Application Of Falciphora Oryzae In Low Nitrogen Condition On Plant Promoting In Production Practice

Endophytic fungi live within plant tissue for at least part of their life cycle,without causing obvious plant diseases symptoms under normal growth condition.Some endophytic fungi promote plant growth or resistance under biotic and abiotic stresses.Falciphora oryzae is one kind of dark septate endophytic fungus isolated from wild rice.When applied to the cultivated rice,F.oryzae significantly promotes rice growth and resistance to the most destructive blast disease,suggesting that F.oryzae has the potential to be a bio-fertilizer and bio-fungicide.Therefore,this study examined whether F.oryzae promoted plant vegetative growth under nutrient starvation conditions.The main results are as follows:1.F.oryzae alleviated nitrogen deficiency stress in Arabidopsis thaliana seedlings and mature plantsUnder normal growth condition,F.oryzae can colonize Arabidopsis roots,which significantly promotes root development,but has no significant effect on shoot growth and fresh weight.Previous studies have shown that many endophytic fungi,especially dark septate endophytic fungi,could enhance plants tolerance to biotic and abiotic stresses.Hence,we examined the effects of F.oryzae on Arabidopsis growth under nutrient starvation conditions.Our study found that the co-cultivation of F.oryzae could promote the shoot growth and fresh weight of Arabidopsis seedlings in the nitrogen starvation media,but not phosphorus,potassium or iron starvation media.When the nitrogen concentration was lower than 100μM,F.oryzae significantly increased the chlorophyll content and reduced the anthocyanin accumulation in Arabidopsis seedlings.However,this promotion effect was not observed when the nitrogen concentration was higher than 100 p.M,When the nitrogen concentration is higher than 100 μM,suggesting that F.oryzae alleviated the nitrogen deficiency stress in Arabidopsis seedlings.Similarly,F.oryzae alleviated nitrogen deficiency stress in Arabidopsis mature plants.2.F.oryzae alleviated the nitrogen deficiency stress of cruciferous plants and riceIn order to better apply F.oryzae to the field,We examined whether F.oryzae can alleviate the nitrogen deficiency stress of other plants,including Oryza sativa(Gramineae,monocotyledon),Solanum lycopersicum and Nicotiana benthamiana(Solanaceae),Glycine max(Leguminousae),Brassica campestris and Brassica rapa(Cruciferae).The plants were cultured in a mixed matrix of vermiculite and perlite,and watered with low nitrogen nutrient solution.Compared to the uninoculated control,the fresh weight of Oryza sativa,Brassica campestris and Brassica rapa were significantly increased after co-cultivation with F.oryzae.Therefore,F.oryzae could efficiently alleviate the nitrogen deficiency stress of cruciferous plants and Oryza sativa.3.F.oryzae increased the endogenous nitrogen content of plants under the nitrogen deficiency condition.The most possible mechanism of F.oryzae-mediated alleviation of nitrogen deficiency stress in plants is to increase the nitrogen uptake,transport or assimilation.Expression of all genes involved in nitrogen uptake and assimilation were up-regulated in F.oryzae under low nitrogen condition without co-cultivation,whereas genes involved in ammonium transport and assimilation were further up-regulated after co-cultivation with Arabidopsis.On the other hand,the ammonium transport gene AtAMT1;1 and nitrogen assimilation gene AtNRT2.5 in Arabidopsis were significantly up-regulated after co-cultivation with F.oryzae,and the endogenous nitrogen level in Arabidopsis was significantly increased.Taken together,the nitrogen deficiency stress of Arabidopsis was partially alleviated by F.oryzae through increased nitrogen uptake,transport and assimilation.4.F.oryzae alleviated nitrogen deficiency stress by regulating cytokinin and ethylene signaling pathway in ArabidopsisNitrogen deficiency stress is tightly regulated by plant hormone signaling pathways.Therefore,we examined whether the F.oryzae regulated plant hormone signaling and consequently alleviated nitrogen deficiency stress.In all tested mutants defective in hormone signaling,we found that ethylene mutants ein2 and ein3/eil1 and cytokinin mutants arr1/10/12 and ahp6 were insensitive to F.oryzae-mediated growth promotion,suggesting that F.oryzae can partially alleviate the nitrogen deficiency stress of Arabidopsis by regulating cytokinin and ethylene signaling pathway.Anthocyanin accumulation is a typical response to nitrogen deficiency stress.F.oryzae can significantly reduce the accumulation of anthocyanin induced by nitrogen deficiency.Interestingly,F.oryzae could not suppress anthocyanin accumulation in ethylene mutants ein2 and ein3/eil1.Co-cultivation of F.oryzae promoted the expression of AtEIN4,AtCTR1,AtEIL1,and AtEBF1 in Arabidopsis.Consistent with this,exogenous application of ethylene synthesis precursor ACC can alleviate low nitrogen-induced anthocyanin accumulation.These results indicate that F.oryzae suppressed low nitrogen-induced anthocyanin accumulation through ethylene signaling pathway.In summary,low nitrogen condition enhanced the acquisition and assimilation of nitrogen in F.oryzae.F.oryzae could improve the absorption of nitrogen,especially ammonium,of Arabidopsis thaliana.F.oryzae could also regulate the ethylene and cytokinin signaling pathways to alleviate the nitrogen deficiency stress of Arabidopsis.In addition,F.oryzae can increase low nitrogen stress tolerance of cruciferous plants which belong to one of the fewer families that can not build symbiosis relationship with arbuscular mycorrhizal fungi.Therefore,F.oryzae can fill the gaps of mycorrhizal fungi and applies to cruciferous leafy crops.