Yu Hui-Wen, Lu Zhi-Hao, Wang Xia, Liu Dan, He Jia-Xian, Jiang Xiao-Lin, Ke Ling-Jun, Guo Wen-Wu, Deng Xiu-Xin, Xu Qiang
Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, 430070, China.
Key Laboratory of Landscape Plants with Fujian and Taiwan Characteristics of Fujian Colleges and Universities, Minnan Normal University, Zhangzhou, 363000, China.
Sci China Life Sci. 2021 Jul;64(7):1165-1173. doi: 10.1007/s11427-020-1790-0. Epub 2020 Sep 29.
Delayed greening of young leaves is an unusual phenomenon of plants in nature. Citrus are mostly evergreen tree species. Here, a natural mutant of "Guanxi" pummelo (Citrus maxima), which shows yellow leaves at the young stage, was characterized to identify the genes underlying the trait of delayed leaf greening in plants. A segregating population with this mutant as the seed parent and a normal genotype as the pollen parent was generated. Two DNA pools respectively from the leaves of segregating seedlings with extreme phenotypes of normal leaf greening and delayed leaf greening were collected for sequencing. Bulked segregant analysis (BSA) and InDel marker analysis demonstrated that the delayed leaf greening trait is governed by a 0.3 Mb candidate region on chromosome 6. Gene expression analysis further identified a key candidate gene (Citrus Delayed Greening gene 1, CDG1) in the 0.3 Mb region, which showed significantly differential expression between the genotypes with delayed and normal leaf greening phenotypes. There was a 67 bp InDel region difference in the CDG1 promoter and the InDel region contains a TATA-box element. Confocal laser-scanning microscopy revealed that the CDG1-GFP fusion protein signals were co-localized with the chloroplast signals in the protoplasts. Overexpression of CDG1 in tobacco and Arabidopsis led to the phenotype of delayed leaf greening. These results suggest that the CDG1 gene is involved in controlling the delayed leaf greening phenotype with important functions in chloroplast development.
幼叶延迟变绿是自然界中植物的一种异常现象。柑橘大多是常绿树种。在此，对“琯溪”蜜柚（Citrus maxima）的一个自然突变体进行了表征，该突变体在幼龄期表现为黄叶，以鉴定植物中延迟叶片变绿性状的潜在基因。构建了一个以该突变体为母本、正常基因型为父本的分离群体。分别从具有正常叶片变绿和延迟叶片变绿极端表型的分离幼苗叶片中收集两个DNA池进行测序。混合分离群体分析（BSA）和InDel标记分析表明，延迟叶片变绿性状由6号染色体上一个0.3 Mb的候选区域控制。基因表达分析进一步在0.3 Mb区域鉴定出一个关键候选基因（柑橘延迟变绿基因1，CDG1），该基因在具有延迟和正常叶片变绿表型的基因型之间表现出显著差异表达。CDG1启动子存在67 bp的InDel区域差异，且该InDel区域包含一个TATA盒元件。共聚焦激光扫描显微镜显示，CDG1 - GFP融合蛋白信号与原生质体中的叶绿体信号共定位。CDG1在烟草和拟南芥中的过表达导致了叶片延迟变绿的表型。这些结果表明，CDG1基因参与控制延迟叶片变绿表型，在叶绿体发育中具有重要功能。
