GSE111716
TMK1-mediated transcriptional auxin signaling guides differential growth in plant
Auxin plays diverse and profound roles in plants, regulating essentially all aspects of plant growth and development. Yet how auxin achieves such functional diversity and specificity is largely unknown. Here, we address how different concentrations of auxin determine developmental responses through auxin signaling pathways, which are essential for differential growth including apical hook development. We showed that a high auxin concentration at concave side of the apical hook stimulated the C-terminus cleavage and cytosolic translocation of Transmembrane Kinase 1 (TMK1), which then phosphorylates non-canonical IAA32 and IAA34.  Surprisingly, and in contrast to the previous report that auxin degrades IAA proteins through the TIR1/AFB auxin receptor to regulate gene expression, here we found that non-canonical IAA32 and IAA34 proteins were stabilized by the high auxin concentration through TMK1 cleavage to negatively regulate gene expression and inhibit growth. Thus, we demonstrated that TIR1/AFB-independent transcriptional auxin signaling regulated growth inhibition in response to the high auxin concentration. Overall design: mRNA profiles of Col-0, tmk1-1 and iaa32iaa34 apical hook region