Functions Of CeDGAT1 In Symbiotic Interactions Between Piriformospora Indica And Plants

Fatty acids are the main carbon source obtained from plants by symbiotic fungi,and changes of fatty acid in plants have effects on the interaction between plants and symbiotic fungi.An endophytic fungus Piriformorpora indica has a wide host range,which can greatly improve the stress resistance of host plants.DGAT1,a rate-limiting enzyme for triacylglycerol synthesis,plays important roles in the plant development,but its function on mutualistic symbiosis is unknown.To investigate the effects of fatty acid or DGAT1 on mutualistic symbiosis,in vitro effects of different fatty acid on the growth of P.indica and functions of CeDGAT1 from Chlorella ellipsoidea on symbiosis between Arabidopsis thaliana or Brassica napus and P.indica were evaluated.The results were as follows:1.The effects of exogenous fatty acids on P.indica and its pathogens were investigated.Most fatty acids,such as palmitic acid,linoleic acid,triglyceride,glycerol and sodium oleate,had positive effects on mycelial growth and development of P.indica,among which palmitic acid had the best promoting effect.Most fatty acids inhibited the growth of gibberellus,and linoleic acid showed the strongest inhibition effect,with the inhibition rate of more than 12%in 3-5 days.Most of the fatty acids also showed a certain promotion effect on the growth of Discodia rapescens.The main plant fatty acid palmitic acid can promote the growth of the mycelium of the symbiotic probiotics P.indica,and it also has some effects on the growth of the pathogenic bacteria Fusarium graminoides and Sclerotinia sclerotiorum.2.The effects of endogenous fatty acid changes in Arabidopsis thaliana(overexpression of CeDGAT1 gene and knockout of endogenous DGAT1 gene)on the colonization and growth of P.indica were investigated.The results showed that overexpression of CeDGAT1 gene and inoculation of P.indica both optimized the root structure of A.thaliana and resulted in a dense root phenotype,which further increased the biomass of Arabidopsis thaliana.In Arabidopsis thaliana mutant dgat1,the number of P.indica colonized was significantly reduced due to the influence of fatty acid biosynthesis pathways.3.The effects of increased synthesis of endogenous stored fatty acid TAG(i.e.,overexpression of CeDGAT1)on the growth of rape and the colonization of P.indica were investigated.In addition,the effects of P.indica on the early synthesis and late accumulation of fatty acids in the symbiotic condition were also discussed.The results showed that both overexpression of CeDGAT1 gene and inoculation of P.indica could improve root structure and further promote the growth of host plants.Overexpression of CeDGAT1 promoted the colonization of P.indica chlamydia spores in the root of rape.The expression of WRI,a key gene upstream of fatty acid biosynthesis,was different in the inoculated roots of P.indica,suggesting that the massive colonization of P.indica may regulate the fatty acid biosynthesis pathway in feedback.The fatty acid content in root of rape was detected,and the total fatty acid content of overexpressed CeDGAT1 gene was relatively high,suggesting that exogenous CeDGAT1 gene may promote the accumulation of fatty acid in root of rape.The content of total fatty acids decreased after inoculation with P.indica,which might be related to the increased carbon absorption and energy consumption caused by the colonization of P.indicaOur studies showed DGAT1 played important rolesin the process of symbiotic interaction,and provided a new way to study the interaction between plants and microorganisms and the function of lipid metabolism in the symbiotic process.