PhaR, a Negative Regulator of PhaP, Modulates the Colonization of a Burkholderia Gut Symbiont in the Midgut of the Host Insect, Riptortus pedestris.
Five genes encoding PhaP family proteins and onephaRgene have been identified in the genome ofBurkholderiasymbiont 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 onephaPgene to understand the molecular cross talk betweenRiptortusinsects andBurkholderiagut symbionts. In this study, we constructed four otherphaPgene-depleted mutants (ΔphaP1, ΔphaP2, ΔphaP3, and ΔphaP4mutants), onephaRgene-depleted mutant, and aphaR-complemented mutant (ΔphaR/phaRmutant). To address the biological roles of fourphaPfamily genes and thephaRgene during insect-gut symbiont interaction, theseBurkholderiamutants were fed to the second-instar nymphs, and colonization ability and fitness parameters were examined.In vitro, the ΔphaP3and ΔphaRmutants cannot make a PHA granule normally in a stressful environment. Furthermore, the ΔphaRmutation decreased the colonization ability in the host midgut and negatively affected the host insect's fitness compared with wild-typeBurkholderia-infected insects. However, otherphaPfamily 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 ΔphaP3mutant 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 theBurkholderiagut symbiont in the host insects' midgut.IMPORTANCEBacterial 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 feedingBurkholderiamutant cells (fourphaP-depleted mutants and onephaR-depleted mutant) to the host insects. Analyses of both synthesized PHA granule amounts and CFU numbers suggest that thephaRgene is closely related to synthesis of the PHA granule and the colonization of theBurkholderiagut 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 symbioticBurkholderiacells and that PHA granules may be required to adapt in the host midgut.
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Seong Han
SH
Jang
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Ho Am
HA
Jang
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Junbeom
J
Lee
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Jong Uk
JU
Kim
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Seung Ah
SA
Lee
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Kyoung-Eun
KE
Park
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea.
Byung Hyun
BH
Kim
Division of Plant Biotechnology, Institute of Environmentally-Friendly Agriculture (IEFA), College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea.
Yong Hun
YH
Jo
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan, South Korea brlee@pusan.ac.kr.
Bok Luel
BL
Lee
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019117:Burkholderia / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism*; D004064:Digestive System / Q000382:microbiology; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D020062:Heteroptera / Q000382:microbiology* / Q000502:physiology; D008297:Male; D013559:Symbiosis
D001426:Bacterial Proteins
Burkholderia; PhaP; PhaR; Riptortus pedestris; polyhydroxyalkanoate; symbiosis