(Tuber Magnatum Pico) to Different Natural Environments
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Vita et al. BMC Genomics (2020) 21:90 https://doi.org/10.1186/s12864-020-6522-3 RESEARCH ARTICLE Open Access Tuberomics: a molecular profiling for the adaption of edible fungi (Tuber magnatum Pico) to different natural environments Federico Vita1,2* , Beatrice Giuntoli3,4, Edoardo Bertolini4,5, Cosimo Taiti1, Elettra Marone6, Chiara D’Ambrosio7, Emanuela Trovato8, Danilo Sciarrone9, Mariosimone Zoccali9, Raffaella Balestrini10, Andrea Scaloni7, Luigi Mondello8, Stefano Mancuso1, Massimo Alessio11 and Amedeo Alpi2 Abstract Background: Truffles are symbiotic fungi that develop underground in association with plant roots, forming ectomycorrhizae. They are primarily known for the organoleptic qualities of their hypogeous fruiting bodies. Primarily, Tuber magnatum Pico is a greatly appreciated truffle species mainly distributed in Italy and Balkans. Its price and features are mostly depending on its geographical origin. However, the genetic variation within T. magnatum has been only partially investigated as well as its adaptation to several environments. Results: Here, we applied an integrated omic strategy to T. magnatum fruiting bodies collected during several seasons from three different areas located in the North, Center and South of Italy, with the aim to distinguish them according to molecular and biochemical traits and to verify the impact of several environments on these properties. With the proteomic approach based on two-dimensional electrophoresis (2-DE) followed by mass spectrometry, we were able to identify proteins specifically linked to the sample origin. We further associated the proteomic results to an RNA-seq profiling, which confirmed the possibility to differentiate samples according to their source and provided a basis for the detailed analysis of genes involved in sulfur metabolism. Finally, geographical specificities were associated with the set of volatile compounds produced by the fruiting bodies, as quantitatively and qualitatively determined through proton transfer reaction-mass spectrometry (PTR-MS) and gas-chromatography- mass spectrometry (GC-MS). In particular, a partial least squares-discriminant analysis (PLS-DA) model built from the latter data was able to return high confidence predictions of sample source. Conclusions: Results provide a characterization of white fruiting bodies by a wide range of different molecules, suggesting the role for specific compounds in the responses and adaptation to distinct environments. Keywords: Tuber magnatum Pico, Sulfur compounds, Environment, Volatile organic compounds, Integrated approach Background produced by other Tuber species within the Puberulum The ectomycorrhizal fungus Tuber magnatum Pico is group sensu lato [2]. Despite some valuable truffle spe- one of the best-known species belonging to the genus cies being amenable to cultivation, such as Tuber mela- Tuber, which includes between 180 and 220 species [1]. nosporum, Tuber borchii, Tuber aestivum [3, 4] and T. magnatum is characterized as “whitish truffles”, fruit- Tuber formosanum [5], many attempts performed since ing bodies with white-colored gleba that are also 1984 to cultivate T. magnatum [6] have been unsuccess- ful. Due to the scarcity of samples harvested in the nat- * Correspondence: [email protected] ural environment, the annual production does not cover 1 Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e the high demand for T. magnatum truffles, whose prices Forestali (DAGRI), University of Florence, Viale delle idee 30, 50019 Florence, € − 1 Italy are ranging from 300 to 400 hg [6, 7]. Different re- 2A.R.E.A. Foundation, via Tavoleria 28, 56125 Pisa, Italy tail prices are applied to fruiting bodies depending on Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Vita et al. BMC Genomics (2020) 21:90 Page 2 of 25 their harvesting place, considering that the geographical the T. magnatum, T. aestivum [23] and T. borchii [24] distribution of the species extends from Italy to East genomes have been very recently completed by inter- Europe (Croatia, Slovenia, and Hungary), including national consortiums. Greece [8], South of France [9] and Switzerland [10]. Recently, the profile of volatile compounds emitted by One distinct feature of the white truffle, as well as of the fruiting bodies has been taken into consideration as an fruiting bodies of different Tuber species, is in fact the additional biomarker