Metabolomics Response Of Mung Beans During Germination Under Cadmium Stress

Mung bean(Vigna radiata L.)belongs to Leguminosae,which is a widely popular medicinal and edible food,and is also an important economic crop in China.With the rapid development of industrial economy,soil and water bodies were suffered from different degrees of heavy metal pollution in China.Cadmium pollution is one of the heavy metal pollution,which is easy to enrich to high levels in organism and then threatening human health through the food chain.On the other hand,cadmium pollution is an important factor to global crop reduction,as it can cause serious adverse effects on crop growth,development and fruiting.Therefore,it has become one of the important problems about solving crop yield and quality that we need to solve to study the metabolic mechanism of plants under cadmium stress,as well as to find ways to prevent and control cadmium pollution.In recent years,metabolomics research has become an effective way for studying plant under abiotic stress.In this study,we used the traditional high performance liquid chromatography(HPLC)method and the novel internal extraction electrospray ionization spectroscopy(i EESI-MS)method to analyze the small molecular substances in mung bean sprouts under cadmium stress,providing a theoretical basis and valuable data for further analyzing metabolic network in plant under cadmium stress.The main contents and results are as follows.1?The effects of cadmium stress on seed germination and growth of mung bean were studied with the standard germination test.The results showed that low concentration of cadmium stress had no significant effect on seed germination rate.When CdCl2 concentration was higher than 32 mg/mL,the seed germination rate was reduced significantly,and the root length and bud length showed a significantly negative correlation with CdCl2 concentration.2 ? The dynamic changes of phenolic compounds were analyzed during the germination process of mung bean seeds.The results showed that the total contents of phenolic compounds increased significantly,and reached the highest at 3508.8 ?g / g(DW)at the 7th.And the specific content of the different compounds is the highest.Such as gallic acid and caffeic acid contents increased during germination.At the 7th dayafter germination,rutin,daidzein,keampferol,p-coumaric,ferulic acid and genistein reached their maximum levels of 1574.5,114.3,80.3,43.3,207.9 and 45.3?g/g respectively.Quercetin contents had the maximum concentration of 28.0 ?g/g at the 4th day.Protocatechuic acid,hesperedin,cinnamic acid and naringenin contents showed the maximum levels of 89.1,297.4,84.6 ?and 30.6 ?g/g respectively at the5 th day.Contents of resvaratrol,4-nitrobenzoic acid and biochanin A were the maximum at the 2nd dayof 89.6,70.8 and 237.0 ?g/g respectively.Myricetin,protocatechuic acid and hesperetin exhibited their maximum levels at the 6th day of40.7,712.1 and 58.2 ?g/g,respectively.The total content of 19 kinds of phenolic compounds at the 7th day has the maximum value,reaching 3508.8 ?g/g.3?The effects of cadmium stress were studied on the metabolism of phenolic compounds during the germination of mung bean.The results showed that cadmium stress had a significant effect on the phenolic compounds during mung bean germination,such as,the contents of protocatechuic acid,p-coumaric acid,ferulic acid,hesperidin,genistein and p-nitrobenzoic acid increased with the increase of CdCl2 concentration,especially,hesperidin and nitrobenzoic acid contents increased obviously.Among the 19 phenolic compound,the p-coumaric acid,ferulic acid,hesperidin,genistein and p-nitrobenzoic acid contents reached the maximum at the 7th day of germination,which were 181.6 ?g/g,45.5 ?g/g,3506.9 ?g/g,256.7 ?g/g and3306.1 ?g/g respectively.The protocatechuic acid content reached the maximum,314.1 ?g/g,at the 6th day of germination.The content of resveratrol,cinnamic acid,hesperetin,olecranon and biochanin A increased first and then decreased with the increase of CdCl2 concentration.When the CdCl2 concentration was 32 mg/L.they reached their maximum levels of,270.8 ?g/g,489.5 ?g/g,354.6 ?g/g and 1517.5 ?g/g,respectively.The contents of daidzein,quercetin,naringenin,keampferol and catechins increased at first,and then with the increase of CdCl2 concentration to 16mg/L,they reached their maximum levels of1258.7 ?g/g,441.4 ?g/g,316.5 ?g/g and2154.6 ?g/g,respectively.Rutin and poplar ketone reached the highest levels,when the CdCl2 concentration were 4 mg/L and 8 mg/L,respectively.4 ? The i EESI-MS method was used to obtain chemical fingerprints from the internal tissues of mung bean sprouts under cadmium stress.The results showed that the m/z 171 [M+H] + ion,m/z 181 [M+H] + ion and m/z 175 [M+H] + ion were qualitatively analyzed with tandem mass spectrometry,in comparison with the characteristic fragment ions and references inferred as gallic acid,caffeic acid and arginine,respectively.By analyzed the relative abundance of three compounds,results showed that the relative abundance of the three compounds showed a tendency to increase first and then decrease with the increase of cadmium concentration.The PCA extracted three principal components,PC1 mainly m/z 91,108,279,PC2 mainly m/z91,108,PC3 mainly m/z 108,158,195,279,and their cumulative contribution rate was 99.3%.Indicated that these characteristics of the peak ion to distinguish between different cadmium stress mung bean bud radium contribution is greater.In this study,HPLC and iEESI-MS were used as the research platforms to analyze the small molecular metabolites of mung bean sprouts under cadmium stress.Some of the small molecule metabolites were analyzed qualitatively and quantitatively.It could provide a new insight into the establishment of a metabolomics analysis method for plant abiotic stress without complicated pretreatment.