The grapevine NIP2;1 aquaporin is a silicon channel.

Silicon (Si) supplementation has been shown to improve plant tolerance to different stresses, and its accumulation in the aerial organs is mediated by NIP2;1 aquaporins (Lsi channels) and Lsi2-type exporters in roots. In the present study, we tested the hypothesis that grapevine expresses a functional NIP2;1 that accounts for root Si uptake and, eventually, Si accumulation in leaves. Own-rooted grapevine cuttings of the cultivar Vinhão accumulated >0.2% Si (DW) in leaves when irrigated with 1.5 mM Si for 1 month, while Si was undetected in control leaves. Real-time PCR showed that VvNIP2;1 was highly expressed in roots and in green berries. The transient transformation of tobacco leaf epidermal cells mediated by Agrobacterium tumefaciens confirmed VvNIP2;1 localization at the plasma membrane. Transport experiments in oocytes showed that VvNIP2;1 mediates Si and arsenite uptake, whereas permeability studies revealed that VvNIP2;1 expressed in yeast is unable to transport water and glycerol. Si supplementation to pigmented grape cultured cells (cv. Gamay Freáux) had no impact on the total phenolic and anthocyanin content, or on the growth rate and VvNIP2;1 expression. Long-term experiments should help determine the extent of Si uptake over time and whether grapevine can benefit from Si fertilization.

Effect of cadmium stress on inductive enzymatic and nonenzymatic responses of ROS and sugar metabolism in multiple shoot cultures of Ashwagandha (Withania somnifera Dunal).

Withania somnifera is one of the most important medicinal plant and is credited with various pharmacological activities. In this study, in vitro multiple shoot cultures were exposed to different concentrations (5-300 µM) of cadmium (Cd) as cadmium sulphate to explore its ability to accumulate the heavy metal ion and its impact on the metabolic status and adaptive responses. The results showed that supplemental exposure to Cd interfered with N, P, and K uptake creating N, P, and K deficiency at higher doses of Cd that also caused stunting of growth, chlorosis, and necrosis. The study showed that in vitro shoots could markedly accumulate Cd in a concentration-dependent manner. Enzymatic activities and isozymic pattern of catalase, ascorbate peroxidase, guaiacol peroxidase, peroxidase, glutathione-S-transferase, glutathione peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase were altered substantially under Cd exposure. Sugar metabolism was also markedly modulated under Cd stress. Various other parameters including contents of photosynthetic pigments, phenolics, tocopherol, flavonoids, reduced glutathione, nonprotein thiol, ascorbate, and proline displayed major inductive responses reflecting their protective role. The results showed that interplay of enzymatic as well as nonenzymatic responses constituted a system endeavor of tolerance of Cd accumulation and an efficient scavenging strategy of its stress implications.

Effect of prolonged water stress on specialized secondary metabolites, peltate glandular trichomes, and pathway gene expression in Artemisia annua L.

Artemisia annua L. accumulates substantial quantities of unique sesquiternoid artemisinin and related phytomolecules and characteristic essential oil in glandular trichomes, present on its leaves and inflorescence. Water stress is a major concern in controlling plant growth and productivity. In this study, our aim was to find out the modulation of artemisinin and essential oil constituents in plants grown under prolonged water stress conditions. A. annua CIM-Arogya plants grown in pots were subjected to mild (60% ± 5) and moderate (40% ± 5) water stress treatment and continued during entire developmental period. Results revealed that artemisinin, arteannuin-B, artemisinic acid, dihydroartemisinic acid and essential oil content were positively controlled by the growth and development however negatively modulated by water deficit stress. Interestingly, some of minor monoterpenes, all sesquiterpenes and other low molecular weight volatiles of essential oil components were induced by water deficit treatment. Camphor which is the major essential oil constituents did not alter much while 1, 8 cineole was modulated during development of plant as well as under water stress conditions. Water deficit stress induces a decrease in glandular trichome density and size as well. The dynamics of various secondary metabolites is discussed in the light of growth responses, trichomes and pathway gene expression in plants grown under two levels of prolonged water stress conditions.

Qualitative and quantitative variations in withanolides and expression of some pathway genes during different stages of morphogenesis in Withania somnifera Dunal.

Withania somnifera Dunal is an important and extensively studied medicinal plant; however, there is no report available that relates withanolide content and its profile in relation to the expression of pathway genes during different morphogenic stages. In this study, withanolide A, withaferin A, and withanone, the major withanolides of W. somnifera, were measured in different in vitro stages during organogenesis, viz., shoot to root (direct rhizogenesis)/root to shoot (indirect via callus phase) transition vis-à-vis expression levels of key pathway genes involved in withanolide biosynthetic pathways. The morphogenic transitions were found to be tightly linked to the pattern of accumulation of withanolides. The high expression levels of most of the pathway genes in in vitro shoots in comparison to in vitro root and callus tissues exhibited a direct co-relation with the maximum withanolide content (>2.7 mg/gDW). The biogenesis of withaferin A, a major constituent of the leaves, was however found to be tightly linked to shoots/green tissue. In addition, we were also able to establish an efficient regeneration system from roots for their further utilization in biotechnological applications.

Bioconversion of artemisinin to its nonperoxidic derivative deoxyartemisinin through suspension cultures of Withania somnifera Dunal.

Biotransformation of artemisinin was investigated with two different cell lines of suspension cultures of Withania somnifera. Both cell lines exhibited potential to transform artemisinin into its nonperoxidic analogue, deoxyartemisinin, by eliminating the peroxo bridge of artemisinin. The enzyme involved in the reaction is assumed to be artemisinin peroxidase, and its activity in extracts of W. somnifera leaves was detected. Thus, the non-native cell-free extract of W. somnifera and suspension culture-mediated bioconversion can be a promising tool for further manipulation of pharmaceutical compounds.