Promoter Variations Strongly Enhance the Transcription Level of the BoLMI1 Gene, Causing Lobed Leaves in Ornamental Kale (Brassica Oleracea L. Var. Acephala)

Background: Leaf shape is an important agronomic trait in ornamental kale ( Brassica oleracea L. var. acephala ). Although some leaf shape-related genes have been reported in ornamental kale, the detailed mechanism underlying leaf shape formation is still unclear. Here, we report a lobed-leaf trait in ornamental kale, aiming to analyze its inheritance and identify the strong candidate gene. Results: : Genetic analysis of F 2 and BC 1 populations demonstrate that the lobed-leaf trait in ornamental kale is controlled by a single dominant gene, termed BoLl-1 . By performing whole-genome resequencing and linkage analyses, the BoLl-1 gene was finely mapped to a 127-kb interval on chromosome C09 flanked by SNP markers SL4 and SL6, with genetic distances of 0.6 cM and 0.6 cM, respectively. Based on annotations of the genes within this interval, Bo9g181710 , an orthologous gene of LATE MERISTEM IDENTITY 1 ( LMI1 ) in Arabidopsis , was predicted as the candidate for BoLl-1 , and was renamed BoLMI1 . The expression level of BoLMI1 in lobed-leaf parent 18Q2513 was significantly higher compared with unlobed-leaf parent 18Q2515. Sequence analysis of the parental alleles revealed no sequence variations in the coding sequence of BoLMI1 , whereas a 1737-bp deletion, a 92-bp insertion and an SNP were identified within the BoLMI1 promoter region of parent 18Q2513. Verification analyses with BoLMI1 -specific markers corresponding to the promoter variations revealed that the variations were present only in the lobed-leaf ornamental kale inbred lines. Conclusions: : This study demonstrated that promoter variations strongly enhance the transcription level of BoLMI1 and cause the leaf shape change from unlobed to lobed, providing new insight into the molecular mechanism underlying leaf shape formation in ornamental kale.