Effects Of Dopamine On Arbuscular Mycorrhizal Symbiosis Of Apple

Apple(Malus domestica Borkh.)is one of the most important fruit trees in China.Its output,planting area and export volume rank first in the world.However,abiotic stresses,such as drought,salinity,low temperature and nutrient deficiency,have become the main factors restricting the yield and quality of apple trees,and seriously restricting the sustainable development of apple industry.Arbuscular mycorrhiza(AM)is a mutually beneficial symbiosis between plants and AM fungi(AMF),which can effectively promote the growth of fruit trees,improve water and mineral nutrition metabolism,and improve stress resistance of fruit trees.However,there is no report on the effect of dopamine on AM symbiosis.Firstly,the effects of exogenous dopamine on the symbiosis of M.hupehensisand AM,and their synergistic effects under salt stress were studied through field experiments.Secondly,MdTYDCapplewas inoculated AMF.Then,the molecular mechanism of MdTYDC regulating AM symbiosis in apple was preliminarily revealed by RNA-Seq.The main results are as follows:1.The effect of exogenous dopamine on AM symbiosis under salt stress was studied by pot experiment with M.hupehensisRhed as test material.The results showed that under salt stress,100μM dopamine could increase the carbon source of AM by increasing the content of glucose and fructose in apple roots,and promote the AM symbiosis,thus improving the salt tolerance of apple plants.In addition,dopamine and AMF had some synergistic effects under salt stress,which can alleviate the membrane damage of apples under salt stress;increased root carbohydrate content;increased photosynthetic capacity and chlorophyll content;increased plant P content,and increased plant K~+/Na~+ratio;increased plant antioxidant enzyme activity;increased soil available phosphorus and alkaline phosphatase activity.2.The effect of overexpression of MdTYDC on AM symbiosis of apple was studied by pot experiment with MdTYDC transgenic apple.The results showed that over-expression of MdTYDC could promote AM symbiosis and increase PT4 gene expression in apple roots.In addition,the chlorophyll a,total chlorophyll content and carotenoid content,F_V/F_M of wild type and transgenic plants were significantly increased after AMF inoculation.After inoculation with AMF,chlorophyll a,total chlorophyll content and alkaline phosphatase content of transgenic plants were significantly higher than those of wild type plants.3.In this study,the root of MdTYDC transgenic apple plants inoculated with AMF for 4weeks was sequenced by transcriptome sequencing.From the perspective of RNA omics,it was found that overexpression of MdTYDC may affect AM symbiosis by affecting phenylpropanoid biosynthesis,cytochrome P450-related metabolism and MAPK signaling pathways in apple plants.