- 著者
- Nobuhiro Kotoda Satoshi Matsuo Ichiro Honda Kanako Yano Tokurou Shimizu
- 出版者
- 一般社団法人 園芸学会
- 雑誌
- The Horticulture Journal (ISSN:21890102)
- 巻号頁・発行日
- pp.OKD-016, (Released:2016-09-27)
- 被引用文献数
- 5
Gibberellins (GAs) are involved in many aspects of plant growth and development in higher plants. In this study, we aimed to characterize Satsuma mandarin (Citrus unshiu Marc.) GA 2-oxidase genes encoding enzymes with GA inactivation activity because the accumulation of active GAs is regulated by the balance between their synthesis and inactivation. We showed that CuGA2ox4, CuGA2ox2/3, and CuGA2ox8 were differentially expressed in various tissues in Satsuma mandarin and that these genes functioned like GA 2-oxidase genes in transgenic Arabidopsis. The expression pattern of CuGA2ox4 resembled that of CuGA20ox1, which was reported previously as a Satsuma mandarin GA 20-oxidase gene, in the reproductive tissues of the adult trees in that both genes were expressed in juice sacs in November and December and peel in December, suggesting that CuGA2ox4 and CuGA20ox1 act in concert to regulate the accumulation of active GAs in fruit at the maturing stage. On the other hand, CuGA2ox2/3 and CuGA2ox8 were more highly expressed in seeds and flower buds, respectively. Further study of GA biosynthetic genes, including GA 2-oxidase genes, would provide insight into the mechanism of flowering, fruit development, seedlessness, biennial bearing, and peel puffins of citrus such as Satsuma mandarin.
- 著者
- Nobuhiro Kotoda Satoshi Matsuo Ichiro Honda Kanako Yano Tokurou Shimizu
- 出版者
- 一般社団法人 園芸学会
- 雑誌
- The Horticulture Journal (ISSN:21890102)
- 巻号頁・発行日
- pp.MI-085, (Released:2015-11-28)
- 被引用文献数
- 14
Satsuma mandarin (Citrus unshiu Marc.) has two GA 20-oxidase genes, CuGA20ox1 and CuGA20ox2, and the genomic sequence for CuGA20ox1 is shorter than that for CuGA20ox2, although the coding region of cDNA for CuGA20ox1 is slightly longer than that for CuGA20ox2. Southern blot analysis revealed that 12 Citrus cultivars examined and trifoliate orange [Poncirus trifoliata (L.) Raf.] have at least two types of GA 20-oxidase genes, such as CuGA20ox1 and CuGA20ox2 genes. CuGA20ox1 and CuGA20ox2 were differentially expressed in various tissues. CuGA20ox1 was expressed in almost all of the tissues investigated with relatively higher expression in vegetative than in reproductive tissues, whereas CuGA20ox2 was specifically expressed in flower buds just before anthesis. These distinct expression patterns of CuGA20ox1 and CuGA20ox2 imply that function of these two genes diverged in the process of evolution. The specific and relatively higher expression of CuGA20ox2 in flower buds would explain why GA-like activity was higher in Satsuma mandarin’s ovaries at anthesis. Transgenic Arabidopsis [Arabidopsis thaliana (L.) Heynh] plants ectopically expressing CuGA20ox1 or CuGA20ox2 were examined to elucidate the function of these two Satsuma mandarin genes. Phenotypic analysis revealed that both CuGA20ox1 and CuGA20ox2 caused elongated inflorescence but did not affect the timing of flowering in transgenic Arabidopsis as compared with wild-type controls. Ectopic expression of CuGA20ox1 and CuGA20ox2 significantly affected the levels of GA24 and GA34 on the non-13-hydroxylation pathway; GA24 decreased and GA34 increased. This observation indicates that both CuGA20ox1 and CuGA20ox2 accelerated the conversion of GA24, a substrate of a GA 20-oxidase, to GA9, a precursor of an active form of GA4. Likewise, on the early-13-hydroxylation pathway, ectopic expression of CuGA20ox1 significantly decreased GA19 and increased GA29 and GA8, inactive metabolites of 2-hydroxylation of GA20 and GA1, respectively, suggesting the activation of this biosynthetic pathway. CuGA20ox2 also had a tendency to activate the early-13-hydroxylation pathway although it increased only GA20 with a statistically significant difference. Taken together, we concluded that CuGA20ox1 and/or CuGA20ox2 activated both the early-13- and non-13-hydroxylation pathways for increasing active GAs, resulting in elongated inflorescences in transgenic Arabidopsis.