Analysis of Colored Lesions of Chilli Yellow Ringspot Orthotospovirus Infection in Tomato Fruits

Chilli yellow ringspot orthotospovirus (CYRSV) causes colored lesions in tomato fruits. In this study, tomato fruits with different-colored lesions were used as experimental materials to explore the color formation mechanism. After CYSRV infection, the structure of chromoplasts inside the cells of tomato fruits was distorted and the number of plastoglobules per chromoplast significantly decreased, but the plastoglobule areas increased, as determined via ultrathin sectioning and transmission electron microscopy. Transcriptome and metabolome analyses revealed enrichment of secondary metabolites, carotenoids, and flavonoids in tomatoes with colored lesions. Metabolome analysis revealed markedly reduced carotenoid metabolites (lycopene and α-carotene) in both red-yellow and yellow tomatoes. The flavonoid metabolites rutin, catechin, and naringenin chalcone were markedly increased in the yellow group only. RT-qPCR analysis revealed that the expression of genes involved in carotenoid and flavonoid synthesis increased, but the expression of <i>C4H</i> decreased. Transcription regulators such as <i>AP2</i> and <i>MYB12</i> play important roles in flavonoid and carotenoid biosynthesis in CYRSV-infected tomato fruits. The results of greenhouse isolation experiments revealed that CYRSV may induce color lesions via decreases in plastoglobule numbers and chromoplast areas, the absence of carotenoid metabolites, and the presence of yellow-colored flavonoid metabolites. These results provide new insights into the interaction between CYRSV and tomato plants.