Regulation of tomato fruit elongation by transcription factor BZR1.7 through promotion of gene expression.

Fruit shape is an important biological trait that is also of special commercial value in tomato. The gene has been known as a key regulator of tomato fruit elongation for years, but the molecular mechanisms underlying its transcriptional regulation remain little understood. Here, a unique BZR1-like transcription factor, BZR1.7, was identified as a -acting factor of the gene promoter that bound to the conserved E-box of the promoter to promote gene expression. Overexpression of in tomato led to elevated gene expression and formation of elongated fruits. Plants of the knockout mutant created by gene editing did not exhibit an observable fruit shape phenotype, suggesting possible functional redundancy of -like genes in tomato. There were seven -like genes in the tomato genome and overexpression of and led to elongated fruit phenotypes similar to those observed in the overexpression lines, further supporting the notion of functional redundancy of -like genes in tomato fruit shape specification. Microscopic analysis revealed that there was a decreased number of cell layers in the fruit pericarp in the overexpression lines. These findings offer new insights into the regulatory mechanism by which BZR1.7 promotes gene expression and regulates fruit elongation in tomato.