Two inositol hexakisphosphate kinases drive inositol pyrophosphate synthesis in plants
Two inositol hexakisphosphate kinases drive inositol pyrophosphate synthesis in plants
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DOI：
10.1111/tpj.12669
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发表时间：
2014-11-01
期刊：
影响因子：
7.2
通讯作者：
Gillaspy, Glenda E.
中科院分区：
文献类型：
--
作者：
Desai, Mintu;Rangarajan, Padma;Gillaspy, Glenda E.
肌醇焦磷酸是一种独特的细胞信号分子，最近被发现在能量感应和代谢中发挥作用。在真核生物中的研究表明，这些化合物具有快速的周转，因此只有少量积累。肌醇焦磷酸还没有成为植物研究的主题，即使种子产生大量的前体肌醇六磷酸（InsP（6））。在这里，我们报告了拟南芥和玉米InsP（6）转运蛋白突变体在其种子中的肌醇焦磷酸水平升高，这为它们在植物组织中的存在提供了明确的鉴定。我们还表明，植物种子储存略高于1%的肌醇磷酸库作为InsP（7）和InsP（8）。许多组织，包括种子、幼苗、根和叶积累InsP（7）和InsP（8），因此合成不限于具有高InsP（6）的组织。我们已经确定了两个高度相似的拟南芥基因，AtVip1和AtVip2，这是直向酵母和哺乳动物VIP激酶。AtVip1和AtVip2都编码能够恢复酵母突变体中InsP（7）合成的蛋白，因此AtVip1和AtVip2可以作为真正的InsP（6）激酶发挥功能。AtVip1和AtVip2在植物组织中差异表达，表明在植物中的非冗余或非重叠功能。这些结果有助于我们对肌醇磷酸代谢的认识，并为了解InsP（7）和InsP（8）在植物中的作用奠定了基础。
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 (InsP(6)). Here, we report that Arabidopsis and maize InsP(6) 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 InsP(7) and InsP(8). Many tissues, including, seed, seedlings, roots and leaves accumulate InsP(7) and InsP(8), thus synthesis is not confined to tissues with high InsP(6). 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 InsP(7) synthesis in yeast mutants, thus AtVip1 and AtVip2 can function as bonafide InsP(6) 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 InsP(7) and InsP(8) in plants.