State Key Laboratory of Biocontrol and Key Laboratory of Gene Engineering of the Ministry of Education, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China.
BMC Plant Biol. 2010 Dec 19;10:281. doi: 10.1186/1471-2229-10-281.
WRKY transcription factors are involved in plant responses to both biotic and abiotic stresses. Arabidopsis WRKY18, WRKY40, and WRKY60 transcription factors interact both physically and functionally in plant defense responses. However, their role in plant abiotic stress response has not been directly analyzed.
We report that the three WRKYs are involved in plant responses to abscisic acid (ABA) and abiotic stress. Through analysis of single, double, and triple mutants and overexpression lines for the WRKY genes, we have shown that WRKY18 and WRKY60 have a positive effect on plant ABA sensitivity for inhibition of seed germination and root growth. The same two WRKY genes also enhance plant sensitivity to salt and osmotic stress. WRKY40, on the other hand, antagonizes WRKY18 and WRKY60 in the effect on plant sensitivity to ABA and abiotic stress in germination and growth assays. Both WRKY18 and WRKY40 are rapidly induced by ABA, while induction of WRKY60 by ABA is delayed. ABA-inducible expression of WRKY60 is almost completely abolished in the wrky18 and wrky40 mutants. WRKY18 and WRKY40 recognize a cluster of W-box sequences in the WRKY60 promoter and activate WRKY60 expression in protoplasts. Thus, WRKY60 might be a direct target gene of WRKY18 and WRKY40 in ABA signaling. Using a stable transgenic reporter/effector system, we have shown that both WRKY18 and WRKY60 act as weak transcriptional activators while WRKY40 is a transcriptional repressor in plant cells.
We propose that the three related WRKY transcription factors form a highly interacting regulatory network that modulates gene expression in both plant defense and stress responses by acting as either transcription activator or repressor.
WRKY 转录因子参与植物对生物和非生物胁迫的反应。拟南芥 WRKY18、WRKY40 和 WRKY60 转录因子在植物防御反应中物理和功能上相互作用。然而，它们在植物非生物胁迫反应中的作用尚未被直接分析。
我们报告称，这三个 WRKY 参与了植物对脱落酸（ABA）和非生物胁迫的反应。通过对 WRKY 基因的单突变体、双突变体和过表达系进行分析，我们已经表明 WRKY18 和 WRKY60 对植物 ABA 敏感性有积极影响，可抑制种子萌发和根生长。这两个 WRKY 基因也增强了植物对盐和渗透胁迫的敏感性。另一方面，WRKY40 在萌发和生长测定中拮抗 WRKY18 和 WRKY60 对植物 ABA 和非生物胁迫敏感性的影响。WRKY18 和 WRKY40 都能被 ABA 快速诱导，而 WRKY60 的诱导则延迟。在 wrky18 和 wrky40 突变体中，ABA 诱导的 WRKY60 表达几乎完全被消除。WRKY18 和 WRKY40 在 WRKY60 启动子中识别 W 框序列簇，并在原生质体中激活 WRKY60 表达。因此，WRKY60 可能是 ABA 信号通路中 WRKY18 和 WRKY40 的直接靶基因。使用稳定的转基因报告基因/效应子系统，我们已经表明，WRKY18 和 WRKY60 都作为弱转录激活子，而 WRKY40 在植物细胞中作为转录抑制子。
我们提出，这三个相关的 WRKY 转录因子形成了一个高度相互作用的调控网络，通过作为转录激活子或抑制子来调节植物防御和应激反应中的基因表达。
