Alignment of a plant natriuretic peptide from Arabidopsis thaliana (AtPNP-A; Accession No. AAD08935) and the plant natriuretic peptide-like protein from Xanthomonas axonopodis (Accession No. NP_642965). Solid triangles delineate the domain in AtPNP-A that has been shown to be sufficient to induce increased water uptake into plant protoplasts . The gray sequence represents the signal peptide and the underlined sequence is the domain spanning the first psi loop. The α helices are marked in red, the dotted red line spans an α helix with a 3–10 helix component (between QNG). The β sheets are marked in blue. Asterisks (*) identify identical amino acid, colons (:) are conservative amino acid replacements and dots (.) are semi-conservative amino acid replacements. Arrows (↑) mark conserved cysteines, the open arrow (↑) marks a position where other PNP-like molecules have a tyrosine or a phenylalanine.