Update on Nox function, site of action and regulation in Botrytis cinerea.

Robert Marschall,Ulrike Siegmund,Joachim Burbank,Paul Tudzynski

doi:10.1186/s40694-016-0026-6

Abstract

BackgroundThe production of reactive oxygen species (ROS) and a balanced redox homeostasis are essential parameters, which control the infection process of the plant pathogen Botrytis cinerea. The necrotrophic fungus is able to cope with the plants’ oxidative burst and even produces its own ROS to overcome the plants’ defense barrier. Major enzyme complexes, which are responsible for the production of superoxide, are NADPH oxidase (Nox) complexes. They play a central role in various growth, differentiation and pathogenic processes. However, information about their regulation and the integration in the complex signaling network of filamentous fungi is still scarce.ResultsIn this work, we give an update on Nox structure, function, site of action and regulation. We show that functionality of the catalytic Nox-subunits seems to be independent from their transcriptional regulation and that the membrane orientation of BcNoxA would allow electron transport inside the ER. Following previous studies, which provided evidence for distinct functions of the NoxA complex inside the ER, we highlight in this work that the N-terminus of BcNoxA is essential for these functions. Finally, we elucidate the role of BcNoxD and BcNoxB inside the ER by complementing the deletion mutants with ER bound alleles.ConclusionsThis study provides a deeper analysis of the Nox complexes in B. cinerea. Besides new insights in the overall regulation of the complexes, we provide further evidence that the NoxA complex has a predominant role inside the ER, while the NoxB complex is mainly important outside the ER, likely at the plasma membrane. By considering all other putative Nox complex members, we propose a putative model, which describes the distinct complex pattern upon certain differentiation processes.Electronic supplementary materialThe online version of this article (doi:10.1186/s40694-016-0026-6) contains supplementary material, which is available to authorized users.

Highlights

The production of reactive oxygen species (ROS) and a balanced redox homeostasis are essential parameters, which control the infection process of the plant pathogen Botrytis cinerea
The most recent studies focused on the identification of new members of both NADPH oxidase (Nox) complexes [32, 43, 44]
Transcriptional regulation of BcNoxA/B is not important for their distinct function To elucidate whether transcriptional regulation of both catalytic subunits does have any influence on their function, hybrid constructs were generated

Summary

Introduction

The production of reactive oxygen species (ROS) and a balanced redox homeostasis are essential parameters, which control the infection process of the plant pathogen Botrytis cinerea. Major enzyme complexes, which are responsible for the production of superoxide, are NADPH oxidase (Nox) complexes They play a central role in various growth, differentiation and pathogenic processes. Botrytis cinerea is a filamentous fungus, which is classified as second most devastating plant pathogen [10] infecting more than 500 economically important hosts [13]. It is the causative agent of the gray mold disease diminishing harvest yields of strawberries, raspberries and grapes [52]. While plants produce ROS during the so-called “oxidative burst” as first defensive line upon contact with pathogen derived elicitors, B. cinerea produces ROS to trigger plant’s defense reactions, on which it depends to achieve full pathogenicity [18]

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