Affiliation:
1. Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan
Abstract
ABSTRACT
We disrupted the
rtxC
gene on the chromosome of
Bradyrhizobium elkanii
USDA94 by insertion of a nonpolar
aph
cartridge. The
rtxC
mutant, designated Δ
rtxC
, produced serinol and dihydrorhizobitoxine but no rhizobitoxine, both in culture and in planta. The introduction of cosmids harboring the
rtxC
gene into the Δ
rtxC
mutant complemented rhizobitoxine production, suggesting that
rtxC
is involved in the final step of rhizobitoxine biosynthesis in
B. elkanii
USDA94.
Glycine max
cv. Lee inoculated with Δ
rtxC
or with a null mutant, Δ
rtx
::Ω1, showed no foliar chlorosis, whereas the wild-type strain USDA94 caused severe foliar chlorosis. The two mutants showed significantly less nodulation competitiveness than the wild-type strain on
Macroptilium atropurpureum
. These results indicate that dihydrorhizobitoxine, the immediate precursor of the oxidative form of rhizobitoxine, has no distinct effect on nodulation phenotype in these legumes. Thus, desaturation of dihydrorhizobitoxine by
rtxC
-encoded protein is essential for the bacterium to show rhizobitoxine phenotypes in planta. In addition, complementation analysis of
rtxC
by cosmids differing in
rtxC
transcription levels suggested that rhizobitoxine production correlates with the amount of
rtxC
transcript.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Reference41 articles.
1. Akao, S., and H. Kouchi. 1989. Light microscopic observation of root hair curling of soybean induced by Rhizobium infection. Jpn. J. Soil Sci. Plant Nutr.60:53-55. (In Japanese.)
2. Ausubel F. M. R. Brent R. E. Kingston D. D. Moore J. G. Seidman J. A. Smith and K. Struhl. 1987. Current protocols in molecular biology. John Wiley & Sons Inc. New York N.Y.
3. Transmissible Resistance to Penicillin G, Neomycin, and Chloramphenicol in
Rhizobium japonicum
4. Duodu, S., T. V. Bhuvaneswari, T. J. W. Stokkermans, and N. K. Peters. 1999. A positive role for rhizobitoxine in Rhizobium-legume symbiosis. Mol. Plant Microbe Interact.12:1082-1089.
5. Fallay, R., J. Frey, and H. Kirsch. 1987. Interposon mutagenesis of soil and water bacteria: a family of DNA fragments designed for in vitro insertion mutagenesis of gram-negative bacteria. Gene52:147-154.
Cited by
29 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献