Dynamic proteomic profile of potato tuber during its in vitro development.

Potato tuberization is a complicated biochemical process, which is dependent on external environmental factors. Tuber development in potato consists of a series of biochemical and morphological processes at the stolon tip. Signal transduction proteins are involved in the source-sink transition during potato tuberization. In the present study, we examined protein profiles under in vitro tuber-inducing conditions using a shotgun proteomic approach involving denaturing gel electrophoresis and liquid chromatography-mass spectrometry. A total of 251 proteins were identified and classified into 9 groups according to distinctive expression patterns during the tuberization stage. Stolon stage-specific proteins were primarily involved in the photosynthetic machinery. Proteins specific to the initial tuber stage included patatin. Proteins specific to the developing tuber stage included 6-fructokinase, phytoalexin-deficient 4-1, metallothionein II-like protein, and malate dehydrogenase. Novel stage-specific proteins identified during in vitro tuberization were ferredoxin-NADP reductase, 34 kDa porin, aquaporin, calmodulin, ripening-regulated protein, and starch synthase. Superoxide dismutase, dehydroascorbate reductase, and catalase I were most abundantly expressed in the stolon; however, the enzyme activities of these proteins were most activated at the initial tuber. The present shotgun proteomic study provides insights into the proteins that show altered expression during in vitro potato tuberization.

Transgenic potato overproducing L-ascorbic acid resisted an increase in methylglyoxal under salinity stress via maintaining higher reduced glutathione level and glyoxalase enzyme activity.

Salt-tolerance was studied in transgenic potato. It was conferred by overexpression of ascorbate pathway enzyme (D-galacturonic acid reductase, GalUR). As genetic engineering of the GalUR gene in potato enhances its ascorbic acid content (L-AsA), and subsequently plants suffered minimal oxidative stress-induced damage, we now report on the comprehensive aptness of this engineering approach for enhanced salt tolerance in transgenic potato (Solanum tuberosum L. cv. Taedong Valley). Potatoes overexpressing GalUR grew and tuberized in continuous presence of 200 mM of NaCl. The transgenic plants maintained a higher reduced to oxidized glutathione (GSH:GSSG) ratio together with enhanced activity of glutathione dependent antioxidative and glyoxalase enzymes under salinity stress. The transgenics resisted an increase in methylglyoxal that increased radically in untransformed control plants under salinity stress. This is the first report of genetic engineering of ascorbate pathway gene in maintaining higher level of GSH homeostasis along with higher glyoxalase activity inhibiting the accumulation in methylglyoxal (a potent cytotoxic compound) under salt stress. These results suggested the engineering of ascorbate pathway enzymes as a major step towards developing salinity tolerant crop plants.