| Chinese cordyceps is a rare herbal medicine in Qinghai-Tibet Plateau of China.It is a complex of fungi and larvae body,and its growth is restricted by many environmental factors.At present,the effects of temperature,light and other environmental factors on Chinese cordyceps have been reported,but the research data on the effects of water on its growth and development are rare.In this study,Ophiocordyceps sinensis culured on artificial medium was used as the material,and 3.8% Na Cl was added to the medium to simulate the growth and development of Ophiocordyceps sinensis under water stress enviroment.Meanwhile,including control group(CK),water stress of 5 days(Y5),10 days(Y10),20 days(Y20),30days(Y30).Mycelial morphology was observed with the microscope.The differentially expressed genes(DEGs)were analyzed by transcriptome sequencing,and differentially expressed metabolites(DEMs)were analyzed by metabolomics between control group and Y20 group.This study deeply explored the effects of water stress on the growth and development of Ophiocordyceps sinensis from phenotypic,physiological and molecular levels.This study aims to provide a theoretical basis of water condition for culture of Chinese cordyceps.The main results are as follows:1.With the extension of treatment time under water stress,the morphological characteristics of Ophiocordyceps sinensis were significantly different: the growth of the colony was significantly inhibited.The outermost mycelium of the colony was white and transparent,and there was no air mycelium growth on the surface.The mycelium was twisted,thickened and arranged in a network,and no obvious conidia and sporulation structure was observed.2.After water stress treatment,the contents of polysaccharide,urea,mannitol and polyphenol in the mycelium of Ophiocordyceps sinensis showed a similar that trend increasd firstly and then decreasd.However the content of mannitol was accumulated again after 30 days of water stress treatment,and the content of adenosine was significantly decreased after water stress treatment.3.Transcriptome sequencing results showed that the gene expression of Ophiocordyceps sinensis began to differ after Y5;and reached the peak after Y10.Compared with treatment for10 days,the expression of differential genes decreased for 20 days,the number of down-regulated genes reached the maximum;the expression level of differential genes decreased after Y30 and gradually stabilized.4.Functional annotation analysis of DEGs showed that water stress had the greatest effect on the components of Ophiocordyceps sinensis membrane,and the change of polysaccharide content might be related to the expression of alpha-galactosidase related genes;the change of mannitol content may be related to the expression of mannitol-1-phosphate5-dehydrogenase related genes;the change of polyphenol content may be related to the expression of phenylalanine ammonia-lyase related genes;the change of urea content was related to the expression of argininosuccinate synthase related genes;the changes in adenosine content were related to 5’-nucleotidase related gene expression.5.Under water stress,Ophiocordyceps sinensis activated CAT1,peroxisome and heat shock protein family through MAPK pathway cascade reaction to help the body to resist adversity.6.Functional annotation of DEMs analysis showed water stress treatment had the greatest effect on linoleic acid metabolism,alpha-Linolenic acid metabolism and arachidonic acid metabolism.Betaine and amino acids are the osmotic regulatory substances of Ophiocordyceps sinensis under water stress.7.Through combined transcriptome and metabolome analysis,galactose metabolic pathway,arginine biosynthesis pathway and tyrosine metabolism pathway were found to influence the change of polysaccharide content,urea content and L-dopa conten. |
