Chemical genetic dissection of brassinosteroid-ethylene interaction.

Molecular plant

PubMedID: 19825546

Gendron JM, Haque A, Gendron N, Chang T, Asami T, Wang ZY. Chemical genetic dissection of brassinosteroid-ethylene interaction. Mol Plant. 2008;1(2):368-79.
We undertook a chemical genetics screen to identify chemical inhibitors of brassinosteroid (BR) action. From a chemical library of 10,000 small molecules, one compound was found to inhibit hypocotyl length and activate the expression of a BR-repressed reporter gene (CPD::GUS) in Arabidopsis, and it was named brassinopride (BRP). These effects of BRP could be reversed by co-treatment with brassinolide, suggesting that BRP either directly or indirectly inhibits BR biosynthesis. Interestingly, the compound causes exaggerated apical hooks, similar to that caused by ethylene treatment. The BRP-induced apical hook phenotype can be blocked by a chemical inhibitor of ethylene perception or an ethylene-insensitive mutant, suggesting that, in addition to inhibiting BR, BRP activates ethylene response. Analysis of BRP analogs provided clues about structural features important for its effects on two separate targets in the BR and ethylene pathways. Analyses of the responses of various BR and ethylene mutants to BRP, ethylene, and BR treatments revealed modes of cross-talk between ethylene and BR in dark-grown seedlings. Our results suggest that active downstream BR signaling, but not BR synthesis or a BR gradient, is required for ethylene-induced apical hook formation. The BRP-related compounds can be useful tools for manipulating plant growth and studying hormone interactions.