Identification and Analysis of R2R3-MYB Genes in Sweet Potato Genome

The plant MYB is a transcription factor family large in number and with important functions. In this study, the MYB family genes were screened and identified via bioinformatic methods from the raw sequence of sweet potato ( Ipomoea batatas ) genome and the gene structure and function of R2R3-MYB were analyzed. The results showed that there were 88 R2R3-MYB genes with intact R2 and R3 conservative domains, which contained 8 and 9 highly conserved basic amino acids. The results of MEME analysis showed that there were 10 conserved motifs within the I. batatas R2R3-MYB protein sequences. For the I. batatas R2R3-MYB protein sequences, over 80% contained motif 1, motif 2, motif 3, motif 4, motif 5 and motif 7. The R2R3-MYB genes were distributed unevenly across the 15 chromosomes. The number of R2R3-MYB genes in chromosome No.5 was 15, which was the largest; the numbers of R2R3-MYB genes in chromosome No. 4 and 13 were both only 2, which was the smallest. Analysis of the sequence alignment showed that there were 6 pairs of interchromosomal duplication and there were 20 pairs of intrachromosomal duplication, 19 of which existed in clusters. The function prediction and categorization via sequence analysis showed that 44 R2R3-MYB genes of the I. batatas could be categorized to the 13 subgroups of the A. thaliana R2R3-MYB genes, which were involved in the responses to biotic stress and abiotic stress, anthocyanin biosynthesis, anther development, etc. Further analysis showed that 36 R2R3-MYB genes might play important roles in dealing with biotic stress and abiotic stress, 9 of which showed significant up/down-regulation under Fusarium oxysporum f. sp. batatas stress and 27 of which showed significant up/down-regulation under low temperature stress. The domains of I. batatas R2R3-MYB transcription factors were highly conservative, which contained highly conserved motifs within R2 and R3 domains. The phylogenetic tree and transcriptomics data analysis showed that some R2R3-MYB genes might play roles in growth and development, metabolism regulation, biotic stress and abiotic stress, which lent support to I. batatas breeding.