Vitamin C (Ascorbic Acid) plays important roles in the growth and development of plants.Its metabolism and function had been studied in depth by Nicholas Smirnoff. Broadly the function of ascorbic acid in plants may be divided into four categories, i.e, i) antioxidant, ii) enzyme co-factor, iii) electron transport and iv) Oxalate and tartrate synthesis. Antioxidant function is relevant with photoprotection.
Jennifer Mach, Science Editor in the recent issue of 'The Plant Cell' (published online on 26th February) has reported the factors regulating the biosynthetic enzyme 'GDP-Mannose Pyrophosphorylase' (an important enzyme involved in biosynthesis of ascorbic acid). Through gel filtration, bimolecular fluorescence complementtation and coimmunoprecipitation Mach confirms that protein, COP9 singalosome (CSN) subunit CSN5B that interacts with GDP-Mannose Pyrophosphorylase to form CSN complex. Further report says that the csn5b mutants showed substantially increased Ascorbic acid in darkness and double mutantsshowed partially restored AsA levels,indicating that CSN5B acts to decrease AsA.
Author reports that high Ascorbic acid can be beneficial in stress responses as it was found that csn5b mutants, which have highAsA contents even in the dark, also hadhigher salt tolerance and reduced sensitivity to oxidative stress generated by treat-ment with methyl viologen.
Author recommends that these findings will provide an avenue for resech in metabolic engineering towards a simple solution to stress tolerance in plants thereby resulting in plant specific ecological adaptation.