| Title: | Suppression of Aflatoxin Biosynthesis in Aspergillus flavus by 2-Phenylethanol Is Associated with Stimulated Growth and Decreased Degradation of Branched-Chain Amino Acids |
| Author(s): | Chang PK; Hua SS; Sarreal SB; Li RW; |
| Address: | "Southern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, New Orleans, LA 70124, USA. perngkuang.chang@ars.usda.gov. Western Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Albany, CA 94710, USA. sylvia.hua@ars.usda.gov. Western Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Albany, CA 94710, USA. siov.sarreal@ars.usda.gov. Animal Genomics and Improvement Laboratory, Agricultural Research Service, U. S. Department of Agriculture, Beltsville, MD 20705, USA. robert.li@ars.usda.gov" |
| ISSN/ISBN: | 2072-6651 (Electronic) 2072-6651 (Linking) |
| Abstract: | "The saprophytic soil fungus Aspergillus flavus infects crops and produces aflatoxin. Pichia anomala, which is a biocontrol yeast and produces the major volatile 2-phenylethanol (2-PE), is able to reduce growth of A. flavus and aflatoxin production when applied onto pistachio trees. High levels of 2-PE are lethal to A. flavus and other fungi. However, at low levels, the underlying mechanism of 2-PE to inhibit aflatoxin production remains unclear. In this study, we characterized the temporal transcriptome response of A. flavus to 2-PE at a subinhibitory level (1 muL/mL) using RNA-Seq technology and bioinformatics tools. The treatment during the entire 72 h experimental period resulted in 131 of the total A. flavus 13,485 genes to be significantly impacted, of which 82 genes exhibited decreased expression. They included those encoding conidiation proteins and involved in cyclopiazonic acid biosynthesis. All genes in the aflatoxin gene cluster were also significantly decreased during the first 48 h treatment. Gene Ontology (GO) analyses showed that biological processes with GO terms related to catabolism of propionate and branched-chain amino acids (valine, leucine and isoleucine) were significantly enriched in the down-regulated gene group, while those associated with ribosome biogenesis, translation, and biosynthesis of alpha-amino acids OPEN ACCESS Toxins 2015, 7 3888 were over-represented among the up-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that metabolic pathways negatively impacted among the down-regulated genes parallel to those active at 30 degrees C, a condition conducive to aflatoxin biosynthesis. In contrast, metabolic pathways positively related to the up-regulated gene group resembled those at 37 degrees C, which favors rapid fungal growth and is inhibitory to aflatoxin biosynthesis. The results showed that 2-PE at a low level stimulated active growth of A. flavus but concomitantly rendered decreased activities in branched-chain amino acid degradation. Since secondary metabolism occurs after active growth has ceased, this growth stimulation resulted in suppression of expression of aflatoxin biosynthesis genes. On the other hand, increased activities in degradation pathways for branched-chain amino acids probably are required for the activation of the aflatoxin pathway by providing building blocks and energy regeneration. Metabolic flux in primary metabolism apparently has an important role in the expression of genes of secondary metabolism" |
| Keywords: | "Aflatoxins/*biosynthesis Amino Acids, Branched-Chain/*metabolism Antifungal Agents/isolation & purification/*pharmacology Aspergillus flavus/drug effects/genetics/*growth & development/metabolism Dose-Response Relationship, Drug Gene Expression Regulation;" |
| Notes: | "MedlineChang, Perng-Kuang Hua, Sui Sheng T Sarreal, Siov Bouy L Li, Robert W eng Switzerland 2015/09/26 Toxins (Basel). 2015 Sep 24; 7(10):3887-902. doi: 10.3390/toxins7103887" |
