Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520, USA.
Proc Natl Acad Sci U S A. 2012 Jun 26;109(26):10552-7. doi: 10.1073/pnas.1116431109. Epub 2012 Jun 11.
Beneficial microbe functions range from host dietary supplementation to development and maintenance of host immune system. In mammals, newborn progeny are quickly colonized with a symbiotic fauna that is provisioned in mother's milk and that closely resembles that of the parent. Tsetse fly (Diptera: Glossinidae) also depends on the obligate symbiont Wigglesworthia for nutritional supplementation, optimal fecundity, and immune system development. Tsetse progeny develop one at a time in an intrauterine environment and receive nourishment and symbionts in mother's milk. We show that the host Peptidoglycan Recognition Protein (PGRP-LB) is expressed only in adults and is a major component of the milk that nourishes the developing progeny. The amidase activity associated with PGRP-LB may scavenge the symbiotic peptidoglycan and prevent the induction of tsetse's Immune Deficiency pathway that otherwise can damage the symbionts. Reduction of PGRP-LB experimentally diminishes female fecundity and damages Wigglesworthia in the milk through induction of antimicrobial peptides, including Attacin. Larvae that receive less maternal PGRP-LB give rise to adults with fewer Wigglesworthia and hyperimmune responses. Such adults also suffer dysregulated immunity, as indicated by the presence of higher trypanosome densities in parasitized adults. We show that recPGRP-LB has antimicrobial and antitrypanosomal activities that may regulate symbiosis and impact immunity. Thus, PGRP-LB plays a pivotal role in tsetse's fitness by protecting symbiosis against host-inflicted damage during development and by controlling parasite infections in adults that can otherwise reduce host fecundity.
有益微生物的功能范围从宿主的饮食补充到宿主免疫系统的发育和维持。在哺乳动物中，新生后代很快就会被共生动物定植，这些共生动物存在于母奶中，与母体的非常相似。采采蝇（双翅目： Glossinidae）也依赖于专性共生菌 Wigglesworthia 来补充营养、提高繁殖力和发育免疫系统。采采蝇后代在子宫内环境中一次发育一个，并从母奶中获得营养和共生菌。我们表明，宿主肽聚糖识别蛋白（PGRP-LB）仅在成体中表达，是滋养发育后代的奶的主要成分。与 PGRP-LB 相关的酰胺酶活性可能会清除共生肽聚糖，防止采采蝇的免疫缺陷途径被诱导，否则会损害共生菌。实验减少 PGRP-LB 的表达会通过诱导抗菌肽（包括 Attacin）减少雌性的繁殖力并破坏奶中的 Wigglesworthia。从母奶中获得较少 PGRP-LB 的幼虫会产生携带较少 Wigglesworthia 和过度免疫反应的成虫。这些成虫也会遭受免疫失调，这表现为寄生成虫中锥虫密度更高。我们表明，recPGRP-LB 具有抗菌和抗锥虫活性，可能调节共生关系并影响免疫。因此，PGRP-LB 通过在发育过程中保护共生体免受宿主损伤，并通过控制可能降低宿主繁殖力的成虫中的寄生虫感染，在采采蝇的适应性中发挥关键作用。
