A one-bp deletion in BoDW1 encoding microtubule-associated kinase causes dwarfing in Brassica oleracea

Cabbage (Brassica oleracea var. capitata) is an important vegetable crop that is widely cultivated throughout the world. Plant height is a key agronomic trait in cabbage, influencing architecture and yield, and is mainly determined by cell division and stem expansion. Previously, we identified a natural cabbage dwarf mutant, 99-198dw, which displays compact plant architecture, shortened internodes, and small leaves with reduced cell numbers. However, the molecular mechanism underlying this trait remains unknown. In this study, we identified the causal gene Bodw1 using a map-based cloning approach. A 1-bp deletion in the eighth exon of BoDW1 resulted in the mutant phenotype. Knockdown and knockout of BoDW1 in wild-type cabbage lines via RNAi and CRISPR/Cas9 resulted in abnormal phenotypes observed in 99-198dw. BoDW1, homologous to the Arabidopsis gene RUNKEL, encodes a microtubule-associated kinase-like protein localized to microtubules and is mainly expressed in proliferating young tissues. Co-IP-MS, yeast two-hybrid, and BiFC showed that BoDW1 interacts directly with BoCDC48C, a key factor in membrane fusion at the cell division plane. Transcriptome analysis further identified differentially expressed genes associated with membrane fusion and cell plate formation. Our results suggest that BoDW1 probably regulates cabbage development by participating in cell division. Together, our study provides new insights into the molecular control of plant height.