Inactivation of pqq genes of Enterobacter intermedium 60-2G reduces antifungal activity and induction of systemic resistance.
Enterobacter intermedium 60-2G, a phosphate solubilizing bacterium, has the ability to induce systemic resistance in plants against soft rot pathogen Erwinia carotovora. Glucose dehydrogenase, an enzyme that utilizes pyrroloquinoline quinone (PQQ) as a cofactor, is required for the synthesis of gluconic acid by E. intermedium 60-2G. Here, we report that the pqqA and pqqB genes are required for phosphate solubilization and induced systemic resistance against a soft rot pathogen in tobacco. Mutations in either the pqqA or pqqB gene abolished the production of 2-ketogluconic acid and eliminated the ability of E. intermedium to solubilize hydroxyapatite. Addition of gluconic acid to the growth media restored the ability of the pqqA mutant to produce 2-ketogluconic acid. Interestingly, both pqqA and pqqB mutants of E. intermedium lost their ability to inhibit the growth of the rice pathogen Magnaporthe grisea KI-409. Additionally, induced systemic resistance against the soft rot pathogen was attenuated in the pqq mutants. These functions were restored by complementation with the wild-type pqq gene cluster. Our findings suggest that PQQ plays an important function in beneficial traits including phosphate solubilization, antifungal activity, and induced systemic resistance of E. intermedium, possibly by acting as a cofactor for several enzymes including glucose dehydrogenase.
Han
Song Hee
SH
Department of Plant Biotechnology and Biotechnology Research Center, Chonnam National University, Gwangju, Korea.
Kim
Chul Hong
CH
Lee
Jang Hoon
JH
Park
Ju Yeon
JY
Cho
Song Mi
SM
Park
Seur Kee
SK
Kim
Kil Yong
KY
Krishnan
Hari B
HB
Kim
Young Cheol
YC
D000898:Antibiosis; D004754:Enterobacter / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D020868:Gene Silencing; D054884:Host-Pathogen Interactions; D020082:Magnaporthe / Q000472:pathogenicity / Q000502:physiology; D009930:Organic Chemicals / Q000032:analysis / Q000378:metabolism; D045542:PQQ Cofactor / Q000235:genetics* / Q000378:metabolism*; D016973:Pectobacterium carotovorum / Q000472:pathogenicity / Q000502:physiology; D010641:Phenotype; D010710:Phosphates / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D014026:Nicotiana / Q000254:growth & development / Q000382:microbiology
D009930:Organic Chemicals; D010710:Phosphates; D045542:PQQ Cofactor