimulated GFP expression. The effects of GFP gene expression at different temperatures and in different onion epidermis culture patterns were compared. Results showed that the MKK4 promoter could respond to low temperature and salt stress. These results suggested that MKK4 is possibly important for the regulation of cold- and salt-stress responses in plants.

A Rice OsAP23, Functioning as an AP2/ERF Transcription Factor, Reduces Salt Tolerance in Transgenic Arabidopsis

The AP2/ERF transcription factors of higher plants regulate transcriptional networks that control development and responses to biotic and abiotic stresses. In this study, the rice OsAP23 gene, which encodes an AP2/ERF transcription factor, was isolated from rice using a yeast-one-hybrid system. The OsAP23 transcription factor belongs to the B3 group of the ERF subfamily. Germination results for transgenic Arabidopsis plants hosting the OsAP23 gene revealed greater inhibition at the germination and seedling stages with increasing concentration of NaCl compared to the wild-type plants. Exogenous ABA also reduced the rate of germination of transgenic Arabidopsis seeds that over-express OsAP23 compared with wild-type Arabidopsis seeds. In addition, following exposure to high salt concentrations, several stress-responsive regulatory genes were induced to a significantly greater extent in the wild-type lines compared with lines that over-express OsAP23. These results suggested that OsAP23 might be a negative regulator of the salt stress response in higher plants.

Protein Contribution to Plant Salinity Response and Tolerance Acquisition

The review is focused on plant proteome response to salinity with respect to physiological aspects of plant salt stress response. The attention is paid to both osmotic and ionic effects of salinity stress on plants with respect to several protein functional groups. Therefore, the role of individual proteins involved in signalling, changes in gene expression, protein biosynthesis and degradation and the resulting changes in protein relative abundance in proteins involved in energy metabolism, redox metabolism, stressand defence-related proteins, osmolyte metabolism, phytohormone, lipid and secondary metabolism, mechanical stress-related proteins as well as protein posttranslational modifications are discussed. Differences between salt-sensitive (glycophytes) and salt-tolerant (halophytes) plants are analysed with respect to differential salinity tolerance. In conclusion, contribution of proteomic studies to understanding plant salinity tolerance is summarised and discussed.

Global identification of miRNAs and targets in Populus euphratica under salt stress

Populus euphratica, a typical hydro-halophyte, is ideal for studying salt stress responses in woody plants. MicroRNAs (miRNAs) are endogenous non-coding small RNAs that fulfilled an important post-transcriptional regulatory function. MiRNA may regulate tolerance to salt stress but this has not been widely studied in P. euphratica. In this investigation, the small RNAome, degradome and transcriptome were studied in salt stress treated P. euphratica by deep sequencing. Two hundred and eleven conserved miRNAs between Populus trichocarpa and P. euphratica have been found. In addition, 162 new miRNAs, belonging to 93 families, were identified in P. euphratica. Degradome sequencing experimentally verified 112 targets that belonged to 51 identified miRNAs, few of which were known previously in P. euphratica. Transcriptome profiling showed that expression of 15 miRNA-target pairs displayed reverse changing pattern under salt stress. Together, these results indicate that, in P. euphratica under salt stress, a large number of new miRNAs could be discovered, and both known and new miRNA were functionally cleaving to their target mRNA. Expression of miRNA and target were correspondingly induced by salt stress but that it was a complex process in P. euphratica.

Physiological and molecular aspects of salt stress in plants

The study of salt stress mechanisms in plants has become an important issue for the modern agricultural development, climate change, and global food crisis. The plant response to high salt concentrations is complex and comprehensive; it includes many different processes, which should be correctly coordinated. The effect of excessive salt concentrations on plants results in osmotic stress and creates an ionic inbalance due to the accumulation of toxic ions, such as Cl− and, especially, Na+. Salt stress also has negative impact on mineral homeostasis, in particular Ca2+ and K+. The progress in transcryptomics, genomics, and molecular biology revealed a new gene families that participate in the formation of salt stress response in plants. This review describes the fundamental principles and mechanisms of plant salt tolerance, maintenance of ion homeostasis. In this paper the detailed analysis of the maine transport membrane systems responsible for the transport of ions and their role in plant salt stress were conducted. The perspectives and directions for the further biotechnological and genetic improvement of salt tolerance in plants are underlied.

