Objective  To mine the sequence information of the β-amylase gene family of Ipomoea batatas genome, and analyze the structure and function of genes.

Method  Based on the whole genome sequence data of I. batatas cultivar ‘Taizhong 6’, the bioinformatic methods were applied to analyze the identified 12 members of the β-amylase gene family and conduct the domain conservation analysis, chromosomal localization, screening of potential duplication genes, conservative motif analysis, phylogenetic tree construction. The gene expression under low temperature stress was analyzed using the transcriptomics data.

Result  Twelve β-amylase genes were located on chromosomes No. 2, 4, 5, 6, 11, 12, 13 and 14 of I. batatas, and eight pairs showed potential duplication relationship. Multiple sequence alignment and functional domain search indicated that there were three highly conserved domains and 10 conservative motifs in the amino acid sequences of I. batatas β-amylase family. Phylogenetic trees of β-amylase proteins in I. batatas and other species showed that 62 β-amylase family members were divided into seven subgroups of S1−S7. The β-amylases of I. batatas were mainly distributed in the subgroups of S2, S4, S5, S6 and S7, most of which belonged to the same branches with Arabidopsis thaliana, Solanum tuberosum and S. lycopersicum. The results of transcriptomics data showed that six β-amylase genes expressed differentially during the low temperature storage period, of which two were up-regulated and four were down-regulated in ‘Xushu 15-1’, while only two genes were down-regulated in ‘Xushu 15-4’.

Conclusion  The β-amylases are a key class of starch hydrolyzing enzymes that play important roles in the degradation of starch into reducing sugars during the process of I. batatas growth, development and tuber storage stages. The sequences of the identified 12 sweet potato β-amylase genes provide data reference for further study on the biological functions of I. batatas β-amylase gene family.