Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Wallace, Lisa [1], Bobo, Rachel [2].

Molecular variation of the Nod factor receptor Nfr5 does not reflect specificity between Chamaecrista fasciculata (Fabaceae) and its nitrogen-fixing bacterial symbionts.

Through symbiotic relationships with nitrogen-fixing bacteria, legumes can efficiently access proper nitrogen for growth. Effective symbioses are formed after nodulation (Nod) factors are released by the bacterial symbiont to initiate symbiosis. Host plant receptors, including Nfr1 and Nfr5, are among the earliest acting genes to respond to Nod factors and establish symbiosis in the roots of legumes; these regulating receptors may therefore be useful in determining symbiotic specificity and host choice. The objective of this study was to test the hypothesis that host plants that associate with genetically diverse rhizobia symbionts are able to do so because they harbor genetic diversity at Nod factor receptors involved in establishing symbioses. To test this hypothesis, DNA sequences of a portion of the Nfr5 gene were assessed in Chamaecrista fasciculata host plants containing multiple nodules with either genetically divergent or genetically similar rhizobia, previously determined by genotyping with two bacterial genes. Plants forming symbiosis with more divergent rhizobia were predicted to exhibit higher levels of diversity in Nfr5 compared to plants with more similar rhizobia, and the highest levels of polymorphism were expected in the LsyM2 region. Contrary to our predictions, host plants in the two groups exhibited similar levels of diversity (divergent group nucleotide diversity (π) = 0.00057, haplotype diversity (Hd) = 0.490; non-divergent group π = 0.00034 and Hd = 0.324. Individuals in both groups exhibited a high number of heterozygous sites. However, no signal of adaptive evolution in Nfr5 was found in C. fasciculata. The high degree of diversity observed in Nfr5 may underlie the broad symbiotic tolerance of C. fasciculata across Bradyrhizobium. It is also likely that other genes are involved in recognizing suitable rhizobia for symbioses in this host species. Future studies will include analysis of other genes present in host plant interactions with bacterial Nod factors to further knowledge of how legumes and rhizobia establish symbioses.

1 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA
2 - Mississippi School for Mathematics and Sciences, 1100 College St. MUW-1627, Columbus, MS, 39701, USA

Keywords:
Legume-rhizobia symbiosis
Nfr5
Molecular evolution
LysM receptor kinase
Chamecrista fasciculata.

Presentation Type: Oral Paper
Session: 35, Symbioses: Plant, Animal, and Microbe Interactions
Location: 202/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 8:00 AM
Number: 35001
Abstract ID:728
Candidate for Awards:None