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Arabidopsis inositol phosphate kinases IPK 1 and ITPK 1 constitute a metabolic pathway in maintaining phosphate homeostasis
Author(s) -
Kuo HuiFen,
Hsu YuYing,
Lin WeiChi,
Chen KaiYu,
Munnik Teun,
Brearley Charles A.,
Chiou TzyyJen
Publication year - 2018
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13974
Subject(s) - biology , inositol , arabidopsis , kinase , inositol phosphate , biochemistry , mutant , microbiology and biotechnology , second messenger system , homeostasis , arabidopsis thaliana , signal transduction , receptor , gene
Summary Emerging studies have suggested that there is a close link between inositol phosphate (InsP) metabolism and cellular phosphate (P i ) homeostasis in eukaryotes; however, whether a common InsP species is deployed as an evolutionarily conserved metabolic messenger to mediate P i signaling remains unknown. Here, using genetics and InsP profiling combined with P i ‐starvation response ( PSR ) analysis in Arabidopsis thaliana , we showed that the kinase activity of inositol pentakisphosphate 2‐kinase ( IPK 1), an enzyme required for phytate (inositol hexakisphosphate; InsP 6 ) synthesis, is indispensable for maintaining P i homeostasis under P i ‐replete conditions, and inositol 1,3,4‐trisphosphate 5/6‐kinase 1 ( ITPK 1) plays an equivalent role. Although both ipk1‐1 and itpk1 mutants exhibited decreased levels of InsP 6 and diphosphoinositol pentakisphosphate ( PP ‐InsP 5 ; InsP 7 ), disruption of another ITPK family enzyme, ITPK 4, which correspondingly caused depletion of InsP 6 and InsP 7 , did not display similar P i ‐related phenotypes, which precludes these InsP species from being effectors. Notably, the level of d / l ‐Ins(3,4,5,6)P 4 was concurrently elevated in both ipk1‐1 and itpk1 mutants, which showed a specific correlation with the misregulated P i phenotypes. However, the level of d / l ‐Ins(3,4,5,6)P 4 is not responsive to P i starvation that instead manifests a shoot‐specific increase in the InsP 7 level. This study demonstrates a more nuanced picture of the intersection of InsP metabolism and P i homeostasis and PSRs than has previously been elaborated, and additionally establishes intermediate steps to phytate biosynthesis in plant vegetative tissues.