Research articleSuppression of the MADS-box gene SlMBP8 accelerates fruit ripening of tomato (Solanum lycopersicum)

•Gene SlMBP8 plays an important role in fruit ripening.•A yeast two-hybrid assay revealed a clear interaction between SlMBP8 and SlMADS-RIN.•Silencing of SlMBP8 reduces the storability of fruits.

MADS-box genes encode important transcription factors that are involved in many biological processes of plants, including fruit ripening. In our research, a MADS-box gene, SlMBP8, was identified, and its tissue-specific expression profiles were analysed. SlMBP8 was highly expressed in fruits of the B+4 stage, in senescent leaves and in sepals. To further characterize its function, an RNA interference (RNAi) expression vector of SlMBP8 was constructed and transferred into tomato. In the transgenic plants, the ripening of fruits was shortened by 2-4 days compared to that of wild type. At the same time, carotenoids accumulated to higher levels and the expression of phytone synthase 1 (PSY1), phytoene desaturase (PDS) and ς-carotene desaturase (ZDS) was enhanced in RNAi fruits. The transgenic fruits and seedlings showed more ethylene production compared with that of the wild type. Furthermore, SlMBP8-silenced seedlings displayed shorter hypocotyls due to higher endogenous ethylene levels, suggesting that SlMBP8 may modulates the ethylene triple response negatively. A yeast two-hybrid assay indicated that SlMBP8 could interact with SlMADS-RIN. Besides, the expression of ethylene-related genes, including ACO1, ACO3, ACS2, ERF1, E4 and E8, was simultaneously up-regulated in transgenic plants. In addition, SlMBP8-silenced fruits showed higher ethylene production, suggesting that suppressed expression of SlMBP8 promotes carotenoid and ethylene biosynthesis. In addition, the fruits of transgenic plants displayed more rapid water loss and decreased storability compared to wild type, which was due to the significantly induced expressions of cell wall metabolism genes such as PG, EXP, HEX, TBG4, XTH5 and XYL. These results suggest that SlMBP8 plays an important role in fruit ripening and softening.