Effect And Mechanism Of MeJA On Tropane Alkaloids In Atropa Belladonna L.

Atropa belladonna L.is the important medicinal plant species,belonging to the family of Solanaceae.Hyoscyamine and scopolamine are the main secondary metabolites,which are the important anticholinergic agents.As the content of hyoscyamine and scopolamine are very low in plant,the production of two can not meet the need of market.The treatment of plants with exogenous additives is a commonly used and effective method.Methyl jasmonate(MeJA)as a substance that has a broad regulatory effect on plant growth.It has been found to improve the secondary metabolites content of medicinal plants.In this study,the Atropa belladonna L.as material.Five MeJA treatment groups with different concentrations were set which included: 0 ?mol·L-1,100 ?mol·L-1,200 ?mol·L-1,300 ?mol·L-1,400 ?mol·L-1.The effects of MeJA on the growth,physiological characteristics and the main alkaloid content in leaves of Atropa belladonna L.Were studied.Then,the regulatory mechanism of MeJA on the TAs of Atropa belladonna L.will be studied from nitrogen metabolism,the key intermediates in the biosynthetic pathway of TAs and the expression of key enzymes.The main conclusions are as follows:1.Comparing the effects of MeJA with different concentration on physiological characteristics of Atropa belladonna L.Leaves.Results showed that contents of chlorophyll a and chlorophyll b in Atropa belladonna L.leaves were significantly decreased after MeJA treatment.It suggests that MeJA can promote chlorophyll degradation or inhibit the synthesis of chlorophyll.The low concentration of MeJA(100?mol·L-1,200 ?mol·L-1)treatment can increase the content of proline in leaves of Atropa belladonna L.during the whole treatment period.The higher concentration of MeJA(300 ?mol·L-1,400 ?mol·L-1)increased first and then decreased or balance with the prolongation of time.MeJA can improve the content of proline in leaves of Atropa belladonna L.,reduce its osmotic potential,keep water pressure and reduce damage to cells.MeJA treatment increased significantly the content of soluble protein in Atropa belladonna L.Leaves.MeJA may stimulate the synthesis of defensive proteins.And the defense system started a variety of catalytic enzymes synthesis.Thereby MeJA can affect the physiological metabolism of Atropa belladonna L..2.The effects of MeJA on the growth and main alkaloid contents of Atropa belladonna L.were studied.MeJA treatment can inhibit the growth of Atropa belladonna L.And the inhibitory effect was more obvious with the prolongation of treatment time.The content of hyoscyamine and scopolamine in Atropa belladonna L.leaves was similar to that in MeJA treatment.100 ?mol·L-1MeJA treatment for 14 days can significantly improve the main alkaloid content,and treating with 200 ?mol·L-1,300 ?mol·L-1,400 ?mol·L-1 MeJA 7 d can be significantly improved the content of two alkaloids in Atropa belladonna L.Leaves.The content of hyoscyamine and scopolamine reached the maximum at 28 days under treatment with 200 ?mol·L-1,which was 1.706 times and 1.807 times of that of control respectively.Overall,methyl jasmonate can promote the synthesis of hyoscyamine and scopolamine in Atropa belladonna L..3.In order to elucidate the mechanism of MeJA regulation of hyoscyamine and scopolamine in Atropa belladonna L.leaves,we studied the NO content,key enzymes of nitrogen metabolism,arginine decarboxylase(ADC)and ornithine decarboxylase(ODC),polyamine content and key enzyme gene expression after treating 28 d.The results showed that MeJA could stimulate the burst of NO in Atropa belladonna L.leaves,but the change trend was different from the main alkaloid content.MeJA could decrease the content of nitrate nitrogen.And with the concentration of treatment going higer,the activity of nitrate reductase(NR)and glutamine synthetase(GS)tend to become same.The activity of NR got improvmend after MeJA treatment.And the activity of GS got improvmend too,except 400?mol·L-1 treatment.Overall,MeJA increased the level of nitrogen metabolism.MeJA also increased the activity of ADC,And the activity of ODC was also improved at 200 ?mol·L-1and 300 ?mol·L-1treatment.The content of putrescine was increased significantly after MeJA treatment,while spermine and spermidine slightly changeed.But the content of putrescine is not consistent with the change of the main alkaloid content,and may also be related to the downstream key enzymes of TAs synthesis pathway.MeJA had no significant effect on the expression of pmt in the roots of Atropa belladonna L.expect 100 ?mol·L-1treatment.But promoted the expression of tr? in leaves,also promoted the expression of tr? and h6 h in roots.The change trend of tr? expression in roots was consistent with that of hyoscyamine and scopolamine.Tr? can promote the metabolism to the synthesis of hyoscyamine and scopolamine in the direction of movement.H6 h can promote hyoscyamine generate scopolamine.In summary,it is suggested that the mechanism of MeJA on the alkaloid content of Atropa belladonna L.is mainly by promoting the expression of tr? and h6 h genes in Atropa belladonna L.Roots.So the secondary metabolism is more directed towards synthetic hyoscyamine and scopolamine.In addition,the appropriate concentration of MeJA can also improve the level of nitrogen metabolism in Atropa belladonna L.,ADC and ODC enzyme activity increased,then improve the content of putrescine.So as to provide the sufficient precursor for the synthesis of TAs.