An Overview of Gibberellin Metabolism Enzyme Genes and Their Related Mutants in Rice  

Abstract

To enhance our understanding of GA metabolism in rice (Oryza sativa), we intensively screened and identified 29 candidate genes encoding the following GA metabolic enzymes using all available rice DNA databases: ent-copalyl diphosphate synthase (CPS), ent-kaurene synthase (KS), ent-kaurene oxidase (KO), ent-kaurenoic acid oxidase (KAO), GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox). In contrast to the Arabidopsis genome, multiple CPS-like, KS-like, and KO-like genes were identified in the rice genome, most of which are contiguously arranged. We also identified 18 GA-deficient rice mutants at six different loci from rice mutant collections. Based on the mutant and expression analyses, we demonstrated that the enzymes catalyzing the early steps in the GA biosynthetic pathway (i.e. CPS, KS, KO, and KAO) are mainly encoded by single genes, while those for later steps (i.e. GA20ox, GA3ox, and GA2ox) are encoded by gene families. The remaining CPSlike, KS-like, and KO-like genes were likely to be involved in the biosynthesis of diterpene phytoalexins rather than GAs because the expression of two CPS-like and three KS-like genes (OsCPS2, OsCPS4, OsKS4, OsKS7, and OsKS8) were increased by UV irradiation, and four of these genes (OsCPS2, OsCPS4, OsKS4, and OsKS7) were also induced by an elicitor treatment.

Stemar‐13‐ene synthase, a diterpene cyclase involved in the biosynthesis of the phytoalexin oryzalexin S in rice

“…3B). The induction of OsKS8 (OsDTC2) mRNA by UV irradiation was also reported by Sakamoto et al [21] quite recently. GC-MS analysis indicated that the production of stemar-13-ene was induced in the rice leaves after UV irradiation (Fig.…”

“…It is thus suggested that OsDTC2 is localized in plastids, as are OsDTC1 (ent-cassa-12,15-diene synthase) [12] and other plant diterpene cyclases such as ent-CPS and ent-kaurene synthase (ent-KS) [19,20]. Quite recently, it was suggested that several diterpene cyclase genes found in the rice genome are involved in the phytoalexin biosynthesis in rice [21], one of them tentatively named OsKS8 being identical to OsDTC2. However, functional analysis of OsKS8 has not been carried out.…”

“…The stemar-13-ene synthase cDNA isolated here will be a useful tool to investigate the regulatory mechanisms of the biosynthesis of the diterpenoid phytoalexin oryzalexin S in rice. Based on the information from a rice genome database, at least 10 diterpene cyclase genes are expressed in rice including genes encoding ent-cassa-12,15-diene synthase [12], stemar-13-ene-synthase [this study], OsCyc1 (syn-CPS), OsCyc2 (ent-CPS involved in phytoalexin biosynthesis), and ent-CPS involved in gibberellin biosynthesis [15,21]. Cloning and functional analysis of other diterpene cyclase cDNAs are now under way.…”

Gibberellin homeostasis and plant height control by EUI and a role for gibberellin in root gravity responses in rice

“…Many GA-related mutants have been isolated from the model plant species Arabidopsis thaliana and rice (Oryza sativa L.), and the majority of the underlying genes have been found to encode enzymes that are related to GA metabolism or components of GA signaling [1][2][3][4][5][6][7]. Many GA mutants show dramatically reduced plant height and hence increased yield potential and lodging resistance of modern cereal varieties, thus greatly contributing to the success of the 'green revolution' [8][9][10].…”

The application of synthetic biology to elucidation of plant mono-, sesqui- and diterpenoid metabolism

“…Indeed, in a report on rice gibberellin metabolism, these regions had been previously noted to also contain genes encoding a number of CYPs, as well as short-chain alcohol dehydrogenases (Sakamoto et al, 2004). Many of these genes were found to be coregulated, specifically inducible by the fungal cell wall component chitin, as well .…”