BioProject

The capacity for sustained cell division is a critical determinant of plant meristem development, and ultimately, organ size. More...

The capacity for sustained cell division is a critical determinant of plant meristem development, and ultimately, organ size. This capacity is diminished in mutants lacking the microtubule-associated protein CLASP, and when brassinosteroid signaling is increased. Here, we discovered that CLASP is both targeted by and promotes activity of the brassinosteroid pathway in Arabidopsis root apical meristems. We show that enhanced brassinosteroid signalling reduces CLASP transcript and protein levels, and dramatically shifts microtubule organization to promote exit from the cell division cycle. Notably, CLASP sustains brassinosteroid signalling by fostering retrieval of endocytosed BRI1 receptors to the plasma membrane through the tethering of SNX1 vesicles to microtubules. clasp-1 null mutants have fewer BRI1 receptors, and impaired BR-mediated transcriptional activity and responses. Global transcript profiling confirmed the collapse of cell cycle activity in clasp-1 and revealed hormone crosstalk. Together, these findings reveal an unprecedented form of negative feedback that supports meristem homeostasis. Overall design: mRNA profiling of response of clasp-1 mutant and wild type root tips to epibrassinolide Less...