PIN2 - tossed and turned: Brassinosteroid signaling delimits root gravitropism via sorting of the Arabidopsis PIN2 auxin transporter
(Institute of Experimental Botany of Academy of Sciences of Czech Republic, Laboratory of Hormonal Regulations in Plants)
Crosstalk between brassinolide and auxin signaling shapes plant development, and brassinolide signaling has been implicated in sorting and steady-state level control of root-specific PIN2. However, mechanisms orchestrating such post-transcriptional control and its significance for auxin transport remained obscure. By using a constitutively endocytosed allele of PIN2, we demonstrate that brassinolide modulates vacuolar degradation of PIN2, specifically in gravity-responding roots. Assessment of crosstalk between brassinolide and PIN2 sorting, together with modeling of auxin flow in gravistimulated roots, revealed a mechanism, by which brassinolide delimits root curvature via differential sorting of PIN2.