de Vries Sophie, von Dahlen Janina K, Uhlmann Constanze, Schnake Anika, Kloesges Thorsten, Rose Laura E
Institute of Population Genetics, Heinrich-Heine University Duesseldorf, Duesseldorf, 40225, Germany.
iGRAD-Plant Graduate School, Heinrich-Heine University Duesseldorf, Duesseldorf, 40225, Germany.
Mol Plant Pathol. 2017 Jan;18(1):110-124. doi: 10.1111/mpp.12465. Epub 2016 Oct 2.
Phytophthora infestans is a devastating pathogen in agricultural systems. Recently, an RNA silencing suppressor (PSR2, 'Phytophthora suppressor of RNA silencing 2') has been described in P. infestans. PSR2 has been shown to increase the virulence of Phytophthora pathogens on their hosts. This gene is one of the few effectors present in many economically important Phytophthora species. In this study, we investigated: (i) the evolutionary history of PSR2 within and between species of Phytophthora; and (ii) the interaction between sequence variation, gene expression and virulence. In P. infestans, the highest PiPSR2 expression was correlated with decreased symptom expression. The highest gene expression was observed in the biotrophic phase of the pathogen, suggesting that PSR2 is important during early infection. Protein sequence conservation was negatively correlated with host range, suggesting host range as a driver of PSR2 evolution. Within species, we detected elevated amino acid variation, as observed for other effectors; however, the frequency spectrum of the mutations was inconsistent with strong balancing selection. This evolutionary pattern may be related to the conservation of the host target(s) of PSR2 and the absence of known corresponding R genes. In summary, our study indicates that PSR2 is a conserved effector that acts as a master switch to modify plant gene regulation early during infection for the pathogen's benefit. The conservation of PSR2 and its important role in virulence make it a promising target for pathogen management.
致病疫霉是农业系统中一种极具破坏力的病原体。最近，在致病疫霉中发现了一种RNA沉默抑制因子（PSR2，“疫霉RNA沉默抑制因子2”）。PSR2已被证明可增强疫霉病原体对宿主的毒力。该基因是许多经济上重要的疫霉物种中存在的少数效应子之一。在本研究中，我们调查了：（i）PSR2在疫霉物种内和物种间的进化历史；以及（ii）序列变异、基因表达和毒力之间的相互作用。在致病疫霉中，PiPSR2的最高表达与症状表达的降低相关。在病原体的活体营养阶段观察到最高的基因表达，这表明PSR2在早期感染期间很重要。蛋白质序列保守性与宿主范围呈负相关，表明宿主范围是PSR2进化的驱动力。在物种内部，我们检测到氨基酸变异增加，这与其他效应子的情况相同；然而，突变的频率谱与强烈的平衡选择不一致。这种进化模式可能与PSR2宿主靶标的保守性以及已知相应R基因的缺失有关。总之，我们的研究表明，PSR2是一种保守的效应子，它作为一个主开关，在感染早期修改植物基因调控以利于病原体。PSR2的保守性及其在毒力中的重要作用使其成为病原体管理的一个有前景的靶点。
