Brassinosteroid selectively regulates PIN gene expression in Arabidopsis.

When brassinosteroid (BR)-deficient mutant (det2) or wild-type (WT) seedlings were treated with brassinolide (BL), the most active BR, for 3 h, the abundance of PIN4 and PIN7 transcripts decreased, and there were fewer PIN4 and PIN7 transcripts in det2 than in the WT. This suggests that BL selectively regulates the PIN gene in a complex manner.