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Using reliable salt tolerance markers is a key component in barley breeding programs. In this study, physiological and antioxidative markers of two Tunisian barley salinity tolerance contrasting genotypes Boulifa (B) and Manzel Habib (MH) were assessed at 0, 3, 6 and 9 days of 200 mM salt treatment. Salinity caused decrease in growth, degraded photosynthetic activity and reduced water-holding capacity in both genotypes with more pronounced negative effects in the salt-sensitive (MH) compared to the salt-tolerant (B) genotype. On the other hand, the lower oxidative damage in B compared to MH under salt stress could be explained by higher activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR). Additionally, a genotype-specific pattern of enzyme activity and corresponding gene expression was revealed in the two barleys under salt stress. In this context, a positive correlation was noted for the SOD. On the other hand, multivariate analysis marked SOD and APX as the most discriminating factors between both stressed genotypes. Our findings could be considered for selection in breeding programs for salt stress tolerance in barley. [ABSTRACT FROM AUTHOR]

To identify and isolate genes related to abiotic stress (salinity and drought) tolerance in grapevine, a candidate gene approach led to the isolation from Cabernet Sauvignon cultivar of a full-length cDNA of dehydrin gene. he latter, named VvDhn, which is highly and mainly induced in late embryogenesis in seeds, encodes for a protein of 124 amino acids with a predicted molecular mass of 13.3 kDa. Details of the physicochemical parameters and structural properties (molecular mass, secondary structure, conserved domains and motives, and putative posttranslational modification sites) of the encoded protein have also been elucidated. he expression study of VvDhn was carried out within plant organs and tissues as well as under drought and salt stresses. VvDhn was not detected in vegetative tissue, whereas it was only expressed during seed development (during late embryogenesis) at extremely high levels and was induced by salt and drought stresses as well as ABA application. Moreover, salt stress induced VvDhn expression in the tolerant variety (Razegui) but not the sensitive variety (Syrah), which did not display expression variation during stress; VvDhn expression level and salt-stress response depend on regulatory mechanisms that are efficient only in the tolerant variety. On the other hand, under drought stress VvDhn was induced in both tolerant and sensitive varieties, with higher levels in the tolerant variety. In addition, stress signal molecules such as ABA (applied alone or in combination with saccharose) induced VvDhn expression, even at low levels. Minimal knowledge about the role and functionality of this gene is necessary and constitutes a prerequisite for including VvDhn in grapevine abiotic stress tolerance improvement programs. [ABSTRACT FROM AUTHOR]

Proteomic and transcriptomic analyses of pathogenesis-related proteins, PR10, were carried out by subjecting adult plants of the salt-tolerant grapevine cv. Razegui to 100 mM NaCl for 6 and 24 h under controlled greenhouse conditions. Within 6 h of salt exposure, an increase in levels of RzPR10 was observed in the roots. PR10 mRNA levels in leaves were significantly different than those in roots; moreover, significant differences for mRNA levels were found between treated and control plants. Within 24 h of salt treatment, roots exhibited the highest levels of RzPR10 protein, but no differences were observed for mRNA levels in both leaves and roots. Overexpression of Vvpr10 cDNA, under the control of the Gal promoter, in the yeast Saccharomyces cerevisiae revealed that growth of transformed cells on a minimal medium containing 500 mM NaCl is similar to that of cells cultivated on NaCl-free medium. This indicated that Vvpr10 gene was functional in yeast and conferred tolerance to high salt concentrations. [ABSTRACT FROM AUTHOR]

Barley is characterized by a rich genetic diversity, making it an important model for studies of salinity response with great potential for crop improvement. Moreover, salt stress severely affects barley growth and development, leading to substantial yield loss. Leaf and root transcriptomes of a salt-tolerant Tunisian landrace (Boulifa) exposed to 2, 8, and 24 h salt stress were compared with pre-exposure plants to identify candidate genes and pathways underlying barley's response. Expression of 3585 genes was upregulated and 5586 downregulated in leaves, while expression of 13,200 genes was upregulated and 10,575 downregulated in roots. Regulation of gene expression was severely impacted in roots, highlighting the complexity of salt stress response mechanisms in this tissue. Functional analyses in both tissues indicated that response to salt stress is mainly achieved through sensing and signaling pathways, strong transcriptional reprograming, hormone osmolyte and ion homeostasis stabilization, increased reactive oxygen scavenging, and activation of transport and photosynthesis systems. A number of candidate genes involved in hormone and kinase signaling pathways, as well as several transcription factor families and transporters, were identified. This study provides valuable information on early salt-stress-responsive genes in roots and leaves of barley and identifies several important players in salt tolerance. [ABSTRACT FROM AUTHOR]

Abstract: To identify and isolate genes related to abiotic stresses (salinity and drought) tolerance in grapevine, a candidate gene approach was developed and allowed isolating a full-length cDNA of rd22 gene from the Cabernet Sauvignon variety. The latter, named Vvrd22, is a dehydration-responsive gene that is usually induced by the application of exogenous ABA. Details of the physicochemical parameters and structural properties (molecular mass, secondary structure, conserved domains and motives, putative post-translational modification sites…) of the encoded protein have also been elucidated. The expression study of Vvrd22 was carried out at the berry growth stages and at the level of plant organs and tissues as well as under both drought and salt stresses. The results showed that Vvrd22 is constitutively expressed at a low level in all analyzed tissues. Moreover, salt stress induced Vvrd22 expression, particularly for the tolerant variety (Razegui), contrary to the sensitive one (Syrah), which did not display any expression variation during the stress, which means that Vvrd22 is involved in salt stress response and that its expression level depends on regulatory mechanisms that are efficient only for the tolerant variety. On the other hand, under drought stress, Vvrd22 is induced in an identical manner for both tolerant and sensitive varieties. In addition, stress signal molecules such as ABA (lonely applied or in combination with sucrose) induced Vvrd22 expression, even at a low level. A minimal knowledge about the role and the functionality of this gene is necessary and constitutes a prerequisite condition before starting and including Vvrd22 in any program of improvement of grapevine''s abiotic stress tolerance. To cite this article: M. Hanana et al., C. R. Biologies 331 (2008). [Copyright &y& Elsevier]

Abstract: In order to quickly and efficiently evaluate the grapevine''s salt tolerance, salinity tests were conducted on some grapevine varieties and rootstocks under in vitro conditions. Plant materials used in the salinity test were propagated using the axillary buds culture method. Single-node shoots were subjected to seven different NaCl concentrations (0, 20, 50, 100, 150, and 200 mM NaCl) in MS medium for 45 days. The different growth parameters analysed were: survival capacity, length of shoot, bud formation, and rooting capacity. Our results showed that salinity reduced in vitro growth and development of grapevine. Proliferation, growth, rooting and viability of explants decreased due to the increase in NaCl concentration. First symptoms of stress (leaves necrosis) appeared after 10 days of treatment with 80 mM NaCl, which may lead to total desiccation. It was determined that severity of salt treatment injury varied depending on the genotype and NaCl concentration. A positive correlation was found between the vigour of plants in saline medium and their faculty to tolerate salt. The most tolerant grapevine genotypes to salt treatment were Sejnene and Asli, followed by the moderately sensitive Saouadi and Sakasly genotypes, and last Razegui, 1103P, 41B, and SO4, which were particularity sensitive. Thus, grapevine''s salt tolerance seems to be linked to the genetic background. To cite this article: L. Hamrouni et al., C. R. Biologies 331 (2008). [Copyright &y& Elsevier]