Cui Fengchao, Taier Geli, Wang Xiangfeng, Wang Kehua
Department of Turfgrass Science and Engineering, College of Grassland Science and Technology, China Agricultural University, Beijing, China.
National Maize Improvement Center, College of Agronomy and Biotechnology, China Agricultural University, Beijing, China.
Front Genet. 2021 Sep 8;12:732812. doi: 10.3389/fgene.2021.732812. eCollection 2021.
African bermudagrass ( Burtt-Davy) is an important warm-season turfgrass and forage grass species. Heat shock protein 20 (HSP20) is a diverse, ancient, and important protein family. To date, genes have not been characterized genome-widely in African bermudagrass. Here, we confirmed 41 genes in African bermudagrass genome. On the basis of the phylogenetic tree and cellular locations, the HSP20 proteins were classified into 12 subfamilies. Motif composition was consistent with the phylogeny. Moreover, we identified 15 pairs of paralogs containing nine pairs of tandem duplicates and six pairs of WGD/segmental duplicates of genes. Unsurprisingly, the syntenic genes revealed that African bermudagrass had a closer evolutionary relationship with monocots (maize and rice) than dicots ( and soybean). The expression patterns of genes were identified with the transcriptome data under abiotic stresses. According to the expression profiles, genes could be clustered into three groups (Groups I, II, and III). Group I was the largest, and these genes were up-regulated in response to heat stress as expected. In Group II, one monocot-specific , maintained higher expression levels under optimum temperature and low temperature, but not high temperature. Moreover, a pair of WGD/segmental duplicates and were among the most conserved across different plant species, and they seemed to be positively selected in response to extreme temperatures during evolution. A total of 938 -elements were captured in the putative promoters of genes. Almost half of the -elements were stress responsive, indicating that the expression pattern of genes under abiotic stresses might be largely regulated by the -elements. Additionally, three-dimensional structure simulations and protein-protein interaction networks were incorporated to resolve the function mechanism of HSP20 proteins. In summary, the findings fulfilled the HSP20 family analysis and could provide useful information for further functional investigations of the specific (e.g., , , and ) in African bermudagrass.
非洲狗牙根（Burtt-Davy）是一种重要的暖季型草坪草和饲草品种。热激蛋白20（HSP20）是一个多样、古老且重要的蛋白质家族。迄今为止，尚未在非洲狗牙根中对基因进行全基因组表征。在此，我们在非洲狗牙根基因组中确认了41个基因。基于系统发育树和细胞定位，HSP20蛋白被分为12个亚家族。基序组成与系统发育一致。此外，我们鉴定出15对旁系同源基因，其中包含9对串联重复基因和6对基因的全基因组复制/片段重复基因。不出所料，共线性基因表明非洲狗牙根与单子叶植物（玉米和水稻）的进化关系比与双子叶植物（和大豆）更密切。利用非生物胁迫下的转录组数据鉴定了基因的表达模式。根据表达谱，基因可分为三组（第一组、第二组和第三组）。第一组最大，这些基因如预期那样在热胁迫下上调。在第二组中，一个单子叶植物特有的基因在最适温度和低温下保持较高表达水平，但在高温下不高。此外，一对全基因组复制/片段重复基因和是不同植物物种中最保守的基因之一，它们似乎在进化过程中因极端温度而受到正选择。在基因的假定启动子中总共捕获到938个顺式作用元件。几乎一半的顺式作用元件是胁迫响应元件，这表明基因在非生物胁迫下的表达模式可能在很大程度上受顺式作用元件调控。此外，还纳入了三维结构模拟和蛋白质-蛋白质相互作用网络来解析HSP20蛋白的功能机制。总之，这些发现完成了HSP20家族分析，并可为进一步研究非洲狗牙根中特定基因（如、和）的功能提供有用信息。
