| Erigeron breviscapus has the functions of removing blood stasis,clearing the meridian and activating collaterals,reducing inflammation and pain.As an very importan kind of econdary metabolites,the flavonoids demonstrate special physiological activity and multiple biological functions in plants.The R2R3myb gene is the most important regulatory elements in the phenylpropanoid metabolism network.Through differential regulating the different key target genes in the metabolic network,they not only control to product of the most abundant secondary metabolites in plants,but also is the key to synthesis specific component in specific plants.The scarcity of wild Erigeron breviscapus resources makes it particularly important to develop artificially domesticated cultivars.Low nitrogen or stimulation of exogenous substances will affect the synthesis of plant secondary metabolites,such as flavonoids.The R2R3myb gene is one of the most important regulatory elements in the phenylpropane metabolism network,and plays an important role in plant growth and development,regulation of secondary metabolism,and response to stimuli from biological and non-biological factors.This experiment used low nitrogen,salicylic acid（SA）and methyl jasmonate（Me JA）treatments to study the total flavonoids content of breviscapine leaves,the expression of Eb MYB06 gene in Erigeron breviscapus and the expression of flavonoids metabolism network related genes,and explore the effect of Eb MYB06 on Erigeron breviscapus the anabolism of flavonoids.The leaves of Erigeron breviscapus were treated with exogenous SA and Me JA,and the changes of chlorophyll fluorescence parameters in the early,middle and late hours were measured,and the effects of SA and Me JA treatment on light adaptation of Erigeron breviscapus under natural light conditions were explored.The above experiments provide a certain theoretical basis for reasonable addition of nitrogen fertilizer for Erigeron breviscapus,measures to increase the accumulation of total flavonoids,and cultivation of high-quality Erigeron breviscapus.The specific research results are as follows:1.Low nitrogen treatment can increase the total flavonoids content of Erigeron breviscapus,which is inversely proportional to the amount of nitrogen applied,but in the test nitrogen level interval,the biomass of Erigeron breviscapus is proportional to the amount of nitrogen applied.When the nitrogen application level is 0.4kg/m2,the biomass can be maximized while ensuring the accumulation of flavonoids.2.SA and Me JA treatments will increase the total flavonoids synthesis of Erigeron breviscapus,and the difference in treatment concentration will cause the difference in flavonoids synthesis.The salicylic acid treatment group had the highest flavonoids synthesis at a concentration of 0.05 mmol·L-1,and the methyl jasmonate treatment had the highest flavonoids synthesis at a concentration of 5 mmol·L-1.SA and Me JA treatments can reduce the daily fluctuations caused by light intensity and improve the adaptability of leaves to the external environment.The higher the total flavonoids content of leaves,the better the adaptability to the external environment.3.The expression of Eb MYB06 in Erigeron breviscapus treated with nitrogen,SA,and Me JA all changed with the treatment factors,but the response mode to nitrogen and exogenous stimuli may be different.Low nitrogen treatment resulted in the down-regulation of the expression of Eb MYB06,which is speculated to have a negative regulatory effect on the flavonoids synthesis of Erigeron breviscapus.The genes that are co-expressed with it are ANR,CAD,COMT,F3’5’H,FSⅡ,PAL,UFGT,FMT.SA and Me JA treatments will up-regulate the expression of Eb MYB06.It is speculated that under exogenous salicylic acid and methyl jasmonate treatment,Eb MYB06 has a positive regulatory effect on the flavonoid synthesis of breviscapine.Under SA or Me JA treatment,the up-regulation or down-regulation of scutellaria flavonoid anabolic genes was consistent.The genes co-expressed with Eb MYB06were PAL,4CL,C3H,C4H,CAD,CCR,CHS,COMT,F3’H,F3’5’H,FMT,FSⅡ,LAR,the expression of 5,3GT,ANR,CHI,DFR,HCT,UFGT is down-regulated.It is speculated that the expression patterns between the two are similar.The research conclusions show that in the cultivation of Erigeron breviscapus,the total flavonoids content of cultivated breviscapine can be increased by reducing nitrogen fertilizer,spraying salicylic acid and methyl jasmonate,which has certain practical significance for the field cultivation of Erigeron breviscapus.Nitrogen,SA and Me JA have differences in the expression control mode of Eb MYB06 and flavonoids synthesis-related genes in Erigeron breviscapus,revealing that the expression regulation mechanism of Eb MYB06 in Erigeron breviscapus on different flavonoids synthesis-related genes is similar to that of the currently reported Arabidopsis thaliana MYB gene family.The regulation of the seventh group and the fourth group is different,indicating that MYB in the breviscapine genome regulates the phenylpropane metabolic network more complicated.The research conclusion has certain theoretical value for supplementing the details regulation of MYB of phenylpropane metabolic network. |
