Multiple determinants influence root colonization and induction of induced systemic resistance by Pseudomonas chlororaphis O6.
SUMMARY Colonization of the roots of tobacco by Pseudomonas chlororaphis O6 induces systemic resistance to the soft-rot pathogen, Erwinia carotovora ssp. carotovara SCC1. A screen of the transposon mutants of P. chlororaphis O6 showed mutants with about a fivefold reduction in ability to induce systemic resistance to the soft-rot disease. These mutations disrupted genes involved in diverse functions: a methyl-accepting chemotaxis protein, biosynthesis of purines, phospholipase C, transport of branched-chain amino acids and an ABC transporter. Additional mutations were detected in the intergenic spacer regions between genes encoding a GGDEF protein and fumarate dehydratase, and in genes of unknown function. The mutants in the ABC transporters did not display reduced root colonization. However, the other mutants had up to 100-fold reduced colonization levels. Generally the production of metabolites important for interactions in the rhizosphere, phenazines and siderophores, was not altered by the mutations. A reduced induction of systemic resistance by a purine biosynthesis mutant with a disrupted purM gene correlated with poor growth rate, lesser production of phenazines and siderophore and low levels of root colonization. These studies showed that multiple determinants are involved in the induction of systemic resistance, with there being a requirement for strong root colonization.
Han
Song Hee
SH
Agricultural Plant Stress Research Center and Environmental-Friendly Agriculture Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea.
Anderson
Anne J
AJ
Yang
Kwang Yeol
KY
Cho
Baik Ho
BH
Kim
Kil Yong
KY
Lee
Myung Chul
MC
Kim
Yong Hwan
YH
Kim
Young Cheol
YC