The adaxial–abaxial axes play a crucial role in normal leaf growth. While recent studies have explored the molecular mechanisms underlying these developmental processes, the functions of BELL homologous genes remain insufficiently understood. In this study, we demonstrate that silencing the SlBL4 gene in tomatoes ( Solanum lycopersicum cv. Micro-Tom) affects leaf polarity development. RNA sequencing (RNA-seq) analysis indicates that SlBL4 regulates numerous differentially expressed genes (DEGs) associated with leaf polarity, auxin transporters, LOB domain-containing proteins, chlorophyll accumulation, and chloroplast development. Furthermore, SlBL4 positively regulated the expression of SlGH3.1 , SlGH3.2 , and SlLOB4 genes associated with leaf growth polarity. These findings elucidate the roles of SlBL4 and propose a novel function for BELL genes in regulating plant leaf polarity.
Hu et al. (2026) studied this question.