Genome-wide mining of B-type cytokinin response regulators in wheat reveals the involvement of

Context Cytokinin response regulators (RRs) are important components of the two component signal systems that are involved in the regulation of plant growth and development, and in the response to abiotic stresses. Plant cytokinin response regulators (RR) were divided into type A and type B. A-type RR proteins act as negative feedback to regulate cytokinin signals, while B-type RRs could regulate A-type RR gene expression, and B-type RR genes have proved to play important roles in regulating cytokinin signal transduction in various biological processes. Aims We aimed to explore and analyse B-type RR genes in wheat in a preliminary fashion. Methods Using bioinformatics methods, wheat type B RR genes were identified, and type B Triticum aestivum RR (TaRR) genes were analysed using quantitative real-time polymerase chain reaction. In order to further analyse the function of TaRR, staining experiments were performed. Key results Twenty-nine B-type TaRR genes were identified in the wheat genome, divided into three groups according to their phylogenetic relationships. Chromosome mapping showed that 29 TaRRs were evenly distributed on 12 chromosomes, while there were no genes located on the other nine chromosomes, which may have experienced gene loss during evolution. The polymerase chain reaction results showed that TaRRs were significantly up-regulated under polyethylene glycol treatments. Under sodium chloride stress, TaRRs were up-regulated to varying degrees, reaching the maximum at 24 h. The study also found that the expression pattern of TaRRs was different in the root and leaf under different abiotic stresses. In addition, staining experiments also showed that TaRR5.1-6A could induce the self-defence function of leaves. Conclusions These results form the basis for further exploring the role of B-type TaRR genes in plant response to drought stress and salt stress. Implications This study lays the molecular biology foundation for the functional study of the B-type TaRR genes.