MAP65 proteins influence crop traits

The plant cytoskeleton is composed of microtubules and actin microfilaments that play instrumental roles in critical processes throughout the cell cycle, including cytokinesis and interphase cell expansion. To facilitate these processes, cytoskeletal polymers are organized into arrays decorated with numerous proteins that modulate array organization and function. Plant genomes contain multiple M icrotubule A ssociated P rotein 65 (MAP65) genes, and only a subset of MAP65’s have been functionally characterized. MAP65 proteins bind and crosslink adjacent microtubules in mitotic, cytokinetic, and interphase arrays in plant cells. The nomenclature used to name different MAP65 genes and subgroups is inconsistent between plant species, which hinders evaluation of MAP65 genes across different species. This review compares and clarifies the MAP65 naming systems to aid the transfer of information across plant species. Proteins in the MAP65–3 group may have a conserved cellular role in organizing the phragmoplast array needed for cytokinesis. Phragmoplasts are disorganized and cytokinesis is incomplete in Arabidopsis thaliana, Cucumis sativus, Oryza sativa, and Zea mays map65–3 loss-of-function mutants. However, the phenotypic severity of map65–3 alleles differs among species. For example, Os MAP65–3 is necessary for rice seedling growth and survival, while cucumber plants lacking Cs MAP65–3 appear wildtype but are less susceptible to Meloidogyne incognita infection. MAP65–1 proteins are involved morphogenesis, cold tolerance, and resistance to specific pathogens in Arabidopsis thaliana, Glycine max, and Solanum lycopersicon . Future studies in model and agricultural plants that better define MAP65 subgroups and evaluate the function of MAP65 proteins in multiple processes could be useful to inform the development of new crop strains.