Genome-Wide Analysis of Citrus <i>R2R3MYB</i> Genes and Their Spatiotemporal Expression under Stresses and Hormone Treatments

<div><p>The R2R3MYB proteins represent one of the largest families of transcription factors, which play important roles in plant growth and development. Although genome-wide analysis of this family has been conducted in many species, little is known about <i>R2R3MYB</i> genes in citrus, In this study, 101 <i>R2R3MYB</i> genes has been identified in the citrus (<i>Citrus sinesis</i> and <i>Citrus clementina</i>) genomes, which are almost equal to the number of rice. Phylogenetic analysis revealed that they could be subdivided into 21 subgroups. The evolutionary relationships and the intro-exon organizations were also analyzed, revealing strong gene conservation but also the expansions of particular functional genes during the plant evolution. Tissue-specific expression profiles showed that 95 citrus <i>R2R3MYB</i> genes were expressed in at least one tissue and the other 6 genes showed very low expression in all tissues tested, suggesting that citrus <i>R2R3MYB</i> genes play important roles in the development of all citrus organs. The transcript abundance level analysis during abiotic conditions (NaCl, abscisic acid, jasmonic acid, drought and low temperature) identified a group of <i>R2R3MYB</i> genes that responded to one or multiple treatments, which showed a promising for improving citrus adaptation to stresses. Our results provided an essential foundation for the future selection of the citrus <i>R2R3MYB</i> genes for cloning and functional dissection with an aim of uncovering their roles in citrus growth and development.</p></div>