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Title: Characterization of mechamisms underlying degradation of sclerotia of Sclerotinia sclerotiorum by Aspergillus aculeatus Asp-4 using a combined qRT-PCR and proteomic approach

Author
item HU, XIAOJIA - Oil Crops Research Institute - China
item QIN, LU - Oil Crops Research Institute - China
item Roberts, Daniel
item Lakshman, Dilip
item GONG, YANGMIN - Oil Crops Research Institute - China
item Maul, Jude
item XIA, LIHUA - Oil Crops Research Institute - China
item YU, CHANGBING - Oil Crops Research Institute - China
item LI, YINSHUI - Oil Crops Research Institute - China
item HU, LEI - Oil Crops Research Institute - China

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2017
Publication Date: 11/1/2017
Citation: Hu, X., Qin, L., Roberts, D.P., Lakshman, D.K., Gong, Y., Maul, J.E., Xie L., Yu, C., Li, Y., Hu, L., Liao, X., Liao, X. 2017. Characterization of mechamisms underlying degradation of sclerotia of Sclerotinia sclerotiorum by Aspergillus aculeatus Asp-4 using a combined qRT-PCR and proteomic approach. BMC Genomics. 18:674. https://doi.org/10.1186/s12864-017-4016-8.
DOI: https://doi.org/10.1186/s12864-017-4016-8

Interpretive Summary: The soilborne plant pathogen Sclerotinia sclerotiorum causes disease on a number of important crops that result in major economic losses to farmers in the United States. These diseases are controlled primarily through the use of chemical pesticides. Biological control measures need to be developed for this pathogen due to the loss of efficacy of existing chemical control measures and to the environmental problems associated with these chemicals. The mycoparasite Aspergillus Asp-4 colonizes, degrades, and kills sclerotia of S. sclerotiorum resulting in reduced disease caused by this important plant pathogen. We employed molecular approaches including transcriptomics, proteomics, and qRT-PCR to more thoroughly understand the processes by which Aspergillus Asp-4 kills S. sclerotiorum so that we can devise strategies to improve its effectiveness as a biological control agent. We found that the mycoparasite Aspergillus Asp-4 produces a diverse array of enzymes that degrade the compounds that comprise the sclerotium. This mycoparasite also expresses a number of genes that help to mitigate stress caused by the sclerotial environment. This study furthers the analysis of mycoparasitism of sclerotial pathogens by providing the basis for molecular characterization of a previously uncharacterized mycoparasite-sclerotial interaction. The information in this manuscript will be useful to scientists studying mycoparasitic interactions and to scientists devising strategies for the control of soilborne plant pathogens.

Technical Abstract: Background: The biological control agent Aspergillus Asp-4 colonizes and degrades sclerotia of Sclerotinia sclerotiorum resulting in reduced germination and disease caused by this important plant pathogen. Molecular mechanisms of mycoparasites underlying colonization, degradation, and reduction of germination of sclerotia of this and other important plant pathogens remain poorly understood. Results: An RNA-Seq screen of Asp-4 growing on autoclaved, ground sclerotia of S. sclerotiorum for 48 h identified 997 up-regulated and 777 down-regulated genes relative to this mycoparasite growing on potato dextrose agar (PDA) for 48 h. qRT-PCR time course experiments characterized expression dynamics of select genes encoding enzymes functioning in degradation of sclerotial components and management of environmental conditions, including environmental stress. This analysis suggested co-temporal up-regulation of genes functioning in these two processes. Proteomic analysis of Asp-4 growing on this sclerotial material for 48 h identified 26 up-regulated and 6 down-regulated proteins relative to the PDA control. Certain proteins with increased abundance had putative functions in degradation of polymeric components of sclerotia and the mitigation of environmental stress. Conclusions: Our results suggest co-temporal up-regulation of genes involved in degradation of sclerotia compounds and mitigation of environmental stress. This study furthers the analysis of mycoparasitism of sclerotial pathogens by providing the basis for molecular characterization of a previously uncharacterized mycoparasite-sclerotial interaction.