Proteomic analysis of salt‐responsive ubiquitin‐related proteins in rice roots

Ubiquitination of proteins plays an important role in regulating a myriad of physiological functions in plants such as xylogenesis, senescence, cell cycle control, and stress response. However, only a limited number of proteins in plants have been identified as being ubiquitinated in response to salt stress. The relationships between ubiquitination and salt-stress responses in plants are not clear. Rice (Oryza sativa) seedlings from the same genetic background with various salt tolerances exposed to salt stress were studied. The proteins of roots were extracted then analyzed using western blotting against ubiquitin. Differentially expressed ubiquitinated proteins were identified by nanospray liquid chromatography/tandem mass spectrometry (nano-LC/MS/MS) and quantified by label-free methods based on the Exponentially Modified Protein Abundance Index (emPAI) and on the peak areas of XIC spectra derived from ubiquitinated peptides. In addition, we performed a gel-based shotgun proteomic analysis to detect the ubiquitinated proteome that may be involved in response to salt stress. The expressions of ubiquitination on pyruvate phosphate dikinase 1, heat shock protein 81-1, probable aldehyde oxidase 3, plasma membrane ATPase, cellulose synthase A catalytic subunit 4 [UDP-forming] and cyclin-C1-1 were identified and compared before and after salt treatment. The functions of those ubiquitinated proteins were further discussed for defence against salt stress. In addition, a large number of ubiquitinated proteins were successfully identified as well in this study. The ubiquitination of proteins affected the protective mechanisms in rice seedlings to resist the salt stress during the initial phase. The findings in the present study also demonstrate that the regulated mechanisms through protein ubiquitination are important for rice seedlings against salt stress.

Cotton GhMKK5 affects disease resistance, induces HR-like cell death, and reduces the tolerance to salt and drought stress in transgenic Nicotiana benthamiana

Mitogen-activated protein kinase (MAPK) cascades are involved in various processes from plant growth and development to biotic and abiotic stress responses. MAPK kinases (MAPKKs), which link MAPKs and MAPKK kinases (MAPKKKs), play crucial roles in MAPK cascades to mediate a variety of stress responses in plants. However, few MAPKKs have been functionally characterized in cotton (Gossypium hirsutum). In this study, a novel gene, GhMKK5, from cotton belonging to the group C MAPKKs was isolated and characterized. The expression of GhMKK5 can be induced by pathogen infection, abiotic stresses, and multiple defence-related signal molecules. The overexpression of GhMKK5 in Nicotiana benthamiana enhanced the plants’ resistance to the bacterial pathogen Ralstonia solanacearum by elevating the expression of pathogen resistance (PR) genes, including PR1a, PR2, PR4, PR5, and NPR1, but increased the plants’ sensitivity to the oomycete pathogen Phytophthora parasitica var. nicotianae Tucker. Importantly, GhMKK5-overexpressing plants displayed markedly elevated expression of reactive oxygen species-related and cell death marker genes, such as NtRbohA and NtCDM, and resulted in hypersensitive response (HR)-like cell death characterized by the accumulation of H2O2. Furthermore, it was demonstrated that GhMKK5 overexpression in plants reduced their tolerance to salt and drought stresses, as determined by statistical analysis of seed germination, root length, leaf water loss, and survival rate. Drought obviously accelerated the cell death phenomenon in GhMKK5-overexpressing plants. These results suggest that GhMKK5 may play an important role in pathogen infection and the regulation of the salt and drought stress responses in plants.

The vacuolar Na+-H+ antiport gene TaNHX2 confers salt tolerance on transgenic alfalfa (Medicago sativa).

TaNHX2, a vacuolar Na+-H+ antiport gene from wheat (Triticum aestivum L.), was transformed into alfalfa (Medicago sativa L.) via Agrobacterium-mediated transformation to evaluate the role of vacuolar energy providers in plant salt stress responses. PCR and Southern blotting analysis showed that the target gene was integrated into the Medicago genome. Reverse transcription-PCR indicated that gene TaNHX2 was expressed at the transcriptional level. The relative electrical conductivity in the T2 transgenic plants was lower and the osmotic potential was higher compared to the wild-type plants under salt stress conditions. The tonoplast H+-ATPase, H+-pyrophosphatase (PPase) hydrolysis activities and ATP-dependent proton pump activities in transgenic plants were all higher than those of wild-type plants, and the enzyme activities could be induced by salt stress. The PPi-dependent proton pump activities decreased when NaCl concentrations increased from 100mM to 200mM, especially in transgenic plants. The vacuolar Na+-H+ antiport activities of transgenic plants were 2-3 times higher than those of the wild -type plants under 0mM and 100mM NaCl stress. Na+-H+ antiport activity was not detectable for wild-type plants under 200mM NaCl, but for transgenic plants, it was further increased with an increment in salt stress intensity. These results demonstrated that expression of the foreign TaNHX2 gene enhanced salt tolerance in transgenic alfalfa.

