RNA interference-induced silencing of the SlHSP17.7 gene delays fruit ripening in tomato

Delayed ripening in tomato (Solanum lycopersicum L.) increases the supply of fruit during the growing season. Small heat shock proteins (sHSPs) are expressed during specific periods of plant growth and development. SlHSP17.7 gene is specifically expressed at different stages of fruit ripening; however, the mechanism by which SlHSP17.7 (Solyc06g076540.1.1) regulates tomato fruit ripening remains unclear. SlHSP17.7-RNA interference (RNAi) lines were already generated from Solanum chmielewskii in previous study. The transverse diameter, vertical diameter, average single fruit weight, and abscisic acid (ABA) levels of all fruit remarkably decreased. The fruit became hard at the mature-green stage, and the hardness gradually decreased as the fruit ripened. The expression of fruit softening-related genes significantly increased from the mature-green to completely mature stages. Silencing SlHSP17.7 through RNAi delayed ripening by 10 days. These results suggest that SlHSP17.7 may delay fruit ripening by regulating the ABA content. This study provides a new theoretical basis for regulating fruit ripening by sHSPs and broadens the understanding of the regulation pathways of fruit ripening.