Identification and Expression Analysis of NAC Gene Family in Weeping Trait of Lagerstroemia indica

Lagerstroemia indica is a widely used ornamental plant in summer gardens because of its desirable plant shape. The weeping traits of plants are related to secondary cell wall thickness and hormone signaling. NAC (NAM-ATAF1/2-CUC2), as one of the plant-specific transcription factors, is a switch for the secondary cell wall and also involved in leaf senescence, phytohormone signaling, and other growth processes. We identified a total of 21 LiNAC genes from the transcriptome data, which we divided into 14 subgroups and 2 groups. The physicochemical characteristics of amino acids, subcellular localization, transmembrane structure, GO and KEGG enrichment, and expression patterns were also examined. The qRT-PCR analysis showed that the expressions of LiNAC8 and LiNAC13 in upright L. indica 'Shaoguifei' and weeping L. indica 'Xiariwuniang' were significantly higher from the beginning to the end of growth stage (S1-S3), and the expressions of 'Shaoguifei' were always higher than those of 'Xiariwuniang'. However, LiNAC2 showed a downward trend in S1-S3 and the relative expression level of 'Shaoguifei' was lower than that of 'Xiariwuniang'. It is hypothesized that these LiNAC genes may be involved in the regulation of weeping traits in L. indica. The results of this study provide a basis for analyzing the functions of LiNAC genes and help to explore the molecular regulatory mechanisms related to the weeping traits in L. indica.