No abstract

Plant cells are surrounded by rigid cell walls, and hence, their division is associated with a plant-specific mode of cytokinesis in which the cell plate, a new cell wall, is generated and separates 2 daughter nuclei. The successful execution of cytokinesis requires the timely activation of multiple regulatory pathways, which include the AtNACK1/ HINKEL kinesin-induced MAPK cascade and MYB3R1/4-mediated transcriptional activation of G2/M-specific genes. However, it remains unclear whether and how these pathways are functionally interconnected to each other. By analyzing enhancer mutations of myb3r4, here we found a close genetic interaction between the 2 pathways; a mutation in ANP3, which encodes MAPKKK (acting downstream of AtNACK1/HINKEL), strongly enhanced the defective cytokinesis observed in the myb3r4 mutant. This interaction may not be due to the direct activation of MYB3R1/4 by the MAPK cascade; rather, possibly to the downstream targets of these 2 signaling pathways, acting in close proximity. Our results showed that MYB3R1/4 may positively affect cytokinesis via multiple pathways, one of which may act independently from the KNOLLE-dependent pathway defined previously, and affect the downstream events that may also be under the control of the AtNACK1/HINKEL-mediated MAPK cascade.Unlike animals, plants typically have a rigid cell wall outside of each cell, which provides mechanical strength that sustains their shape and growth. Because of the presence of the cell wall, plants have evolved a unique mode of cytokinesis, which accompanies the generation of a new cell wall, called the cell plate. During cell division, a microtubule-based structure, the phragmoplast, appears between 2 separating daughter nuclei and fulfills functions that are essential for the accumulation and fusion of Golgi-derived vesicles at the equatorial region.1,2 The molecular mechanisms underlying the formation of the cell plate are largely unknown; however, recent genetic studies have revealed components of signaling pathways that are essential for the execution of cytokinesis in Arabidopsis thaliana. 2,3