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Integrating Genetics and Genomics to Advance Soybean Research



Reference Report for AP20210802.1
Title:Symbiotic incompatibility between soybean and Bradyrhizobium arises from one amino acid determinant in soybean Rj2 protein
Authors:Sugawara, M., Umehara, Y., Kaga, A., Hayashi, M., Ishimoto, M., Sata, S., Mitsui, H., Minamisawa, K.
Source:Sugawara et al. 2019 PLoS One, 14(9): e0222469
Abstract:Cultivated soybean (Glycine max) carrying theRj2allele restricts nodulation with specificBradyrhizobiumstrains via host immunity, mediated by rhizobial type III secretory protein NopP and the host resistance protein Rj2. Here we found that the single isoleucine residue I490 in Rj2 is required for induction of symbiotic incompatibility. Furthermore, we investigated the geographical distribution of theRj2-genotype soybean in a large set of germplasm by single nucleotide polymorphism (SNP) genotyping using a SNP marker for I490. By allelic comparison of 79 accessions in the Japanese soybean mini-core collection, we suggest substitution of a single amino acid residue (R490 to I490) in Rj2 induces symbiotic incompatibility withBradyrhizobium diazoefficiensUSDA 122. The importance of I490 was verified by complementation ofrj2-soybean by the dominant allele encoding the Rj2 protein containing I490 residue. TheRj2allele was also found inGlycine soja, the wild progenitor ofG.max, and their single amino acid polymorphisms were associated with theRj2-nodulation phenotype. By SNP genotyping against 1583 soybean accessions, we detected theRj2-genotype in 5.4% ofG.maxand 7.7% ofG.sojaaccessions. Distribution of theRj2-genotype soybean plants was relatively concentrated in the temperate Asian region. These results provide important information about the mechanism of host genotype-specific symbiotic incompatibility mediated by host immunity and suggest that theRj2gene has been maintained by environmental conditions during the process of soybean domestication.






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