Does the brassinosteroid signal pathway in photomorphogenesis overlap with the gravitropic response caused by auxin

Brassinosteroid(BR) and auxin co-regulateplant growth in a process termed cross-talking. Based on the assumption that their signal transductionsare partially shared, inhibitory chemicals for both signal transductionswere screened from a commercially available library. A chemical designated as NJ15 (ethyl 2-[5-(3,5-dichlorophenyl)-1,2,3,4- tetrazole-2-yl]acetate) diminished the growth promotion of both adzuki bean epicotyls and Arabidopsis seedlings, by the application of either BR or auxin. To understand its target site(s), bioassays with a high dependence on the signal transductionof either BR (BR-signaling) or auxin(AX-signaling) were performed. NJ15 inhibited the photomorphogenesisof Arabidopsis seedlings grown in the dark, which mainly depends on BR-signaling, while NJ15 also inhibited their gravitropicresponses mainly depending on AX-signaling. On the study for the structure–activity relationships of NJ15 analogs, they showed strong correlations on the inhibitory profiles between BR- and AX-si...