Abstract
Botrytis cinerea is a plant pathogen causing the gray mold disease in a plethora of host plants. The control of the disease is based mostly on chemical pesticides, which are responsible for environmental pollution, while they also pose risks for human health. Furthermore, B. cinerea resistant isolates have been identified against many fungicide groups, making the control of this disease challenging. The application of biocontrol agents can be a possible solution, but requires deep understanding of the molecular mechanisms in order to be effective. In this study, we investigated the multitrophic interactions between the biocontrol agent Bacillus subtilis MBI 600, a new commercialized biopesticide, the pathogen B. cinerea and their plant host. Our analysis showed that this biocontrol agent reduced B. cinerea mycelial growth in vitro, and was able to suppress the disease incidence on cucumber plants. Moreover, treatment with B. subtilis led to induction of genes involved in plant immunity. RNA-seq analysis of B. cinerea transcriptome upon exposure to bacterial secretome, showed that genes coding for MFS and ABC transporters were highly induced. Deletion of the Bcmfs1 MFS transporter gene, using a CRISP/Cas9 editing method, affected its virulence and the tolerance of B. cinerea to bacterial secondary metabolites. These findings suggest that specific detoxification transporters are involved in these interactions, with crucial role in different aspects of B. cinerea physiology.
Highlights
Botrytis cinerea is a filamentous ascomycete and a notorious plant pathogen, causing the gray mold disease in more than 200 host plants and belongs to the top 10 list of the most important plant pathogenic fungi (Dean et al, 2012; Dewey and Grant-Downton, 2016)
Dual cultures of the biocontrol agent and the pathogen were established on three different media (PDA, Luria Broth (LB), PEG)
We demonstrated that B. cinerea deploys specific efflux membrane transporters to cope with stress caused by this biocontrol agent and we showed that Bs MBI 600 could trigger defense mechanisms in cucumber plants
Summary
Botrytis cinerea (teleomorph Botyotinia fuckeliana de Bary Whetz) is a filamentous ascomycete and a notorious plant pathogen, causing the gray mold disease in more than 200 host plants and belongs to the top 10 list of the most important plant pathogenic fungi (Dean et al, 2012; Dewey and Grant-Downton, 2016). (Droby and Lichter, 2004) It can grow effectively during cold storage on fruits such as kiwifruit, apples and pears, causing postharvest rots (Michailides and Elmer, 2000). It is one of the most serious fungal diseases in nurseries causing damping-off in seedlings (Capieau et al, 2004; Konstantinou et al, 2014). This pathogen forms sclerotia, which are structures able to survive for long periods under harsh environmental conditions. They play a crucial role in survival and epidemiology of the pathogen, being able to start a new disease cycle
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