RabA2b Overexpression Alters the Plasma-Membrane Proteome and Improves Drought Tolerance in Arabidopsis.

Rab proteins are small GTPases that are important in the regulation of vesicle trafficking. Through data mining, we identified RabA2b to be stress responsive, though little is known about the involvement of RabA in plant responses to abiotic stresses. Analysis of the RabA2b native promoter showed strong activity during osmotic stress, which required the stress hormone Abscisic acid (ABA) and was restricted to the vasculature.

Elucidating the role of shikimate dehydrogenase in controlling the production of anthocyanins and hydrolysable tannins in the outer peels of pomegranate.

Background: The outer peels of pomegranate (Punica granatum L.) possess two groups of polyphenols that have health beneficial properties: anthocyanins (ATs, which also affect peel color); and hydrolysable tannins (HTs). Their biosynthesis intersects at 3-dehydroshikimate (3-DHS) in the shikimate pathway by the activity of shikimate dehydrogenase (SDH), which converts 3-DHS to shikimate (providing the precursor for AT biosynthesis) or to gallic acid (the precursor for HTs biosynthesis) using NADPH or NADP as a cofactor.

The level of threonine in tobacco seeds is limited by substrate availability, while the level of methionine is limited also by the activity of cystathionine γ-synthase.

Methionine and threonine are two essential amino acids whose low levels limit the nutritional quality of seeds. The current objective was to define factors that regulate and might increase their levels in seeds. Feeding experiments carried out on receptacles of developing tobacco (Nicotiana tabacum) capsules showed that 1 mM of S-methylmethionine increased the level of methionine to contents similar to 2.

Transgenic tobacco plants having a higher level of methionine are more sensitive to oxidative stress.

Methionine is an essential amino acid the low level of which limits the nutritional quality of plants. We formerly produced transgenic tobacco (Nicotiana tabacum) plants overexpressing CYSTATHIONE γ-SYNTHASE (CGS) (FA plants), methionine's main regulatory enzyme. These plants accumulate significantly higher levels of methionine compared with wild-type (WT) plants.

Seed-specific expression of a feedback-insensitive form of CYSTATHIONINE-γ-SYNTHASE in Arabidopsis stimulates metabolic and transcriptomic responses associated with desiccation stress.

With an aim to elucidate novel metabolic and transcriptional interactions associated with methionine (Met) metabolism in seeds, we have produced transgenic Arabidopsis (Arabidopsis thaliana) seeds expressing a feedback-insensitive form of CYSTATHIONINE-γ-SYNTHASE, a key enzyme of Met synthesis. Metabolic profiling of these seeds revealed that, in addition to higher levels of Met, the levels of many other amino acids were elevated. The most pronounced changes were the higher levels of stress-related amino acids (isoleucine, leucine, valine, and proline), sugars, intermediates of the tricarboxylic acid cycle, and polyamines and lower levels of polyols, cysteine, and glutathione.