Department of Botany, Savitribai Phule Pune University (Formerly University of Pune), Pune, India.
Division of Biochemical Sciences, Plant Molecular Biology Unit, CSIR-National Chemical Laboratory, Pune, India.
Plant Biotechnol J. 2018 Aug;16(8):1502-1513. doi: 10.1111/pbi.12892. Epub 2018 May 24.
Early blight (EB), caused by Alternaria solani, is a major threat to global tomato production. In comparison with cultivated tomato (Solanum lycopersicum), a wild relative, S. arcanum exhibits strong resistance against EB. However, molecular cascades operating during EB resistance in wild or cultivated tomato plants are largely obscure. Here, we provide novel insight into spatio-temporal molecular events in S. arcanum against A. solani. Transcriptome and co-expression analysis presented 33-WRKYs as promising candidates of which 12 SaWRKYs displayed differential expression patterns in resistant and susceptible accessions during EB disease progression. Among these, SaWRKY1 exhibited induced expression with significant modulation in xyloglucan endotrans hydrolase 5 (XTH5) and MYB2 expressions that correlated with the disease phenotypes. Electro-mobility shift assay confirmed physical interaction of recombinant SaWRKY1 to SaXTH5 and SaMYB2 promoters. Comparative WRKY1 promoter analysis between resistant and susceptible plants revealed the presence of crucial motifs for defence mechanism exclusively in resistant accession. Additionally, many defence-related genes displayed significant expression variations in both the accessions. Further, WRKY1 overexpressing transgenic plants exhibited higher levels of EB resistance while RNAi silencing lines had increased susceptibility to A. solani with altered expression of XTH5 and MYB2. Overall, these findings demonstrate the positive influence of WRKY1 in improving EB resistance in wild tomato and this could be further utilized as a potential target through genetic engineering to augment protection against A. solani in crop plants.
早疫病（EB）由交链格孢菌引起，是全球番茄生产的主要威胁。与栽培番茄（Solanum lycopersicum）相比，野生近缘种 S. arcanum 表现出对 EB 的强抗性。然而，野生或栽培番茄植物中 EB 抗性相关的分子级联反应在很大程度上仍不清楚。在这里，我们提供了 S. arcanum 对 A. solani 抗性的时空分子事件的新见解。转录组和共表达分析表明，33 个 WRKY 是有希望的候选基因，其中 12 个 SaWRKYs 在 EB 发病过程中在抗性和敏感品系中表现出不同的表达模式。其中，SaWRKY1 的表达被诱导，与疾病表型相关的木葡聚糖内转糖苷酶 5（XTH5）和 MYB2 的表达显著调节。电泳迁移率变动分析证实了重组 SaWRKY1 与 SaXTH5 和 SaMYB2 启动子的物理相互作用。抗性和敏感植物之间的 WRKY1 启动子比较分析表明，防御机制的关键基序仅存在于抗性品种中。此外，许多防御相关基因在两个品种中都表现出显著的表达变化。此外，WRKY1 过表达转基因植物表现出更高水平的 EB 抗性，而 RNAi 沉默系对 A. solani 的敏感性增加，XTH5 和 MYB2 的表达发生改变。总的来说，这些发现表明 WRKY1 对提高野生番茄的 EB 抗性有积极影响，这可以通过遗传工程进一步利用作为潜在的靶标，增加对作物中 A. solani 的保护。
