Genome-wide identification of the Pyrus R2R3-MYB gene family and PhMYB62 regulation analysis in Pyrus hopeiensis flowers at low temperature

The R2R3-MYB gene family play an important role in plant growth, development and stress responses. In this study, a total of 122 PcoR2R3-MYB genes were identified and grouped into 26 clades in pear. And these PcoMYBs were unevenly distributed among 17 chromosomes. The sequence characteristics, conversed motifs, exon/intron structures, classification, duplication events and cis-acting elements were also investigated. The gene duplication events showed that segmental duplication may play key roles in expansion of the PcoMYB gene family. Pyrus hopeiensis, which is a valuable wild resource, has strong cold resistance. An integrative analyses of miRNA and mRNA showed that PhMYB62 was involved in regulating low-temperature stress in P. hopeiensis flower organs. Subcellular localization analysis showed that PhMYB62 protein was specifically localized to the nucleus. The result of DAP-seq showed that PhMYB62 responded to low-temperature stress in P. hopeiensis by regulating TFs, which were associated with plant stress resistance, and POD, GAUT12, AUX28 and CHS genes. Subsequently, yeast one-hybrid verified that PhMYB62 could bind and activate the promoter of POD gene. The current study would provide a comprehensive information for further functional research on the stress-responsive R2R3-MYB gene candidates in pear, and may help to identify the genes associated with cold resistance for the cultivation of cold-resistant pear varieties.