Fig. 7: Alignment and features of the terminal four C3, eJM, and TM region in LRR-RLKs and LRR-RLPs.

a Alignment of the C3, eJM, and TM region in LRR-RLKs (from subgroups II, XII, XI, Xa, Xb) and LRR-RLPs. The BRI1/BRL clade is highlighted in purple; PSKR/PSY1R clade is highlighted in cyan and LRR-RLP with the ID + 4LRR clade (see Fig. 4c) is highlighted in light green. Amino acid residues involved in brassinosteroid (BR) binding for BRI/BRL and residues required for SERK interaction for BRI1/BRL, PSKR1, and RXEG1 (LRR-RLP) are highlighted. The colour code for each highlight is indicated in the box on top. For the eJM region, amino acid residues with negative charges are highlighted in red, and amino acids with positive charges are in highlighted blue. The GxxxG motif in the TM region is highlighted in yellow. The interaction sites were calculated using iCn3D⁹⁸ with the following thresholds: hydrogen bonds: 4.2 Å; salt bridges/ionic bonds: 6 Å; contacts/interactions: 4 Å. For details, please refer Fig. 5. b Percentages of LRR-RLKs or LRR-RLPs with the stated amino acid residues in the corresponding position in a. Percentages (%) were calculated by the number of LRR-RLKs or LRR-RLPs in the subgroup with the stated residue divided by the number of LRR-RLKs or LRR-RLPs in the subgroup without the stated residue × 100. c Sequence similarity tree of the eJM-TM-cJM region from all LRR-containing cell-surface receptors of 350 species. Branches are colour-labelled as indicated. The inner ring and middle ring indicate the lineage and subclass/order of the corresponding protein (species) from the branch. Outer ring represents the LRR-RLP or LRR-RLK classification, which is indicated in Fig. 4d. Characterized LRR-RLK-Xb and LRR-RLP members are labelled. The BRI/BRL-clade and the PSKR/PSY1R-clades are also labelled. d Overall charge distribution in eJM (left), percentage of receptors with GxxxG (middle), and GxxxGxxxG (right) in the TM region. For b, d RLP/RLK-Xb (outside clade) refers to receptors outside the light grey clade in Fig. 4f. RLP/RLK-Xb (within clade) refers to receptors inside the light grey clade in Fig. 4f. Number of cell-surface receptors (n) in each LRR-RLK subgroup: I, n  =  752; II, n = 682; III, n = 6572; IV, n = 1033; V, n = 8; VI-1, n = 84; V1-2, n = 146; VII, n  =  1720; VIII-1, n  =  195; VIII-2, n  =  411; IX, n  =  70; Xa, n  =  96; Xb, n  =  3182; XI, n  =  8807; XII, n  =  12863; XIIIa, n  =  739; XIIIb, n  =  465; XIV, n  =  241; XV, n  =  548; Xb (outside clade), n  =  580; Xb (within clade), n = 2527; BRI/BRL clade, n = 1170; PSKR/PSY1R clade, n = 1347. Number of cell-surface receptors (n) in each LRR-RLP subgroup: LRR-RLP (RLP), n = 24970; RLP (outside clade), n = 5000; RLP (within clade), n = 19970. Boxplot elements: center line, median; bounds of box, 25th and 75th percentiles; whiskers, 1.5 × IQR from 25th and 75th percentiles.