title: Possible involvement of phosphoinositide-Ca2+ signaling in the regulation of alpha-amylase expression and germination of rice seed (Oryza sativa L.).
abstract: We have studied the effects of neomycin, a potent inhibitor of inositol phospholipid-specific phospholipase C (PLC), on the germination of rice seed and the gibberellin-induced expression of alpha-amylase in the aleurone layer and the scutellar tissues. It was shown that, in the absence of exogenous Ca2+, neomycin markedly reduced the germination speed and seedling growth of rice seeds and inhibited the gibberellin-induced expression of alpha-amylase in both secretory tissues. In addition, neomycin decreased the formation of inositol 1,4,5-trisphosphate (IP3) in the gibberellin-treated aleurone layer and the scutellar tissues. However, the inhibitory effects on the germination speed and the expression of alpha-amylase activity were overcome by supplementation of Ca2+. In addition, gibberellin elevated the level of IP3, and ABA prevented the gibberellin-induced formation of IP3, although ABA alone did not alter the IP3 level. The expression of a membrane-bound PLC molecule in rice aleurone layer was shown to be induced by gibberellin, and the gibberellin-induced expression of PLC was markedly delayed by treatment with ABA. These results strongly suggest that the phosphoinositide-Ca2+ signal transduction pathway may play an important role in the gibberellin-induced expression of alpha-amylase molecules closely related to the germination processes of rice seed.
authors.affiliation: Laboratories of Molecular Life Sciences, Graduate School of Science and Technology, Niigata University, Japan.
authors.forename: M A
authors.initials: MA
authors.lastname: Kashem
authors.forename: K
authors.initials: K
authors.lastname: Itoh
authors.forename: S
authors.initials: S
authors.lastname: Iwabuchi
authors.forename: H
authors.initials: H
authors.lastname: Hori
authors.forename: T
authors.initials: T
authors.lastname: Mitsui
mesh_terms: D020013:Calcium Signaling / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D009355:Neomycin / Q000494:pharmacology; D012275:Oryza / Q000187:drug effects / Q000502:physiology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000502:physiology; D000516:alpha-Amylases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D010716:Phosphatidylinositols; D000516:alpha-Amylases; D009355:Neomycin