Molecular and functional characterization of plant inositol pyrophosphate kinase

Abstract

The inositol pyrophosphates(PPx-InsPs): InsP7 and InsP8 are novel signaling molecules possessing high- energy pyrophosphate bonds. These unique group of inositol metabolites are involved in multiple physiological processes including bioenergetics and phosphate homeostasis. Herein, we have discerned two VIP-like homologs from wheat: TaVIH1 and TaVIH2 possessing a dual-domain structure. Analysis of transcript abundance revealed that TaVIHs were differentially expressed across various tissue samples. Both VIH genes showed contrasting transcriptional changes under phosphate limiting conditions, which depicted their involvement in regulation of phosphate starvation response. Biochemical assays showed that recombinant wheat VIHs exhibit in vitro IP6 kinase activity. The GUS-reporter assays in homozygous transgenic lines of Arabidopsis displayed strong reporter activity for VIH2-promoter in response to Pi-starvation, dehydration and drought conditions. Overall, our results confirm the new functional link of inositol pyro-phosphate kinases with stress response in wheat.