茉莉酸促进‘纽荷尔’脐橙果皮着色的分子机制

柑橘色泽调控对提高果实品质及商品价值有重要意义。β-柠乌素是影响‘纽荷尔’脐橙等柑橘果实色泽的重要类胡萝卜素，申请人前期发现茉莉酸能促进柑橘果皮着色，但其调控机制尚未明确。茉莉酸处理‘纽荷尔’脐橙上调β-柠乌素合成关键基因CsCCD4b及其关键转录因子CsMYC2表达，且CsMYC2能结合CsCCD4b启动子。基于此，本项目拟以‘纽荷尔’为材料，检测茉莉酸处理后柑橘果皮β-柠乌素含量变化；利用ChIP-PCR、LUC报告基因等实验明确CsMYC2对CsCCD4b等β-柠乌素合成基因启动子的结合与调控模式；在柑橘果皮及愈伤组织沉默及过表达CsMYC2，检测β-柠乌素含量及其合成基因表达变化，明确其在β-柠乌素合成中的功能，最终明确茉莉酸通过CsMYC2促进柑橘果皮β-柠乌素合成的分子机制。本项目实施对深入解析茉莉酸促进果实着色的机理以及人工调控柑橘果实着色具有重要的理论意义和实践应用价值。

Regulation of fruit peel color is important to improve fruit quality and value for citrus. The carotenoid β-citraurin greatly contributes to fruit coloration in ‘Newhall’ citrus. The applicant found jasmonate (MeJA) treatment to ‘Newhall’ citrus significantly promoted fruit peel coloration. However, the underlying mechanism of which jasmonate regulates β-citraurin biosynthesis is still unclear. The gene expression analysis showed that rate-limiting gene of β-citraurin synthesis CsCCD4b and key transcription factor CsMYC2 of jasmonate signaling were obviously induced by MeJA treatment. And CsMYC2 could bind the promoter of CsCCD4b. In this project, the ‘Newhall’ citrus will be used as material, β-citraurin content will be detected in control and MeJA treated fruit; The binding and regulation of CsMYC2 to promoters of CsCCD4b and other β-citraurin biosynthetic genes will be confirmed using chromatin immunoprecipitation assay, LUC reporter system et al. In addition, to reveal the role of CdMYC2 in β-citraurin biosynthesis, it will be over- and down-regulated in citrus fruit peel and calli, then the changes of β-citraurin biosynthetic genes and β-citraurin content will be detected. Collectively, these results will reveal the regulatory mechanism in CsMYC2 mediated citrus fruit coloration by jasmonate. This project will extend the knowledge of jasmonate promoted fruit coloration, and contribute to artificially regulate citrus fruit color.