Analysis Of Antioxidant Activity And Synthesis Regulation Of Anthocyanin In Non-heading Chinese Cabbage

Non-heading Chinese cabbage(Brassica campestris ssp.chinensis Makino)is a kind of Brassica vegetables,which is originated from China.Purple non-heading Chinese cabbage is a new cultivated species in recent years,which is colorful brightly and rich in antioxidants,such as anthocyanins.Purple non-heading Chinese cabbage not only can provide the necessary vitamins and minerals for our body,but also has a good health function because of rich in anthocyanins.At present,researches about the health function of purple non-heading Chinese cabbage and the genes controlling the synthesis of anthocyanins are rarely reported.Herein,we use six non-heading Chinese cabbage cultivars as materials to compare pigment contents and the antioxidant activity in the leaves of non-heading Chinese cabbage and to screen the candidate genes controlling the anthocyanin synthesis.Simultaneously,we explored the effects of plant growth regulators(abscisic acid and salicylic acid),drought,shading stress treatments on the expression of the candidate genes,total anthocyanin and total phenolic content and the antioxidant activity of non-heading Chinese cabbage leaves.Results are as follows:1.Total anthocyanin content was significantly higher in purple leaf cultivars than in green leaf cultivars,and the carotenoids content in green leave leaf cultivars was consistent with purple leaf cultivars.The chlorophyll content and ratio of chlorophyll a to chlorophyll b was significantly higher in green leaf cultivar SZQ than that in purple leaf cultivars;indicating that the differences between total anthocyanin content and chlorophyll content lead to different leaf color.Total phenolic content,the value of DPPH and the Ferric reducing ability of plasma(FARP)was significantly higher in purple leaf cultivars than in green leaf cultivars;The correlation among total anthocyanin content,total phenolic content,DPPH radical scavenging and FRAP antioxidant capacity were extremely significant;indicting that total anthocyanin content plays an important in the antioxidant capacity in leaves.2.Expression levels of BrcF3H,BrcDFR and BrcANS genes were significantly higher in purple cultivars than the green cultivar,and there was positive correlation between the genes expression and total anthocyanin content.BrcGL3,BrcEGL3.1 and BrcTT8 genes were expressed in all the materials and BrcTT8 gene was upregulated with the increasing of total anthocyanin content;BrcMYB75 gene was expressed only in deep purple cultivar NJZX1-3;The expression of BrcTTG1 gene was higher in deep purple cultivar NJZX1-3 than SZQ;indicting that BrcGL3,BrcEGL3.1,BrcTT8,BrcMYB75 and BrcTTG1genes can affect the anthocyanin accumulation in non-heading Chinese cabbage leaves by regulating the expression of BrcF3H,BrcDFR and BrcANS genes.3.The nucleotides and amino acids sequences of BrcANS were exactly same in NJZX1-3,NJZX1-0 and Chinese cabbage,and a 20G-Fe(?)dioxygenase super family domain was found in the amino acid sequence from the 211th to the 307th amino acids.The homology between BrcANS protein and BjANS protein in Brassica juncea was up to 99%,in accordance with the close relationship between them.The expression level of BrcANS was positively correlated with the increasing trend of total anthocyanin content.The mRNA of BrcANS exhibited tissue-specific expression in non-heading Chinese cabbage,showing high level in leaves and low level in other organs.In addition,the expression of the gene in two materials was significantly different:The expression of BrcANS in cultivar NJZX1-3 leaves was obviously higher than that in its' mutant line NJZX1-0.With the increasing of leaf age,the leaf color became shallow and the expression of BrcANS reduced.Meanwhile,the difference of expression between NJZX1-3 and NJZX1-0 decreased significantly.Salicylic acid,abscisic acid and drought treatment could positively regulate the expression of BrcANS gene,but the expression of BrcANS gene was influenced by different regulation pathways under shading treatment.These results indicated that BrcANS gene can regulate the formation of the anthocyanin in leaves at transcriptional level and its expression is modified by the different stress signal transduction pathways.4.Total anthocyanins content was not detected in green leaf cultivar NJZX1-0 leaves under four stress treatments.Total anthocyanin content was increased significantly in purple leaf cultivar NJZX1-3 at the early stage of exogenous salicylic acid(SA)and abscisic acid(ABA)treatments;SA could significantly increase total phenolic content of leaves,and ABA had no significant on total phenolic content.Total anthocyanin content was significantly increased in purple leaf cultivar and total phenolic content in cultivars under drought treatment.The antioxidant activity was increased in cultivars under two kinds of plant growth regulators and drought treatments.Shading treatment could not only decrease total anthocyanin content in purple leaf cultivar,but also reduce total phenolic content and the antioxidant activity in cultivars.There was a good correlation between BrcANS expression and total anthocyanin content in purple leaf cultivar under two kinds of plant growth regulators or drought treatments.However,total anthocyanin content was a decreasing tendencay and its change was inconsistent with the trend of BrcANS expression under shading treatment.These results indicated that the synthesis of anthocyanin is influnced by regulating the BrcANS expression under two kinds of plant growth regulators and drought treatments,however,there exsits other effects on the synthesis of anthocyanin except inhibiting BrcANS expression,and related mechanism needs to be further studied.