Multiplex gene precise editing and large DNA fragment deletion by the CRISPR-Cas9-TRAMA system in edible mushroom Cordyceps militaris.

The medicinal mushroom Cordyceps militaris contains abundant valuable bioactive ingredients that have attracted a great deal of attention in the pharmaceutical and cosmetic industries. However, the development of this valuable mushroom faces the obstacle of lacking powerful genomic engineering tools. Here, by excavating the endogenous tRNA-processed element, introducing the extrachromosomal plasmid and alongside with homologous template, we develop a marker-free CRISPR-Cas9-TRAMA genomic editing system to achieve the multiplex gene precise editing and large synthetic cluster deletion in C. militaris. We further operated editing in the synthetases of cordycepin and ergothioneine to demonstrate the application of Cas9-TRAMA system in protein modification, promoter strength evaluation and 10 kb metabolic synthetic cluster deletion. The Cas9-TRAMA system provides a scalable method for excavating the valuable metabolic resource of medicinal mushrooms and constructing a mystical cellular pathway to elucidate the complex cell behaviours of the edible mushroom.

Enhancement of ergothioneine production by discovering and regulating its metabolic pathway in Cordyceps militaris.

BACKGROUND: Cordyceps militaris is a traditional medicinal fungus contains a variety of functional ingredients and has been developed as an important mushroom food recently. Ergothioneine, one of the antioxidative compounds in C. militaris, is benefits on aging-related diseases and therefore became a novel functional food nutritive fortifier. Currently, the main diet source of ergothioneine is mushroom food. However, the mushroom farming faces the problems such as rather low ingredient yield and spontaneous degeneration associated fruiting body that restricts large scale production of ergothioneine. RESULTS: In this study, we excavated the ergothioneine synthetases in mushroom and modified the genes in C. militaris to construct a new ergothioneine synthesis pathway. By further introducing this pathway into C. militaris genome, we succeeded to increase the ingredients' production of engineering strain, the highest amount of ergothioneine and cordycepin were up to 2.5 g/kg dry weight and 2 g/L, respectively. Additionally, the expression of ergothioneine synthetase genes in the shape-mutated degenerative C. militaris could recover the ability of degenerative strain to produce high amount of ingredients, suggesting the metabolic regulation of ergothioneine might release the symptom of mushroom degeneration. CONCLUSION: This study reveals a new pathway to fulfill the market needs of functional mushroom food and food fortifier ergothioneine. It implied the mycelium of C. militaris could be engineered as a novel medicinal mushroom food which could produce higher amount of valuable ingredients.

Transcriptome Analysis Reveals the Flexibility of Cordycepin Network in Cordyceps militaris Activated by L-Alanine Addition.

Cordycepin, isolated from the traditional medicinal fungus Cordyceps militaris, has gained much attention due to its various clinical functions. Previous reports of L-alanine addition could significantly improve cordycepin production, but the molecular mechanism remains unknown. In this study, transcriptome analysis of C. militaris with doubled cordycepin production induced by L-alanine addition provides an insight into the flexibility of the cordycepin network. The biopathways of energy generation and amino acid conversion were activated so that cordycepin substrate generation was consequently improved. Specific genes of rate-limiting enzymes in these pathways, as well as related transcription factors, were figured out. Two key Zn2Cys6-type transcription factors CmTf1 and CmTf2 were verified to play the roles of doubling the cordycepin production by overexpression of their coding genes in C. militaris wild type. These results provide a complete map of the cordycepin network in C. militaris with a distinct understanding of the flexibility of joints, giving a better foundation for increasing cordycepin yield and strain breeding in the future.

Optimized method to harvest both kidneys from one donor rat for transplantation.

BACKGROUND: Rat renal transplantation is an essential experimental model for studies of transplantation immunobiology. Harvesting both kidneys from one donor rat for transplantation is widely used to reduce the number of experimental animals. Using the conventional method, both kidneys of the donor rat are harvested simultaneously, which leads to the prolonged warm ischemic times during transplantation of the second donor kidney. Prolonged warm ischemia time is the main risk factor for delayed graft function. METHODS: Two different approaches are compared. Method 1, conventional method: both kidneys of the donor rat are harvested simultaneously and then transplanted into two recipients. During transplantation, the first and second donor kidneys were regarded as Group 1 and 2, respectively. Method 2, step-by-step method: after left nephrectomy, the donor rat survives, and we perform left renal transplantation (Group 3). Then, the right kidney of the surviving donor rat is incised and transplanted into the left side of the second recipient (Group 4). RESULTS: The success rates were 86.7, 93.3, 93.3 and 86.7% in groups 1, 2, 3 and 4, respectively. The warm ischemia times increased significantly in group 2 compared with the other 3 groups (p < 0.05) but differed non-significantly between groups 3 and 4 (p > 0.05). Serum creatinine levels, blood urea nitrogen and 24-h urine protein level obviously increased after kidney transplantation in group 2 compared with other groups (p < 0.05). CONCLUSIONS: We developed an optimized method for reducing warm ischemia time, thereby minimizing delayed graft function.