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Breakthroughs Made by NAU in the Interaction Mechanism between Rhizobium and its Host Plants

The research team led by Professor Jun Zhu at NAU has recently published a paper entitled Plant nodulation inducers enhance horizontal gene transfer of Azorhizobium caulinodans symbiosis island on the Proceeding of the National Academy of Sciences of the USA, one of the most authoritative journals in the world with an IF of 9.4. The paper is co-first authored by NAU Dr. Jun Ling and associate professor Hui Wang from College of Life Sciences, and co-corresponding authored by NAU Professor Jun Zhu and Professor Zengtao Zhong. Faculty and students including Tao Li, Ping Wu, Yu Tang, Huiming Zheng are also major participants of this project.

Horizontal gene transfer (HGT) of genomic islands endows recipient bacteria with new physiological functions and serves as a driving force of bacterial evolution. Many pathogens and symbionts use this mechanism to spread mobile genetic elements that carry genes important for interaction with their eukaryotic hosts. However, the role of the host in this process remains unclear. Azorhizobium caulinodans ORS571, the symbiont of Sesbania rostrate, is able to enhance the growth of host by symbiotic nitrogen fixation. Thesymbiosis island of Azorhizobium caulinodans is an 87.6-kbintegrative and conjugative element which contains nodulation, conjugational transfer and other processes related genes. This paper comes to an unprecedented conclusion that the symbiotic island in Azorhizobium can be transferred to other rhizobial genera, which enables the recipients that originally cannot live in symbiosis with Sesbania rostrate to form nodule and fix nitrogen. It not only increases the efficiency of nitrogen fixation, but also expanding their host range. During the process, the host plays an important role through secreting in roots flavonoids which induce the nodulation process in the rhizobium-legume mutualistic symbiosis as well as improves the HGT frequency in the rhizosphere.


Our study suggests that rhizobia may sense rhizosphere environments and transfer their symbiosis gene contents to othergenera of rhizobia, thereby broadening rhizobial host-range specificity. The result also enjoys comments from a renowned journal in microbiology under Cell, Trends in Microbiology (IF 9.7).


Professor Jun Zhu and his research team work on the interaction between microbes and hosts and have published many papers on Cell Reports, Molecular Microbiology, Infection and Immunity, Journal of Bacteriology, Applied and Environmental Microbiology, etc. The study published on PNAS were mainly led and completed by scholars at NAU. Suggestions in writing and revising were also made by Catherine Masson-Boivin, researcher from L'Institut National de la Recherche Agronomique de France and Dr. Nawar Naseer from the University of Pennsylvania.


See also:

The paper on PNAShttp://www.pnas.org/content/113/48/13875.full

Comments from Trends in Microbiologyhttp://dx.doi.org/10.1016/j.tim.2015.10.007