SlGH9-15 regulates tomato fruit cracking with hormonal and abiotic stress responsiveness cis-elements

Fruit cracking occurs easily during the late period of fruit development when plants encounter an unsuitable environment,dramatically affecting fruit production and marketing.This study conducted the bulked segregant RNA-Seq(BSR)to identify the key regulatory gene of fruit cracking in tomatoes.BSR-Seq analysis illustrated that two regions associated with irregularly cracking were located on chromosomes 9 and 11,containing 127 candidate genes.Further,through differentially expression analysis and qRT-PCR in cracking-susceptible and cracking-resistant genotypes,the candidate gene SlGH9-15(Solyc09g010210)with significantly differential expression levels was screened.Bioinformatics analysis of the GH9 gene family revealed that 20 SlGH9 genes were divided into three groups.The phylogenetic analysis showed that SlGH9-15 was closely related to cell wall construction-associated genes AtGH9B1,AtGH9B6,OsGH9B1,and OsGH9B3.The cis-acting elements analysis revealed that Sl GH9-15 was activated by various hormones(ethylene and ABA)and abiotic stresses.The expression pattern indicated that 13 SlGH9 genes,especially SlGH9-15,were highly expressed in the cracking-susceptible genotype.Its expression level gradually increased during fruit development and achieved maximum value at the red ripe stage.Additionally,the cracking-susceptible tomato showed higher cellulase activity and lower cellulose content than the cracking-resistant tomato,particularly at the red ripe stage.This study identified SlGH9-15 as a key gene associated with fruit cracking in tomatoes for the first time and gives new insights for understanding the molecular mechanism and complex regulatory network of fruit cracking.