The wall-associated kinase (WAK) gene family, a subfamily of the receptor-like kinase (RLK) gene family, is associated with the cell wall in plants, and has vital functions in cell expansion, pathogen resistance, and heavy metal stress tolerance because of their roles of the extracellular environment sensors to trigger intracellular signals in Arabidopsis. In the present study, 96 Chinese cabbage (Brassica rapa ssp. pekinensis) BrWAK gene family members were identified from the B. rapa genome using a reiterative database search and manual confirmation. The protein domain characterization, gene structure analysis, and phylogenetic analysis of the BrWAKs classified them into three gene groups. Comparative genomic analysis between WAK genes from Chinese cabbage and Arabidopsis revealed that the BrWAK genes have undergone the gene expansion and deletion events during evolution. Furthermore, the conserved motifs in the kinase domains of the WAK proteins and eukaryotic protein kinase family proteins were compared and some non-RD kinase proteins among the BrWAKs were identified. Ultimately, expression analysis of BrWAK genes in six tissues and under various stress conditions revealed that some tissue-specific WAK genes might function in callus cell growth and reproduction process; Bra012273, Bra016426, Bra016427, and Bra025882 might be involved in downy mildew resistance and high humidity stress; Bra012273, Bra025882, and Bra025883 might be responded to drought and heat stress. Taken together, this research was identified and classified the WAK gene family in Chinese cabbage and provided valuable resources to explore the potential roles of BrWAK genes in plant development and stress responses.

中文翻译：

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大白菜（Brassica rapa ssp. pekinensis）壁相关激酶基因及其在非生物和生物胁迫下表达的综合分析

壁相关激酶 (WAK) 基因家族是受体样激酶 (RLK) 基因家族的一个亚家族，与植物细胞壁相关，在细胞扩增、病原体抗性和重金属胁迫耐受方面具有重要作用因为它们的细胞外环境传感器在拟南芥中触发细胞内信号的作用。在本研究中，使用重复数据库搜索和手动确认从白菜基因组中鉴定了 96 个大白菜 (Brassica rapa ssp. pekinensis) BrWAK 基因家族成员。BrWAKs 的蛋白质结构域表征、基因结构分析和系统发育分析将它们分为三个基因组。大白菜和拟南芥 WAK 基因的比较基因组分析表明，BrWAK 基因在进化过程中经历了基因扩增和缺失事件。此外，比较了 WAK 蛋白和真核蛋白激酶家族蛋白激酶结构域中的保守基序，并鉴定了 BrWAK 中的一些非 RD 激酶蛋白。最终，BrWAK基因在6种组织和不同胁迫条件下的表达分析表明，一些组织特异性WAK基因可能在愈伤组织细胞生长和繁殖过程中发挥作用；Bra012273、Bra016426、Bra016427和Bra025882可能与抗霜霉病和高湿胁迫有关；Bra012273、Bra025882 和 Bra025883 可能对干旱和热应激有反应。综合起来，