PSIG1 is required for flg22-induced cell death suppression.

a, Phosphoregulation of PSIG1 in the PAMP-signaling mutants. Relative abundance of the ‘DIQGSDNAIPLpSPQWLLSKPGENK’ phosphopeptide upon flg22 treatment. Arabidopsis seedlings were treated with 1 μM flg22 for 10 min or received a mock treatment (dH₂O) prior to phosphoproteome analysis. Data are shown as the mean ± SD from three independent experiments. b, The bak1-5 and bik1 pbl1 mutants induce cell death upon Hpa Noco2 infection. Plants were inoculated with spores of Hpa Noco2, and dead cells on true leaves were visualized by trypan blue staining 5 days after inoculation. The scale bar represents 200 μm. c, Induction of RPS4-triggered cell death is pronounced in the bak1-5 and bik1 pbl1 mutants. Plants were spray inoculated with 1 x 10⁸ c.f.u. ml^-1 of Pto AvrRPS4, and dead cells were visualized by trypan blue staining 2 days after inoculation. The scale bar represents 200 μm. d, Flg22-induced restriction of effector injection by Pto is intact in the psig1-1 mutant. Leaves were infiltrated with 100 nM flg22 or received a mock treatment (dH₂O). Twenty-four h after the pretreatments, plants were spray inoculated with 1 x 10⁸ c.f.u. ml^-1 of Pto AvrRPM1, and dead cells were visualized by trypan blue staining 24 h after inoculation. The scale bar represents 200 μm. e, Suppression of flg22-induced FB1-triggered cell death is compromised in the psig1-1 mutant. Leaves were infiltrated with FB1 after mock (dH₂O) or flg22 pretreatments. Control leaves were infiltrated with dH₂O (mock) after mock (dH₂O) or flg22 pretreatments. Photographs were taken 4 days after FB1 infiltration. Dead cells were visualized by trypan blue staining. The scale bar represents 200μm.