Deng Juan, Lu Zhuoyue, Wang Huifang, Li Ning, Song Guimei, Zhu Qiankuan, Sun Jingxin, Zhang Yongjun
Biotechnology Research Center, Academy of Agricultural Sciences, Southwest University, Chongqing, China.
College of Plant Protection, Southwest University, Chongqing, China.
Insect Sci. 2022 Dec;29(6):1685-1702. doi: 10.1111/1744-7917.13029. Epub 2022 Apr 5.
Secretory phospholipase A2s (sPLA2s) are found in a wide range of organisms from bacteria to higher plants and animals and are involved in varied and cellular processes. However, roles of these enzymes in microbial pathogens remain unclear. Here, an sPLA2 (BbPLA2) was characterized in the filamentous insect pathogenic fungus, Beauveria bassiana. BbPLA2 was exclusively expressed in insect hemolymph-derived cells (hyphal bodies), and its expression was induced by insect-derived nutrients and lipids, and nutrient starvation. High levels of secretion of BbPLA2 were observed as well as its distribution in hyphal body lipid drops (LDs). Overexpression of BbPLA2 increased the ability of B. bassiana to utilize insect-derived nutrients and lipids, and promoted LD accumulation, indicating functions for BbPLA2 in mediating LD homeostasis and assimilation of insect-derived lipids. Strains overexpressing BbPLA2 showed moderately increased virulence, including more efficient penetration of the insect cuticle and evasion of host immune responses as compared to the wild type strain. In addition, B. bassiana-activated host immune genes were downregulated in the BbPLA2 overexpression strain, but upregulated by infections with a ΔBbPLA2 strain. These data demonstrate that BbPLA2 contributes to LD homeostasis, assimilation of insect-derived lipids, and repression of host immune responses.
分泌型磷脂酶A2（sPLA2s）存在于从细菌到高等植物和动物等广泛的生物体中，并参与各种细胞过程。然而，这些酶在微生物病原体中的作用仍不清楚。在此，对丝状昆虫病原真菌球孢白僵菌中的一种sPLA2（BbPLA2）进行了表征。BbPLA2仅在昆虫血淋巴来源的细胞（菌丝体）中表达，其表达受昆虫来源的营养物质、脂质和营养饥饿诱导。观察到BbPLA2的高水平分泌及其在菌丝体脂滴（LDs）中的分布。BbPLA2的过表达提高了球孢白僵菌利用昆虫来源的营养物质和脂质的能力，并促进了脂滴积累，表明BbPLA2在介导脂滴稳态和昆虫来源脂质同化方面具有功能。过表达BbPLA2的菌株显示出适度增加的毒力，与野生型菌株相比，包括更有效地穿透昆虫表皮和逃避宿主免疫反应。此外，球孢白僵菌激活的宿主免疫基因在BbPLA2过表达菌株中下调，但在ΔBbPLA2菌株感染后上调。这些数据表明BbPLA2有助于脂滴稳态、昆虫来源脂质的同化以及宿主免疫反应的抑制。
