Thangavel Tamilarasan, Tegg Robert S, Wilson Calum R
Tasmanian Institute of Agriculture, School of Land and Food, University of Tasmania, New Town Research Laboratories, 13 St John's Avenue, Tasmania 7008, Australia.
Phytopathology. 2016 May;106(5):474-83. doi: 10.1094/PHYTO-08-15-0191-R. Epub 2016 Mar 21.
Common scab, a globally important potato disease, is caused by infection of tubers with pathogenic Streptomyces spp. Previously, disease-resistant potato somaclones were obtained through cell selections against the pathogen's toxin, known to be essential for disease. Further testing revealed that these clones had broad-spectrum resistance to diverse tuber-invading pathogens, and that resistance was restricted to tuber tissues. The mechanism of enhanced disease resistance was not known. Tuber periderm tissues from disease-resistant clones and their susceptible parent were examined histologically following challenge with the pathogen and its purified toxin. Relative expression of genes associated with tuber suberin biosynthesis and innate defense pathways within these tissues were also examined. The disease-resistant somaclones reacted to both pathogen and toxin by producing more phellem cell layers in the tuber periderm, and accumulating greater suberin polyphenols in these tissues. Furthermore, they had greater expression of genes associated with suberin biosynthesis. In contrast, signaling genes associated with innate defense responses were not differentially expressed between resistant and susceptible clones. The resistance phenotype is due to induction of increased periderm cell layers and suberization of the tuber periderm preventing infection. The somaclones provide a valuable resource for further examination of suberization responses and its genetic control.
普通疮痂病是一种全球范围内重要的马铃薯病害，由致病性链霉菌属感染块茎引起。此前，通过针对已知对病害至关重要的病原菌毒素进行细胞筛选，获得了抗病马铃薯体细胞无性系。进一步测试表明，这些克隆对多种侵染块茎的病原菌具有广谱抗性，且这种抗性仅限于块茎组织。抗病性增强的机制尚不清楚。在用病原菌及其纯化毒素进行挑战后，对抗病克隆及其感病亲本的块茎周皮组织进行了组织学检查。还检测了这些组织中与块茎木栓质生物合成和先天防御途径相关基因的相对表达。抗病体细胞无性系对病原菌和毒素的反应是在块茎周皮中产生更多的木栓细胞层，并在这些组织中积累更多的木栓质多酚。此外，它们与木栓质生物合成相关的基因表达更高。相比之下，与先天防御反应相关的信号基因在抗病和感病克隆之间没有差异表达。抗性表型是由于诱导周皮细胞层增加和块茎周皮木栓化从而防止感染。这些体细胞无性系为进一步研究木栓化反应及其遗传控制提供了宝贵资源。
