Postembryonic developmental roles of the Arabidopsis KEULE gene

Cytokinesis in plant cells begins with the fusion of vesicles that transport cell wall materials at the center of the cell division plane, where the cell plate forms and expands radially until it fuses with the parental cell wall at the preprophase band. Vesicle fusion is facilitated by trans-SNARE complexes, with assistance from Sec1/Munc18 (SM) proteins. The SNARE protein KNOLLE and the SM protein KEULE are required for membrane fusion at the cell plate. Due to the crucial function of KEULE, all Arabidopsis (Arabidopsis thaliana) keule mutants identified to date are seedling lethal. Here, we identified the Arabidopsis serrata4-1 (sea4-1) and sea4-2 mutants, which carry recessive, hypomorphic alleles of KEULE. Homozygous sea4-1 and sea4-2 plants are viable and fertile but exhibit smaller rosettes and fewer leaves at bolting than the wild type. Their leaves are serrated, small, and undulated, with a complex venation pattern, develop necrotic patches, and undergo premature senescence. We established a likely relationship between these phenotypes and their defects in cytokinesis through reduced cell wall integrity and increased unfolded protein response. These findings shed light on the roles of KEULE in postembryonic development, particularly in the patterning of rosette leaves and leaf margins.