Figure 5.

Divergence of RALF protein sequences across the four major phylogenetic clades. (A) WebLogo3 plots to demonstrate residue conservation within the mature peptide region of the four major clades. Clade I and II (A) are shown together as the mature peptides of these sub-clades are very similar. (B) A schematic representation of the motif structure of RALF proteins from clades I, II and III in comparison to the shorter RALFs of clade IV. Proteins from both clades contain an N-terminal signal peptide, but the variable and acidic region downstream of this is much shorter and frequently absent within the clade IV RALFs. The di-basic mature peptide cleavage site is absent within clade IV, suggesting an alternate cleavage mechanism. Additionally, the YISY motif thought to be required for receptor binding is highly variable within clade IV RALFs and many proteins in this clade do not contain the second of the four typically conserved cysteine residues.