THE ARABIDOPSIS TMK SUBFAMILY OF RECEPTOR-LIKE KINASES FUNCTIONS IN REGULATING CELL DIVISION PATTERN DURING LATERAL ROOT INITIATION

Abstract

During plant development, cell division orientation is the key to establish the three-dimensional structures/organs. Yet, the precise mechanisms underlying the programmed cell division pattern remain elusive. Here, we demonstrate that a subfamily of leucine-rich repeat (LRR) receptor-like kinases called Transmembrane Kinases (TMKs) is involved in regulating cell division pattern during lateral root initiation. Our study shows that TMK1, one of the members in this subfamily, regulates PIN1 polar localization in dividing cells during lateral root initiation. We provide the evidences that TMK1 exert its functions through two distinct mechanisms. TMK1 interacts with RhoGTPases to regulate PIN1 trafficking to the plasma membrane. In addition, TMK1 functions as a scaffold and recruits BASL, a novel regulator of asymmetric divisions, and its interacting mitogen-activated protein kinases (MAPK) cascade to spatially concentrate signalling on the plasma membrane. As a result, the downstream activated MPK6 phosphorylates PIN1 directly. Taken together, our results put forward an important role for TMKs in regulating division plane orientation throughout plant development.