Plant and Cell Physiology Advance Access originally published online on November 23, 2005
Plant and Cell Physiology 2006 47(2):181-191; doi:10.1093/pcp/pci233
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EUI1, Encoding a Putative Cytochrome P450 Monooxygenase, Regulates Internode Elongation by Modulating Gibberellin Responses in Rice
1 National Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, PR China
2 China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, PR China
3 National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Shanghai 200032, PR China
4 College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
5 The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, PR China
* Corresponding authors: Chengcai Chu, E-mail, ccchu{at}genetics.ac.cn; Fax, +86-10-6487-7570; Da Luo, E-mail, dluo{at}sibs.ac.cn; Fax, +86-21-5492-4106.
Elongation of rice internodes is one of the most important agronomic traits, which determines the plant height and underlies the grain yield. It has been shown that the elongation of internodes is under genetic control, and various factors are implicated in the process. Here, we report a detailed characterization of an elongated uppermost internode1 (eui1) mutant, which has been used in hybrid rice breeding. In the eui1-2 mutant, the cell lengths in the uppermost internodes are significantly longer than that of wild type and thus give rise to the elongated uppermost internode. It was found that the level of active gibberellin was elevated in the mutant, whereas its growth in response to gibberellin is similar to that of the wild type, suggesting that the higher level accumulation of gibberellin in the eui1 mutant causes the abnormal elongation of the uppermost internode. Consistently, the expression levels of several genes which encode gibberellin biosynthesis enzymes were altered. We cloned the EUI1 gene, which encodes a putative cytochrome P450 monooxygenase, by map-based cloning and found that EUI1 was weakly expressed in most tissues, but preferentially in young panicles. To confirm its function, transgenic experiments with different constructs of EUI1 were conducted. Overexpression of EUI1 gave rise to the gibberellin-deficient-like phenotypes, which could be partially reversed by supplementation with gibberellin. Furthermore, apart from the alteration of expression levels of the gibberellin biosynthesis genes, accumulation of SLR1 protein was found in the overexpressing transgenic plants, indicating that the expression level of EUI1 is implicated in both gibberellin-mediated SLR1 destruction and a feedback regulation in gibberellin biosynthesis. Therefore, we proposed that EUI1 plays a negative role in gibberellin-mediated regulation of cell elongation in the uppermost internode of rice.
6 These authors contributed equally to this work.
(Received November 4, 2005; Accepted November 18, 2005)
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