The basic helix-loop-helix (bHLH) transcription factor family is the second largest in plants. bHLH transcription factor is not only universally involved in plant growth and metabolism, including photomorphogenesis, light signal transduction, and secondary metabolism, but also plays an important role in plant response to stress. However, the function of bHLH TFs in Pseudoroegneria species has not been studied yet. Pseudoroegneria (Nevski) Á. Löve is a perennial genus of the Triticeae. Pseudoroegneria species are mostly distributed in arid/semi-arid areas and they show good drought tolerance. In this study, we identified 152 PlbHLH TFs in Pseudoroegneria libanotica, which could be classified into 15 groups. Collinearity analysis indicates that 122 PlbHLH genes share homology with wbHLH genes in wheat, and it has lower homology with AtbHLH genes in Arabidopsis. Based on transcriptome profiling under an experiment with three PEG concentrations (0%, 10%, and 20%), 10 up-regulated genes and 11 down-regulated PlbHLH genes were screened. Among them, PlbHLH6, PlbHLH55 and PlbHLH64 as candidate genes may be the key genes related to drought tolerance response at germination, and they have been demonstrated to respond to drought, salt, oxidative, heat, and heavy metal stress in yeast. This study lays the foundation for an in-depth study of the biological roles of PlbHLHs in Pse. libanotica, and discovered new drought-tolerance candidate genes to enhance the genetic background of Triticeae crops.

碱性螺旋-环-螺旋（bHLH）转录因子家族是植物中第二大转录因子家族。bHLH转录因子不仅普遍参与植物生长和代谢，包括光形态建成、光信号转导和次生代谢，而且在植物对逆境的响应中发挥着重要作用。然而，bHLH TF 在拟鹅观草属物种中的功能尚未被研究。Pseudoroegneria (Nevski) Á. Löve 是小麦科多年生属。拟鹅观草属物种多分布于干旱/半干旱地区，具有良好的耐旱性。在本研究中，我们在Pseudoroegneria libanotica中鉴定了 152 个 PlbHLH TF ，可分为 15 个类群。共线性分析表明，122个PlbHLH基因与小麦中的wbHLH基因具有同源性，与拟南芥中的AtbHLH基因同源性较低。基于三种PEG浓度（0%、10%和20%）实验下的转录组分析，筛选出10个上调基因和11个下调PbHLH基因。其中，PlbHLH6、PlbHLH55和PlbHLH64作为候选基因可能是与发芽时耐旱反应相关的关键基因，并且已被证明能够响应酵母中的干旱、盐、氧化、热和重金属胁迫。本研究为深入研究PlbHLHs在Pse中的生物学作用奠定了基础。libanotica，并发现了新的耐旱候选基因，以增强小麦科作物的遗传背景。