Over-expression of GmKR3, a TIR-NBS-LRR type R gene, confers resistance to multiple viruses in soybean.

KEY MESSAGE: That overexpression of GmKR3 enhances innate virus resistance by stimulating. Soybean mosaic virus (SMV) is found in many soybean production areas, and SMV infection is one of the prevalent viral diseases that can cause significant yield losses in soybean. In plants, resistance (R) genes are involved in pathogen reorganization and innate immune response activation. Most R proteins have nucleotide-binding site and leucine-rich repeat (NBS-LRR) domains, and some of the NBS-LRR type R proteins in dicots have Toll/Interleukin-1 Receptor (TIR) motifs. We report here the analysis of the over-expression of GmKR3, a soybean TIR-NBS-LRR type R gene on virus resistance in soybean. When over-expressed in soybean, GmKR3 enhanced the plant's resistance to several strains of SMV, the closely related potyviruses bean common mosaic virus (BCMV) and watermelon mosaic virus (WMV), and the secovirus bean pod mottle virus (BPMV). Importantly, over-expression of GmKR3 did not affect plant growth and development, including yield and qualities of the seeds. HPLC analysis showed that abscisic acid (ABA) content increased in the 35S:GmKR3 transgenic plants, and in both wild-type and 35S:GmKR3 transgenic plants in response to virus inoculation. Consistent with this observation, we found that the expression of two ABA catabolism genes was down-regulated in 35S:GmKR3 transgenic plants. We also found that the expression of Gm04.3, an ABA responsive gene encoding BURP domain-containing protein, was up-regulated in 35S:GmKR3 transgenic plants. Taken together, our results suggest that overexpression of GmKR3 enhanced virus resistance in soybean, which was achieved at least in part via ABA signaling.