禹氏三角物种WRKY18基因家族的全基因组鉴定、进化特征及表达分析

Genome-Wide Identification, Evolutionary Characteristics, and Expression Analysis of the WRKY18 Gene Family in U’s Triangle Species

摘要: WRKY18转录因子在植物生长发育及逆境响应中发挥重要调控作用。禹氏三角物种为研究基因家族的进化规律提供了材料。本研究采用生物信息学方法，对禹氏三角物种中的WRKY18基因家族进行全基因组鉴定，并结合系统发育、基因结构、蛋白特性、保守基序及转录组数据，分析其进化特征与表达模式。结果表明，在二倍体基本种白菜、甘蓝、黑芥中分别鉴定出3个WRKY18基因，在四倍体复合种芥菜型油菜、甘蓝型油菜中鉴定出6个基因，而在埃塞俄比亚芥中仅鉴定出5个，基因数量变化符合禹氏三角的杂交与多倍化规律，并存在多倍体化后的基因丢失现象。系统发育与结构分析显示，26个WRKY18可分为三组，其WRKY结构域均由两个外显子编码且高度保守。保守基序分析显示，各成员均包含核心基序，但种内基序组成的差异暗示了功能上的潜在分化。转录组表达分析发现，甘蓝型油菜WRKY18基因在核盘菌胁迫下呈现复杂的时序性表达差异，且抗病品系中的诱导强度普遍高于感病品系。本研究揭示了WRKY18基因家族在芸薹属多倍体进化过程中的保留、扩张与丢失规律，证实其成员在生物胁迫响应中具有时序协同与功能分化特征，为芸薹属作物抗逆遗传改良提供了重要的基因资源与理论依据。

Abstract: The WRKY18 transcription factor plays an important regulatory role in plant growth, development, and stress responses. The species of U’s triangle provide a model for studying the evolutionary patterns of gene families. In this study, we performed a genome-wide identification of the WRKY18 gene family across U’s triangle species using bioinformatics approaches. Their evolutionary characteristics and expression patterns were analyzed by integrating phylogenetic, gene structure, protein property, conserved motif, and transcriptomic data. The results showed that three WRKY18 genes were identified in each of the diploid foundational species (B. rapa, B. oleracea, B. nigra), six genes were identified in the tetraploid complex species B. napus and B. juncea, while only five were identified in B. carinata. This variation in gene number aligns with the hybridization and polyploidization patterns of U’s triangle, with evidence of gene loss following polyploidization. Phylogenetic and structural analyses revealed that the 26 WRKY18 members could be divided into three groups, with the WRKY domain being encoded by two exons and highly conserved. Conserved motif analysis showed that all members contained the core motif; however, differences in intra-species motif composition suggested potential functional differentiation. Transcriptomic expression analysis revealed that WRKY18 members in B. napus exhibited complex temporal expression patterns under Sclerotinia sclerotiorum stress, with induction levels generally higher in resistant lines than in susceptible lines. This study reveals the retention, expansion, and loss patterns of the WRKY18 gene family during the polyploidization of Brassica species, confirms the temporal coordination and functional differentiation of its members in response to biotic stress, and provides important genetic resources and a theoretical basis for stress resistance breeding in Brassica crops.