Although Lilium brownii (L.brownii) bulbs are popular fresh vegetables, a series of quality problems still remain after harvest. In this study, fresh L.brownii bulbs were placed in the dark at 25, 4, and −20 °C and under light at 25 °C from 0 to 30 days; the chemical compositions were analyzed by ultraviolet spectrophotometry (UV) and high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). During the 30-day storage period, the browning degree increased over the storage time and with increasing temperature, but the contents of proteins and free amino acids decreased and were aggravated by light. The total polyphenol content increased until the 6th day at 25 °C (dark or light), but it did not significantly accumulate at −20 or 4 °C. The reducing sugar content showed a dynamic balance, but the total polysaccharide content decreased constantly in the four storage conditions. The polyphenol oxidase (PPO) activity increased with storage time and increasing temperature, while it was inhibited by light. The increase rates of malondialdehyde (MDA) content at −20 °C and light (25 °C) were higher than those at 4 and 25 °C. In addition, 12 secondary metabolites were identified, most of which accumulated during the storage period, for example, 1-O-feruloyl-3-O-β-D-glucopyranosylglycerol; 1,3-O-di-p-coumaroylglycerol; 1-O-feruloyl-3-O-p-coumaroylglycerol; and 1,2-O-diferuloylglycerol. The variations in nutrient levels had a low correlation with browning, but the variations in MDA, PPO, and secondary metabolite (phenolic acids) levels had a high correlation with browning. In conclusion, fresh L.brownii bulbs should be stored at a low temperature (4 °C) and in dark condition, and browning bulbs are excellent materials for secondary metabolite utilization.

Background: Adenosine has been getting increasing attention due to its positive role in immunomodulation, anti-inflammation, and anti-cancer, etc.. The low production of Ganoderma adenosine is a bottleneck for clinical trials and commercial applications. Regulating the expression of key adenosine biosynthetic gene is an optimized way to increase the production of adenosine in submerged culture of Ganoderma lucidum. Results: In this study, we correlated the expression of adenosine synthase genes (including GlATIC, GlPNP, GlADK) with the adenosine content in mycelium at different fermentation time points. The results showed that GlPNP was positively correlated with Ganoderma adenosine contents. Then the key biosynthetic gene GlPNP was cloned, characterized and overexpressed in G. lucidum. The cDNA of GlPNP gene was 969-bp in length, with a predicted molecular weight of 34.6 kDa and PI of 5.89. The GlPNP displayed a trimeric quaternary structure by theoretically modelling with SWISS-MODEL. The transcript levels of GlPNP overexpression transformants (namely OE::GlPNP-5 and OE::GlPNP-7) were approximately 2.9-3.9-fold higher than those of the WT strains on day 4, while the adenosine contents were increased by 78% and 63%, respectively, by compared with vector-containing strain. In addition, the GlPNP overexpression strains showed decreased colony growth and reduced biomass in submerged cultivation. Conclusions: GlPNP gene overexpression is an effective strategy to improve the production of adenosine in G. lucidum. This study is the first report about the manipulation of adenosine biosynthesis in medicinal fungi.

Adenosine has been getting increasing attention due to its positive role in immunomodulation, anti-inflammation, and anti-cancer, etc.. The low production of Ganoderma adenosine is a bottleneck for clinical trials and commercial applications. Regulating the expression of key biosynthetic gene is an optimized way to increase the adenosine production in submerged culture of Ganoderma lucidum. In this study, we correlated the expression of adenosine synthase genes (including GlATIC, GlPNP, GlADK) with the adenosine content. The results showed that GlPNP was positively correlated with Ganoderma adenosine contents. Then the key biosynthetic gene GlPNP was cloned, characterized and overexpressed in G. lucidum. The cDNA of GlPNP gene was 969-bp in length, with a predicted molecular weight of 34.6 kDa. The GlPNP displayed a trimeric quaternary structure. The transcript levels of GlPNP overexpression transformants were approximately 2.9-3.9-fold higher than those of the WT strains on day 4, while the adenosine contents were increased by 78% and 63%, respectively, by compared with vector-containing strain. The GlPNP overexpression strains showed decreased colony growth and reduced biomass. In conclusion, GlPNP gene overexpression is an effective strategy to improve the production of adenosine. This study is the first report about the manipulation of adenosine biosynthesis in medicinal fungi.