Identification of a novel Arabidopsis thaliana nitric oxide-binding molecule with guanylate cyclase activity in vitro.

While there is evidence of nitric oxide (NO)-dependent signalling via the second messenger cyclic guanosine 3',5'-monophosphate (cGMP) in plants, guanylate cyclases (GCs), enzymes that catalyse the formation of cGMP from guanosine 5'-triphosphate (GTP) have until recently remained elusive and none of the candidates identified to-date are NO-dependent. Using both a GC and heme-binding domain specific (H-NOX) search motif, we have identified an Arabidopsis flavin monooxygenase (At1g62580) and shown electrochemically that it binds NO, has a higher affinity for NO than for O(2) and that this molecule can generate cGMP from GTP in vitro in an NO-dependent manner.

The Arabidopsis wall associated kinase-like 10 gene encodes a functional guanylyl cyclase and is co-expressed with pathogen defense related genes.

Background: Second messengers have a key role in linking environmental stimuli to physiological responses. One such messenger, guanosine 3',5'-cyclic monophosphate (cGMP), has long been known to be an essential signaling molecule in many different physiological processes in higher plants, including biotic stress responses. To date, however, the guanylyl cyclase (GC) enzymes that catalyze the formation of cGMP from GTP have largely remained elusive in higher plants.

A recombinant plant natriuretic peptide causes rapid and spatially differentiated K+, Na+ and H+ flux changes in Arabidopsis thaliana roots.

Plant natriuretic peptides (PNPs) belong to a novel class of systemically mobile molecules that are structurally similar to the N-terminal domain of expansins and affect physiological processes such as protoplast volume regulation at nano-molar concentrations. Here we demonstrate that AtPNP-A, a recombinant Arabidopsis thaliana PNP causes rapid H(+) influx in the elongation zone of A. thaliana roots but not in the mature zone.

AtPNP-A is a systemically mobile natriuretic peptide immunoanalogue with a role in Arabidopsis thaliana cell volume regulation.

Cellular and physiological evidence suggests the presence of a novel class of systemically mobile plant molecules that are recognized by antibodies against vertebrate atrial natriuretic peptides (ANPs). In order to characterize the function of these immunoanalogues we have expressed the full-length recombinant (AtPNP-A[1-126]) and demonstrate that this molecule induces osmoticum-dependent H(2)O uptake into protoplasts at nanomolar concentrations and thus affects cell volume. A similar response is also seen with a recombinant that does not contain the signal peptide (AtPNP-A[26-126]) as well as a short domain (AtPNP-A[33-66]) that shows homology to the vertebrate peptide.