Fig. 5: Functional characterization of the C3 region in LRR-RLPs and LRR-RLK-Xb.
From: Evolutionary trajectory of pattern recognition receptors in plants
a–c Structures and interaction interfaces of LRR-RLKs and LRR-RLPs with SERKs. Published structures of a NbRXEG1-NbBAK153, b AtPSKR1-AtSERK148, and c AtBRI1-AtBAK150 and are shown. The left panels show the full structure, and the middle panels show the interaction sites between LRR-RLKs or LRR-RLP and SERKs. Hydrogen bonds are indicated by green dotted lines, and salt bridges are shown as cyan dotted lines. The positions of LRR residues (counting from N to C for SERKs and counting from C to N for LRR-RLKs and LRR-RLP) are shown. Amino acid residues that are important for the interactions are labelled and the QxxT motifs are highlighted in yellow (red text). The right panel represents the 2D interaction network between SERKs and the receptors. Contacts/interactions are shown in grey lines, hydrogen bonds are shown in green lines, and salt bridges are shown in cyan lines. Amino acids are labelled in colours according to their positions in the LRR motifs (counting from N to C for SERKs and counting from C to N for LRR-RLKs and LRR-RLP l). Residues around and within the QxxT motifs in BRI1, PSKR1, and RXEG1 are highlighted in yellow. Residues in SERKs that are involved in the interactions with QxxT motifs are also highlighted in yellow. Structures were visualized in iCn3D98. For a–c, the interaction sites are calculated by iCn3D with the following thresholds: hydrogen bonds: 4.2 Å; salt bridges/ionic bonds: 6 Å; contacts/interactions: 4 Å. d Structure of the terminal LRR motif of N. benthamiana (Nb)RXEG1, A. thaliana (At)RLP23, AtPSY1R, AtPSKR1, AtPSKR2, AtBRI1 and AtEFR. Structures of NbRXEG1, AtPSKR1, and AtBRI1 were published48,50,51,52,53,54. Structures of AtRLP23, AtPSY1R, AtPSKR2 and AtEFR were predicted by Alphafold297. Ectodomains are visualised in iCn3D98. e Alignment of amino acids in the last LRR motifs from NbRXEG1, AtRLP23, AtPSY1R, AtPSKR1, AtPSKR1T (G > T), AtPSKR2, AtPSKR2T (G > T), AtBRI1, AtBRI1T (G > T), and AtEFR. Amino acid residues involved in the interaction between NbRXEG1 and BAK1 are highlighted in green. The QxxT motif positions are highlighted in yellow. Amino acids with similar properties to AtRLP23 are highlighted in grey. f Design of AtRLP23 chimeras. The last LRR motif of AtRLP23 is exchanged with either AtPSY1R, AtPSKR1, AtPSKR2, AtBRI1, or AtEFR. The glycine g residues in AtPSKR1, AtPSKR2, AtBRI1 have also been mutated to threonine (T). g, l Immuno-precipitation to test interactions between AtRLP23 chimeras, AtBAK1 and AtSOBIR1. Nb leaves expressing the indicated constructs were treated with either mock or 1 μM nlp20 for 5 min. h–k Functionality testing of AtRLP23 chimeras. Nb leaves expressing the indicated constructs were treated with 1 μM nlp20 and samples were collected at indicated time points. Phosphorylation of NbSIPK and NbWIPK was detected with p-P42/44 antibody. i, k Nb leaf discs expressing the indicated constructs were collected and treated with either mock or 1 μM nlp20, and ROS production was measured for indicated time points. For i and k, solid line, mean; shaded band, s.e.m. RLU, relative light units. For details of experiential design in g–l, refer to the methods section. For g, h, j and l, the experiments were repeated at least twice with similar results.
