Overexpression of maize sucrose non-fermenting-1-related protein kinase 1 genes, ZmSnRK1s, causes alteration in carbon metabolism and leaf senescence in Arabidopsis thaliana.

Sucrose non-fermenting-1 (SNF1) -related protein kinase 1 (SnRK1) is a key regulator of catabolic homeostasis and plays critical roles in plant development and stress response. In this study, three SNF1-related protein kinase 1 genes, ZmSnRK1.1, ZmSnRK1.2 and ZmSnRK1.3, which are highly conserved in plants, were isolated from maize (Zea mays L.). Expression profiling experiments indicated that the three genes were constitutively expressed in all tested tissues with the highest expression level in young ears. Subcellular localization analysis indicated that ZmSnRK1.1, ZmSnRK1.2 and ZmSnRK1.3 are localized to both the nucleus and cytoplasm. Transgenic Arabidopsis lines overexpressing ZmSnRK1.1, ZmSnRK1.2 or ZmSnRK1.3 exhibited hypersensitivity to exogenous sugar treatment and accumulated less glucose but more sucrose in the rosette leaves and mature seeds compared to the wild type. Time to flowering was shortened in the ZmSnRK1.1 over-expressing lines but prolonged in the ZmSnRK1.2 and ZmSnRK1.3 lines. Leaf senescence was delayed in all transgenic lines, especially in the ZmSnRK1.3 lines, which led to enhanced biomass and seed yield at maturity. Key genes that are involved in carbon metabolism, senescence and flowering time were differentially regulated in the transgenic lines as revealed by the RNA-seq analysis. This study demonstrated that maize ZmSnRK1 members play important roles in energy sensing and carbon metabolism, they regulate the architecture shaping and developmental transition when heterogeneously expressed in Arabidopsis and may provide potentially valuable characteristics for high yield breeding of crops in the future.