Copper amine oxidase 8 regulates arginine-dependent nitric oxide production in Arabidopsis thaliana.

Felicitas Groß,Eva-Esther Rudolf,Jörg Durner,Jeremy Astier,Björn Thiele

doi:10.1093/jxb/erx105

Felicitas Groß, Eva-Esther Rudolf + Show 3 more

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https://doi.org/10.1093/jxb/erx105

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Abstract

Nitric oxide (NO) is a key signaling molecule in plants, regulating a wide range of physiological processes. However, its origin in plants remains unclear. It can be generated from nitrite through a reductive pathway, notably via the action of the nitrate reductase (NR), and evidence suggests an additional oxidative pathway, involving arginine. From an initial screen of potential Arabidopsis thaliana mutants impaired in NO production, we identified copper amine oxidase 8 (CuAO8). Two cuao8 mutant lines displayed a decreased NO production in seedlings after elicitor treatment and salt stress. The NR-dependent pathway was not responsible for the impaired NO production as no change in NR activity was found in the mutants. However, total arginase activity was strongly increased in cuao8 knockout mutants after salt stress. Moreover, NO production could be restored in the mutants by arginase inhibition or arginine addition. Furthermore, arginine supplementation reversed the root growth phenotype observed in the mutants. These results demonstrate that CuAO8 participates in NO production by influencing arginine availability through the modulation of arginase activity. The influence of CuAO8 on arginine-dependent NO synthesis suggests a new regulatory pathway for NO production in plants.

Highlights

Nitric oxide (NO) is a ubiquitous radical gas that possesses a wide range of functions in plants
nitrate reductase (NR), putative nitric oxide synthase (NOS), electron transport, and putative polyamine oxidases have been suggested as sources of NO in plants
As PAs are able to induce NO production in root seedlings (Scheler et al, 2013) and the cuao1 mutant displayed an impaired NO production in response to abscisic acid (ABA) or PA treatment (Wimalasekera et al, 2011), we sought to determine the NO production in mutant lines for each copper amine oxidase (CuAO) predicted gene of A. thaliana (Planas-Portell et al, 2013) using seedlings submitted to an elicitor treatment (Fig. 1A)

Summary

Introduction

Nitric oxide (NO) is a ubiquitous radical gas that possesses a wide range of functions in plants. This signaling molecule is involved in developmental processes, such as germination or flowering, as well as in the adaptive response to biotic or abiotic stresses (for reviews, see Scheler et al, 2013; Yang et al, 2014; Hichri et al, 2015; Sanz et al, 2015; Simontacchi et al, 2015). An extensive in silico study demonstrated that NOS homologs could not be found in the transcriptome of >1000 different photosynthetic organisms, with the notable exception of ~12 algae, including the recently characterized NOS from Osterococcus tauri (Foresi et al, 2010; Jeandroz et al, 2016). No homologs were found in the transcriptomes of embryophytes (Jeandroz et al, 2016)

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