A TIR-NLR Gene from Arabidopsis Pla-1 Confers Resistance to Geminivirus Infection
Geminiviruses are single-stranded DNA viruses that infect and cause diseases in many plant species including economically important crops. Finding genetic resources that specify resistance to geminivirus infection would help us not only to understand the virus pathogenesis and plant defense mechanisms but also to decrease agricultural losses. Arabidopsis thaliana accession Pla-1 was shown to resist infections from several geminivirus species and the major resistance determining locus, GRP1, has been mapped to chromosome 1. In this study, we fine-mapped the GRP1 locus and narrowed it to a 0.6-Mb region. We performed RNA-Seq to screen for genes in this region upregulated in Pla-1 compared to the susceptible Col-0 plants when infected by Cabbage leaf curl virus. Among such genes AT1G31540 and AT1G32230 encode proteins with variations between Pla-1 and Col-0. When expressed in Col-0, only AT1G31540 conferred resistance to Cabbage leaf curl virus by limiting viral DNA accumulation and suppressing leaf chlorosis. AT1G31540 encodes a TIR type NLR protein with two segments in the leucine-rich repeat domain and a C-JID integrated domain at the C-terminus. A shorter isoform from this gene lacking the second leucine-rich repeat segment and the integrate domain did not show any resistance. This study has expanded the pool of geminivirus resistance genes and demonstrated that the TIR-NLR mediated effector triggered plant innate immunity is also involved in defense against geminivirus infection.