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Chinese black truffle (Tuber indicum) is a hypogenous fungus of great value due to its distinctive aroma. In this study, both transcriptome and physicochemical analyses were performed to investigate the changes of nutrients and gene expression in truffle fruiting bodies during cold storage. The results of physicochemical analysis revealed the active metabolism of fruiting bodies in cold storage, showing the decreased contents of protein and soluble sugar, the variations in both polyphenol oxidase activity and total phenol content, and the detrimental effect of reactive oxygen species production caused by heavy metals (cadmium and lead) in truffles. Transcriptome analysis identified a total of 139,489 unigenes. Down-regulated expression of genes encoding the catalase-like domain-containing protein (katE), glutaredoxin protein (GRX), a copper/zinc superoxide dismutase (Sod_Cu), and aspartate aminotransferase (AAT) affected the degradation metabolism of intracellular oxides. Ribulose-5-phosphate-3-epimerase (RPE) was a key enzyme in response to oxidative stress in truffle cells through the pentose phosphate pathway (PPP). A total of 51,612 simple sequence repeats were identified, providing valuable resources for further genetic diversity analysis, molecular breeding, and genetic map-ping in T. indicum. Transcription factors GAL4 and SUF4-like protein were involved in glucose metabolism and histone methylation processes, respectively. Our study provided a fundamental characterization of the physicochemical and molecular variations in T. indicum during the cold storage at 4°C, providing strong experimental evidence to support the improvement of storage quality of T. indicum.

Chinese black truffle ( Tuber indicum ) is a hypogenous fungus of great value due to its distinctive aroma. In this study, both transcriptome and physicochemical analyses were performed to investigate the changes of nutrients and gene expression in truffle fruiting bodies during cold storage. The results of physicochemical analysis revealed the active metabolism of fruiting bodies in cold storage, showing the decreased contents of protein and soluble sugar, the variations in both polyphenol oxidase activity and total phenol content, and the detrimental effect of reactive oxygen species production caused by heavy metals (cadmium and lead) in truffles. Transcriptome analysis identified a total of 139,489 unigenes. Down-regulated expression of genes encoding the catalase-like domain-containing protein (katE), glutaredoxin protein (GRX), a copper/zinc superoxide dismutase (Sod_Cu), and aspartate aminotransferase (AAT) affected the degradation metabolism of intracellular oxides. Ribulose-5-phosphate-3-epimerase (RPE) was a key enzyme in response to oxidative stress in truffle cells through the pentose phosphate pathway (PPP). A total of 51,612 simple sequence repeats were identified, providing valuable resources for further genetic diversity analysis, molecular breeding, and genetic map-ping in T. indicum . Transcription factors GAL4 and SUF4-like protein were involved in glucose metabolism and histone methylation processes, respectively. Our study provided a fundamental characterization of the physicochemical and molecular variations in T. indicum during the cold storage at 4°C, providing strong experimental evidence to support the improvement of storage quality of T. indicum ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhang, Yang, Yao, Fang, Wu, Lin and Qing.)

The Chinese black truffle Tuber indicum is the main commercial truffle species in China and has strong potential for cultivation. Most studies have focused so far on the production and planting of mycorrhizal seedlings of tree species native to China. Here, we selected four exotic tree species, Quercus pubescens, Q. ilex, Q. palustris and Pinus pinea and inoculated axenically germinated seedlings, five replicates per tree species, with T. indicum spore suspension. As shown by morphological, anatomical and molecular analyses, mycorrhizae were successfully synthesized under greenhouse conditions from 6 months after inoculation and the mycorrhization was stable for at least 24 months in the glasshouse environment. Despite slight morphological variations, T. indicum mycorrhizae were similar on all tree species, i.e. swollen, red-brownish with long hyaline emanating hyphae showing right-angle ramifications. Our observations confirmed the similarity of T. indicum mycorrhizae with those of T. melanosporum regardless of the geographic origin of host trees. Four out of five T. indicum-inoculated pine seedlings were cross-contaminated by T. borchii that was inoculated to another group of P. pinea seedlings raised in the same glasshouse. This is the first study to document the mycorrhization of exotic tree species by T. indicum in China and the first report for Q. palustris. With two successful out of five inoculated seedlings, Q. palustris was less receptive to T. indicum mycorrhization than the other two oak species. Further work is needed to assess whether the T. indicum symbioses obtained here are maintained after planting in the field and if ascomata can be produced by exotic tree species under Chinese environmental conditions. [ABSTRACT FROM AUTHOR]

