Fleshy fruits are vital to the human diet, providing essential nutrients, such as sugars, organic acids, and dietary fibers. RNA-binding proteins play critical functions in plant development and environment adaption, but their specific contributions to fruit development remain largely unexplored. In this study, we centered on the function of SlRBP1 in tomato fruit and reported an unexpected finding that SlRBP1 controls fruit size by regulating its targets SlFBA7 and SlGPIMT. Here, the fruit-specific silencing of SlRBP1 was achieved by artificial miRNA which subsequently led to a marked reduction of fruit size. Cytological analysis suggested that SlRBP1 silencing decreased cell division and expansion of fruit pericarp. Those key genes involved in cell development were significantly repressed in SlRBP1 knock-down mutants. Furthermore, native RNA immunoprecipitation sequencing deciphered 83 SlRBP1-binding target RNAs in fruit, including two targets that are highly expressed in fruit: SlFBA7 and SlGPIMT, which are involved in developing fruit. Indeed, silencing either SlFBA7 or SlGPIMT resulted in fruit size reduction identical to that seen with SlRBP1 silencing. These results suggest that SlRBP1 modulates fruit size through its targets SlFBA7 and SlGPIMT. Our findings provide novel perspectives on the molecular mechanisms though which RNA-binding proteins control fruit size.

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