Nitric oxide, gravity response, and a unified schematic of plant signaling

• Published in: Plant science (Limerick) Vol. 314; p. 111105
• Main Authors: Kruse, Colin P.S., Wyatt, Sarah E.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.01.2022
• Subjects: Ethylene; Gravitropism; Gravitropism - drug effects; Gravity Sensing - drug effects; Molecular signaling; Nitric oxide; Nitric Oxide - metabolism; Plant Development - drug effects; Plant Roots - metabolism; Reactive oxygen species; S-nitrosation; Signal Transduction - drug effects; Space biology; S-nitrosation; Reactive oxygen species; Nitric oxide; Space biology; Ethylene; Gravitropism; Molecular signaling
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2021.111105

•An extensive literature meta-analysis in the context of published RNA and protein expression data has allowed for the assembly of a cohesive schematic of gravity signaling pathways.•Nitric oxide signaling (opposed by ethylene) and the actions of reactive oxygen species are central to the signaling elements integrated by the schematic.•The causal links between schematic signaling components fits existing physiological data in Arabidopsis roots (the most well studied gravity-sensing tissue in plants).•The conservation of S-nitrosation events relevant to the schematic provides insights into the evolutionary pressures for retention of nitric oxide signaling events in schematic pathways and indicates a potential for use of these pathways in other tropic cascades. Plant signaling components are often involved in numerous processes. Calcium, reactive oxygen species, and other signaling molecules are essential to normal biotic and abiotic responses. Yet, the summation of these components is integrated to produce a specific response despite their involvement in a myriad of response cascades. In the response to gravity, the role of many of these individual components has been studied, but a specific sequence of signals has not yet been assembled into a cohesive schematic of gravity response signaling. Herein, we provide a review of existing knowledge of gravity response and differential protein and gene regulation induced by the absence of gravity stimulus aboard the International Space Station and propose an integrated theoretical schematic of gravity response incorporating that information. Recent developments in the role of nitric oxide in gravity signaling provided some of the final contextual pillars for the assembly of the model, where nitric oxide and the role of cysteine S-nitrosation may be central to the gravity response. The proposed schematic accounts for the known responses to reorientation with respect to gravity in roots—the most well studied gravitropic plant tissue—and is supported by the extensive evolutionary conservation of regulatory amino acids within protein components of the signaling schematic. The identification of a role of nitric oxide in regulating the TIR1 auxin receptor is indicative of the broader relevance of the schematic in studying a multitude of environmental and stress responses. Finally, there are several experimental approaches that are highlighted as essential to the further study and validation of this schematic.