Expression and functions of myo-inositol monophosphatase family genes in seed development of Arabidopsis

• Published in: Journal of plant research 2011-05, Vol.124 (3), p.385-394
• Main Authors: Sato, Yuko, Yazawa, Katsumi, Yoshida, Seiji, Tamaoki, Masanori, Nakajima, Nobuyoshi, Iwai, Hiroaki, Ishii, Tadashi, Satoh, Shinobu
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biomedical and Life Sciences; Biosynthesis; Catalysis; Cell walls; Dephosphorylation; Embryos; Enzymes; Gene expression; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Gene Knockout Techniques; Genes, Lethal; Genetic Complementation Test; Histidine; Histidine - metabolism; Inosine monophosphate; Lethality; Life Sciences; Metabolism; Multigene Family; Mutagenesis, Insertional; Mutation; Myo-inositol-1 (or 4)-monophosphatase; Myo-Inositol-1-Phosphate Synthase - genetics; Myo-Inositol-1-Phosphate Synthase - metabolism; Phosphate; phosphatidylinositol; Phytic acid; Plant Biochemistry; Plant biology; Plant Ecology; Plant Physiology; Plant Sciences; polyphosphates; Polysaccharides; Regular Paper; Reproductive organs; RNA, Plant - genetics; Saccharides; Seeds; Seeds - enzymology; Seeds - growth & development
• ISSN: 0918-9440; 1618-0860
• DOI: 10.1007/s10265-010-0381-y

Myo -inositol monophosphatase (IMP) catalyzes the dephosphorylation of myo -inositol 3-phosphate in the last step of myo -inositol biosynthesis. IMP is also important in phosphate metabolism and is required for the biosynthesis of cell wall polysaccharides, phytic acid, and phosphatidylinositol. In Arabidopsis, IMP is encoded by VTC4 . There are, however, two additional IMP candidate genes, IMPL1 and IMPL2 , which have not yet been elucidated. In our genetic studies of Arabidopsis IMP genes, only the loss-of-function mutant impl2 showed embryonic lethality at the globular stage. All IMP genes were expressed in a similar manner both in the vegetative and reproductive organs. In developing seeds, expression of IMP genes was not coupled with the expression of the genes encoding myo -inositol phosphate synthases, which supply the substrate for IMPs in the de novo synthesis pathway. Instead, expression of IMP genes was correlated with expression of the gene for myo -inositol polyphosphate 1-phosphatase ( SAL1 ), which is involved in the myo -inositol salvage pathway, suggesting a possible salvage pathway role in seed development. Moreover, the partial rescue of the impl2 phenotype by histidine application implies that IMPL2 is also involved in histidine biosynthesis during embryo development.