Effect Of Exogenous Hormone On The Contents Of Glucosinolate And Sulforaphane In Radish(Raphanus Sativus L.) Taproot

Radish(Raphanus sativus L.)is an annual or biennial herb of the Brassicaceae family.The edible part of radish is its taptaproot,which is rich in glucosinolates.Glucosinolates is a class of plants secondary metabolites containing nitrogen and sulfur,and it commonly occurred in Brassicaceae vegetables.Glucoraphanin,one of the aliphatic glucosinolates,can form sulforaphane when hydrolyzed by enzyme myrosinase.The sulforaphane has attracted much interest since it was known to be the most promising anticancer agent.So it has become of vital importance to study the formation and influencing factors of glucosinolate and sulforaphane in radish taproots.Previous studies have been investigated the environment stress on glucosinolate content in radish sprouts.However,little is known about the effect of glucosinolate and sulforaphane accumulation under hormones treatment in radish taproots.In this study,the advanced inbred line 'NAU-ZQH' was used to study the regulatory of glucosinolate and sulforaphane accumulation under methyl jasmonate(MeJA),salicylic acid(SA),abscisie acid(ABA)treatment in radish taproots.The main achievements obtained were listed as following:1.The effect of MeJA on the accumulation of glucosinolate and sulforaphane in radish taproots was studied.MeJA have a great influence on the content of glucosinolate.The results showed that glucosinolate content of radish taproot was the highest by 1.5 mM MeJA treatment for 3d.Compared with the control,the glucosinolate content showed a 1.54 fold increase,and the expression level of MYB28,MYB34 together with the key biosynthetic genes such as MAM1,CYP79F1,CYP83A1,SOT18,UGT74B1 and FMOGS-OXI were higher.Myrosinase activity was increased 1.26 fold in radish taproots under 0.5 mM MeJA treatment,and the myrosinase gene TUG4 was also significantly up-reglulated.Meanwhile,MeJA also enhanced the content of sulforaphane after 6 d treatment,while there was no significant change in sulforaphane content between different concentrations of MeJA.2.The effect of SA on the accumulation of glucosinolate and sulforaphane in radish taproots was studied.The application of SA could induce or suppress the accumlaiation of glucosinolate.The contents of glucosinolates under 0.5 mM SA treatment for 3 d showed a 0.12 fold reduction compared with the control.The application of 1.5 mM SA treatment for 6d resulted in the highest glucosinolate content,increased by 0.79 fold.The highest GRA content was observed in 1.0 mM SA treatment,and the expression of genes CYP83Aland FMOGS-OXi wichh related to GRA biosynthesis were up-regulation.SA also played an important role in myrosinase activity in radish taproot.The expression of myrosinase activity genes TGG4 and TGG5 were also up-reglulation.The myrosinase activity,GRA content and the sulforaphane content was increased by 1.0 mM SA treatment for 3 d.3.The effect of ABA on the accumulation of glucosinolate and sulforaphane in radish taproot was studied.The contents of total glucosinolates were significantly decreased under ABA treatment.The contents of glucosinolate were decreased with the increase ABA concentration after treated for 3 d.The expression level of glucosinolates synthesis genes were lower,only MYB34,CYP79F1 and FMOGS-OXI showed a little higher expression.However,the content of GRA was found to increase by ABA treatment.This fact may be due to the higher expression level of FMOGS-OXI,and the relatively lower expression of AOP2.The expression levels of TGG4 were increased by ABA treatment for 3 d.However,the effect of ABA on myrosinase activity relied on the concentration of ABA at 3d treatment.The application of 30 mg L-1 ABA treatment resulted in the highest myrosinase activity.Similarly,significant increase in sulforaphane contents was also observed.4.It is a fundamental step to explanation the effect of hormones treatment in glucosinolate and sulforaphane accumulation by the variety of genes in expression level.The increased glucosinolate content is due to the elevated expression of genes involved in glucosinolate biosynthesis.Myrosinase activity was consistent with the expression level of TGG4 and TGG5.The enhanced in sulforaphane content was associated with the increased myrosinase activity and GRA content caused by MeJA,SA and ABA treatment.