Reactive Oxygen Species in the Botrytis – Host Interaction

Abstract

Reactive oxygen species (ROS) are unavoidable byproducts of several metabolic processes. Due to their high reactivity they can cause molecular damages such as protein oxidations or DNA mutations, but they also serve as important signalling molecules within cells. Intracellular ROS primarily originate in the mitochondria; however enzymatic ROS generating systems such as the membrane associated NADPH oxidase complex (Nox) contribute to their production. In particular, during host-pathogen interactions ROS are of key importance for plant defence but also for fungal attack. As an early response to pathogen infestation the plant releases high amounts of reactive oxygen species to counteract the pathogen, known as the oxidative burst. It was shown that Botrytis exploits this plant defence reaction and even contributes to this oxidative burst by forming its' own ROS. Thus, the fungus needs a robust oxidative stress responsive (OSR) system to cope with ROS. In order to balance the intracellular redox state, effective antioxidant systems, including the thioredoxin and the glutathione system, are indispensable. Furthermore, catalases, superoxide dismutases and several peroxidases support ROS scavenging by enzymatic inactivation. Transcription factors such as the Botrytis activator protein (Bap1) and the response regulator Skn7 were shown to be involved in OSR. In this chapter we discuss the role of ROS in Botrytis -host interaction and both ROS generating and detoxifying systems and their importance for Botrytis pathogenicity. Keywords ROS • NADPH oxidases • Thioredoxin • Glutathione • Oxidative stress Reactive Oxygen Species (ROS)Reactive oxygen species (ROS) are generated in all aerobic environments and play a major role for all organisms dependent on oxygen. The oxygen in our atmosphere facilitated the evolution of multi-cellular organisms, but is also the source for several

Botrytis cinerea differentially induces postharvest antioxidant responses in ‘Braeburn’ and ‘Golden Delicious’ apple fruit

“…Some of the antioxidant activity that was measured in the fruit samples could therefore have originated from B. cinerea . However, the pathogen does not appear to need all these enzymes when invading a number of different plant species . Instead, recent evidence suggests that thioredoxin and thioredoxin reductase have more crucial roles in B. cinerea pathogenicity because they enable the pathogen to survive and respond to high levels of oxidative stress .…”

“…However, the pathogen does not appear to need all these enzymes when invading a number of different plant species. 14,28,30 Instead, recent evidence suggests that thioredoxin and thioredoxin reductase have more crucial roles in B. cinerea pathogenicity because they enable the pathogen to survive and respond to high levels of oxidative stress. 31 The elevated antioxidant enzyme activities detected in 'Br' during onset of disease proved unsuccessful as a defense strategy to B. cinerea.…”

“…The plant‐generated oxidative burst is induced and utilized by B. cinerea to colonize the plant successfully . The functions of ROS in plants and Botrytis are multiple, including signaling aspects . During pathogenesis, there is histochemical evidence that B. cinerea produces O 2 .‐ and H 2 O 2 in hyphal germ tubes at the infection site, and that its superoxide dismutases (SOD; EC 1.15.1.1) may be involved in pathogenicity …”

“…11,12 The functions of ROS in plants and Botrytis are multiple, including signaling aspects. 13,14 During pathogenesis, there is histochemical evidence that B. cinerea produces O 2 .and H 2 O 2 in hyphal germ tubes at the infection site, 15 and that its superoxide dismutases (SOD; EC 1.15.1.1) may be involved in pathogenicity. 16 Two apple cultivars, 'Braeburn' and 'Golden Delicious' were selected to elucidate further the influence of preharvest sun exposure and antioxidant metabolism on subsequent postharvest disease development caused by B. cinerea.…”

The pH regulator PacC: a host‐dependent virulence factor in Botrytis cinerea

“…During the early phase of the plant‐fungus interaction, reactive oxygen species (ROS) are considered of key importance because they play a role in fungal colonization as well as in plant defence (for a review, see Siegmund and Viefhues, ). To investigate the capacity of the mutant to produce ROS, the WT, the BcpacC deletion and complemented mutant strains were grown on complete medium and equal amounts of biomass were incubated in diaminobenzidine (DAB) solution as described by Schumacher and colleagues ().…”