Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang, 110866, China.
ISME J. 2021 Jun;15(6):1655-1667. doi: 10.1038/s41396-020-00877-8. Epub 2021 Jan 11.
Intracellular symbionts in insects often have reduced genomes. Host acquisition of genes from bacteria is an important adaptation that supports symbionts. However, the function of horizontally transferred genes in insect symbiosis remains largely unclear. The primary symbiont Portiera housed in bacteriocytes lacks pantothenate synthesis genes: panB and panC, which is presumably complemented by a fused gene panB-panC (hereafter panBC) horizontally transferred from bacteria in Bemisia tabaci MEAM1. We found panBC in many laboratory cultures, and species of B. tabaci shares a common evolutionary origin. We demonstrated that complementation with whitefly panBC rescued E. coli pantothenate gene knockout mutants. Portiera elimination decreased the pantothenate level and PanBC abundance in bacteriocytes, and reduced whitefly survival and fecundity. Silencing PanBC decreased the Portiera titer, reduced the pantothenate level, and decreased whitefly survival and fecundity. Supplementation with pantothenate restored the symbiont titer, PanBC level, and fitness of RNAi whiteflies. These data suggest that pantothenate synthesis requires cooperation and coordination of whitefly PanBC expression and Portiera. This host-symbiont co-regulation was mediated by the pantothenate level. Our findings demonstrated that pantothenate production, by the cooperation of a horizontally acquired, fused bacteria gene and Portiera, facilitates the coordination of whitefly and symbiont fitness. Thus, this study extends our understanding on the basis of complex host-symbiont interactions.
昆虫细胞内共生体通常具有缩小的基因组。宿主从细菌中获取基因是支持共生体的重要适应。然而，昆虫共生关系中外源基因的功能在很大程度上仍不清楚。寄生于菌细胞内的初级共生体 Portiera 缺乏泛酸合成基因：panB 和 panC，这可能由从烟粉虱 MEAM1 中的细菌水平转移而来的融合基因 panB-panC（以下简称 panBC）来补充。我们在许多实验室培养物中发现了 panBC，并且烟粉虱属的物种具有共同的进化起源。我们证明了与粉虱的 panBC 互补可拯救大肠杆菌泛酸基因敲除突变体。Portiera 的消除降低了菌细胞内的泛酸水平和 PanBC 丰度，并降低了粉虱的存活率和繁殖力。沉默 PanBC 降低了 Portiera 的滴度，降低了泛酸水平，并降低了粉虱的存活率和繁殖力。泛酸的补充恢复了共生体的滴度、PanBC 水平以及 RNAi 粉虱的适应能力。这些数据表明，泛酸的合成需要粉虱 PanBC 表达和 Portiera 的合作与协调。这种宿主-共生体的共同调控是由泛酸水平介导的。我们的发现表明，通过水平获得的、融合的细菌基因和 Portiera 的合作，泛酸的产生促进了粉虱和共生体适应能力的协调。因此，这项研究扩展了我们对复杂的宿主-共生体相互作用的理解。
