Abstract
The structural complexity of plant proteins, particularly receptor-like kinases, has garnered significant attention in recent research. This research identifies Physcomitrium patens ERECTA-like receptor 1 (PpERL1) as a new guanylate cyclase (GC) within the cytoplasmic kinase domain by examining its structural and functional properties. Comprehensive sequence alignment analyses reveal substantial variability among ERECTA-like proteins from mosses in contrast to vascular plants, while GC motifs display remarkable conservation, suggesting a critical functional relevance. In vitro tests validate the GC activity of recombinant PpERL1, with key residue substitutions at positions 1 and 14 leading to a decrease in GC activity. Notably, cGMP does not impact PpERL1's kinase activity, while inhibits its enzymatic function, contrasting with regulatory mechanisms observed in vascular plant GCs. Independent regulatory mechanisms are shown by calcium ions increasing GC activity without affecting kinase functioning. These results demonstrate an evolutionary divergence in the regulatory interactions between GC and kinase domains in mosses versus vascular plants, reflecting adaptive strategies unique to non-vascular plant lineages. Supplementary information: The online version contains supplementary material available at 10.1007/s12298-025-01606-1.