Genome-wide analyses of the NAC transcription factor family to reveal the potential candidate genes responding to powdery mildew in balsam pear

Powdery mildew (PM) is the most serious disease in balsam pear and usually causes severe yield and quality decreases. Although NAC transcription factors involved in the growth, development, and regulation of biotic and abiotic stress responses have been published for many crops, comprehensive data regarding the structure, evolution, and functions of the NAC family in balsam pear are still unavailable. In this study, a comprehensive analysis of the NAC transcription factor family in balsam pear was performed, and 90 NAC genes of balsam pear ( McNAC ) were identified and divided into 18 subfamilies. Gene structure and protein motif analyses revealed that the functions of McNAC proteins exhibit diversity during evolution and are mainly involved in the response to light, growth, development, and abiotic and biotic stresses. Fifteen McNAC genes ( McNAC03 , McNAC09 , McNAC15 , McNAC19 , McNAC25 , McNAC29 , McNAC34 , McNAC47 , McNAC55 , McNAC59 , McNAC61 , McNAC69 , McNAC71 , McNAC73 , and McNAC78 ) were differentially expressed after PM pathogen infection. Moreover, the predicted interacting proteins of 7 genes ( McNAC09 , McNAC15, McNAC25, McNAC29, McNAC34, McNAC73, and McNAC78 ) were related to the plant hormone signal transduction, betalain biosynthesis, and sphingolipid metabolism pathways by transcriptomic data, implying that the 7 genes participated in PM pathogen infection through these pathways. Metabolome data showed that nine metabolites in the same pathways were changed after PM infection, which suggests that these 7 McNAC genes could regulate these metabolites through the pathways mentioned above to respond to PM infection. The expression levels of McNAC09 , McNAC15 , McNAC25 and McNAC34 were further confirmed by qPCR to show the reliability of the obtained RNA-seq data. Interestingly, McNAC34 was predicted to be targeted by miRNA164, indicating that McNAC34 might be involved in the response to PM infection by the miRNA-regulated pathway. This study will provide deep insight into NAC gene family evolution and functions, especially in the response to PM pathogen infection in balsam pear.