Plant NB-LRR genes mediate plant innate immunity and cause the programmed cell death of plant cells. Very little, however, is known about these processes. Taken advantage of easy manipulation of bacteria, genetic analysis was made to understand the mechanism of lethality of NB-LRR proteins to bacteria and correlate the information back to how NB-LRR proteins cause cell death in plants. It was found that only L3 encoded by NB-LRR gene L3 (At1g15890) specifically caused significant death of BL21(DE3), while other NBS-LRR proteins did not, and 760-851, the truncated form of 13, was essential to the lethality of L3. Gene yedZ (EG14048) and nupG (EG10664) were identified by genome re-sequencing from E. coli, both of which mediate the toxicity of L3 in E. coli. Furthermore, NupG can affect the activity of peroxidase and significantly suppress plant cell death, which is induced by NB-LRR protein RPM1(D505V) encoded by RPM1 (At3g07040) in N. benthamiana. These findings provide evidence that functional analysis of plant NB-LRR genes in microorganisms might be a potential and rapid method. (C) 2016 Elsevier Inc. All rights reserved.