SlPRE2 is gibberellin inducible and mediates plant response to gibberellin. Silencing of SlPRE2 decreases tomato fruit size, pericarp thickness, placenta size and seed size by regulating cell expansion. Gibberellin is one of the crucial hormones essential for plant growth and developmental processes, including seed germination, stem elongation, and sex expression. Previous studies indicated gibberellin could control fruit development by regulation of genes downstream gibberellin pathway. In the present study, we found that the SlPRE2, a bHLH family transcription factor gene, is highly expressed in immature green fruit. Silencing of SlPRE2 caused reduction of fruits size, pericarp thickness, and placenta size. Meanwhile, smaller seeds were observed in SlPRE2 silenced lines. In addition, the SlPRE2-silenced fruit mesocarp had reduced cell size and expression of SlXTH2 and SlXTH5 which are involved in cell enlargement. Further research showed that SlPRE2 is gibberellic acid-inducible and the expression of gibberellin metabolism-related genes in immature green fruit was affected by the downregulation of SlPRE2. Moreover, the SlPRE2-silenced plants had changed responses to application of exogenous gibberellic acid and paclobutrazol, an inhibitor of gibberellin biosynthesis. These findings indicated that SlPRE2 is a regulator of fruit development and affects plant response to gibberellic acid via the gibberellin pathway.
Keywords: Cell expansion; Fruit size; Seed size; bHLH transcription factor.