Genome-wide systematic survey and analysis of NAC transcription factor family and their response to abiotic stress in sweetpotato

Abstract

Sweetpotato is a pivotal crop that can tolerate various edaphic and climatic conditions. The plant-specific NAC transcription factors are involved in regulating various adverse environmental conditions, while currently NAC genes have not been systematically characterized in sweetpotato. Herein, 175 putative NAC or NAC-like genes (IbNACs) were identified in sweetpotato. These genes were unevenly scattered onto all 15 chromosomes, among which 12 pairs of tandem duplications and 12 groups of fragment duplications existed. The collinearity analysis between IbNACs and the related orthologs from nine other plant species further depicted evolutionary insights into NAC gene family. Phylogenetic analysis displayed that IbNAC proteins were classified into 22 subfamilies including four sweetpotato-specific subfamilies, with the support of gene structure and motif analyses. Transcriptome analysis showed that IbNAC genes differed significantly in expression under salt stress, and significant and varying expression of ten selected genes under multiple abiotic stresses was detected by qRT-PCR. Moreover, IbNAC006 and IbNAC143, which were significantly induced by abiotic stress, exhibited obvious transactivation activities, while IbNAC-029/-138/-148 did not. These results will lay the foundation for further evolutionary analysis and functional characterization of IbNACs, particularly with regards to the potential applications of multiple IbNAC regulators in the breeding of tolerant sweetpotato.