Journal Article

R gene-controlled host specificity in the legume-rhizobia symbiosis

Zhu, Hongyan, Gao, Muqiang, Tang, Fang, Yang, Shengming, Krishnan, Hari B

2010

Overview

Leguminous plants can enter into root nodule symbioses with nitrogen-fixing soil bacteria known as rhizobia. An intriguing but still poorly understood property of the symbiosis is its host specificity, which is controlled at multiple levels involving both rhizobial and host genes. It is widely believed that the host specificity is determined by specific recognition of bacterially derived Nod factors by the cognate host receptor(s). Here we describe the positional cloning of two soybean genes Rj2 and Rfg1 that restrict nodulation with specific strains of Bradyrhizobium japonicum and Sinorhizobium fredii, respectively. We show that Rj2 and Rfg1 are allelic genes encoding a member of the Toll-interleukin receptor/nucleotide-binding site/leucine-rich repeat (TIR-NBS-LRR) class of plant resistance (R) proteins. The involvement of host R genes in the control of genotype-specific infection and nodulation reveals a common recognition mechanism underlying symbiotic and pathogenic host-bacteria interactions and suggests the existence of their cognate avirulence genes derived from rhizobia. This study suggests that establishment of a root nodule symbiosis requires the evasion of plant immune responses triggered by rhizobial effectors.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Alleles / Bacteria / bacterial diseases of plants / Base Sequence / binding sites / Biological Sciences / Bradyrhizobium - genetics / Bradyrhizobium japonicum / Cloning / Cloning, Molecular / DNA, Plant - genetics / double prime R protein / Evolution, Molecular / Fabaceae / Fabaceae - genetics / Fabaceae - metabolism / Fabaceae - microbiology / Genes / Genes, Bacterial / Genes, Plant / Genetic Complementation Test / Genetic loci / genetic resistance / Genomics / genotype / Genotype & phenotype / Glycine max / Glycine max - genetics / Glycine max - microbiology / host plants / Host specificity / host-pathogen relationships / Immune response / Infection / Infections / leucine / molecular cloning / Molecular Sequence Data / Mutation / Nitrogen Fixation / Nod factors / Nodulation / plant proteins / Plant Proteins - genetics / Plant resistance / Plant roots / Plants / Proteins / receptors / Rhizobium / Rhizobium - genetics / RNA Interference / root nodules / Roots / Sinorhizobium fredii / Sinorhizobium fredii - genetics / Soil microorganisms / Soybeans / Symbiosis / Symbiosis - genetics