Molecular Mechanism Of Biological Nitration Inhibitor (MHPP) Regulating Perilla Frutescens Growth And Secondary Metabolite Accumulation

Methyl 3-(4-hydroxyphenyl)propionate(MHPP),is a chemical secreted by the roots of sorghum.It not only acts as a nitrification inhibitor in soil,but also regulates plant growth and root structure.However,the physiological and molecular mechanisms of MHPP-mediated plant growth and development are still unclear.In this study,the effects of MHPP treatment on growth and accumulation of secondary metabolites of Perilla frutescens seedlings were studied by adding different concentrations of MHPP in the process of hydroponics,to explore the molecular mechanism of MHPP on the growth and accumulation of secondary metabolites in seedlings.Based on the combined analysis of physiology,transcriptome and metabolome,the main findings are as follows:1.The treatments with 20 and 40 μM MHPP inhibited the seedling primary root growth,but induced the formation of lateral roots,significantly improved the root system architecture.Seedling fresh weight increased 9.94% and 21.46% in leaves and increased 11.88% and 3.88% in roots with 20 and 40 μM MHPP separately.The 60 and 80 μM MHPP treatment not only inhibited the growth of seedling primary root and lateral root formation,while seedling biomass decreased significantly.The results showed that the relatively low concentration of MHPP treatment can promote the growth of Perilla seedlings.2.Different concentrations of MHPP could induce the expression of peroxidase related genes in roots,and the activity of peroxidase in roots was significantly increased.The 40 μM MHPP treatment also induced the expression of zinc and iron regulatory proteins(ZIPs)in roots and promoted the absorption of Zn,Fe and Mn in roots.Compared with the control,the contents of Zn,Fe and Mn in roots of MHPP treatment were increased 9.08%,16.30% and 39.75%,separately.3.40 μM MHPP treatment modulated carbon and nitrogen metabolism(glycolysis,tricarboxylic acid cycle,primary nitrogen metabolism and amino acid decomposition approach)related genes and in the Phenylpropanoid metabolic pathway(phenylalnine ammonia-lyase PAL,synthase halcone CHS,flavanone3-hydroxylase FLS)related genes,to regulate of Perilla seedling growth and the accumulation of secondary metabolites.4.40 μM MHPP treatment induced the accumulation of medicinal secondary metabolites such as flavonoids and terpenoids alkaloids in Perilla seedlings.The contents of resveratrol 4’-gluco-side,arbutin,isomangiferin,monotropein,methyl orsellinate,persiconin and neoliquiritin were higher than the contrast in the roots,and in the leaves,oleanolic acid,included acid,6-hydroxy scopolamine contents were induced compared with the contrast.From above results,the appropriate concentration of MHPP treatment can regulate the growth of Perilla seedlings and the accumulation of secondary metabolites by improving root architecture,regulating the differential expression of related genes in carbon and nitrogen metabolism and phenylpropanoid metabolic pathways,as well as peroxidase,metal transporter and other related genes.Taken together,these results provided a theoretical basis for MHPP in Perilla cultivation,Perilla variety selection and functional product development.