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

Abstract

Major 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, SnRK1 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 suggest TaSnRK1 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 TaSnRK1 activity. Sub-cellular localization identified nuclear and cytoplasmic localization of TaSnRK1 in tobacco leaves. Further, heterologous over-expression (O/E) of TaSnRK1 in Arabidopsis not only led to increase in starch content but also enlarges the starch granules. TaSnRK1 was found to restore starch accumulation in Arabidopsis kin10. Remarkably, TaSnRK1 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 TaSnRK1 interacts with AGPase large sub-unit. Overall, our findings indicate that TaSnRK1 plays role in starch biosynthesis by regulating AGPase activity. HighlightsO_LITaSnRK1 is Ser/Thr kinase in wheat and show dual localization in nucleus and cytoplasm. C_LIO_LIOverexpression of TaSnRK1 increases starch content and enlarges starch granules in Arabidopsis. C_LIO_LITaSnRK1 enhances AGPase activity thereby regulating starch biosynthesis. C_LIO_LITaSnRK1 directly interact with AGPase large subunit in vivo and in vitro. C_LI