Inhibition of seed germination and induction of systemic disease resistance by Pseudomonas chlororaphis O6 requires phenazine production regulated by the global regulator, gacS.
Seed coating by a phenazine-producing bacterium, Pseudomonas chlororaphis O6, induced dose-dependent inhibition of germination in wheat and barley seeds, but did not inhibit germination of rice or cucumber seeds. In wheat seedlings grown from inoculated seeds, phenazine production levels near the seed were higher than in the roots. Deletion of the gacS gene reduced transcription from the genes required for phenazine synthesis, the regulatory phzI gene and the biosynthetic phzA gene. The inhibition of seed germination and the induction of systemic disease resistance against a bacterial soft-rot pathogen, Erwinia carotovora subsp. carotovora, were impaired in the gacS and phzA mutants of P chlororaphis O6. Culture filtrates of the gacS and phzA mutants of P chlororaphis 06 did not inhibit seed germination of wheat, whereas that of the wild-type was inhibitory. Our results showed that the production of phenazines by P chlororaphis O6 was correlated with reduced germination of barley and wheat seeds, and the level of systemic resistance in tobacco against E. carotovora.
Agricultural Plant Stress Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Korea.
Beom Ryong
BR
Kang
Song Hee
SH
Han
Rob E
RE
Zdor
Anne J
AJ
Anderson
Matt
M
Spencer
Kwang Yeol
KY
Yang
Yong Hwan
YH
Kim
Myung Chul
MC
Lee
Baik Ho
BH
Cho
Young Cheol
YC
Kim
D001426:Bacterial Proteins / Q000502:physiology*; D018525:Germination; D001467:Hordeum / Q000382:microbiology; D010619:Phenazines / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D011549:Pseudomonas / Q000502:physiology*; D012639:Seeds / Q000382:microbiology; D014157:Transcription Factors / Q000502:physiology*; D014908:Triticum / Q000382:microbiology*
D001426:Bacterial Proteins; D010619:Phenazines; D014157:Transcription Factors; C074165:lemA protein, bacterial