Activation of abscisic acid biosynthesis in the leaves of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> in response to water deficit

It is well known that endogenous abscisic acid (ABA) levels increase rapidly in response to drought stress and that this induces stomatal closure. In Arabidopsis thaliana, ABA levels increased rapidly in the leaves and roots when intact wild-type whole plants were exposed to drought stress. However, if the leaves and roots were separated and exposed to drought independently, the ABA level increased only in the leaves. These results suggest that, under our experimental conditions, ABA is synthesized mainly in the leaves in response to drought stress and that some of the ABA accumulated in the leaves is transported to the roots. Tracer experiments using isotope-labeled ABA indicate that the movement of ABA from leaves to roots is activated by water deficit in the roots. We also demonstrate that the endogenous ABA level in the leaves increased only when the leaves themselves were exposed to drought stress, suggesting that leaves play a major role in the production of ABA in response to acute water shortage.     

Differences in abscisic acid concentration in roots and leaves of two young Olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.) cultivars in response to water deficit

Differences in abscisic acid (ABA) accumulation between two olive cultivars were studied by enzyme-linked immunosorbent assay in roots and leaves, leaf water potential (Ψ_l), stomatal conductance (g _s) as well as photosynthetic rate (A) were also determined in well-watered (WW) and water-stressed (WS) plants of two olive cultivars ‘Chemlali’ and ‘Chetoui’. ‘Chemlali’ was able to maintain higher leaf CO₂ assimilation rate and leaf stomatal conductance throughout the drought cycle when compared with ‘Chetoui’. Furthermore, leaf water potential of ‘Chemlali’ decreased in lower extent than in Chetoui in response to water deficit. Interestingly, significant differences in water-stress-induced ABA accumulation were observed between the two olive cultivars and reflect the degree of stress experienced. Chemlali, a drought tolerant cultivar, accumulated lower levels of ABA in their leaves to regulate stomatal control in response to water stress compared to the drought sensitive olive cultivar ‘Chetoui’ which accumulated ABA in large amount.     

干旱胁迫对苗期大豆异黄酮合成的影响

以不同耐旱性的2个大豆品种(高耐旱JP-6、低耐旱JP-16)为研究材料,采用高效液相色谱和实时荧光定量PCR技术,分析不同时间持续干旱胁迫下,大豆叶片和根系中异黄酮的积累变化及关键酶基因的表达情况.结果表明:大豆根部异黄酮含量显著高于叶部,而异黄酮关键酶基因的表达量则在叶片中更高,耐旱品种JP-6根部的异黄酮积累量更大.随着干旱胁迫持续时间的增加,不同耐旱品种的异黄酮合成与积累变化规律存在显著差异:强耐旱品种JP-6的根和叶中,异黄酮积累量均呈现先下降后升高的趋势;而弱耐旱品种JP-16则相反,异黄酮积累量在不同部位中均呈现先上升后降低的趋势;除JP-6叶中C4H、4CL、IFS2等异黄酮合成上游基因外,其他不同品种、不同部位的关键酶基因表达量均随着干旱胁迫持续时间的增加,呈现先下降后上升的趋势.大豆叶片是异黄酮的主要合成部位,大豆根部也存在少量的异黄酮合成.弱耐旱大豆根部的异黄酮合成和最终积累量均较低,强耐旱品种则较高.根部异黄酮积累量高的大豆品种,其耐旱性更强.     

Coronatine promotes maize water uptake by directly binding to the aquaporin ZmPIP2;5 and enhancing its activity

Water uptake is crucial for crop growth and development and drought stress tolerance. The water channel aquaporins(AQP) play important roles in plant water uptake. Here, we discovered that a jasmonic acid analog, coronatine(COR), enhanced maize(Zea mays) root water uptake capacity under artificial water deficiency conditions. COR treatment induced the expression of the AQP gene Plasma membrane intrinsic protein 2;5(ZmPIP2;5).In vivo and in vitro experiments indicated that COR also directly acts ...     

Aquaporin gene expression and physiological responses of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> L. to the mycorrhizal fungus <Emphasis Type="Italic">Rhizophagus irregularis</Emphasis> and drought stress

The influence of arbuscular mycorrhiza (AM) and drought stress on aquaporin (AQP) gene expression, water status, and photosynthesis was investigated in black locust (Robinia pseudoacacia L.). Seedlings were grown in potted soil inoculated without or with the AM fungus Rhizophagus irregularis, under well-watered and drought stress conditions. Six full-length AQP complementary DNAs (cDNAs) were isolated from Robinia pseudoacacia, named RpTIP1;1, RpTIP1;3, RpTIP2;1, RpPIP1;1, RpPIP1;3, and RpPIP2;1. A phylogenetic analysis of deduced amino acid sequences demonstrated that putative proteins coded by these RpAQP genes belong to the water channel protein family. Expression analysis revealed higher RpPIP expression in roots while RpTIP expression was higher in leaves, except for RpTIP1;3. AM symbiosis regulated host plant AQPs, and the expression of RpAQP genes in mycorrhizal plants depended on soil water condition and plant tissue. Positive effects were observed for plant physiological parameters in AM plants, which had higher dry mass and lower water saturation deficit and electrolyte leakage than non-AM plants. Rhizophagus irregularis inoculation also slightly increased leaf net photosynthetic rate and stomatal conductance under well-watered and drought stress conditions. These findings suggest that AM symbiosis can enhance the drought tolerance in Robinia pseudoacacia plants by regulating the expression of RpAQP genes, and by improving plant biomass, tissue water status, and leaf photosynthesis in host seedlings.     

Intrinsic morphology and spatial distribution of non-structural carbohydrates contribute to drought resistance of two mulberry cultivars

• Drought is one of the most adverse environmental stresses limiting plant growth and productivity. However, the underlying mechanisms regarding metabolism of non-structural carbohydrates (NSC) in source and sink organs are still not fully elucidated in woody trees.
• Saplings of mulberry cv Zhongshen1 and Wubu were subjected to a 15-day progressive drought stress. NSC levels and gene expression involved in NSC metabolism were investigated in roots and leaves. Growth performance and photosynthesis, leaf stomatal morphology, and other physiological parameters were also analysed.
• Under well-watered conditions, Wubu had a higher R/S, with higher NSC in leaves than in roots; Zhongshen1 had a lower R/S with higher NSC in roots than leaves. Under drought stress, Zhongshen1 showed decreased productivity and increased proline, abscisic acid, ROS content and activity of antioxidant enzymes, while Wubu sustained comparable productivity and photosynthesis. Interestingly, drought resulted in decreased starch and slightly increased soluble sugars in leaves of Wubu, accompanied by notable downregulation of starch-synthesizing genes and upregulation of starch-degrading genes. Similar patterns in NSC levels and relevant gene expression were also observed in roots of Zhongshen1. Concurrently, soluble sugars decreased and starch was unchanged in roots of Wubu and leaves of Zhongshen1. However, gene expression of starch metabolism in roots of Wubu was unaltered, but in leaves of Zhongshen1 starch metabolism was more activated.
• These findings revealed that intrinsic R/S and spatial distribution of NSC in roots and leaves concomitantly contribute to drought resistance in mulberry.