Genome-wide analysis of the MADS-box gene family in Rhododendron hainanense Merr. and expression analysis under heat and waterlogging stresses

The MADS-box transcription factor gene family plays an important role in the growth and development of plants as well as in biotic and abiotic stress. We conducted a genome-wide identification of the members of the MADSbox family of Rhododendron hainanense to determine the molecular evolutionary characteristics of the MADS-box gene family and the expression profile of this gene family under different abiotic stress conditions. A total of 55 MADS-box gene family members with complete domains were identified, which were unevenly distributed on 13 chromosomes. The construction of a phylogenetic tree showed that the 55 MADS-box proteins were divided into five categories and distributed on 8 chromosomes unevenly. Conserved motif analysis shows that motif 1 and motif 2 are highly conserved in most RhMADS proteins. Proteins belonging to the same category show similar gene structures. Analysis of gene replication events suggested that there were one pair of tandem repeats and eight pairs of fragment repeat events. In addition, analysis of cis-acting elements and protein interaction networks indicated that some genes are involved in abiotic stress processes in plants. The transcriptome data were used to analyze the expression of the members of the MADS-box family under different temperatures and waterlogging period treatments, which were then verified by qRT-PCR. The expressions of RhMADS24, RhMADS25, RhMADS39 and RhMADS44 were significantly regulated under temperature and waterlogging stresses. The identified MADS-box candidate genes of R. hainanense play an important role in resisting abiotic stress and lay the foundation for future applications in breeding and gardening.