It is well known that the microbes associated with truffle fruiting bodies play a very important role during the truffle lifecycle. Tuber indicum, commonly called Chinese black truffle, is a species endemic to Eastern Asia and in the genus of Tuber. Here, we reported the bacterial communities of T. indicum from different geographical regions and described the bacterial diversity from three compartments (soil, ectomycorrhizae and ascocarps) of T. indicum using high-throughput sequencing combined tissue culture. The results revealed that Bradyrhizobium was the dominant genus in fruiting bodies of T. indicum from nine geographical sites in China, and the microbes in T. indicum ascocarps were influenced by geological locations and soil characteristics. More specific bacterial taxa were enriched in the fruiting bodies than in the ectomycorrhizae and soil. In addition, 60 cultural bacteria were isolated from T. indicum fruiting bodies (4 families, 24 genera), and Pseudomonas, Alcaligenes faecalis, Microbacterium, and Arthrobacter were dominant. One of 13 strains that have potential nitrogen-fixation activities was further verified by an acetylene reduction assay (ARA). Together, this research provides new and important data for better understanding of the interaction between truffle and associated microbe and the biology of truffle itself.

It is well known that the microbes associated with truffle fruiting bodies play a very important role during the truffle lifecycle. Tuber indicum , commonly called Chinese black truffle, is a species endemic to Eastern Asia and in the genus of Tuber. Here, we reported the bacterial communities of T. indicum from different geographical regions and described the bacterial diversity from three compartments (soil, ectomycorrhizae and ascocarps) of T. indicum using high-throughput sequencing combined tissue culture. The results revealed that Bradyrhizobium was the dominant genus in fruiting bodies of T. indicum from nine geographical sites in China, and the microbes in T. indicum ascocarps were influenced by geological locations and soil characteristics. More specific bacterial taxa were enriched in the fruiting bodies than in the ectomycorrhizae and soil. In addition, 60 cultural bacteria were isolated from T. indicum fruiting bodies (4 families, 24 genera), and Pseudomonas, Alcaligenes faecalis, Microbacterium , and Arthrobacter were dominant. One of 13 strains that have potential nitrogen-fixation activities was further verified by an acetylene reduction assay (ARA). Together, this research provides new and important data for better understanding of the interaction between truffle and associated microbe and the biology of truffle itself. [ABSTRACT FROM AUTHOR]

Nutritional and health-promoting properties of Tuber indicum are still unclear. In this study, total phenol content (TPC) and total flavonoid contents (TFC) were determined by colorimetric methods; free phenolic acids, vitamin D 2 and ergosterol content were determined by HPLC; antioxidant activity were evaluated using ABTS, DPPH, and FRAP assays; in vitro anti-inflammatory activity was evaluated by protease inhibitory assay. Our results indicated that geographical origin exhibits a significant impact on the nutritional and pharmaceutical properties of Tuber indicum. The samples collected from Sichuan present significant higher proteins (23.2 g/100 g dw), ash (6.38 g/100 g dw), 1,3:1,6- β -glucan (14.7 g/100 g dw) and ergosterol content (0.76 mg/g dw); whereas the samples collected from Yunnan present the highest amount of pectin (4.52 g/100 g dw), food energy (345.20 kcal/100 g dw), TPC (1.53 mg GAE/g dw), TFC (1.66 mg CAE/g dw) and the highest ABTS and DPPH values, and potent anti-inflammatory effects. In addition, the samples collected from Jilin presented the highest amount of total carbohydrate (51.7 g/100 g dw), reducing sugar (7.3 g/100 g dw) and total phenolic acids (66.76 μg/g dw). These results will enhance current knowledge about nutritional values, chemical compositions, and biological properties of T. indicum. • Truffles contain significant amounts of pectin, glucan, vitamin D 2 , ergosterol. • Truffle present potent antioxidant activity and anti-inflammatory effect. • Geographical origin affects the nutritional and pharmaceutical properties of truffles. [ABSTRACT FROM AUTHOR]