Preliminary Studies On The Effects Of Exogenous Glutathione On Glucosinolate Synthesis In Pakchoi

Glucosinolates(GS)are nitrogen-and sulfur-containing secondary metabolites mainly found in the Brassicaceae plants.Glutathiones(GSH)are bioactive substances widely found in plants.The relationship between GSH and the biosynthesis of glucosinolates mainly include two aspects.Firstly,GSH is sulfur donor in the formation of the core glucosinolate structure.Secondly,GSH can indirectly affect the biosynthesis of glucosinolates by regulating the pathway of primary sulfur metabolite.This study uses pakchoi to study the effect of reduced glutathione(GSH),oxidized glutathione(GSSG)and glutathione inhibitor(L-Buthionine-sulfoximine,BSO)on the biosynthesis of glucosinolates,and the treatment concentration is 25 mg/L.The metabolites of glutathione and glucosinolate,and the expression levels of primary sulfur metabolic genes have been studied after treatment.The main results are as follows:(1)With the treatment of 25 mg/L GSH,the expression levels of GS biosynthetic genes decreased,but the contents of aliphatic and indole GS were not changed.At the same time,the contents of GSH and Cys increased with the decreased expression levels of sulfate metabolic genes and GSH biosynthetic gene BcGSH1 after treatment.(2)After the treatment of 25 mg/L GSSG,the expression levels of GS biosynthetic genes and the contents of aliphatic and indole GS both enhanced,which may account for the increased content of GSSG,improved activity of glutathione reductase(GR)and increased expression levels of sulfate metabolic genes.(3)With the treatment of 25 mg/L BSO,the expression levels of GS biosynthetic genes decreased,but the expression levels of BcST5 a and BcST5 c were induced transitorily,and the contents of aliphatic and indole GS were not changed.Moreover,the contents of Cys increased with the decreased expression levels of sulfate metabolic genes and BcGSH1 after treatment.(4)The results above indicated that the different effects of GSH,GSSG and BSO on the biosynthesis of GS may be related to the pathway of primary sulfur metabolite.GSSG induced the biosynthesis of GS,meanwhile,the expression levels of sulfate metabolic genes were up-regulated.After the treatment of GSH and BSO,the down regulation of primary sulfur metabolite may be responsible for the down regulation of the expression levels of GS biosynthetic genes.The the opposite trend that GSH and GSSG treatments showed may be caused by feedback inhibition of high concentration of GSH,or it was the oxidative stress that result form GSSG treatment induced the biosynthesis of GS.