Fig. 1: BcSSP2 is an effector protein.
a Venn diagram shows the overlap of B. cinerea genes which are upregulated during infection and predicted to encode putative effectors. The 15 overlapping genes were shortlisted as effector candidates. b The lesion area and edge area of Arabidopsis leaves infected by B. cinerea. A representative B. cinerea-infected leaf (48 hpi) with trypan blue staining shows the hyphae and plant cells in the edge and lesion area. c Heatmap represents fold change (FC) of expression levels of 15 effector candidates in the edge area relative to the lesion area in B. cinerea-infected leaves. The effector candidate with the most elevated expression (namely effector candidate # 1, designated BcSSP2) was selected for further study. d qRT-PCR analysis on the expression levels of BcSSP2 in the in vitro culture, the edge or lesion area of B. cinerea infection in Arabidopsis leaves. Candidates # 2 and # 12 serve as the controls. Data are mean ± SD (n = 3). Statistical significance was determined by two-sided Student’s t test. e Yeast YTK12 strain carrying SUC2 invertase (fused with the signal peptide of BcSSP2) reduces 2,3,5-triphenyltetrazolium chloride to red formazan, indicating invertase secretion. Mg87 and Avr1b serve as the negative and positive controls, respectively. See also Supplementary Fig. S2B. f Entry of BcSSP2 protein into Arabidopsis root cells. Arabidopsis root tips were incubated with Alexa 546-labeled BcSSP2 or control protein (TrxA-His) for 12–16 h, and then washed 4 times before imaging. Scale bar: 100 μm. BL bright light. g BcSSP2 is translocated into host cells in the infection process. Tobacco leaves expressing GFP1-10 (engineered GFP protein consists of strands 1–10 with a specific exclusion of strand 11) for 24 h were then drop-inoculated with B. cinerea expressing GFP11 tagged BcSSP2 (BcSSP2-GFP11) or signal peptide of BcSSP2 (SP-GFP11 serves as a control). The edge area was visualized by confocal imaging at 24 hpi for effector translocation. Scale bar: 100 μm. BL, bright light. Source data are provided as a Source Data file.
