PMID:16085833

Citation	Baek, SH and Shapleigh, JP (2005) Expression of nitrite and nitric oxide reductases in free-living and plant-associated Agrobacterium tumefaciens C58 cells. Appl. Environ. Microbiol. 71:4427-36
Abstract	A number of the bacteria that form associations with plants are denitrifiers. To learn more about how the association with plants affects expression of denitrification genes, the regulation of nitrite and nitric oxide reductases was investigated in Agrobacterium tumefaciens. Analysis of free-living cells revealed that expression of the genes encoding nitrite and nitric oxide reductases, nirK and nor, respectively, requires low-oxygen conditions, nitric oxide, and the transcriptional regulator NnrR. Expression of nor was monitored in plant-associated bacteria using nor-gfp fusion expression. In root association experiments, only a small percentage of the attached cells were fluorescent, even when they were incubated under a nitrogen atmosphere. Inactivation of nirK had no significant effect on the ability of A. tumefaciens to bind to plant roots regardless of the oxygen tension, but it did decrease the occurrence of root-associated fluorescent cells. When wild-type cells containing the gfp fusion were infiltrated into leaves, most cells eventually became fluorescent. The same result was obtained when a nirK mutant was used, suggesting that nitric oxide activated nor expression in the endophytic bacteria. Addition of a nitric oxide synthase inhibitor to block nitric oxide generation by the plant prevented gfp expression in infiltrated nitrite reductase mutants, demonstrating that plant-derived nitric oxide can activate nor expression in infiltrated cells.
Links	PubMed PMC1183285 Online version:10.1128/AEM.71.8.4427-4436.2005
Keywords	Agrobacterium tumefaciens/enzymology; Agrobacterium tumefaciens/growth & development; Agrobacterium tumefaciens/metabolism; Arabidopsis/microbiology; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Fluorescent Dyes; Gene Expression Regulation, Bacterial; Indoles; Microscopy/methods; Nitric Oxide/metabolism; Nitrite Reductases/genetics; Nitrite Reductases/metabolism; Nitrites; Oxidoreductases/genetics; Oxidoreductases/metabolism; Oxygen/pharmacology; Plant Leaves/microbiology; Plant Roots/microbiology; Transcription, Genetic
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
AGRT5:Q7CUT2		GO:0016966:	ECO:0000314:				Nir K is one of the first steps in the nitric oxide reductase process.Table 2 showed that the regulation of nirK was dependent on changes in oxygen level. Table 2 also showed that nitrogen oxide must be present for maximal expression of the NirK gene. Article stated production of nitric oxide is key to nirK and nor expression, as shown by the requirement for Nir and the observation that SNP increased expression of nirK-lacZ in A002.	complete

References

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