Abstract Detail

Ecological Section

Bamba, M. [1], Nakata, S. [2], Aoki, S. [3], Takayama, K. [4], Farfán, J. N. [5], Ito, M. [6], Miya, M. [1], Kajita, T [7].

Analysis of nodulating bacteria associated with pantropical legumes with sea-drifted seeds.

The symbiotic relationship between leguminous plants and nodulating bacteria is a well-known example of mutualism. Legumes provide photosynthetic products and a safe habitat to their bacterial symbionts. On the other hand, nodulating bacteria perform nitrogen fixation and give the products to their host plant. Thereby, nodulating bacteria proliferate in host root nodules, and legumes can grow with a low level of nitrogen in the soil. Thus, symbiosis with nodulating bacteria significantly enhances the fitness of legumes. Nevertheless, legumes do not develop symbiosis with every rhizobium that they encounter due to the host specificity. Previous researches suggested that host specificity limit the distribution of legumes in the wild. If distribution of legumes is limited by the presence of the bacterial symbionts, what is the distribution of nodulating bacteria around the world? To answer this question, we focused on “Pantropical plants with sea-drifting seeds.” These plants are widely distributed across the tropical and subtropical coastal regions, and their seeds are dispersed through ocean currents. In legumes, Canavalia rosea and Vigna marina are known as sea-dispersed plants. Almost all of them succeed in establishing a symbiotic relationship upon colonizing a new habitat. The purpose of this study is to clarify which bacteria are associated with C. rosea and V. marina. Their nodules were collected from eight countries, and nodule-associated bacteria were phylogenetically identified by 16S rRNA and nodC genes. NodC gene is one of the nodulation genes related to the host specificity. It is widely thought that horizontal transfer of nod genes has allowed host-specific nodulation abilities to be transmitted between different bacterial lineages. Thus, we chose the nodC gene to investigate effects of horizontal transfer on symbiotic specificity of C. rosea and V. marina. Phylogenetic analysis of the 16S rRNA gene showed the nodule-associated bacteria are closely related to either the genus Sinorhizobium or Bradyhrizobium. Among these bacteria, four strains from the two genera were associated with C. rosea, and five strains from the two genera were associated with V. marina. NodC phylogeny did not show any evidence for horizontal gene transfer in the nodule bacteria associated with C. rosea and V. marina. Therefore, it seems that the horizontal gene transfer of nod genes may not be related to the broad host specificity of C. rosea and V. marina. It is possible that the pantropical plants with sea-drifting seeds may recognize multiple Nod factors to allow their association with multiple nodule bacteria.

1 - Chiba university, Department of Biology, Yayoi-cho, Inage-ku, Chiba-shi, Chiba, Chiba-shi, Chiba, Chiba, 263-8522, Japan
2 - Chiba university, Department -f Biology, Yayoi-cho, Inage-ku, Chiba-shi, Chiba, Chiba-shi, Chiba, Chiba, 263-8522, Japan
3 - University of Tokyo, Department of General Systems Studies, Komaba, ,Meguro-ku, Tokyo, Japan, Tokyo, 153-8914, Japan
4 - 7-3-1 Hongo, Bunkyo-ku, The University Museum, The University Of Tokyo, Tokyo, N/A, 113-0033, Japan
5 - Avenida Xochimilco 288, Santiago Tepalcatlalpan, Mexico Distrito Federal, N/A, 16200, Mexico
6 - University Of Tokyo, Dept Of Systems Sciences, 3-8-1 Komaba, Meguro-ku, Tokyo, N/A, 153-8902, Japan
7 - Chiba University, Department Of Biology, Faculty Of Science, Chiba U, 1-33 Yayoi-cho, Inage-ku, Chiba, N/A, 263-8522, Japan

Keywords:
Nodule bacteria
Pantropical legumes with sea drifted seeds.

Presentation Type: Oral Paper:Papers for Sections
Session: 35
Location: Salon 6/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 11:45 AM
Number: 35015
Abstract ID:1041
Candidate for Awards:None