Bridging receptors and microtubules in the control of plant growth – MICROBRIDGE

Directional cell growth is a critical determinant in plant developmental processes, together with cell division and differentiation. Plant hormones, a group of endogenous bioactive small molecules, are essential cell growth modulators. Among them, brassinosteroids (BRs) have vital activities for plant growth and cell elongation. BRs are perceived by a cell surface receptor, BRASSINOSTEROID INSENSITIVE 1 (BRI1), inducing transcriptional changes and reorganization of microtubule arrays that substantially affect anisotropic cell growth. Although genomic responses to BRs are well-characterized, how BRs impact on microtubule regulation is still largely unknown. Recently, our team explored new BRI1 interactors and identified a new family of proteins called DEPs that localize to cortical microtubules underlying the plasma membrane, strongly suggesting DEPs intimately interconnect BRI1 and BR signaling to microtubules.
The goal of MICROBRIDGE is to understand the reciprocal regulations between microtubules and the BRI1 receptor through DEPs. Preliminary results show that a combination of dep double mutants is hypersensitive to BR, suggesting that DEPs are indeed involved in BR signaling. By combining the coordinator’s and team’s expertise with state-of-the-art equipment in the laboratory, MICROBRIDGE aims at unraveling 1) molecular functions of DEPs in BR signaling, 2) the role of DEPs and BR signaling in the regulation of microtubules, 3) roles of microtubules and DEPs in the control of BRI1 dynamics at the plasma membrane by super-resolution microscopy. Finally, as a long-term goal, MICROBRIDGE will identify new DEP-interacting cell surface receptors to expand the concept of mutual regulation of microtubule-cell surface receptors in plants. Altogether, MICROBRIDGE will provide a molecular framework of crosstalks between two well-known growth regulators, uncovering a new mode of cell-surface receptor regulation and hinting at ways of plant engineering to improve key agricultural traits.