van de Mortel Martijn, Recknor Justin C, Graham Michelle A, Nettleton Dan, Dittman Jaime D, Nelson Rex T, Godoy Cláudia V, Abdelnoor Ricardo V, Almeida Alvaro M R, Baum Thomas J, Whitham Steven A
Department of Plant Pathology, Iowa State University, Ames 50011, USA.
Mol Plant Microbe Interact. 2007 Aug;20(8):887-99. doi: 10.1094/MPMI-20-8-0887.
Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is now established in all major soybean-producing countries. Currently, there is little information about the molecular basis of ASR-soybean interactions, which will be needed to assist future efforts to develop effective resistance. Toward this end, abundance changes of soybean mRNAs were measured over a 7-day ASR infection time course in mock-inoculated and infected leaves of a soybean accession (PI230970) carrying the Rpp2 resistance gene and a susceptible genotype (Embrapa-48). The expression profiles of differentially expressed genes (ASR-infected compared with the mock-inoculated control) revealed a biphasic response to ASR in each genotype. Within the first 12 h after inoculation (hai), which corresponds to fungal germination and penetration of the epidermal cells, differential gene expression changes were evident in both genotypes. mRNA expression of these genes mostly returned to levels found in mock-inoculated plants by 24 hai. In the susceptible genotype, gene expression remained unaffected by rust infection until 96 hai, a time period when rapid fungal growth began. In contrast, gene expression in the resistant genotype diverged from the mock-inoculated control earlier, at 72 h, demonstrating that Rpp2-mediated defenses were initiated prior to this time. These data suggest that ASR initially induces a nonspecific response that is transient or is suppressed when early steps in colonization are completed in both soybean genotypes. The race-specific resistance phenotype of Rpp2 is manifested in massive gene expression changes after the initial response prior to the onset of rapid fungal growth that occurs in the susceptible genotype.
亚洲大豆锈病（ASR）由大豆层锈菌引起，目前在所有主要大豆生产国都有发生。目前，关于ASR与大豆相互作用的分子基础的信息很少，而这对于未来开发有效抗性的努力是必需的。为此，在携带Rpp2抗性基因的大豆种质（PI230970）和易感基因型（Embrapa - 48）的模拟接种和感染叶片上，在7天的ASR感染时间进程中测量了大豆mRNA的丰度变化。差异表达基因（与模拟接种对照相比的ASR感染）的表达谱显示，每种基因型对ASR都有双相反应。在接种后最初12小时内（hai），这对应于真菌萌发和表皮细胞穿透，两种基因型中差异基因表达变化都很明显。这些基因的mRNA表达在24 hai时大多恢复到模拟接种植物中的水平。在易感基因型中，直到96 hai（此时真菌开始快速生长）锈病感染对基因表达仍无影响。相比之下，抗性基因型中的基因表达在72 h时就早于模拟接种对照出现差异，表明Rpp2介导的防御在此之前就已启动。这些数据表明，ASR最初诱导的是非特异性反应，在两种大豆基因型中，当定殖的早期步骤完成时，这种反应是短暂的或被抑制的。Rpp2的小种特异性抗性表型表现在易感基因型中快速真菌生长开始之前的初始反应之后大量的基因表达变化。
