Jang Seong Han, Jang Ho Am, Lee Junbeom, Kim Jong Uk, Lee Seung Ah, Park Kyoung-Eun, Kim Byung Hyun, Jo Yong Hun, Lee Bok Luel
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Division of Plant Biotechnology, Institute of Environmentally-Friendly Agriculture (IEFA), College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea.
Appl Environ Microbiol. 2017 May 17;83(11). doi: 10.1128/AEM.00459-17. Print 2017 Jun 1.
Five genes encoding PhaP family proteins and one gene have been identified in the genome of symbiont strain RPE75. PhaP proteins function as the surface proteins of polyhydroxyalkanoate (PHA) granules, and the PhaR protein acts as a negative regulator of PhaP biosynthesis. Recently, we characterized one gene to understand the molecular cross talk between insects and gut symbionts. In this study, we constructed four other gene-depleted mutants (Δ, Δ, Δ, and Δ mutants), one gene-depleted mutant, and a -complemented mutant (Δ mutant). To address the biological roles of four family genes and the gene during insect-gut symbiont interaction, these mutants were fed to the second-instar nymphs, and colonization ability and fitness parameters were examined. , the Δ and Δ mutants cannot make a PHA granule normally in a stressful environment. Furthermore, the Δ mutation decreased the colonization ability in the host midgut and negatively affected the host insect's fitness compared with wild-type -infected insects. However, other family gene-depleted mutants colonized well in the midgut of the fifth-instar nymph insects. However, in the case of females, the colonization rate of the Δ mutant was decreased and the host's fitness parameters were decreased compared with the wild-type-infected host, suggesting that the environment of the female midgut may be more hostile than that of the male midgut. These results demonstrate that PhaR plays an important role in the biosynthesis of PHA granules and that it is significantly related to the colonization of the gut symbiont in the host insects' midgut. Bacterial polyhydroxyalkanoate (PHA) biosynthesis is a complex process requiring several enzymes. The biological roles of PHA granule synthesis enzymes and the surface proteins of PHA granules during host-gut symbiont interactions are not fully understood. Here, we report the effects on colonization ability in the host midguts and the fitness of host insects after feeding mutant cells (four -depleted mutants and one -depleted mutant) to the host insects. Analyses of both synthesized PHA granule amounts and CFU numbers suggest that the gene is closely related to synthesis of the PHA granule and the colonization of the gut symbiont in the host insect's midgut. Like our previous report, this study also supports the idea that the environment of the host midgut may not be favorable to symbiotic cells and that PHA granules may be required to adapt in the host midgut.
在共生菌株RPE75的基因组中已鉴定出五个编码PhaP家族蛋白的基因和一个基因。PhaP蛋白作为聚羟基脂肪酸酯（PHA）颗粒的表面蛋白发挥作用，而PhaR蛋白作为PhaP生物合成的负调控因子。最近，我们对一个基因进行了表征，以了解昆虫与肠道共生体之间的分子相互作用。在本研究中，我们构建了另外四个基因缺失突变体（Δ、Δ、Δ和Δ突变体）、一个基因缺失突变体和一个基因互补突变体（Δ突变体）。为了研究四个家族基因和该基因在昆虫-肠道共生体相互作用中的生物学作用，将这些突变体喂食给二龄若虫，并检测其定殖能力和适合度参数。结果表明，Δ和Δ突变体在应激环境下不能正常形成PHA颗粒。此外，与野生型感染昆虫相比，Δ突变降低了在宿主中肠的定殖能力，并对宿主昆虫的适合度产生负面影响。然而，其他家族基因缺失突变体在五龄若虫的中肠中定殖良好。然而，对于雌性而言，与野生型感染宿主相比，Δ突变体的定殖率降低，宿主的适合度参数也降低，这表明雌性中肠的环境可能比雄性中肠更具敌意。这些结果表明，PhaR在PHA颗粒的生物合成中起重要作用，并且它与肠道共生体在宿主昆虫中肠的定殖显著相关。细菌聚羟基脂肪酸酯（PHA）的生物合成是一个需要多种酶的复杂过程。PHA颗粒合成酶和PHA颗粒表面蛋白在宿主-肠道共生体相互作用中的生物学作用尚未完全了解。在此，我们报告了将突变体细胞（四个基因缺失突变体和一个基因缺失突变体）喂食给宿主昆虫后对宿主中肠定殖能力和宿主昆虫适合度的影响。对合成的PHA颗粒数量和CFU数量的分析表明，该基因与PHA颗粒的合成以及肠道共生体在宿主昆虫中肠的定殖密切相关。与我们之前的报告一样，本研究也支持宿主中肠环境可能不利于共生细胞，并且可能需要PHA颗粒来适应宿主中肠的观点。
