Table_6_MeWRKY IIas, Subfamily Genes of WRKY Transcription Factors From Cassava, Play an Important Role in Disease Resistance.XLS

Cassava (Manihot esculenta Crantz) is an important tropical crop for food, fodder, and energy. Cassava bacterial blight (CBB) caused by Xanthomonas axonopodis pv. manihotis (Xam) occurs in all cassava growing regions and threatens global cassava production. WRKY transcription factor family plays the essential roles during plant growth, development, and abiotic or biotic stress. Particularly, previous studies have revealed the important role of the group IIa WRKY genes in plant disease resistance. However, a comprehensive analysis of group IIa subfamily in cassava is still missing. Here, we identified 102 WRKY members, which were classified into three groups, I, II, and III. Transient expression showed that six MeWRKY IIas were localized in the nucleus. MeWRKY IIas transcripts accumulated significantly in response to SA, JA, and Xam. Overexpression of MeWRKY27 and MeWRKY33 in Arabidopsis enhanced its resistance to Pst DC3000. In contrast, silencing of MeWRKY27 and MeWRKY33 in cassava enhanced its susceptibility to Xam. Co-expression network analysis showed that different downstream genes are regulated by different MeWRKY IIa members. The functional analysis of downstream genes will provide clues for clarifying molecular mechanism of cassava disease resistance. Collectively, our results suggest that MeWRKY IIas are regulated by SA, JA signaling, and coordinate response to Xam infection.

木薯（Manihot esculenta Crantz）是一类重要的热带作物，可用于粮食、饲料及能源生产。由野油菜黄单胞菌木薯致病变种（Xanthomonas axonopodis pv. manihotis, Xam）引发的木薯细菌性枯萎病（CBB）在全球所有木薯种植区均有发生，严重威胁全球木薯生产。WRKY转录因子家族（WRKY transcription factor family）在植物生长发育、非生物胁迫与生物胁迫响应过程中发挥核心调控作用。既往研究已证实，IIa亚族WRKY基因在植物抗病过程中具有关键功能，但目前针对木薯IIa WRKY亚家族的系统性分析仍较为匮乏。本研究共鉴定得到102个WRKY家族成员，可划分为I、II、III三个类群。瞬时表达实验显示，6个木薯MeWRKY IIa成员定位于细胞核内。转录水平分析表明，MeWRKY IIa家族成员的转录本可在水杨酸（SA）、茉莉酸（JA）处理及Xam侵染条件下显著上调积累。在拟南芥（Arabidopsis）中过表达MeWRKY27与MeWRKY33，可显著增强其对丁香假单胞菌番茄致病变种DC3000（Pseudomonas syringae pv. tomato DC3000, Pst DC3000）的抗性；与之相反，在木薯中沉默MeWRKY27与MeWRKY33，则会提升木薯对Xam的感病性。共表达网络分析表明，不同的MeWRKY IIa成员可调控不同的下游基因，对这些下游基因的功能解析将为阐明木薯抗病的分子机制提供重要线索。综上，本研究结果表明，MeWRKY IIa家族成员受SA、JA信号通路调控，并协同参与木薯对Xam侵染的防御应答。