First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia.
Phytopathology. 2018 Apr;108(4):495-509. doi: 10.1094/PHYTO-09-17-0307-R. Epub 2018 Feb 14.
Plants have developed complex defense mechanisms to protect themselves against pathogens. A wide-host-range fungus, Austropuccinia psidii, which has caused severe damage to ecosystems and plantations worldwide, is a major threat to Australian ecosystems dominated by members of the family Myrtaceae. In particular, the east coast wetland foundation tree species Melaleuca quinquenervia, appears to be variably susceptible to this pathogen. Understanding the molecular basis of host resistance would enable better management of this rust disease. We identified resistant and susceptible individuals of M. quinquenervia and explored their differential gene expression in order to discover the molecular basis of resistance against A. psidii. Rust screening of germplasm showed a varying degree of response, with fully resistant to highly susceptible individuals. We used transcriptome profiling in samples collected before and at 5 days postinoculation (dpi). Differential gene expression analysis showed that numerous defense-related genes were induced in susceptible plants at 5 dpi. Mapping reads against the A. psidii genome showed that only susceptible plants contained fungal-derived transcripts. Resistant plants exhibited an overexpression of candidate A. psidii resistance-related genes such as receptor-like kinases, nucleotide-binding site leucine-rich repeat proteins, glutathione S-transferases, WRKY transcriptional regulators, and pathogenesis-related proteins. We identified large differences in the expression of defense-related genes among resistant individuals.
植物已经进化出复杂的防御机制来保护自己免受病原体的侵害。一种广泛宿主范围的真菌 Austropuccinia psidii 对全球的生态系统和种植园造成了严重破坏，是对以桃金娘科成员为主的澳大利亚生态系统的主要威胁。特别是东海岸湿地基础树种五脉黑荆树（Melaleuca quinquenervia），似乎对这种病原体有不同程度的易感性。了解宿主抗性的分子基础将使这种锈病得到更好的管理。我们鉴定了五脉黑荆树的抗性和敏感性个体，并探索了它们在差异表达基因方面的差异，以发现对 Austropuccinia psidii 抗性的分子基础。种质资源的锈病筛选显示出不同程度的反应，从完全抗性到高度敏感性个体。我们使用接种前和接种后 5 天（dpi）收集的样本进行转录组谱分析。差异表达基因分析表明，易感植物在 5 dpi 时诱导了许多与防御相关的基因。将读取的序列映射到 Austropuccinia psidii 基因组上表明，只有易感植物含有真菌衍生的转录本。抗性植物表现出候选 Austropuccinia psidii 抗性相关基因的过度表达，如受体样激酶、核苷酸结合位点富含亮氨酸重复蛋白、谷胱甘肽 S-转移酶、WRKY 转录因子和病程相关蛋白。我们发现抗性个体之间防御相关基因的表达存在很大差异。
