Abstract
Here, we analyzed axr2/iaa7 and axr3/iaa17 mutants mainly in BR-mediated gene expression. Either of BR- and auxin-induction of IAA5 and IAA19 gene expression was inhibited in both axr2 and axr3 mutants. The inhibition was observed in 7-day-old seedlings, but not in 14-day-old seedlings. In the axr2, auxin induction of the SAUR-AC1 gene expression was inhibited, whereas BR induction of that was not inhibited. Histochemical staining of pSAUR-AC1-GUS was lost in hypocotyl of the axr2. Consistently with this finding, BR induction of hypocotyl elongation was lost in the axr2. The expressions of BR-biosynthetic genes were higher in the axr2 than in WT in 7-day-old seedlings, but some of them were normal in 20-day-old seedlings of the axr2. We also identified genes regulated by axr2 using GeneChip analysis. These results suggested that the IAA proteins regulate expression of each BR-regulated gene in an organ- and a growth-stage-specific manner.
