Anhui Provincial Key Laboratory of Microbial Pest Control, Anhui Agricultural University, Hefei, China.
Anhui Province Key Laboratory of Integrated Pest Management on Crops, School of Plant Protection, Anhui Agricultural University, Hefei, China.
PLoS Pathog. 2023 May 22;19(5):e1011397. doi: 10.1371/journal.ppat.1011397. eCollection 2023 May.
Mycoviruses are widely present in all major groups of fungi but those in entomopathogenic Metarhizium spp. remain understudied. In this investigation, a novel double-stranded (ds) RNA virus is isolated from Metarhizium majus and named Metarhizium majus partitivirus 1 (MmPV1). The complete genome sequence of MmPV1 comprises two monocistronic dsRNA segments (dsRNA 1 and dsRNA 2), which encode an RNA-dependent RNA polymerase (RdRp) and a capsid protein (CP), respectively. MmPV1 is classified as a new member of the genus Gammapartitivirus in the family Partitiviridae based on phylogenetic analysis. As compared to an MmPV1-free strain, two isogenic MmPV1-infected single-spore isolates were compromised in terms of conidiation, and tolerance to heat shock and UV-B irradiation, while these phenotypes were accompanied by transcriptional suppression of multiple genes involved in conidiation, heat shock response and DNA damage repair. MmPV1 attenuated fungal virulence since infection resulted in reduced conidiation, hydrophobicity, adhesion, and cuticular penetration. Additionally, secondary metabolites were significantly altered by MmPV1 infection, including reduced production of triterpenoids, and metarhizins A and B, and increased production of nitrogen and phosphorus compounds. However, expression of individual MmPV1 proteins in M. majus had no impact on the host phenotype, suggesting insubstantive links between defective phenotypes and a single viral protein. These findings indicate that MmPV1 infection decreases M. majus fitness to its environment and its insect-pathogenic lifestyle and environment through the orchestration of the host conidiation, stress tolerance, pathogenicity, and secondary metabolism.
真菌病毒广泛存在于所有主要真菌群中，但在昆虫病原真菌玫烟色棒束孢中仍研究较少。在本研究中，从玫烟色棒束孢中分离到一种新型双链 (ds) RNA 病毒，并将其命名为玫烟色棒束孢二分体病毒 1 (MmPV1)。MmPV1 的完整基因组序列由两个单顺反子 dsRNA 片段（dsRNA1 和 dsRNA2）组成，分别编码 RNA 依赖的 RNA 聚合酶 (RdRp) 和衣壳蛋白 (CP)。基于系统发育分析，MmPV1 被分类为 Partitiviridae 科 Gammapartitivirus 属的一个新成员。与不含 MmPV1 的菌株相比，两个遗传上相同的 MmPV1 感染的单孢子分离株在产孢能力、热激和 UV-B 照射耐受性方面受到损害，而这些表型伴随着参与产孢、热激反应和 DNA 损伤修复的多个基因的转录抑制。MmPV1 降低了真菌的毒力，因为感染导致产孢减少、疏水性、附着力和角质层穿透性降低。此外，MmPV1 感染还显著改变了次级代谢物的产生，包括三萜类化合物、玫烟色棒束孢素 A 和 B 的产量减少，以及氮磷化合物的产量增加。然而，MmPV1 单个蛋白在玫烟色棒束孢中的表达对宿主表型没有影响，这表明缺陷表型与单个病毒蛋白之间没有实质性联系。这些发现表明，MmPV1 感染通过宿主产孢、应激耐受、致病性和次生代谢的协调，降低了玫烟色棒束孢对其环境和昆虫病原生活方式的适应能力。
