Fig. 1: SGP1 is an apoplastic elicitor of cell death in N. benthamiana.

a Systematic identification of SGP1 among U. virens secreted proteins. The numbers in circles represent proteins that met successively stringent criteria. b Regions of SGP1 examined for cell death activity. c Representative N. benthamiana leaves at 5 d after inoculation with Agrobacterium strains carrying the indicated genes in vector pGR107. Similar results were obtained from 3 independent experiments (Supplementary Data 3). d Western blot analysis of the indicated proteins transiently expressed in N. benthamiana. The red asterisks (*) indicate the predicted protein sizes in kDa. e, f Cell death induced by recombinant SGP1 protein from E. coli. MBP protein serves as a control (MBP, as the tag in empty vector, was purified in the same way as SGP1rec). Five independent experiments were performed, with five plants in each experiment. e Determination of purified SGP1rec EC₅₀ values in cell death-inducing activity, based on cell death index (Supplementary Fig. 2). Values are means ± SD of five experiments. Different letters indicate statistically significant differences (P < 0.01; Duncan’s multiple range test). f Representative N. benthamiana leaves infiltrated with purified SGP1rec (1.5 nM to 1.5 μM). Upper panel, photos directly taken at 2 days post-infiltration (dpi). Lower panel, photos taken at 2 dpi after staining with trypan blue.