Characterization of a dominant SmNac-like gene as a candidate for photosensitivity in the fruit peel of eggplant

Anthocyanins in the fruit peel of photosensitive eggplants exhibit a different distribution pattern compared to the photo-insensitive ones. The latter exhibits a uniform anthocyanin content, whereas photosensitive eggplants lack anthocyanin accumulation in areas not exposed to light, such as under the calyx, or have lower concentrations in less-exposed areas. In the current research work, genetic analysis of F1 and F2 populations revealed that the non-photosensitive phenotype in eggplants follows an autosomal dominant inheritance with a 3:1 ratio, indicating that the photosensitive trait is regulated by a single dominant gene. To locate and narrow down the position of the gene underlying photosensitivity, an F2 population segregating for photosensitivity and presence of anthocyanins was used for bulked segregant analysis sequencing (BSA-seq), and RNA-seq analysis of bagged photosensitive and non-photosensitive eggplants was performed. As a result, we identified the SmNAC1-like gene as a candidate for fruit photosensitivity trait in the eggplant materials used in this study. In the photo-insensitive eggplants (DH-ECAVI and IVIA-371) two different high-impact mutations were identified leading to light-insensitive and uniform anthocyanin content. The mutation in DH-ECAVI causes a premature stop codon, while in IVIA-371 an indel mutation occurs in the 3’-UTR sequence. No high-impact mutations were found in SmNAC1-like gene in photo-sensitive eggplants. These findings provide new insight into the regulation of the molecular mechanisms of anthocyanin biosynthesis in non-photosensitive eggplant and have important implications for marker-assisted selection and breeding.