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Abstract
背景回顾：Chlorophyll degradation and carotenoid biosynthesis, which occur almost simultaneously during fruit ripening, are essential for the coloration and nutritional value of fruits.
提出问题：However, the synergistic regulation of these two processes at the transcriptional level remains largely unknown.
主要发现：Here, we identified a WRKY transcription factor, CrWRKY42, from the transcriptome data of the yellowish bud mutant ‘Jinlegan’ [(Citrus unshiu × C. sinensis) × C. reticulata] tangor (MT) and its wild type ‘Shiranuhi’ tangor (WT), which was involved in the transcriptional regulation of both chlorophyll degradation and carotenoid biosynthesis pathways.
结果1-WRKY42-类胡萝卜素合成：CrWRKY42 directly bound to the promoter of β-carotene hydroxylase 1 (CrBCH1) and activated its expression. Overexpression and interference of CrWRKY42 in citrus calli demonstrated that CrWRKY42 promoted carotenoid accumulation by inducing the expression of multiple carotenoid biosynthetic genes. Further assays confirmed that CrWRKY42 also directly bound to and activated the promoters of the genes involved in carotenoid biosynthesis, including phytoene desaturase (CrPDS) and lycopene β-cyclase 2 (CrLCYB2).
结果2-WRKY42-叶绿素降解：In addition, CrWRKY42 could bind to the promoters of NONYELLOW COLORING (CrNYC) and STAY-GREEN (CrSGR) and activate their expression, thus promoting chlorophyll degradation. Overexpression and silencing of CrWRKY42 in citrus fruits indicated that CrWRKY42 positively regulated chlorophyll degradation and carotenoid biosynthesis by synergistically activating the expression of genes involved in both pathways.
结论：Our data revealed that CrWRKY42 acts as a positive regulator of chlorophyll degradation and carotenoid biosynthesis to alter the conversion of citrus fruit color. Our findings provide insight into the complex transcriptional regulation of chlorophyll and carotenoid metabolism during fruit ripening.
摘 要
叶绿素降解和类胡萝卜素合成在果实成果过程中几乎同时进行，对于果实的着色以及营养价值至关重要。但是，这两个进程在转录层面上是如何协同调控的还不清楚。本文中，作者通过比较一个淡黄色芽变品种‘金乐柑’及其野生型‘不知火’中的比较转录组，鉴定到一个同时参与叶绿素降解和类胡萝卜素生物合成途径转录调控的WRKY转录因子，即CrWRKY42。CrWRKY42能够直接结合到β-胡萝卜素羟化酶编码基因CrBCH1的启动子上，激活该基因的表达。通过在柑橘愈伤组织中过表达和干扰表达CrWRKY42基因，显示CrWRKY42能够通过诱导多个类胡萝卜素生物合成基因的表达来促进类胡萝卜素的积累。进一步的研究显示，CrWRKY42还能够直接结合到八氢番茄红素合酶编码基因CrPDS和番茄红素β-环化酶编码基因CrLCYB2的启动子上，激活这些基因的表达。另外，CrWRKY42能够结合到CrNYC和CrSGR基因的启动子上，激活这些基因的表达以促进叶绿素的降解。在柑橘果实中过表达和沉默CrWRKY42基因显示，CrWRKY42能够通过转录调控基因表达来正调控叶绿素的降解和类胡萝素的生物合成。本文的研究结果显示CrWRKY42作为叶绿素降解和类胡萝卜素生物合成的正调控因子，改变柑橘果实颜色的转变。本文的发现为果实成熟过程中叶绿素和类胡萝卜素代谢的复杂转录调控提供了新的视野。
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个人简介：
1978-1981年，湖南农业大学，学士；
1982-1984年，华中农业大学，硕士；
1985-1987年，华中农业大学，博士。
研究方向：
1）种质资源挖掘与利用：野生柑橘资源的收集评价，芽变材料的筛选鉴定，新品种选育；
2）种质创新与遗传改良：杂交群体创建，遗传连锁图谱构建，纯系创制，遗传转化及功能基因组平台构建；
3）果实色泽形成机理与调控：红肉突变体性状形成机理解析，类胡萝卜素代谢调控关键基因挖掘，质体发育分化，类胡萝卜素代谢工程；
4）柑橘生殖生物学研究：单/多胚性状形成机理解析；
5）产业宏观问题研究：现代农业产业体系运行机制，产业安全及可持续发展研究。
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