RIN transcription factor plays an important role in ethylene biosynthesis of tomato fruit ripening.

BACKGROUND: The transcription factor RIN (Ripening Inhibitor) belongs to the MADS box family and regulates tomato ripening. Virus-induced gene silencing (VIGS) is a powerful tool for studying gene function and down-regulation of specific gene expression in plants. In this study, VIGS was employed in silencing the LeRIN gene to determine whether and how RIN transcription factor regulated gene expression of ethylene biosynthesis.

RESULTS: Tobacco rattle virus (TRV)-LeRIN (LeACS2, LeACS4, LeACO1) VIGS fruits significantly developed green colour phenotypes, whereas control fruits turned red normally. Strikingly, 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) and ACC oxidase (ACO) activities in the green sections of VIGS fruits were significantly lower than those in control fruits. Dissection of the silenced areas for analysis showed that silencing of LeRIN represses LeACS2, LeACS4 and LeACO1 expression, which consequently leads to inhibited ripening. In particular, the results indicated that RIN transcription factor binds to the promoter of LeACS4 in vitro and in vivo.

CONCLUSIONS: The syringe infiltration method of VIGS was successfully applied to silence the LeRIN, LeACS2, LeACS4 and LeACO1 genes in tomato fruits. In addition, the target genes of RIN transcription factor in ethylene biosynthesis were identified. The results are critical for understanding the mechanism of ethylene biosynthesis in tomato fruit ripening.