Expression and functions of myo-inositol monophosphatase family genes in seed development of Arabidopsis.
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.
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8572, Japan. s0530456@yahoo.co.jp
Yuko
Y
Sato
Katsumi
K
Yazawa
Seiji
S
Yoshida
Masanori
M
Tamaoki
Nobuyoshi
N
Nakajima
Hiroaki
H
Iwai
Tadashi
T
Ishii
Shinobu
S
Satoh
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005804:Genes, Lethal; D005816:Genetic Complementation Test; D006639:Histidine / Q000378:metabolism; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D009154:Mutation; D007296:Myo-Inositol-1-Phosphate Synthase / Q000235:genetics* / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D012639:Seeds / Q000201:enzymology* / Q000254:growth & development
D029681:Arabidopsis Proteins; D018749:RNA, Plant; D006639:Histidine; D007296:Myo-Inositol-1-Phosphate Synthase