Identification and characterization of the BEL1-like genes reveal their potential roles in plant growth and abiotic stress response in tomato

BEL1-like (BELL) transcription factors, belonging to three-amino acid-loop-extension (TALE) superfamily, are ubiquitous in plants. BELLs regulate a wide range of plant biological processes, but the understanding of the BELL family in tomato (Solanum lycopersicum) remains fragmentary. In this study, a total of 14 members of the SlBELL family were identified in tomato. SlBELL proteins contained the conserved BELL and SKY domains that served as typical structures of the BELL family. Syntenic analysis indicated that the BELL orthologs between tomato and other dicots had close evolutionary relationships. Furthermore, the promoters of SlBELLs contained numerous cis-elements related to plant growth, development, and stress response. The SlBELL genes exhibited different tissue-specific expression profiles and responded to cold, heat, and drought stresses, implying their potential functions in regulating multiple aspects of plant growth, as well as in response to abiotic stresses. Through the interaction network prediction, we found that most SlBELL proteins displayed probable interactions with the KNOTTED1-like (KNOX) proteins, another kind of transcription factor in the TALE superfamily. These findings laid foundations for further dissection of the functions of SlBELL genes in tomato, as well as for exploration of the evolutionary relationships of BELL homologs among different plant species.