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

[EN] The distribution of chlorophylls in eggplant (Solanum melongena) peel exhibits either a uniform pattern or an irregular green netting pattern. The latter, manifested as a gradient of dark green netting that is 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 used over 2300 individuals from different populations, including a multi-parent advanced generation inter-cross population for candidate genomic region identification, an F2 population for bulked segregant analysis by sequencing, and advanced backcrosses for edges-to-core fine-mapping, to identify SmGLK2 gene as responsible for the irregular netting in eggplant fruits. We 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 blot analysis and confocal microscopy observations. SmGLK2 has a major role in regulating chlorophyll biosynthesis in eggplant fruit peel.; SmGLK2 is the gene responsible for the irregular green netting pattern of eggplant fruit peel and can be of practical interest for widening the diversity of the fruit colour palette. This work has been funded by grants PID2021-128148OB-I00 funded by MCIN/AEI/10.13039/501100011033/and by 'ERDF A way of making Europe', PDC2022-133513-I00 funded by MCIN/AEI/10.13039/501100011033/and European Union Next Generation EU/PRTR, CIPROM/2021/020 from Conselleria d'Innovacio, Universitats, Ciencia i Societat Digital (Generalitat Valenciana, Spain), and by European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 677379 (G2P-SOL project: Linking genetic resources, genomes and phenotypes of Solanaceous crops). AA is grateful to Spanish Ministerio de Ciencia, Innovacion y Universidades for a predoctoral (FPU18/01742) contract. VB-F is grateful to Generalitat Valenciana for grant INVEST/2022/146, funded by European Union, Next Generation EU. SM would like to thank funding support from UPV and the Spanish Ministerio de Universidades under the program Maria Zambrano