FUNCTIONAL GAIN OF FRUIT NETTED-CRACKING IN AN INTROGRESSION LINE OF TOMATO WITH HIGHER EXPRESSION OF THE FNC GENE

Fruit cracking is a major disorder that affects the integrity of fruit and reduces the commercial value of tomato and other fleshy fruit.Here,we have found a novel fruit'netted-cracking'(FNC)phenotype in tomato introgression line IL4-4 which is present in neither the donor parent(LA0716)nor the receptor parent(M82).An F2 population was generated by crossing IL4-4 with M82 to genetically characterize the FNC gene and this showed that a single dominant gene determined fruit netted-cracking.Further map-based cloning narrowed down the FNC locus to a 230 kb region on chromosome 4.Sequencing and annotation analysis show that FNC(Solyc04 g082540)was the most likely candidate gene.Functional characterization of FNC by overexpressing FNC^c and FNC1^resulted in the fruit netted-cracking phenotype,suggesting that the FNC transcript level results in the functional gain of fruit netted-cracking.These findings were further confirmed by FNC ortholog in netted-cracking pepper and melon,indicating a common regulatory mechanism in different plant species.Furthermore,cytoplasm and nucleus-localized FNC indicates increased expression of genes involved in suberin,lignin,lipid transport and cell wall metabolism.These findings provide novel genetic insights into fruit netted-cracking and offer a way to promote molecular improvement toward cracking resistant cultivars.