Genome-wide identification, genomic organization and expression profiles ofSlARR-Bgene family in tomato

The type-B authentic response regulators (ARR-Bs) function as positive regulators of cytokinin signal transduction and play important roles in abiotic stress resistance and plant development. However, little of ARR-B family is known in tomato. In this study, we performed a comprehensive analysis of ARR-B family factors in tomato. In total, 12 genes encoding ARR-B transcription factors (named asSlARR-B1-SlARR-B12) were identified from tomato. We analyzed the structures, chromosome locations, phylogeny, protein motifs, and expression profiles of theseSlARR-Bgenes. Gene structure analysis showed that 5-12 exons and 4-11 introns existed in theSlARR-Bgenes. TheseSlARR-Bgenes were asymmetrically distributed on eight chromosomes in tomato. Phylogenetic tree ofSlARR-Bgenes from tomato and other plant species revealed thatSlARR-Bgenes were classified into 6 subfamilies. SlARR-B proteins had typical conserved domains, including Motif 1 and Motif 2. The investigation of the expression profiles ofSlARR-Bgenes in all the examined tissues demonstrated that these genes were differentially expressed, including roots, stems, leaves, flowers, and fruits at developmental stages. Notably, the expression ofSlARR-B11andSlARR-B12exhibited high expression levels in flowers. Each gene was induced by at least one of different phytohormones (SA, IAA, ABA, IBA, 6-BA, JA, GA, and ETH) and four abiotic stress treatments (heat, drought, salt, and cold). This study sets a good foundation for further characterization of theSlARR-Btranscription factors in plant development and abiotic stress responses of tomato.