[Frontiers in Bioscience 16, 2008-2051, June 1, 2011]

Parallel evolution of Nitric Oxide signaling: Diversity of synthesis and memory pathways

Leonid L. Moroz1,2, Andrea B. Kohn1

1The Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd, St. Augustine, FL, 32080-8623, USA, 2Dept. of Neuroscience and McKnight Brain Institute, University of Florida, Gainesville, FL, 32611, USA

TABLE OF CONTENTS

1. Abstract
2. Introduction
2.1. Toxic gases as endogenous messengers in multicellular organisms
2.2. Carbon monoxide (CO)
3. The concept of the NO microenvironment and volume signaling in animal physiology
4. NO in comparative and evolutionary contexts: The ancient messenger
5. Multiplicity of NO synthetic pathways
6. Abiotic Reduction of Nitrites: Alternative Sources of NO formation
7. Biological functions of non-enzymatic NO synthesis
8. Conditions for intracellular non-enzymatic NO formation: Neurons as models
9. Nitrite photolysis as a source of NO in biological systems
10. The Diversity of Animal (Conventional) Nitric Oxide Synthases (NOS): Models, Genes and Phylogeny of NOS
11. NOS in Invertebrates and their nervous systems
12. Do non-conventional L-arginine-NO synthases exist in animals?
13. The role of NO in development and plasticity mechanisms: insights from insects and snails
14. Summary and perspective
15. Acknowledgements
16. References

1. ABSTRACT

The origin of NO signaling can be traceable back to the origin of life with the large scale of parallel evolution of NO synthases (NOSs). Inducible-like NOSs may be the most basal prototype of all NOSs and that neuronal-like NOS might have evolved several times from this prototype. Other enzymatic and non-enzymatic pathways for NO synthesis have been discovered using reduction of nitrites, an alternative source of NO. Diverse synthetic mechanisms can co-exist within the same cell providing a complex NO-oxygen microenvironment tightly coupled with cellular energetics. The dissection of multiple sources of NO formation is crucial in analysis of complex biological processes such as neuronal integration and learning mechanisms when NO can act as a volume transmitter within memory-forming circuits. In particular, the molecular analysis of learning mechanisms (most notably in insects and gastropod molluscs) opens conceptually different perspectives to understand the logic of recruiting evolutionarily conserved pathways for novel functions. Giant uniquely identified cells from Aplysia and related species precent unuque opportunities for integrative analysis of NO signaling at the single cell level.