The heterologous expression in Arabidopsis of a chrysanthemum Cys2/His2 zinc finger protein gene confers salinity and drought tolerance

Zinc finger proteins (ZFPs) play an important role in plant growth and development. Here, we describe the isolation of CgZFP1, a Cys2/His2 (C(2)H(2)) ZFP gene, using RACE PCR from chrysanthemum, and the investigation of its function with ectopic expression in Arabidopsis. CgZFP1 contains two conserved C(2)H(2) regions, a nuclear localization domain (B box), a Leu-rich domain (L box) and a conserved DLN sequence (DLN box) close to its C-terminus. Its expression in the chrysanthemum leaf was strongly induced by salinity or drought, but not by ABA. Subcellular localization assay indicated that CgZFP1 protein is localized in nucleus in vivo. Yeast-one hybrid assay showed that CgZFP1 possesses transcriptional activation ability, heterologous expression of CgZFP1 conferred tolerance of transgenic Arabidopsis plants to both salinity and drought stresses. Under salinity stress, genes involved in osmotic adjustment, ROS scavenging, and ion homeostasis: Atlea3, AtP5CS2, AtProT1, and AtMnSOD, AtPOD, AtAPX1, and AtSOS1, AtSOS2, AtSOS3, AtNHX1 were enhanced in CgZFP1 transgenic Arabidopsis plants. Moreover, genes involved in the osmotic adjustment and oxidative stress responses: Atlea3, AtP5CS2, AtProT1, the aquaporin AtPIP2A, and AtMnSOD, AtPOD, AtAPX1 were induced in CgZFP1 transgenic Arabidopsis under drought stress. These results indicate CgZFP1 is an important regulator involved in the salt and drought stress response in plants.

Waste disposal in the endoplasmic reticulum, ROS production and plant salt stress response

Even under normal conditions, both newly synthesized polypeptides and polypeptides that have already achieved a native conformation can misfold and thus be exposed to the risk of aggregation. Misfolded proteins can be toxic to cells, since they may be prone to spurious interactions or be endowed with undesirable biological activities. The list of possible causes that may lead to the production of a misfolded protein is rather long but includes genetic mutations, error in transcription and translation, and cellular alterations, such as heat shock or oxidative stress. Cells are therefore equipped with efficient systems devoted to the identification, the refolding and, if this fails, the destruction of such aberrant polypeptides. A large fraction of the proteins synthesized in eukaryotic cells is initially targeted to the endoplasmic reticulum (ER). From the ER these proteins then traffic along the secretory pathway to be secreted or delivered to vacuoles or lysosomes, or to the different membranes of the endomembrane system. The ER is therefore equipped with a refined system, called ER protein quality control (ERQC), dedicated to the selective retention and elimination of misfolded polypeptides. Under stress conditions that cause increased accumulation of misfolded proteins, this system may be unable to guarantee ER homeostasis, and the avoidance of the accumulation of such aberrant polypeptides. When this happens, the so called unfolded protein response (UPR) is activated, and this leads to increased synthesis of many components of the ER folding and degradation machineries 1.

Effects of salinity stress on growth, chlorophyll content and osmotic components of two basil (Ocimum basilicum L.) genotypes

