Functional Analysis Of TvHSP70 In Trichoderma Viride Response To High Temperature And Drought Stress

Trichoderma viride is a multifunctional microorganism with important roles in industrial and agricultural production and environmental protection.In this study,T.viride strain Tv-1511 isolated from the rhizosphere of tobacco was used as the experimental material.A systematic study was conducted on the physiological and molecular mechanisms of T.viride Tv-1511 in response to heat and drought stresses.We cloned the TvHSP70 gene,and explored its function and possible mechanism.The main research findings are as follows:1.A Trichoderma strain from the rhizosphere soil of tobacco was obtained by single spore separation.The amplification,sequencing and comparison showed the strain was Trichoderma viride.We designated this T.viride strain with wider environmental adaptability as Tv-1511(CGMCC No.16800).Tv-1511 exhibited significant antifungal activity against pathogenic fungi via the mode of competition,parasitism,and antibiosis.Tv-1511 and the corresponding bio-organic fertilizer have valuable application prospect with growth and yield promotion.2.Transcriptomics analyses was performed to identify the molecular mechanism of Tv-1511 responding to heat and drought stresses.We found that Tv-1511 regulated the biosynthesis of secondary metabolites through a complex signal pathway network,and significantly activated the antioxidant defense system,heat shock protein and antibiotics biosynthesis in response to heat and drought stress.Based on the transcriptome and gene expression analysis,HSP70 gene was identified as a key gene in Tv-1511 responding to heat and drought stresses.TvHSP70 gene with a size of 2022 bp was cloned from Tv-1511,and overexpression vector was constructed by seamless cloning technology.Then,transgenic Tv-1511 overexpressing TvHSP70(TvHSP70-OE)was generated via PEG-mediated protoplast transformation.3.Morphological characteristics and resistance analysis of wide-type(WT)and TvHSP70-OE strains revealed that TvHSP70 overexpressing can significantly promote growth,antifungal activity and stress related traits such as heat,drought,and salt resistance.Further analysis revealed that the TvHSP70 played important role in regulating antifungal activity by upregulating genes involved in fungal,aminoglycoside,and macrolide biosynthesis.Besides,TvHSP70 also plays essential roles in improving stress resistance by upregulating genes related to antioxidant system,such as SOD,CAT,GPX,GSS,CCD,MIOX,and ELO3.4.Soybean plants,inoculated with WT and TvHSP70-OE strains of Tv-1511,were subjected to high temperature and drought treatment.The results showed that TvHSP70-OE strains could promote germination and seedling growth of soybean,and triggered various stress responses in soybean,including photosynthesis,oxidative phosphorylation and antioxidant defense system.Moreover,TvHSP70-OE strains also plays important roles in improving soybean lodging-resistance characters by upregulating lignin synthesis related genes.The function roles and molecular mechanism of TvHSP70 in Trichoderma viride were firstly revealed in our study,and the results contributed to the further understanding of the stress resistance mechanism of heat shock protein,and also provide valuable genetic resources and reference base for the breeding of stress-resistant engineered strains of Trichoderma.