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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL APPROACHES FOR MANAGING DISEASES OF TEMPERATE FRUIT CROPS

Location: Appalachian Fruit Research Laboratory: Innovative Fruit Production, Improvement and Protection

Title: Identification of differentially expressed genes associated with changes in the morphology and pathogenicity of Pichia fermentans on apple and peach fruit

Authors
item Fiori, Stefano -
item Scherm, Barbara -
item Liu, Jia -
item Farrell, Robert -
item Mannazzu, Ilaria -
item Budroni, Marilena -
item Maserti, Biancaslena -
item Wisniewski, Michael
item Mighelli, Quirico -

Submitted to: Federation Of European Microbiological Societies Yeast Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 2012
Publication Date: August 5, 2012
Citation: Fiori, S., Scherm, B., Liu, J., Farrell, R., Mannazzu, I., Budroni, M., Maserti, B., Wisniewski, M.E., Mighelli, Q. 2012. Identification of differentially expressed genes associated with changes in the morphology and pathogenicity of Pichia fermentans on apple and peach fruit. Federation Of European Microbiological Societies Yeast Research. DOI: 10.1111/j.1567-1364.2012.00829.x.

Interpretive Summary: Developing alternative approaches to disease control is a critical objective of NP-303, Plant Diseases, due to consumer demands to lower exposure to chemicals, and reduces the impact of agriculture on the environment. Understanding the biology of biocontrol systems, however, is essential if they are to be used effectively and safely. As an example, the yeast Pichia fermentans, originally isolated from grape must is very effective in controlling postharvest diseases of apple. In contrast, when it is used on peach fruit, it changes its morphology from single cells to pseudo-hyphae (similar to the growth forms of more advanced fungi), and also becomes pathogenic. The present study was undertaken to try and identify changes in gene expression that were associated with the switch in growth form and pathogenicity. Results of the study identified several stress-related genes in P. fermentans that were up-regulated, indicating that the peach environment represented some type of environmental stress to the yeast, thus making it switch into a different growth form and become pathogenic. The discovery of the dual activity of P. fermentans both as a biocontrol agent and a pathogen emphasizes the need for a thorough risk analysis of potential biocontrol agents in order to avoid unpredictable results that could negatively impact the safety and effective use of post-harvest biocontrol strategies. No further research is planned with this organism.

Technical Abstract: Pichia fermentans (strain DISAABA 726) is an effective biocontrol agent against Monilinia fructicola or Botrytis cinerea when inoculated in artificially wounded apple fruit but is an aggressive pathogen when inoculated on wounded peach fruit, causing severe fruit decay. P. fermentans grows as a budding yeast on apple tissue but exhibits pseudohyphal growth on peach tissue, suggesting that dimorphism may be associated with pathogenicity. Two complementary suppressive subtractive hybridization (SSH) strategies, i.e., rapid subtraction hybridization (RaSH) and PCR-based subtraction, were performed to identify genes differentially expressed by P. fermentans after 24-h growth on apple versus peach fruit. Several of the obtained gene products that were more highly expressed on peach than on apple tissue, or vice-versa, were sequenced and compared to available yeast genome sequence databases. Several of the genes more highly expressed when P. fermentans was grown on peach were related to stress response, glycolysis, amino acid metabolism, and alcoholic fermentation but suprisingly not to the cell wall degrading enzymes suchas pectinases or cellulases. This indicates that P. fermentans may not be directly pathogenic on peach and that its invasive growth could be stimulated by a linked series of commodity-related events. The discovery of the dual activity of P. fermentans both as a biocontrol agent and a pathogen emphasizes the need for a thorough risk analysis of potential antagonists in order to avoid unpredictable results that could negatively impact the safety and effective use of post-harvest biocontrol strategies.Pichia fermentans (strain DISAABA 726) is an effective biocontrol agent against Monilinia fructicola or Botrytis cinerea when inoculated in artificially wounded apple fruit but is an aggressive pathogen when inoculated on wounded peach fruit, causing severe fruit decay. P. fermentans grows as a budding yeast on apple tissue but exhibits pseudohyphal growth on peach tissue, suggesting that dimorphism may be associated with pathogenicity. Two complementary suppressive subtractive hybridization (SSH) strategies, i.e., rapid subtraction hybridization (RaSH) and PCR-based subtraction, were performed to identify genes differentially expressed by P. fermentans after 24-h growth on apple versus peach fruit. Several of the obtained gene products that were more highly expressed on peach than on apple tissue, or vice-versa, were sequenced and compared to available yeast genome sequence databases. Several of the genes more highly expressed when P. fermentans was grown on peach were related to stress response, glycolysis, amino acid metabolism, and alcoholic fermentation but suprisingly not to the cell wall degrading enzymes suchas pectinases or cellulases. This indicates that P. fermentans may not be directly pathogenic on peach and that its invasive growth could be stimulated by a linked series of commodity-related events. The discovery of the dual activity of P. fermentans both as a biocontrol agent and a pathogen emphasizes the need for a thorough risk analysis of potential antagonists in order to avoid unpredictable results that could negatively impact the safety and effective use of post-harvest biocontrol strategies.

Last Modified: 4/17/2014
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