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| Title: Involvement of C-22-hydroxylated brassinosteroids in auxin-induced lamina joint bending in rice .
| | Author: Nakamura A Fujioka S Takatsuto S Tsujimoto M Kitano H Yoshida S Asami T Nakano T | | Journal: Plant Cell Physiol Citation: V : 50 P : 1627-35 Year: 2009 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub19605414 Accession (PMID): 19605414 | | Abstract: The rice lamina joint is ideal material for investigating the activity of brassinosteroids ( BRs ) and auxin because of its high sensitivity to these compounds .
Using a series of rice BR biosynthetic and receptor mutants , we conducted lamina joint tests to elucidate the mechanism of cross-talk between BR and auxin signaling in lamina joint bending .
In BR biosynthetic mutants d2 and brd1 , which are defective in C-23 hydroxylase and C-6 oxidase , respectively , the lamina joint response to auxin was significantly higher than that of wild-type plants .
The other BR-biosynthetic mutants , brd2 , osdwarf4 and d11 , which are defective in C-22-hydroxylated BRs , showed less or no response to auxin .
These results suggest that C-22-hydroxylated BRs are involved in auxin-induced lamina joint bending .
The results were supported by the observation that inhibition of the hyper-response to auxin in d2 was reduced by treatment with brassinazole , which inhibits the function of DWARF4 , the C-22 hydroxylase .
In d61 , which is defective in OsBRI1 , a possible BR receptor in rice , the bending angle of the lamina joint in response to auxin and C-22-hydroxylated 6-deoxoBRs was nearly the same as that in wild-type plants .
This implies that C-22-hydroxylated BRs function in auxin signaling independently of OsBRI1 .
From these observations , we propose that C-22-hydroxylated BRs participate in auxin signaling via a novel OsBRI1-independent signaling pathway .
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[ Sen. 6, subscore: 1.00 ]: The results were supported by the observation that inhibition of the hyper-response to auxin in d2 was reduced by treatment with brassinazole , which inhibits the function of DWARF4 , the C-22 hydroxylase .
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