Leaf-color mutations have been studied extensively in plants. However, to better understand the complex mechanisms underlying the formation of leaf color, it is essential to continue discover novel genes involved in the process of leaf color development. In this study, we identified a variegated-leaf (vg) mutant in tomato that exhibited defective phenotypes in thylakoids and photosynthesis. To clone the vg locus, an F₂ population was constructed from the cross between the vg mutant (Solanum lycopersicum) and the wild tomato LA1589 (S. pimpinellifolium). Using the map-based cloning approach, the vg locus was mapped on chromosome 7 and narrowed down to a 128 kb region that contained 21 open reading frames (ORFs). The expression levels of ORF9, ORF10, and ORF13 were significantly lower in vg than in the wild-type plants, while the ORF11 transcript level was elevated in vg. We then mutagenized ORF9, ORF10, and ORF13 by the CRISPR/Cas9 system in the wild-type tomato background and found that only the ORF10 mutation reproduced the phenotype of variegated leaves, indicating that ORF10 represents VG and its down-regulated expression was responsible for the variegated leaf phenotype. ORF10 encodes a thylakoid formation protein and its mutant lines showed reduced levels of chlorophyll synthesis and photosynthesis. Taken together, these results suggest that VG is necessary for chloroplast development, chlorophyll synthesis, and photosynthesis in tomato.

叶色突变已在植物中得到广泛研究。然而，为了更好地了解叶色形成的复杂机制，有必要继续发现参与叶色发育过程的新基因。在这项研究中，我们在番茄中发现了一个杂色叶 ( vg ) 突变体，该突变体在类囊体和光合作用中表现出缺陷表型。为了克隆vg基因座，从vg突变体 ( Solanum lycopersicum ) 和野生番茄 LA1589 ( S. pimpinellifolium )之间的杂交构建了F _2群体。使用基于地图的克隆方法，vg基因座被映射到 7 号染色体上，并缩小到包含 21 个开放阅读框 (ORF) 的 128 kb 区域。ORF9、ORF10 和 ORF13 的表达水平在vg中显着低于野生型植物，而 ORF11 转录物水平在vg中升高。然后我们在野生型番茄背景下通过 CRISPR/Cas9 系统对 ORF9、ORF10 和 ORF13 进行诱变，发现只有 ORF10 突变重现了杂色叶的表型，表明 ORF10 代表 VG，其下调表达负责杂色叶表型。ORF10 编码类囊体形成蛋白，其突变系显示叶绿素合成和光合作用水平降低。综合起来，这些结果表明VG是番茄叶绿体发育、叶绿素合成和光合作用所必需的。