NADPH Oxidase (Rboh) Activity is Up Regulated during Sweet Pepper (Capsicum annuum L.) Fruit Ripening.

Ángela Chu-Puga,José M Palma,Marta Rodríguez-Ruiz,Francisco J Corpas,Salvador González-Gordo

doi:10.3390/antiox8010009

Abstract

In plants, NADPH oxidase (NOX) is also known as a respiratory burst oxidase homolog (Rboh). This highly important enzyme, one of the main enzymatic sources of superoxide radicals (O2•−), is involved in the metabolism of reactive oxygen and nitrogen species (ROS and RNS), which is active in the non-climacteric pepper (Capsicum annuum L.) fruit. We used sweet pepper fruits at two ripening stages (green and red) to biochemically analyze the O2•−-generating Rboh activity and the number of isozymes during this physiological process. Malondialdehyde (MDA) content, an oxidative stress marker, was also assayed as an index of lipid peroxidation. In red fruits, MDA was observed to increase 2-fold accompanied by a 5.3-fold increase in total Rboh activity. Using in-gel assays of Rboh activity, we identified a total of seven CaRboh isozymes (I–VII) which were differentially modulated during ripening. CaRboh-III and CaRboh-I were the most prominent isozymes in green and red fruits, respectively. An in vitro assay showed that CaRboh activity is inhibited in the presence of nitric oxide (NO) donors, peroxynitrite (ONOO−) and glutathione (GSH), suggesting that CaRboh can undergo S-nitrosation, Tyr-nitration, and glutathionylation, respectively. In summary, this study provides a basic biochemical characterization of CaRboh activity in pepper fruits and indicates that this O2•−-generating Rboh is involved in nitro-oxidative stress associated with sweet pepper fruit ripening.

Highlights

NADPH oxidase (NOX) is considered to be the most important enzyme responsible for superoxide radicals (O2 − ) generation in mammalian cells
Which was measured as an index peroxidation, was observed increasetotwofold intwofold red fruits content, which was measured as of anlipid index of lipid peroxidation, was to observed increase in
The data obtained clearly show that total CaRboh activity significantly increases during pepper ripening, which opens up new questions about its potential role as the principal O2 − -generating enzyme [2]

Summary

Introduction

NADPH oxidase (NOX) is considered to be the most important enzyme responsible for superoxide radicals (O2 − ) generation in mammalian cells. The NOX enzyme is referred to as a respiratory burst oxidase homolog (Rboh). It is composed of six conserved transmembrane domains, the C-terminal harboring FAD and NADPH hydrophilic domains, two heme groups, and two N-terminal Ca2+ -binding EF-hand motifs indicating that Rboh activity is regulated by. The Rboh gene is ubiquitously expressed, the distribution and abundance of its different isozymes are cell- and tissue-specific. This suggests that each Rboh isozyme is involved in distinct physiological and stress functions, including seed germination, root hair formation, lignification, Antioxidants 2019, 8, 9; doi:10.3390/antiox8010009 www.mdpi.com/journal/antioxidants

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