| Endophytes(Endophytic fungi)are organisms that inhabit living plants at some or entire stage in their life,without causing apparent harm to the host.At present,a large number of studies have shown that endophytic fungi of medicinal plants can improve the resistance of medicinal plants,promote the growth of medicinal plants and enhance the host contents of active components and so on.Therefore,it is of great significance to study the relationship between endophytic fungi and medicinal plants in order to improve the quality of medicinal herbs.Epichloe bromicola(Clavicipitaceae),an endophytic fungus isolated from the medicinal plant adlay(Coix lacryma-jobi L.var.mayuen.Stapf)by our research group as having a promoting effect on the host,can significantly increase the biomass of adlay,promote the accumulation of Coixol and improve activities of the related enzyme.However,the growth-promoting material basis,functional mechanism of E.bromicola and its effect on other medicinal plants are still not clear.With some characteristics,like unclear genetic background,a long-growth period,bigger plant,adlay is not convenient as the experimental material to research the effects and mechanisms of E.bromicola promoting Arabidopsis growth.And the subsequent studies have found that the fungus could promote the growth of the model plant Arabidopsis and increase its biomass.Therefore,based on the previous study,the model plant Arabidopsis was used as the research object to preliminarily explore the growth-promoting material basis and mechanisms of E.bromicola;and we choose medicinal plant Salvia miltiorrhiza as object applied E.bromicola solid fungus-fertilizer to study the effects of the fungus on the growth and the accumulation of secondary metabolites of other medicinal plant.Methods and results 1.The material basis of the growth-promoting endophytic fungi was studied preliminarily.First,E.bromicola and Arabidopsis were co-cultured by isolated,blocking the transportation of secreta synthesised by endophytic fungi to contact Arabidopsis seedlings,the results showed no significant difference in promoting growth,and were significantly higher than the control group.It is proved that the growth promoting effect may be caused by volatile substances produced by E.bromicola,which were subsequently analyzed by GC-MS.The results showed that the active components contained in the secondary metabolites of E.bromicola were mainly volatile components of 2,3-butanediol;2.These reliminary studies were expected to discuss the molecular mechanism of endophytic fungi promoting Arabidopsis.qRT-PCR technology was used to analyze the expression levels of auxin related genes(including the auxin transport protein gene AUX1,BIG,EIR1 and auxin response gene AXR3,ARF1)and auxin synthesis key enzyme genes(including three upstream genes CYP79B2,CYP79B3,YUCCA1 and two downstream genes NIT1,TAA1)in Arabidopsis in different days of co-culture with E.bromicola.the results showed that E.bromicola could significantly enhance the expression of auxin transport protein genes,auxin response genes and auxin synthesis key enzyme genes in Arabidopsis,and the expression of the auxin transport protein EIR1 gene which controls lateral root germination and auxin synthesis indole-acetaldehyde oxime synthesis pathway auxin synthesis key enzyme upstream gene CYP79B2 in the CYP79B gene family in a 18 day period of which was significantly;and the content of IAA in Arabidopsis was detected by nano-LC-ESI-Q-TOF-MS method,the result showed that the contents of IAA in Arabidopsis inoculated with E.bromicola were significantly higher than control at 1.76 times.3.Preliminary study on the application value of the strain in medicinal plants.The effects of the fungus on the growth of Salvia miltiorrhiza were observed by making the fungus into the form of solid fertilizer which was applied it to the potted plants of Salvia miltiorrhiza,the results showed that the fungus could significantly promote the growth of Salvia miltiorrhiza Bge.It could not only increase the tiller number,plant height,leaf number and leaf area,but also increase the fresh weight and dry weight of root.At the same time,HPLC technology was used to analyze the contents of secondary metabolites.The results showed that the contents of secondary metabolites among the 60th d and 120th d of salvianolic acids in the roots of salvia miltiorrhiza(including salvianolic acid B and rosmarinic acid)and tanshinones(including cryptotanshinone,dihydrodanshoneone Ⅰ,tanshinone Ⅰ and tanshinone ⅡA)increased significantly.In conclusion,the material basis of the growth promoting effect of E.bromicola from adlay may be volatile components,such as 2,3-butanediol or its analogues,produced by E.bromicola.And it states that the functional mechanism may be that the fungus regulate the synthesis and transportation of auxin in Arabidopsis itself,so as to achieve the role of promoting growth.In addition,it was found that E.bromicola could significantly increase the biomass of Salvia miltiorrhiza and promote the synthesis and accumulation of its secondary metabolites,therefore it can be inferred that endophytic fungus E.bromicola is a potential fertilizer microbe in promoting medicine plants,with good development prospects and better application potential of medicinal plants cultivation to improve the quality of medicinal plants. |
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