Rapid identification of the BjRCO gene associated with lobed leaves in Brassica juncea via bulked segregant RNA-seq

Leaf morphology varies significantly among Brassica juncea . However, little is known regarding the causal gene that controls lobed leaf shape in B. juncea . In our study, the BjRCO gene, which is associated with leaf morphological variation, was cloned from chromosome A10 in B. juncea via BSR-seq. Blast analysis suggested that the BjRCO encodes a HD-Zip I transcription factor, which may serve as a positive regulator of lobed leaf formation in leaf mustard. Interestingly, the lobed leaf genes reported in the related species of Brassica ( B. rapa , B. napus , and B. juncea ) were located in A10. Phylogenetic analysis showed that BjRCO was also homologous to the lobed leaf gene BoLl reported on chromosome 9 in B. oleracea . In addition, qRT-PCR results showed that the expression levels of the BjRCO gene were higher expressed in the inner small lobed leaves than in the little sawtooth-like leaves (LSL). These results of this study indicate that the BjRCO gene is related to lobed leaf formation in B. juncea . These findings help to establish a solid foundation for future research investigating the molecular mechanism governing lobed leaf formation in B. juncea .