The Symbiosis Development Of M.cylindrica-AM Fungi And Its Effect On Scp1 Gene Expression

Arbuscular mycorrhizal fungi(AMF),one of the most extensive and ancient fungi,are able to form symbionts with plant roots,which played an extremely important role in the adaptation of early angiosperms to terrestrial environments.Magnolia cylindrica is a Chinese endemic and rare forest plant species of Magnoliaceae.In our study,the representatives of early angiosperms – M.cylindrica and the ancient fungi-AMF(different inoculation of Funneliformis mosseae and Funneliformis caledonium in the greenhouse)were used as research objects for exploring the development process of mycorrhizal symbionts and the differential expression of mycorrhizal specific gene scp1 to reveal the symbiotic relationship and coevolutionary characteristics of Magnoliaceae and AM fungi.The main research results are as follows:(1)In our study,the morphological structure of mycorrhizae in the root cortical tissue were detected by means of microscopic timing detection,and the basic intracellular structure of mycorrhizal symbiosis of M.cylindrica was clarified: the typical development structure of "primary hyphal coils cluster + secondary arbuscular".Using SPSS statistical analysis software,it was found that arbuscular colonization rate and hyphal coils colonization rate were extremely significantly positively correlated(P <0.01).After that,the structural equation model(SEM)was built by Amos software to further analyze the AM development process.It was found that the hyphal coils colonization rate had a significant direct impact on the arbuscular colonization rate(path coefficients were 0.79,0.89 and 0.65,respectively),which verified the development process of mycorrhizal structure of "primary hyphal coils cluster + secondary arbuscular".The typical Paris-type hyphal coils structure in the M.cylindrica root was considered to be an ancient coevolutionary feature preserved in the long-term evolution of the Magnoliaceae and AM fungi.(2)Analysis of the physiological and biochemical indexes of M.cylindrica revealed that the root vigor and P content of roots of M.cylindrica under the AMF inoculation treatments were basically higher than those of the non-inoculated treatment,and that the root vigor and P content of roots of M.cylindrica under the treatment of AM fungi were up to about 0.73 ?g/(g?h)and 12.5 ?mol/g.At the same time,the root vigor and P content of roots under the double inoculation treatment were higher than that of the single inoculation treatments.In addition,we found the similar effective results in chloroplast pigment index.Therefore,we can think that AM fungi can help Magnoliaceae plants adapt to the early terrestrial environment by promoting the absorption of nutrients.(3)Higer purity of total RNA in M.cylindrica roots was got by using the modified CTAB method,which was suitable for the subsequent qRT-PCR molecular experiments.The results of qRT-PCR were used to analyze the differential expression of scp1 gene in the roots of M.cylindrica under different months and different treatments.It can be clearly seen that the ratio of scp1 gene expression within the root tissue of M.cylindrica under the AMF inoculation treatments was much higher than that in non-inoculated treatment.The maximum inoculation rate was about 4.35.Furthermore,compared with single inoculation treatments,scp1 gene expression was more active under double inoculation treatment.In addition,we found that the ratio of scp1 gene expression in the roots of M.cylindrica was the lowest(approximately 0.02)after September,and after that,there was no significant change.We speculated that it was the result of the adaptation of plants to the seasonal environment change.Therefore,we believe that scp1 gene is a specific gene which can promote mycorrhizal formation in the long-term genetic evolution of Magnoliaceae plants.Based on the above results,we believed that Magnoliaceae plants still retain the ancient Paris-type mycorrhizal structure in long-term symbiosis with AMF,although in the long-term coevolution process,arbuscular structure similar to Arum-type was differentiated.These coevolution characteristics help Magnoliaceae plants survive in complex ecological environments.In addition,we found that the host plants had no specific preference for AM fungi from the physiological and biochemical indexes of M.cylindrica and the expression results of mycorrhizal specific gene scp1 and different AM fungi can promote the symbiosis process,which reflects the long-term coevolutionary relationship between plants and AM fungi.