Two inositol hexakisphosphate kinases drive inositol pyrophosphate synthesis in plants

• Published in: The Plant journal : for cell and molecular biology Vol. 80; no. 4; pp. 642 - 653
• Main Authors: Desai, Mintu, Rangarajan, Padma, Donahue, Janet L, Williams, Sarah P, Land, Eric S, Mandal, Mihir K, Phillippy, Brian Q, Perera, Imara Y, Raboy, Victor, Gillaspy, Glenda E
• Format: Journal Article
• Language: English
• Published: England Blackwell Scientific Publishers and BIOS Scientific Publishers in association with the Society for Experimental Biology 01-11-2014; Blackwell Publishing Ltd
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; At3g01310; At5g15070; Biosynthesis; Chromatography, High Pressure Liquid; corn; energy; eukaryotic cells; gene expression regulation; genes; Genetic Complementation Test; inositol kinase; Inositol Phosphates - metabolism; inositol pyrophosphate; InsP6; Kinases; leaves; mammals; Metabolism; mutants; Mutation; myo-inositol; Phosphates; Phosphotransferases (Alcohol Group Acceptor) - genetics; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Phosphotransferases (Phosphate Group Acceptor) - genetics; Phosphotransferases (Phosphate Group Acceptor) - metabolism; Phylogeny; Plant biology; Plant Proteins - genetics; Plant Proteins - metabolism; plant tissues; proteins; pyrophosphates; roots; seedlings; Seeds; Seeds - metabolism; Transcription Factors, General - genetics; Transcription Factors, General - metabolism; yeasts; Yeasts - genetics; Zea mays - genetics; Zea mays - metabolism; Arabidopsis thaliana; At5g15070; inositol pyrophosphate; inositol kinase; InsP6; At3g01310
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.12669

Inositol pyrophosphates are unique cellular signaling molecules with recently discovered roles in energy sensing and metabolism. Studies in eukaryotes have revealed that these compounds have a rapid turnover, and thus only small amounts accumulate. Inositol pyrophosphates have not been the subject of investigation in plants even though seeds produce large amounts of their precursor, myo‐inositol hexakisphosphate (InsP₆). Here, we report that Arabidopsis and maize InsP₆ transporter mutants have elevated levels of inositol pyrophosphates in their seed, providing unequivocal identification of their presence in plant tissues. We also show that plant seeds store a little over 1% of their inositol phosphate pool as InsP₇ and InsP₈. Many tissues, including, seed, seedlings, roots and leaves accumulate InsP₇ and InsP₈, thus synthesis is not confined to tissues with high InsP₆. We have identified two highly similar Arabidopsis genes, AtVip1 and AtVip2, which are orthologous to the yeast and mammalian VIP kinases. Both AtVip1 and AtVip2 encode proteins capable of restoring InsP₇ synthesis in yeast mutants, thus AtVip1 and AtVip2 can function as bonafide InsP₆ kinases. AtVip1 and AtVip2 are differentially expressed in plant tissues, suggesting non‐redundant or non‐overlapping functions in plants. These results contribute to our knowledge of inositol phosphate metabolism and will lay a foundation for understanding the role of InsP₇ and InsP₈ in plants.