Endophytic Occupation of Root Nodules and Roots of Melilotus dentatus by Agrobacterium tumefaciens
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Agrobacterium strains have been frequently isolated from the root nodules of different legumes. Various possible mechanisms have been proposed to explain the existence of these bacteria in nodules, but there is no sufficient experimental evidence to support the estimations. In this work, we proved that the Agrobacterium strain CCBAU 81181, which was originally isolated from the root nodules of Onobrychis viciaefolia, and a symbiotic strain of Sinorhizobium meliloti CCBAU 10062 could coinhabit the root nodules of Melilotus dentatus. Analyses were performed by using a fluorescence marker, reisolation of bacteria from nodules, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) of whole cellular proteins, and polymerase chain reaction amplification of symbiotic genes. The inoculation of A. tumefaciens CCBAU 81181 did not affect the growth and nodulation of plants. CCBAU 81181 and 24 other Agrobacterium strains isolated from nodules were incapable of nodulating on their original or alternative host and 22 strains of these strains were endophytes in the roots and stems of their hosts. Also, the tumor-inducing A. tumefaciens strains IAM 13129T and C58 were found capable of entering the roots of Glycyrrhiza pallidiflora, but did not cause pathogenic symptoms. With these results, we conclude that A. tumefaciens strains could be endophytic bacteria in the roots, stems, and root nodules. This finding partially explains why Agrobacterium strains were frequently isolated from the surface-sterilized nodules.
KeywordsRhizobium Root Nodule Agrobacterium Endophytic Bacterium Agrobacterium Strain
This work was supported by the State Key Basic Research and Development Plan of China (2006CB100206, 2004DKA30560-1 and 2001CB108905). E.T.W. thanks CONACyT, Mexico, for their financial support (grant number 34123-N).
- 1.Alazard, D, Duhoux, E (1990) Development of stem nodules in a tropical forage legume Aeschynomene afraspera. J Exp Bot 41: 1199–1206Google Scholar
- 6.Chen, WM, James, EK, Prescott, AR, Kierans, M, Sprent, JI (2003) Nodulation of Mimosa spp. by the β-Proteobacterium Ralstonia taiwanensis. Mol Plant–Microb Interact 16: 1051–1061Google Scholar
- 7.De Lajudie, P, Willems, A, Nick, G, Mohamed, TS, Torck, U, Filai-Maltouf, A, Kersters, K, Dreyfus, B, Lindström, K, Gillis, M (1999) Agrobacterium bv. 1 strains isolated from nodules of tropical legumes. Syst Appl Microbiol 22: 119–132Google Scholar
- 9.Gao, JL, Turner, SL, Kan, FL, Wang, ET, Tan, ZY, Qiu, YH, Gu, J, Terefework, Z, Young, JP, Lindström, K, Chen, WX (2004) Mesorhizobium septentrionale sp. nov. and Mesorhizobium temperatum sp. nov., isolated from Astragalus adsurgens growing in the northern regions of China. Int J Syst Evol Microbiol 54: 2003–2012PubMedCrossRefGoogle Scholar
- 10.Hallmann, J, Quadt-Hallmann, A, Mahaffee, WF, Kloepper, JW (1997) Bacterial endophytes in agricultural crops. Can J Microbiol 43: 895–914Google Scholar
- 13.Hiroyuki, S, Hiroyuki, I, Izumi, M (1995) PCR detection of Ti and Ri plasmids from phytopathogenic Agrobacterium strains. Appl Environ Microbiol 61: 828–831Google Scholar
- 16.Imshenetskii, AA, Pariiskaia, AN, Gorelova, OP (1976) The presence of Agrobacterium tumefaciens in lucerne root nodules. Mikrobiol 45: 561–563 (in Russian)Google Scholar
- 24.Stuurman, N, Bras, CP, Schlaman, H.R.M., Wijfjes, A.H.M., Bloemberg, G, Spaink, HP (2000) Use of green fluorescent protein color variants expressed on stable broad-host-range vectors to visualize rhizobia interacting with plants. Mol Plant–Microb Interact 13: 1163–1169Google Scholar
- 28.Vincent, JM (1970) A Manual for the Practical Study of Root Nodule Bacteria. Blackwell Scientific, OxfordGoogle Scholar