Anthocyanins are Key Regulators of Drought Stress Tolerance in Tobacco

Abiotic stresses will be one of the major challenges for worldwide food supply in the near future. Therefore, it is important to understand the physiological mechanisms that mediate plant responses to abiotic stresses. When subjected to UV, salinity or drought stress, plants accumulate specialized metabolites that are often correlated with their ability to cope with the stress. Among them, anthocyanins are the most studied intermediates of the phenylpropanoid pathway. However, their role in plant response to abiotic stresses is still under discussion. To better understand the effects of anthocyanins on plant physiology and morphogenesis, and their implications on drought stress tolerance, we used transgenic tobacco plants (AN1), which over-accumulated anthocyanins in all tissues. AN1 plants showed an altered phenotype in terms of leaf gas exchanges, leaf morphology, anatomy and metabolic profile, which conferred them with a higher drought tolerance compared to the wild-type plants. These results provide important insights for understanding the functional reason for anthocyanin accumulation in plants under stress

Age- and season-dependent pattern of flavonol glycosides in Cabernet Sauvignon grapevine leaves

Flavonols play key roles in many plant defense mechanisms, consequently they are frequently investigated as stress sensitive factors in relation to several oxidative processes. It is well known that grapevine (Vitis vinifera L.) can synthesize various flavonol glycosides in the leaves, however, very little information is available regarding their distribution along the cane at different leaf levels. In this work, taking into consideration of leaf position, the main flavonol glycosides of a red grapevine cultivar (Cabernet Sauvignon) were profiled and quantified by HPLC–DAD analysis. It was found that amount of four flavonol glycosides, namely, quercetin-3-O-galactoside, quercetin-3-O-glucoside, kaempferol-3-O-glucoside and kaempferol-3-O-glucuronide decreased towards the shoot tip. Since leaf age also decreases towards the shoot tip, the obtained results suggest that these compounds continuously formed by leaf aging, resulting in their accumulation in the older leaves. In contrast, quercetin-3-O-glucuronide (predominant form) and quercetin-3-O-rutinoside were not accumulated significantly by aging. We also pointed out that grapevine boosted the flavonol biosynthesis in September, and flavonol profile differed significantly in the two seasons. Our results contribute to the better understanding of the role of flavonols in the antioxidant defense system of grapevine

Expression Analysis of Stress-Related genes involved in the response of Durum wheat to salinity and high light

The study of stress-related genes is critical to understand the molecular mechanisms of stress tolerance in plants. Several studies have demonstrated the important role of asparagine synthetase, glutamate decarboxylase and Δ1 -pyrroline-5-carboxylate synthase genes signalling in response to environmental stresses. In order to investigate the expression changes of these genes in durum wheat under salinity and high light, a semi-quantitative RT-PCR analysis was performed. High light increased the gene expression level of TdAsn1 alone (2.6 fold) and in combination with salinity (2 fold) in comparison with the control at low light. The isoforms TdAsn2 was expressed at low levels compared to TdAsn1 and the transcript was present only in leaves in control conditions or simultaneous stresses . A trend similar to that of TdAsn1 was observed for P5CS expression. On the contrary, GAD expression was decreased by salinity and high light (1.1 and 1.5-fold, respectively) and even more under the two combined stresses (3.7 fold) compared to control. The expression levels were compared to the respective enzymatic activities. Our expression data confirmed the pivotal role of the studied genes in the response to abiotic stresses in durum wheat