title: Casuarina root exudates alter the physiology, surface properties, and plant infectivity of Frankia sp. strain CcI3.
abstract: The actinomycete genus Frankia forms nitrogen-fixing symbioses with 8 different families of actinorhizal plants, representing more than 200 different species. Very little is known about the initial molecular interactions between Frankia and host plants in the rhizosphere. Root exudates are important in Rhizobium-legume symbiosis, especially for initiating Nod factor synthesis. We measured differences in Frankia physiology after exposure to host aqueous root exudates to assess their effects on actinorhizal symbioses. Casuarina cunninghamiana root exudates were collected from plants under nitrogen-sufficient and -deficient conditions and tested on Frankia sp. strain CcI3. Root exudates increased the growth yield of Frankia in the presence of a carbon source, but Frankia was unable to use the root exudates as a sole carbon or energy source. Exposure to root exudates caused hyphal "curling" in Frankia cells, suggesting a chemotrophic response or surface property change. Exposure to root exudates altered Congo red dye binding, which indicated changes in the bacterial surface properties at the fatty acid level. Fourier transform infrared spectroscopy (FTIR) confirmed fatty acid changes and revealed further carbohydrate changes. Frankia cells preexposed to C. cunninghamiana root exudates for 6 days formed nodules on the host plant significantly earlier than control cells. These data support the hypothesis of early chemical signaling between actinorhizal host plants and Frankia in the rhizosphere.
authors.affiliation: Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Beauchemin
authors.forename: Teal
authors.initials: T
authors.lastname: Furnholm
authors.forename: Julien
authors.initials: J
authors.lastname: Lavenus
authors.forename: Sergio
authors.initials: S
authors.lastname: Svistoonoff
authors.forename: Patrick
authors.initials: P
authors.lastname: Doumas
authors.forename: Didier
authors.initials: D
authors.lastname: Bogusz
authors.forename: Laurent
authors.initials: L
authors.lastname: Laplaze
authors.forename: Louis S
authors.initials: LS
authors.lastname: Tisa
mesh_terms: D002241:Carbohydrates / Q000032:analysis; D003224:Congo Red / Q000378:metabolism; D005122:Exudates and Transudates / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis; D029624:Ferns / Q000378:metabolism* / Q000382:microbiology*; D040161:Frankia / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology*; D017550:Spectroscopy, Fourier Transform Infrared; D013194:Staining and Labeling; D013499:Surface Properties; D013559:Symbiosis
chemical_list: D002241:Carbohydrates; D005227:Fatty Acids; D003224:Congo Red
references.citation: Proc Natl Acad Sci U S A. 1985 Sep;82(18):6231-5
references.pmid: 3862129
references.citation: FEMS Microbiol Ecol. 2009 Oct;70(1):132-41
references.pmid: 19678845
references.citation: Biotechnol Bioeng. 2005 Feb 20;89(4):373-80
references.pmid: 15643630
references.citation: Infect Immun. 1977 Oct;18(1):94-8
references.pmid: 409688
references.citation: Microbiology (Reading). 2002 Oct;148(Pt 10):3089-3100
references.pmid: 12368442
references.citation: Genome Res. 2007 Jan;17(1):7-15
references.pmid: 17151343
references.citation: Physiol Plant. 2008 Aug;133(4):776-85
references.pmid: 18397207
references.citation: Microbes Environ. 2010;25(4):241-52
references.pmid: 21576879
references.citation: Mol Plant Microbe Interact. 2000 Jan;13(1):107-12
references.pmid: 10656591
references.citation: Plant Physiol. 2010 Nov;154(3):1372-80
references.pmid: 20826704
references.citation: J Plant Growth Regul. 2000 Jun;19(2):167-182
references.pmid: 11038226
references.citation: Glycobiology. 2008 Nov;18(11):832-41
references.pmid: 18723691
references.citation: Microbiology (Reading). 1999 Jun;145 ( Pt 6):1317-1324
references.pmid: 10411258
references.citation: Arch Microbiol. 2012 Jan;194(1):13-20
references.pmid: 21861152
references.citation: Curr Protein Pept Sci. 2011 Mar;12(2):156-64
references.pmid: 21348842
references.citation: Appl Environ Microbiol. 2010 Apr;76(8):2451-60
references.pmid: 20190089
references.citation: Microbiol Rev. 1993 Jun;57(2):293-319
references.pmid: 8336669
references.citation: Eur J Biochem. 2003 Apr;270(7):1365-80
references.pmid: 12653992
references.citation: Plant Physiol. 1999 Sep;121(1):113-22
references.pmid: 10482666
references.citation: Appl Environ Microbiol. 2010 Sep;76(18):6266-76
references.pmid: 20675447
references.citation: Anal Biochem. 1985 Oct;150(1):76-85
references.pmid: 3843705
references.citation: EMBO J. 1987 May;6(5):1173-9
references.pmid: 16453763