Irregular green netting of eggplant fruit peel: a domestication trait controlled by SmGLK2 with potential for fruit colour diversification.

The distribution of chlorophylls in eggplant (Solanum melongena) peel exhibits either a uniform pattern or an irregular green netting. The latter, manifested as a gradient of dark green netting intensified in the proximal part of the fruit on a pale green background, is common in wild relatives and some eggplant landraces. Despite the selection of uniform chlorophylls during domestication, the netting pattern contributes to a greater diversity of fruit colours. Here, we have used over 2,300 individuals from different populations, including a multi-parental MAGIC population for candidate genomic region identification, an F2 population for BSA-Seq, and advanced backcrosses for edges-to-core fine-mapping, to identify SmGLK2 gene as responsible for the irregular netting in eggplant fruits. We have also analysed the gene sequence of 178 S. melongena accessions and 22 wild relative species for tracing the evolutionary changes that the gene has undergone during domestication. Three different mutations were identified leading to the absence of netting. The main causative indel induces a premature stop codon disrupting the protein conformation and function, which was confirmed by western blotting analysis and confocal microscopy observations. SmGLK2 has a major role in regulating chlorophyll biosynthesis in eggplant fruit peel.