叶色突变体往往伴随着叶绿素含量变化及叶绿体结构异常, 是研究叶绿体发育与光合作用相关基因功能的重要材料。该研究通过甲基磺酸乙酯(EMS)诱变籼稻(Oryza sativa subsp. indica)品种华占(HZ)获得黄绿叶突变体, 将其命名为ygl18 (yellow-green leaf 18)。与野生型相比, 黄绿叶突变体ygl18自三叶期起叶片开始变黄且程度不断加深, 同时伴随着光合速率与叶绿素含量下降, 且结实率、千粒重及有效穗数均显著降低。透射电镜观察结果显示, ygl18的叶绿体结构紊乱, 基质片层疏松, 发育受到抑制, 与叶片出现黄绿色表型一致。遗传分析表明, ygl18突变性状受1对隐性等位核基因控制, 这对等位基因位于水稻第3号染色体长臂标记InDel2和InDel3之间115.2 kb范围内。进一步研究发现该突变体表型是编码铁氧还蛋白FdC2的基因LOC_Os03g48040的5'UTR发生突变所致。通过CRISPR转基因实验验证了该基因对表型的控制作用。研究结果揭示了叶色调控网络的遗传基础, 可为今后选育高光效水稻品种提供新线索。

Leaf color mutants are often accompanied by changes in chlorophyll content and abnormal chloroplast structure, and serve as essential materials for studying the functions of chloroplast development and photosynthesis-related genes. In this study, we obtained a yellow-green leaf mutant named yellow-green leaf 18 (ygl18) from Oryza sativa subsp. indica cv. ‘HZ’ with ethyl methanesulfonate (EMS). Compared with the wild type, the leaves of ygl18 turned yellow at three-leaf stage and the degree of yellowing increased as it grew, accompanied by decreasing photosynthetic rate and chlorophyll content. The seed-setting rate, 1 000-grain weight, and effective panicle number were significantly lower than those of the wild type. We observed disordered chloroplast structure, loose stromal lamellas, and stalled development in the mutant using transmission electron microscopy. Genetic analysis indicated that the mutant feature (or phenotype) of ygl18 is controlled by a pair of recessive nuclear alleles, which were located in a 115.2 kb region between markers InDel2 and InDel3 on the long arm of chromosome 3. We found mutations in the 5′UTR of LOC_Os03g48040 encoding FdC2 (ferredoxin C2). The gene’s function on controlling the mutant phenotype was verified using CRISPR transgenic experiments. Our results revealed a genetic basis for leaf color regulatory network and provide new clues for breeding photosynthetically efficient rice varieties in the future.