contributes to leafy head formation by regulating leaf width in Chinese cabbage ( L. ssp. ).

Leafy head is an important agronomic trait that determines the yield and quality of Chinese cabbage. The molecular mechanism underlying heading in Chinese cabbage has been the focus of research, and wide leaves are a prerequisite for leafy head formation. In our study, two allelic leafy heading-deficient mutants ( and ) with narrow leaf phenotypes were screened in an ethyl methanesulfonate mutagenized population from a heading Chinese cabbage double haploid line 'FT'. Genetic analysis revealed that the mutant trait was controlled by a recessive nuclear gene, which was found to be by MutMap and Kompetitive allele-specific PCR analyses. As was the ortholog of in , which has been found to regulate leaf width by controlling cortical microtubule arrangement and pavement cell shape, we named it . in mutant carried an SNP (G to A) on intron 2 that co-segregated with the mutant phenotype, and disrupted the exon-intron splice junction generating intron retention and a putative truncated protein. in mutant carried an SNP (G to A) on exon 4 leading to a premature stop codon. The ectopic overexpression of restored normal leaf phenotype due to abnormal cortical microtubule arrangement and pavement cell shape in the mutant. However, transformation of did not rescue the phenotype. These results indicate that contributes to leafy head formation of Chinese cabbage.