A sucrose non-fermenting-1-related protein kinase 1 gene from wheat, TaSnRK1α regulates starch biosynthesis by modulating AGPase activity

Abstract

AbstractMajor portion of wheat grain consist of carbohydrate, mainly starch. The proportion of amylose and amylopectin in starch greatly influence the end product quality. Advancement in understanding starch biosynthesis pathway and modulating key genes has enabled the genetic modification of crops resulting in enhanced starch quality. However, the regulation of starch biosynthesis genes still remains unexplored. So, to expand the limited knowledge, here, we characterized a Ser/Thr kinase, SnRK1α in wheat and determined its role in regulating starch biosynthesis. SnRK1 is an evolutionary conserved protein kinase and share homology to yeast SNF1. Yeast complementation assay suggestTaSnRK1α restore growth defect and promotes glycogen accumulation. Domain analysis and complementation assay with truncated proteins suggest the importance of ATP-binding and UBA domain in TaSnRK1α activity. Sub-cellular localization identified nuclear and cytoplasmic localization of TaSnRK1α in tobacco leaves. Further, heterologous over-expression (O/E) ofTaSnRK1α in Arabidopsis not only led to increase in starch content but also enlarges the starch granules.TaSnRK1α was found to restore starch accumulation in Arabidopsiskin10.Remarkably,TaSnRK1α O/E increase the AGPase activity suggesting the direct regulation of rate limiting enzyme AGPase involved in starch biosynthesis. Furthermore, in vitro and in vivo interaction assay reveal that TaSnRK1α interacts with AGPase large sub-unit. Overall, our findings indicate that TaSnRK1α plays role in starch biosynthesis by regulating AGPase activity.HighlightsTaSnRK1α is Ser/Thr kinase in wheat and show dual localization in nucleus and cytoplasm.Overexpression of TaSnRK1α increases starch content and enlarges starch granules in Arabidopsis.TaSnRK1α enhances AGPase activity thereby regulating starch biosynthesis.TaSnRK1α directly interact with AGPase large subunit in vivo and in vitro.