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KMID : 0368420060490060469
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Journal of Plant Biology
2006 Volume.49 No. 6 p.469 ~ p.469
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Ricebending lamina 2 (bla2) mutants are defective in a cytochrome P450 (CYP734A6) gene predicted to mediate brassinosteroid catabofism
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Park Wan-Ki
Kim Ho-Bang
Kim Woo-Taek
Park Phun-Bum
An Gyn-Heung
Choe Sung-Hwa
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Abstract
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Desirable morphological traits in rice plants, such as shorter stalks and erect leaves, are being pursued in breeding programs. Rice brassinosteroid (BR)-deficient mutants display the phenotype of reduced heights and erect lamina. Therefore, biotechnology can be used for controlled deactivation of bioactive BRs in specific tissues. Here, we isolated a gene encoding for a BR-deactivating enzyme. Based on its sequence identity with a known enzyme,Arahidopsis Cytochrome P450 734A1, we identified a rice homolog named QsCYP734A6 (LOC_Os01 g29150). A search of the rice T-DNA mutant population for insertional mutants of this gene revealed two alleles. These T-DNA loss-of-function mutants displayed a strongly bending lamina phenotype similar to the morphology of rice plants treated with BRs. These two mutants were namedbending lamina (bla)2-1 andbla2-2. InArahidopsis, the transcript level of a putative BR biosynthetic gene,OsDWARF4, is feed-back down-regulated in response to exogenous application of BRs. Similarly, a steady-state level ofOsDWARF4 transcripts was significantly down-regulated here in the bla2 mutant background. Based on their sequence similarity, the bending-Iamina phenotype in thebla2 mutant, and down-regulation of the BR biosynthetic geneQsDWARF4, we therefore propose that OsCYP734A6 (BLA2) is likely to be involved in BR deactivation.
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KEYWORD
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brassinolide, Cytochrome P450, erect leaves, rice T-DNA mutant, short stature
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