Gibberellin homeostasis and plant height control by EUI and a role for gibberellin in root gravity responses in rice.
The rice Eui (ELONGATED UPPERMOST INTERNODE) gene encodes a cytochrome P450 monooxygenase that deactivates bioactive gibberellins (GAs). In this study, we investigated controlled expression of the Eui gene and its role in plant development. We found that Eui was differentially induced by exogenous GAs and that the Eui promoter had the highest activity in the vascular bundles. The eui mutant was defective in starch granule development in root caps and Eui overexpression enhanced starch granule generation and gravity responses, revealing a role for GA in root starch granule development and gravity responses. Experiments using embryoless half-seeds revealed that RAmy1A and GAmyb were highly upregulated in eui aleurone cells in the absence of exogenous GA. In addition, the GA biosynthesis genes GA3ox1 and GA20ox2 were downregulated and GA2ox1 was upregulated in eui seedlings. These results indicate that EUI is involved in GA homeostasis, not only in the internodes at the heading stage, but also in the seedling stage, roots and seeds. Disturbing GA homeostasis affected the expression of the GA signaling genes GID1 (GIBBERELLIN INSENSITIVE DWARF 1), GID2 and SLR1. Transgenic RNA interference of the Eui gene effectively increased plant height and improved heading performance. By contrast, the ectopic expression of Eui under the promoters of the rice GA biosynthesis genes GA3ox2 and GA20ox2 significantly reduced plant height. These results demonstrate that a slight increase in Eui expression could dramatically change rice morphology, indicating the practical application of the Eui gene in rice molecular breeding for a high yield potential.
Zhang
Yingying
Y
National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
Zhu
Yongyou
Y
Peng
Yu
Y
Yan
Dawei
D
Li
Qun
Q
Wang
Jianjun
J
Wang
Linyou
L
He
Zuhua
Z
D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D005875:Gibberellins / Q000096:biosynthesis* / Q000494:pharmacology; D006112:Gravitation; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics; D018518:Plant Root Cap / Q000201:enzymology* / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000502:physiology; D036226:Seedlings / Q000201:enzymology / Q000235:genetics; D013213:Starch / Q000096:biosynthesis / Q000235:genetics
D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D013213:Starch; D003577:Cytochrome P-450 Enzyme System