Genome-wide characterization of the β-galactosidase gene family and functional analyses reveal CaBGAL14-regulated pepper (Capsicum annuum L.) fruit cracking

Fruit cracking in pepper (Capsicum annuum L.) constitutes a significant issue that affects its quality and commercial value. Our previous RNA-seq data analysis revealed that many β-galactosidase genes were differentially expressed between normal and cracked fruits; however, their involvement in pepper fruit cracking remains poorly understood. Therefore, it is necessary to systematically investigate the β-Gal family genes and their functions in the pepper fruit cracking process. In this study, we identified 17 β-Gal family genes in pepper, designated CaBGAL1-17, which were classified into seven subfamilies based on phylogenetic analysis. The expression levels of CaBGALs in different organs, as well as during several developmental stages and fruit cracking, were assessed via qRT-PCR. Notably, CaBGAL14 was highly expressed in fruits exhibiting no cracking, with a 90-fold higher expression level compared to cracked fruits. Moreover, the function of CaBGAL14 in pepper fruit cracking was verified. We performed Agrobacterium-mediated transient overexpression and virus-induced gene silencing of CaBGAL14 in the pepper cultivar ‘L92’. Compared with the control fruit, the CaBGAL14-silenced fruits exhibited a higher fruit cracking rate, and had a thinner cuticle and more loosely arranged epidermal layer cells. Conversely, the transient overexpression of CaBGAL14 reduced the fruit cracking rate, resulting in a thicker cuticle, higher CDTA -Na2 soluble pectin content, and increased β-Gal activity. This study provides a reference for further elucidating the molecular mechanisms underlying fruit cracking.