Two plant bacteria, S. meliloti and Ca. Liberibacter asiaticus, share functional znuABC homologues that encode for a high affinity zinc uptake system.
The Znu system, encoded for by znuABC, can be found in multiple genera of bacteria and has been shown to be responsible for the import of zinc under low zinc conditions. Although this high-affinity uptake system is known to be important for both growth and/or pathogenesis in bacteria, it has not been functionally characterized in a plant-associated bacterium. A single homologue of this system has been identified in the plant endosymbiont, Sinorhizobium meliloti, while two homologous systems were found in the destructive citrus pathogen, Candidatus Liberibacter asiaticus. To understand the role of these protein homologues, a complementation assay was devised allowing the individual genes that comprise the system to be assayed independently for their ability to reinstate a partially-inactivated Znu system. Results from the assays have demonstrated that although all of the genes from S. meliloti were able to restore activity, only one of the two Ca. Liberibacter asiaticus encoded gene clusters contained genes that were able to functionally complement the system. Additional analysis of the gene clusters reveals that distinct modes of regulation may also exist between the Ca. Liberibacter asiaticus and S. meliloti import systems despite the intracellular-plant niche common to both of these bacteria.
United States Horticultural Research Laboratory, Plant Pathology, United States Department of Agriculture Agricultural Research Service, Fort Pierce, Florida, United States of America.
Cheryl M
CM
Vahling-Armstrong
Huasong
H
Zhou
Lesley
L
Benyon
J Kent
JK
Morgan
Yongping
Y
Duan
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002957:Citrus / Q000382:microbiology; D004492:Edetic Acid / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family; D010944:Plants / Q000382:microbiology*; D012230:Rhizobiaceae / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D016415:Sequence Alignment; D016962:Sinorhizobium meliloti / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D004492:Edetic Acid; D015032:Zinc