Abstract
In order to elucidate the interaction mechanism of BR and auxin, we examined the sensitivity of BL in several auxin mutants (axr1-3, axr1-12, axr2-1, tir1-1, aux1-7 and axr4-1) of Arabidopsis thaliana in hypocotyl and root elongation test. Only axr2-1 mutant was insensitive to BL in hypocotyls among tested mutants. The other mutants showed the same sensitivity of BL as wild type. Thus, in order to clarify whether BR biosynthesis changes in axr2-1 mutant, the levels of endogenous BRs were determined. Interestingly, endogenous 6-deoxotyphasterol of axr2-1 was remarkably accumulated. Furthermore, expression of BR biosynthetic genes was partially affected. Therefore, both sensitivity and biosynthesis of BRs changed in axr2-1. The results suggest that AXR2 protein, which is involved in auxin signaling, plays an important role in regulation of biosynthesis and signal transduction of BR directly or indirectly.
