Volatilome and transcriptome of the mushroom Agrocybe aegerita

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For thousands of years, edible mushrooms have been recognized as high-quality food, not only for their nutritional properties - a high protein content combined with low content of fat and various vitamins - but also for their distinctive flavor. The variety of flavors produced by fungi stems from a highly evolved communication system: to colonize different habitats, to protect themselves from predators and to interact with other organisms. One of these strategies is the production of volatile organic compounds (VOC). The formation of volatile compounds is carried out in the primary (inter alia from the synthesis of amino and fatty acids) and secondary metabolism (of intermediates of the primary metabolism) of fungi. The composition of the volatile compounds, also called volatilome, is not rigid, but varies over the cultivating period of the mushroom. Within this project, the volatile organic compounds from the high-quality mushroom Agrocybe aegerita are analyzed and described during the fungal cultivation. The volatile substances produced by A. aegerita will be detected by gas chromatography mass spectrometry and authentic standards will be applied for identification as well as quantification. Besides, mycelium samples of different cultivation stages (vegetative mycelial growth, hyphal knots, primordia, adult fruiting bodies, basidiospore production) will be harvested and used for determination of the transcription profile of the individual stages by means of RNA-Seq. The transcriptome obtained will be set in conjunction with the volatilome to detect genes that are required in the biosynthetic pathways of the individual volatile compounds. The analysis of the transcriptome in combination with classical methods of instrumental analysis offers an enormous capability to elucidate biosynthetic pathways in mushrooms. The complete biosynthesis is described in detail for only a few fungal VOC. Aside, various diverging hypotheses on possible biosynthetic pathways are postulated, such as for the fungal aroma compound oct-1-en-3-ol and other C8-derivatives. The project therefore aims to clarify the biosynthetic pathways of aroma compounds by applying the described techniques.