Map-based cloning and characterization of yg-2, a gene conferring yellow-green leaf in tomato (Solanum lycopersicum)

Leaves play a critical role in plant growth and development, directly influencing crop yield through their essential functions in photosynthesis and respiration. This study employed inheritance analysis and gene mapping of an F₂ population derived from a cross between a spontaneous yellow-green leaf tomato mutant and a wild-type tomato line. The findings conclusively demonstrated that the yellow-green leaf trait is controlled by a single recessive gene. Subsequent fine-mapping localized this gene to a 270-kb region on chromosome 12 of the reference Heinz 1706 genome. Annotation and functional characterization of genes within this region indicated Solyc12g009470 (yg-2) as the primary candidate gene influencing the yellow-green phenotype trait. Sequencing analysis revealed a 49-bp deletion in the first exon of yg-2, resulting in suppressed yg-2 expression. This functional role was further confirmed through Solyc12g009470 gene editing in tomatoes. Moreover, comparative analyses of photosynthetic pigments and chloroplast ultrastructure revealed notable differences between the mutant and the wild-type lines. Furthermore, the mutant exhibited reduced photosynthetic rate and yield-related agronomic traits. These findings provide valuable insights into the molecular mechanisms underlying yellow-green leaf formation in tomatoes.