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Applied and Environmental Microbiology, November 2005, p. 7271-7278, Vol. 71, No. 11
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.11.7271-7278.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Ascending Migration of Endophytic Rhizobia, from Roots to Leaves, inside Rice Plants and Assessment of Benefits to Rice Growth Physiology

Feng Chi,1,2 Shi-Hua Shen,1 Hai-Ping Cheng,3 Yu-Xiang Jing,1* Youssef G. Yanni,4 and Frank B. Dazzo5

Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People's Republic of China,1 Graduate School of the Chinese Academy of Sciences, Beijing 10039, People's Republic of China,2 Lehman College, City University of New York, New York, New York 10468,3 Sakha Agricultural Research Station, Kafr El-Sheikh 33717, Egypt,4 Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 488245

Received 2 February 2005/ Accepted 6 June 2005

Rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. Despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. We examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. The results indicated a dynamic infection process beginning with surface colonization of the rhizoplane (especially at lateral root emergence), followed by endophytic colonization within roots, and then ascending endophytic migration into the stem base, leaf sheath, and leaves where they developed high populations. In situ CMEIAS image analysis indicated local endophytic population densities reaching as high as 9 x 1010 rhizobia per cm3 of infected host tissues, whereas plating experiments indicated rapid, transient or persistent growth depending on the rhizobial strain and rice tissue examined. Rice plants inoculated with certain test strains of gfp-tagged rhizobia produced significantly higher root and shoot biomass; increased their photosynthetic rate, stomatal conductance, transpiration velocity, water utilization efficiency, and flag leaf area (considered to possess the highest photosynthetic activity); and accumulated higher levels of indoleacetic acid and gibberellin growth-regulating phytohormones. Considered collectively, the results indicate that this endophytic plant-bacterium association is far more inclusive, invasive, and dynamic than previously thought, including dissemination in both below-ground and above-ground tissues and enhancement of growth physiology by several rhizobial species, therefore heightening its interest and potential value as a biofertilizer strategy for sustainable agriculture to produce the world's most important cereal crops.

* Corresponding author. Mailing address: Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People's Republic of China. Phone: 86-10-62836545. Fax: 86-10-62596594. E-mail: yxjing{at}ns.ibcas.ac.cn.

Applied and Environmental Microbiology, November 2005, p. 7271-7278, Vol. 71, No. 11
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.11.7271-7278.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Chen, C., Gao, M., Liu, J., Zhu, H. (2007). Fungal Symbiosis in Rice Requires an Ortholog of a Legume Common Symbiosis Gene Encoding a Ca2+/Calmodulin-Dependent Protein Kinase. Plant Physiol. 145: 1619-1628 [Abstract] [Full Text]  
  • Perrine-Walker, F. M., Prayitno, J., Rolfe, B. G., Weinman, J. J., Hocart, C. H. (2007). Infection process and the interaction of rice roots with rhizobia. J Exp Bot 0: erm181v1-erm181 [Abstract] [Full Text]  


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