Abstract
In plants, much like in animals, nitric oxide (NO) has been established as an important gaseous signaling molecule. However, contrary to animal systems, NO-sensitive or NO-responsive proteins that bind NO in the form of a sensor or participating in redox reactions have remained elusive. Here, we applied a search term constructed based on conserved and functionally annotated amino acids at the centers of Heme Nitric Oxide/Oxygen (H-NOX) domains in annotated and experimentally-tested gas-binding proteins from lower and higher eukaryotes, in order to identify candidate NO-binding proteins in Arabidopsis thaliana. The selection of candidate NO-binding proteins identified from the motif search was supported by structural modeling. This approach identified AtLRB3 (At4g01160), a member of the Light Response Bric-a-Brac/Tramtrack/Broad Complex (BTB) family, as a candidate NO-binding protein. AtLRB3 was heterologously expressed and purified, and then tested for NO-response. Spectroscopic data confirmed that AtLRB3 contains a histidine-ligated heme cofactor and importantly, the addition of NO to AtLRB3 yielded absorption characteristics reminiscent of canonical H-NOX proteins. Furthermore, substitution of the heme iron-coordinating histidine at the H-NOX center with a leucine strongly impaired the NO-response. Our finding therefore established AtLRB3 as a NO-interacting protein and future characterizations will focus on resolving the nature of this response.
Highlights
Nitric oxide (NO) is a reactive oxygen species (ROS) that is utilized as a signaling molecule in many physiological processes in microorganisms, animals, and plants.NO in animals is well-characterized with its complex and pleiotropic roles in regulating immune responses to viral and bacterial infections [2,3], oncogenesis [4,5], and blood pressure maintenance [6], whereas, in plants, the roles and mechanisms of action of NO are currently less exhaustively described.it has been proposed that NO signaling in animals and plants may share considerable functional similarity [7]
These seemingly hidden functional centers often fall below the detection limit of BLAST searches. Such centers may be identified in proteins by applying search motifs that are built based on consensus amino acids in annotated and experimentally-confirmed proteins across species [17,18]
This approach has been successfully applied for the discovery of plant guanylate cyclases (GCs) and adenylate cyclases (ACs), which cannot be identified by querying, e.g., the Arabidopsis proteome with annotated GCs or ACs from animals, fungi, or bacteria [19,20,21,22,23,24,25,26]. This search method has enabled the discovery of an abscisic acid (ABA) binding site in an Arabidopsis guard cell outward rectifying K+ channel (GORK) that has subsequently been shown to be directly modulated by ABA [27]
Summary
Nitric oxide (NO) is a reactive oxygen species (ROS) that is utilized as a signaling molecule in many physiological processes in microorganisms, animals, and plants (for a review, see, e.g., [1]).NO in animals is well-characterized with its complex and pleiotropic roles in regulating immune responses to viral and bacterial infections [2,3], oncogenesis [4,5], and blood pressure maintenance [6], whereas, in plants, the roles and mechanisms of action of NO are currently less exhaustively described.it has been proposed that NO signaling in animals and plants may share considerable functional similarity [7]. Nitric oxide (NO) is a reactive oxygen species (ROS) that is utilized as a signaling molecule in many physiological processes in microorganisms, animals, and plants (for a review, see, e.g., [1]). NO in animals is well-characterized with its complex and pleiotropic roles in regulating immune responses to viral and bacterial infections [2,3], oncogenesis [4,5], and blood pressure maintenance [6], whereas, in plants, the roles and mechanisms of action of NO are currently less exhaustively described. It has been proposed that NO signaling in animals and plants may share considerable functional similarity [7]. It has been demonstrated that NO acts as a critical regulator of development at all stages of the life cycle (for a review, see [8]). Despite the many described NO effects in plants, our fundamental knowledge of NO production, sensing, and transduction in plants remains scarce
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