Salinity stress is a severe environmental factor limiting crop yield worldwide. To better understand salt stress responses in crop plants, we compared effects of salinity stress on growth, chlorophyll content and osmotic components in two basil genotypes. Seedling of two basil genotypes (B1 = Ociumum basilicm L and B2=Ociumum minimum L.) were grown in controlled environment in Hoagland nutrient solution containing 0, 3 and 6 ds/m NaCl, respectively. Proline, soluble carbohydrates, chlorophyll ‘a, b’ and carotenes of leaves were determined 20 days after initiation of salinity stress. The results reveal that salinity caused significant decreases in growth of basil plants as measured by fresh weight. By increasing NaCl levels from 0 to 6 ds/m, the content of chlorophyll a and b, and carotenes reduced. Maximum reduction was observed at 6 ds/m of NaCl. Mean values of data showed that B2 = O. minimum had the maximum reduction of chlorophyll a and b, and carotenes under salinity stress. This indicates that the B2 genotype was more susceptible to salinity stress than B1 genotype. In this study, salinity had no significant effect on soluble carbohydrate but the proline content varied among the basil genotypes whether the plants were grown with or without salinity stress. With 6 ds/m NaCl applied, proline content was enhanced in two genotypes. B2 = O. minimum had the maximum proline content in leaves when plants were exposed to high salinity level. Key words: Salinity, basil, chlorophyll content, osmotic components.

A potato NOA gene increased salinity tolerance in Arabidopsis thaliana

The purpose of this study is to produce recombinant StNOA1 in transgenic plants and to test its potential role in plant salt stress responses. The newly cloned StNOA1 gene from Solanum tuberosum L. was inserted into AtnOA1 mutant plant genome by Agrobaterium-mediated floral dip method. Transgene integration was verified by polymerase chain reaction (PCR) in 4 different lines of transgenic Atnoa1. Expression of StNOA1 gene was further analyzed by reverse trancription (RT)-PCR. Physiological analyses indicated that the transgenic line TL9 had higher proline, soluble protein and chlorophyll contents as well as lower content of malondialdehyde (MDA) compared to its receptor, Atnoa1 mutant, under salt stress condition. Root elongation and survival rate in TL9 were significantly higher than those in Atnoa1 seedlings under salt stress. Present study proved that StNOA1 participated in Arabidopsis thaliana salt stress responses and increased its salinity tolerance.

Isolation and expression analysis of salt induced genes from contrasting grapevine ( Vitis vinifera L.) cultivars

Salt stress adversely affects the growth of grapevine plants. In order to understand the molecular basis of salt stress response in grapevine plants, suppression subtractive hybridization (SSH) and microarray based screening approaches were combined. Two leaf-specific subtractive cDNA libraries were constructed from grapevine plants subjected to a moderate, incremental salt stress treatment. SSH were performed 6 h and 24 h after NaCl peaked at 100 mM using cDNAs prepared from leaves of a salt tolerant cultivar (Razegui) as testers and cDNAs from unstressed leaves as drivers. Then, a pre-screened subset of cDNA clones from these SSH libraries were used to construct a Vitis vinifera cDNA array, in order to verify the expression changes of the genes upon salt treatment. Expression profiles were compared between the salt tolerant and a susceptible cultivar (Syrah) under both control conditions and after salt stress treatment. Seven cDNA clones were identified which were up-regulated by salt stress in two independent growth experiments and confirmed by RNA blot analysis. The transcript expression patterns of the selected genes differed between the contrasting grapevine cultivars tested with respect to stress-regulation. The possible relationship of individual cDNAs with salinity tolerance mechanisms is discussed.

A novel WD40 protein, BnSWD1, is involved in salt stress in Brassica napus

Genes that are expressed early in specific response to high salinity conditions were isolated from rapeseed plant (Brassica napus L.) using an mRNA differential display method. Five PCR fragments (DD1–5) were isolated that were induced by, but showed different response kinetics to, 200 mM NaCl. Nucleotide sequence analysis and homology search revealed that the deduced amino sequences of three of the five cDNA fragments showed considerable similarity to those of β-mannosidase (DD1), tomato Pti-6 proteins (DD5), and the tobacco harpin-induced protein hin1 (DD4), respectively. In contrast, the remaining clones, DD3 and DD2, did not correspond to any substantial existing annotation. Using the DD3 fragment as a probe, we isolated a full-length cDNA clone from the cDNA library, which we termed BnSWD1 (Brassica napus salt responsive WD40 1). The predicted amino-acid sequence of BnSWD1 contains eight WD40 repeats and is conserved in all eukaryotes. Notably, the BnSWD1 gene is expressed at high levels under salt-stress conditions. Furthermore, we found that BnSWD1 was upregulated after treatment with abscisic acid, salicylic acid, and methyl jasmonate. Our study suggests that BnSWD1, which is a novel WD40 repeat-containing protein, has a function in salt-stress responses in plants, possibly via abscisic acid-dependent and/or -independent signaling pathways.