Identification Of Lotus Japonicus Methyltransferase Family Genes And Investigation The Function Effects On AM Fungi Symbiosis

Arbuscular mycorrhizal fungi can establish a symbiotic relationship with about 90% of terrestrial plants including rice(Oryza sativa),maize(Zea mays),wheat(Triticum aestivum),soybeans(Glycine max),etc.In the interaction between arbuscular mycorrhizal fungi and plant,AM fungi can promote plants to absorb mineral elements from soil.Meantime,plants provide carbon and nitrogen sources to AM fungi for exchange to promote their growth.Studies have shown that DNA methylation plays a crucial role in the growth and development of plants,but whether DNA methylation plays a regulatory role in the interaction between plants and AM fungi is still poorly understood.It has been known that methyltransferases play a key role in the regulation of DNA methylation.Therefore,it is very meanningful to investigate the role of methyltransferases in the interaction between plants and AM fungi.In this paper,the functions of candidate methyltransferase genes in the symbiosis between AM fungi and hairy roots were investigated by transgenic plants.The main results are as follows:1.A total of 12 methyltransferase genes were identified from the whole genome of L.japonicus,and the expression of methyltransferase genes can be induced by AM fungi.Among those,LjMET-9 can be induced by the fungus with down-regulation tendency with the prolong time.That is,LjMET-9 was selected as a key candidate regulatory gene for function investigation.2.The LjMET-9 coding region was cloned,and the LjMET-9 overexpression vectors(LjMET-9-OE)and LjMET-9 interference vectors(LjMET-9-RNAi)of the methyltransferase gene were successfully constructed.Eighteen LjMET-9-OE positive transgenic plants and 23 LjMET-9-RNAi positive transgenic plants were obtained.3.The differences in root number,dry weight,infection rate,and symbiosis rate between the control and treatment groups were statistically calculated.The result showed that the expression level of LjMET-9 did not influence the normal growth of hairy roots,but it might influence the growth and development of the roots as well as the interaction between plant and AM fungi.4.Detection transcription level of LjMET-9 in wild-type,LjMET-9-OE,and LjMET-9-RNAi hairy roots by q RT-PCR implies that LjMET-9 indirectly regulated the symbiosis between AM fungi and hairy roots.5.The expression levels of the symbiotic marker genes Lj DIP1 and Lj NSP2 further demonstrated that LjMET-9 indirectly regulated the establishment of symbiosis between AM fungi and hairy roots.However,which genes or regulatory network that LjMET-9 used to regulate the symbiotic relationship between AM fungi and hairy roots remains to be further investigated.