for truffle intraspecific classification. highly different degree of appreciation by the consumers, Biotic and abiotic factors have been shown to influence which is related to the different aroma and flavor speci- truffle aroma, including the nutritional content and the ficities due to truffle growth environment. Development identity of the host tree [25]. In addition, many authors of truffle fruiting bodies is, indeed, known to be influ- [26–29] have suggested that the aroma might vary accord- enced by a range of environmental variables, spanning ing to the geographical origin of truffles of the same spe- from the host plant and the complexity of forest vegeta- cies. For instance, key volatiles were analyzed in the tion [11] to soil characteristics [12], climatic conditions widely distributed species T. aestivum var. uncinatum, [13] and the composition of soil bacterial communities finding that the production of eight-carbon-containing [14]. This observation urged scientists to find reliable compounds, which account for most of the aroma vari- methods to discriminate among truffle accessions be- ability in this species, is likely to be under genetic control longing to the same species. [30]. Experimental evidence on aroma-related proteins in The genetic variation within T. magnatum truffles was truffle is currently limited to nine polypeptides from a T. already investigated, evaluating intraspecific polymor- melanosporum proteome (reconstructed through a com- phisms by simple sequence repeat (SSR) markers [15, bined polyacrylamide gel electrophoresis (1D PAGE) and 16]; eight loci showing polymorphic amplification were high-accuracy liquid chromatography tandem-mass spec- considered useful to assess population dynamics. Not- trometry approach coupled with bioinformatics analysis), ably, an SSR-based analysis of T. magnatum truffles has which were found enrolled in the synthesis of volatiles in revealed, for the first time, the presence of genetic and prior biochemical studies [31]. phylogeographic structures in natural populations of this Neither individual method deployed so far could be Tuber species [16]. In fact, genetic studies have shown considered as a definitive diagnostic method, for the that both the Italian North-westernmost and the South- sake of the attribution of truffle origin. A proteomic ernmost populations are genetically different from all comparison of T. magnatum samples was equally insuffi- the other communities collected all over the species cient to identify their collection locations [20]. It is distributional range. Moreover, Mello and coworkers worth note that truffle fruiting bodies harbor a diverse were able to demonstrate the existence of genetic diver- but poorly understood microbial community of bacteria, sity within Italian populations of T. magnatum using yeasts, and filamentous fungi [32], which might have an SCAR markers as a tool to identify single-nucleotide influence on the metabolism of the ascomata, rendering polymorphisms (SNPs) [17], thereby defining three more difficult the comprehension of the factors influen- different truffle haplotypes. These results were enlarged cing the fruiting bodies formation and functioning. to T. melanosporum [18], where polymorphic SSRs Here we provide an in-depth characterization of the T. suggested that this truffle is a species with relevant intra- magnatum fruiting bodies, collected in regions subjected specific diversity. An extensive SNPs analysis was also to different environmental conditions, through parallel conducted on seven populations of T. melanosporum high-throughput approaches. An expanded proteomic from Italy, France, and Spain, which led to the identifica- assessment, as compared to previous experiments [20], tion of more than 400.000 SNPs able to differentiate the was coupled to the examination of both transcriptome analyzed samples [19]. and volatome profiles (data from RNA-seq and VOC On the other hand, Vita et al. [20] reported the exist- emission measurements, respectively) of samples har- ence of reproducible quantitative differences in the pro- vested in three different Italian areas (Piedmont, Tus- tein patterns of white truffle (T. magnatum) fruiting cany, Molise). The sampling strategy was planned to bodies coming from different Italian areas, suggesting collect them in different years homogenously (e.g. dis- that proteomic characterization might be a promising tance from the plants), to avoid as much as possible the diagnostic method for origin