Main Biological Characteristics Of Isaria Farinosa And Its Omics Analysis Of Responses To Altitude Changes

Biocontrol fungi are widely used under the background of green environmental protection.Therefore,to discover and screen an effective biocontrol fungus strain is significant for agricultural and forestry production.As an entomogenous fungus,Isaria farinosa should have biocontrol potential.At the same time,as a colonizing fungus of Chinese cordyceps,I.farinosa and its biological activity were more and more studied,and the mycelia has the potential of large-scale production as drugs.Since the strain used in this research was isolated from the host insects of Ophiocordyceps sinensis inhabiting in the Qinghai-Tibet Plateau,it is inferred that the growth and metabolism of mycelia may be affected by altitude.So it is necessary to study the biocontrol application of I.farinosa and its omics characteristics in response to altitude variation in production.So as to provide theoretical basis for further development and utilization of I.farinosa.The main results are as follows:1.Grassland pest Thitarodes gonggaensis and 6 agricultural common pests were inoculated with I.farinosa.The results showed that the infection rate to T.gonggaensis was high,which proved that T.gonggaensis was the suitable host of 1.farinosa.While Locusta migratoria could resist I.farinosa.The larva of Galleria mellonella,Aphis glycines,Plutella xylostella,Helicoverpa armigera and Spodoptera exigua were killed at various rate by inoculation with spore suspension,while no larva were killed by spore without water.2.The suitable nutrition and culture conditions for liquid fermentation of I.farinosa mycelia were investigated by single factor and orthogonal experiment.The results showed that,among the 10 factors studied,glucose,beef extract,iron,magnesium and C/N ratio of 7:1 were the optimal nutrition condition,and the suitable culture conditions included 250-mL triangle flask containing 50 mL medium,10%inoculation amount,12 h light/12 h dark,20℃ and under 120 rpm.Based on this result,a further research on the effect of altitude on mycelial metabolites was conducted by the method of LC-MS.The results showed that based on the mycelial metabolism,all mycelial samples produced at altitude of 430 m and 2365 m were grouped successfully.Compared with high altitude mycelia,417 metabolites were down-regulated and 631 were up-regulated in low altitude mycelium.The results showed that altitude is one of the important factors affecting drug quality and safety.Altitude,which regulates the expression of substances,also provides a method for promoting the production of beneficial substances.These results provided theoretical basis for large-scale production of I.farinosa mycelia with stable quality in fermentor.3.The results of fennentation at altitude of 430 m and 2365 m showed that no significant difference was found among them,and which deeply indicated that altitude didn’t affect the mycelial yields of I.farinosa.However,the results of both transcriptome information analysis and q-PCR test showed that the expression of genes relative to respiration,including COX5A,QCR8,UQCRFS1,NDUFV1,NDUFA8 and NDUFS7,increased at high altitude significantly.It was inferred that,to maintain the mycelial yield,I.farinosa must adapt to the stress of oxygen reduction caused by high altitude and change from aerobic respiration to anaerobic respiration that needs more energy consumption for the identification and transmission of respiratory matrix.At the same time,the extra energy produced by the genes relative to respiration that were increased expression,was just to meet this extra energy consumption.Which kept the respiratory system stable so as to ensure the mycelium yield unchanged.This maybe the transcription mechanism of I.farinosa adopting to the stress of reduction oxygen at high altitude.4.For metabolites are regulated by altitude,comparative transcriptome analysis of mycelia fermented at high altitude and low altitude was carried out to identify the corresponding regulatory genes.The metabolic pathways of 6 metabolites,which had significantly different expression between high and low altitude,were enriched and the relative genes were screened out in the pathways.Which disclosed the relationship between metabolic substances and genes.These results provide a preliminary basis for further revealing the gene function and constructing expression vectors of specific active substance.