Fig. 2: SCP8 acts as a suppressor of BAK1 dependent immune responses and an inducer of PSK gene expression.

a Ethylene production in RLP42-transgenic N. benthamiana plants infiltrated with agrobacteria encoding SCP genes, followed by treatment with pg9 (1 µM). SCP proteins were expressed as N-terminal fusions with a leader peptide derived from Arabidopsis PR1 to facilitate protein secretion. SCP8 without N-terminal PR1 leader peptide (ΔspSCP8) was also expressed in this assay. Agroinfiltration was performed 3 days before the pg9 treatment, and ethylene levels were measured 2 h after pg9 treatment. b Reactive oxygen species (ROS) burst in N. benthamiana leaves infiltrated with agrobacteria encoding SCP8 genes, followed by treatment with flg22 (1 µM) and chitin (1 µM). c PSK3a gene expression in N. benthamiana leaves infiltrated with agrobacteria encoding SCP genes. Leaves were collected at 3 days post agroinfiltration for RNA isolation and quantitative PCR (qPCR) analysis. d Schematic diagram illustrating SCP8 and its homologs from different fungi used for agro-infiltration in N. benthamiana. Vd represents Verticillium dahliae SCP8 (VdSCP8), Fo denotes Fusarium oxysporum SCP8 (FoSCP8), and Nc indicates Neurospora crassa SCP8 (NcSCP8). e Ethylene production in N. benthamiana leaves infiltrated with agrobacteria expressing SCP8 homologous genes following treatment with flg22 (2 µM) and PEN (200 µg/ml). Ethylene levels were measured 2 h post elicitor treatments. For a, c, and e, bars represent means ± SE of two or three independent experiments (a, n = 5 for mock, n = 6 for pg9; e, n = 6). Data points are indicated as black dots. b Data points are indicated as black dots from three independent experiments (n = 8 for flg22, n = 12 for chitin) and plotted as box plots (center line, median; bounds of box, the first and the third quartiles; whiskers, 1.5 x IQR; error bar, minima and maxima). Statistical differences to the response observed in GFP-expressing plant are indicated (two-sided Student’s ttest).