DataSheet_1_A BrLINE1-RUP insertion in BrCER2 alters cuticular wax biosynthesis in Chinese cabbage (Brassica rapa L. ssp. pekinensis).xls

Glossiness is an important quality-related trait of Chinese cabbage, which is a leafy vegetable crop in the family Brassicaceae. The glossy trait is caused by abnormal cuticular wax accumulation. In this study, on the basis of a bulked segregant analysis coupled with next-generation sequencing (BSA-seq) and fine-mapping, the most likely candidate gene responsible for the glossy phenotype of Chinese cabbage was identified. It was subsequently named Brcer2 because it is homologous to AtCER2 (At4g24510). A bioinformatics analysis indicated a long interspersed nuclear element 1 (LINE-1) transposable element (named BrLINE1-RUP) was inserted into the first exon of Brcer2 in HN19-G via an insertion-mediated deletion mechanism, which introduced a premature termination codon. Gene expression analysis showed that the InDel mutation of BrCER2 reduced the transcriptional expression levels of Brcer2 in HN19-G. An analysis of cuticular waxes suggested that a loss-of-function mutation to BrCER2 in Chinese cabbage leads to a severe decrease in the abundance of very-long-chain-fatty-acids (> C28), resulting in the production of a cauline leaf, inflorescence stem, flower, and pistil with a glossy phenotype. These findings imply the insertion of the LINE-1 transposable element BrLINE1-RUP into BrCER2 can modulate the waxy traits of Chinese cabbage plants.

光泽度是大白菜（十字花科叶用蔬菜作物）的重要品质相关性状。该光泽性状由角质层蜡质异常积累所引发。本研究依托集群分离分析法结合高通量测序（bulked segregant analysis coupled with next-generation sequencing, BSA-seq）与精细定位技术，成功鉴定出控制大白菜光泽表型的最可能候选基因。该基因因与AtCER2（At4g24510）同源，遂被命名为Brcer2。生物信息学分析显示，HN19-G材料中，长散在核元件1（long interspersed nuclear element 1, LINE-1）类转座因子（命名为BrLINE1-RUP）通过插入介导的缺失机制插入至Brcer2的第一个外显子区域，该插入事件引入了一个提前终止密码子。基因表达分析表明，BrCER2的插入缺失（InDel）突变降低了HN19-G材料中Brcer2的转录表达水平。角质层蜡质检测结果显示，大白菜中BrCER2的功能丧失性突变会导致超长链脂肪酸（>C28）的含量显著下降，进而使植株的茎生叶、花序茎、花以及雌蕊呈现出光泽表型。上述研究结果表明，LINE-1类转座因子BrLINE1-RUP插入BrCER2基因，可调控大白菜植株的蜡质性状。