Fig. 7
Phosphorylation of RGS1 positively regulates immune signaling. a–c Mutations of RGS1 phosphosites modulate chitin-induced defense gene expression. Protoplasts from rgs1-2 plants were transfected with different forms of RGS1-HA plasmids, treated with chitin for 3 h, and qPCR was performed for the expression of NHL6 (a), AT3G18250 (b), and BIP3 (c). Different letters indicate significant difference at P < 0.05 (mean ± SD, one-way ANOVA followed by Tukey’s post hoc test). d RGS1S431A confers increased inhibition of immune signaling. rgs1-2 was complemented with the WT RGS1 (WT) or RGS1S431A mutant (S431A) constructs, and resulting lines were examined for flg22-triggered H2O2 production. Different letters indicate significant difference at P < 0.05 (mean ± SD, n ≥ 6, one-way ANOVA followed by Tukey’s post hoc test). e RGS1S431A confers increased susceptibility to Pst DC300 upon spray inoculation. The indicated genotypes were sprayed with Pst DC3000 at 5 × 108 CFU/mL and bacterium number was determined 3 days later. Different letters indicate significant difference at P < 0.05 (mean ± SD, n ≥ 6, one-way ANOVA followed by Tukey’s post hoc test). f Model for RGS1-Gαβγ regulation by FLS2. In the resting state, the GαGDPβγ heterotrimers associate with FLS2, and this is maintained by interactions of RGS1 with FLS2 and XLG2/GPA1. Perception of flg22 induces the formation of an active FLS2-BAK1 receptor complex and BIK1/PBLs-dependent phosphorylation of RGS1 at Ser428/431, which promotes the dissociation of RGS1 from FLS2 and the G proteins. In the absence of RGS1, GαGDP is spontaneously converted to GαGTP, the latter dissociates from Gβγ to activates its effector proteins such as RbohD. Gα hydrolyzes GTP through its intrinsic GTPase activity and cycles back to GαGDP. The experiments were performed two (a–c) or three (d, e) times with similar results
