Department of Plant Pathology, Washington State University-IAREC, 24106 N Bunn Road, Prosser 99350, WA, U.S.A.
Mol Plant Microbe Interact. 2017 Oct;30(10):842-851. doi: 10.1094/MPMI-03-17-0071-R. Epub 2017 Aug 23.
Viroids are the smallest known plant pathogens that exploit host systems for their replication and cause diseases in many hosts. In this study, the host response of hop plants to Hop stunt viroid (HSVd) infection was studied through transcriptome analysis. RNA sequence analysis of hop leaves infected with HSVd revealed dynamic changes in hop gene expression. Defense-related genes and genes involved in lipid and terpenoid metabolism are the major categories that showed differential expression due to HSVd infection. Additionally, the effect of HSVd on development of hop powdery mildew (Podospheara macularis) (HPM) was studied. Transcriptome analysis followed by quantitative reverse transcription-polymerase chain reaction analysis showed that transcript levels of pathogenesis-related (PR) genes such as PR protein 1, chitinase, and thaumatin-like protein genes are induced in leaves infected with HPM alone. The response in these genes to HPM is significantly down-regulated in leaves with HSVd-HPM mixed infection. These results confirm that HSVd alters host metabolism, physiology, and plant defense responses. Nevertheless, in detached leaf assays, HPM consistently expanded faster on HSVd-negative leaves relative to HSVd-positive leaves. Although HSVd infection suppresses elements associated with the host immunity response, infection by HSVd is antagonistic to HPM infection of hops.
类病毒是已知的最小植物病原体，它们利用宿主系统进行复制，并在许多宿主中引起疾病。在这项研究中，通过转录组分析研究了啤酒花植物对啤酒花矮化病毒（HSVd）感染的宿主反应。感染 HSVd 的啤酒花叶片的 RNA 序列分析显示，啤酒花基因表达发生了动态变化。由于 HSVd 感染，防御相关基因和涉及脂质和萜类代谢的基因是表现出差异表达的主要类别。此外，还研究了 HSVd 对啤酒花白粉病（Podospheara macularis）（HPM）发育的影响。转录组分析随后进行的定量逆转录聚合酶链反应分析表明，单独感染 HPM 的叶片中，病程相关（PR）基因（如 PR 蛋白 1、几丁质酶和类硫素蛋白基因）的转录水平被诱导。在 HSVd-HPM 混合感染的叶片中，这些基因对 HPM 的反应显著下调。这些结果证实 HSVd 改变了宿主的代谢、生理和植物防御反应。然而，在离体叶片测定中，与 HSVd 阳性叶片相比，HSVd 阴性叶片上的 HPM 始终更快地扩展。尽管 HSVd 感染抑制了与宿主免疫反应相关的元素，但 HSVd 感染对抗啤酒花的 HPM 感染。
