AT-Hook Transcription Factors Show Functions in Liriodendron chinense under Drought Stress and Somatic Embryogenesis.

AT-hook motif nuclear localized (AHL) is a transcription factor that can directly induce plant somatic embryogenesis without adding exogenous hormones. One of its functional domains, the AT-hook motif, has a chromatin-modifying function and participates in various cellular processes, including DNA replication and repair and gene transcription leading to cell growth. Liriodendron chinense (Hemsl.) Sargent is an important ornamental and timber tree in China. However, its low drought-resistant ability further leads to a low natural growth rate of its population. Based on bioinformatics analysis, this study identified a total of 21 LcAHLs in L. chinense. To explore the expression pattern of the AHL gene family under drought and somatic embryogenesis, we performed a systematic analysis including basic characteristics, gene structure, chromosome localization, replication event, cis-acting elements and phylogenetic analyses. According to the phylogenetic tree, the 21 LcAHL genes are divided into three separate clades (Clade I, II, and III). Cis-acting element analysis indicated the involvement of the LcAHL genes in drought, cold, light, and auxin regulation. In the generated drought stress transcriptome, a total of eight LcAHL genes showed increased expression levels, with their expression peaking at 3 h and leveling off after 1 d. Nearly all LcAHL genes were highly expressed in the process of somatic embryogenesis. In this study, we performed a genome-wide analysis of the LcAHL gene family and found that LcAHLs take part in resistance to drought stress and the development of somatic embryos. These findings will provide an important theoretical basis for understanding of the LcAHL gene function.