Study Of Trichoderma Asperellum And Its Siderophore On Plant Growth Promotion Under Fe-deficiency

Iron(Fe)is an essential nutrient for plant growth and development,and it serves as a cofactor for a wide variety of cellular processes,such as oxygen transport,cellular respiration,chlorophyll biosynthesis,thylakoid biogenesis and chloroplast development.The total content of iron in the lithosphere is high,but the content soluble iron is very low.However,the Fe bioavailability in well-aerated soils is often severely limited,particularly in calcareous soils.At the same time,the increase of soil pH due to hydrolysis,polymerization and precipitation reaction will decrease the solubility of Fe(?).The decrease of soluble iron content in soils severely limits the yield and quality of agricultural products,and it is urgent to explore the effective way to solve the problem of iron deficiency in crops.Trichoderma spp.is a rhizosphere probiotic fungus that promotes plant growth to increase crop yields and increases plant resistance to both biological and abiotic stresses.But it lacks an in-depth and systematic study on the mechanism of salt and iron deficiency.In this paper,the effects of CdCl2,salt stress and iron deficiency on the growth of Arabidopsis thaliana were studied by plate growth promotion experiment.The effects of Trichoderma asperellum Q1 on the contents of siderophore and IAA at different iron concentrations were studied.Then we determined the effect of Trichoderma asperellum Q1 on the level of IAA in Arabidopsis thaliana auxin marker line DR5::GFP under Fe-deficiency.The effects of IAA on the proliferation of Arabidopsis thaliana IAA14 mutant were determined by platelet experiments using siderophore.Finally,we verified the effect of siderophore on IAA in Arabidopsis thaliana auxin marker line DR5::GFP under Fe-deficiency by plate experiments.The specific results are as follows:(1).The Trichoderma asperellum Q1 showed promotion on the Arabidopsis thaliana development by the plate experiments under CdCl2,salt stress and iron deficiency.Then,we tested the content of siderophore and IAA from Trichoderma asperellum Q1 fermentation under three stress conditions.The results showed that salt stress and iron deficiency could promote the production of IAA and the best concentration of salt was determined between 100 and 200 mM.Besides,the strain Q1 shows high yield of siderophore only in the absence of iron stress;(2).To determine the effect of iron concentration on IAA and siderophore in Trichoderma asperellum Q1 fermentation,we set the concentration gradient for 0 mM,2 mM,4 mM,6 mM in liquid medium.We discovered that the final concentration of IAA and siderophore were gradually increased with the iron concentration decreased.These results indicated that low iron concentration promoted the production of IAA and siderophore in Trichoderma asperellum Q1;(3).Using the plate experiments in Arabidopsis thaliana and Arabidopsis thaliana auxin marker line DR5::GFP under Fe-deficiency,we discovered that the growth of Arabidopsis thaliana seedlings was increased by inoculating Trichoderma asperellum Q1.This strain also exhibited the ability to increase the level of IAA in Arabidopsis thaliana auxin marker line DR5::GFP root system.These results further confirmed the role of this strain in promoting plant growth,and enriched its iron deficiency mechanism.(4).In order to explore the main promoting mechanism of Trichoderma asperellum Q1 under iron deficiency,the plate experiments in IAA14,a mutant defective in auxin singaling of Arabidopsis was conducted under iron deficiency.The results showed that the growth of IAA14 seedlings was effectively increased by purified siderophore from Trichoderma asperellum Q1;(5).Using the plate experiments in Arabidopsis thaliana auxin marker line DR5::GFP under Fe-deficiency,we discovered that the growth of Arabidopsis thaliana seedlings was increased by purified siderophore from Trichoderma asperellum Q1.And the purified siderophore also exhibited the ability to increase the level of IAA in Arabidopsis thaliana auxin marker line DR5::GFP root system.In addition,siderophore also showed a certain degree of plant growth promoting role.The results of this study further enriched the plant growth promoting mechanism of Trichoderma asperellum Q1 under iron deficiency and provided a theoretical basis for further investigation of the relationship between microbial siderophore and IAA signal in plants.