Integrated Transcriptome And Metabonomic Analysis Of Key Metabolic Pathways In Response To Cadmium Stress In Winter Wheat

Wheat is the second largest food crop in China.Soil cadmium pollution not only affects the cadmium content of wheat grains,but also affect the growth,yield and quality of wheat.Exploring the physiological and molecular mechanisms of wheat response to cadmium stress can provide theoretical reference for controlling cadmium content in wheat grains and improving wheat yield and quality.In this study,wheat variety Jinan 17 was used as the experimental material to reveal and verify the key metabolic pathways in response to cadmium stress in winter wheat by integrated analysis of transcriptome and metabolomics data.The main results were as follows:1.Transcriptomics method was used to study the effects of cadmium stress on gene expression in wheat roots.The results showed that 4003 differential genes were detected after 6 h of cadmium stress,of which 2529 were up-regulated and 1474 were down-regulated.Differential genes were enriched in metabolic pathways such as nitrogen metabolism,galactose metabolism,phenylpropanoid biosynthesis,ABC transporter,cysteine and methionine metabolism,and glutathione metabolism and so on.3338 differentially expressed genes were detected at 24 h after cadmium stress,including 2265 up-regulated genes and 1073 down-regulated genes.The differentially expressed genes were mainly enriched in nitrogen metabolism,phenylpropanoid biosynthesis,glutathione metabolism,cytochrome P450 metabolism,starch and sucrose metabolism,cysteine and methionine metabolism and so on.2.The changes of metabolites in wheat roots before and after cadmium stress were studied by non-targeted metabolomics.The results showed that 51 different metabolites were detected after 24 h of cadmium stress,including amino acids,amines,alkaloids,sugars,lipids,organic acids,nucleotides and polyols.Among them,25 metabolites such as stachyose,sucrose,malic acid,ornithine were up-regulated,and 26 metabolites such as palmitic acid,glutamic acid,nucleosides were down-regulated.KEGG analysis showed that the differential metabolites were mainly enriched in the metabolic pathways of galactose metabolism,glycerophospholipid metabolism,amino acid biosynthesis,fructose and mannose metabolism,glycerolipid metabolism,phenylpropanoid biosynthesis,glutathione metabolism,cysteine and methionine metabolism and so onc.3.The results of transcriptome and metabolomics integration analysis showed that there were eight metabolic pathways responsive to gene expression and metabolites after cadmium stress,including galactose metabolism,α-linolenic acid metabolism,ABC transporters,glycerol metabolism,phenylpropanoid biosynthesis,glutathione metabolism,starch and sucrose metabolism,cysteine and methionine metabolism.Quantitative PCR was used to further verify the expression of genes related to galactose metabolism,glutathione metabolism and lipid metabolism.The results showed that the up-regulation of SIP gene and down-regulation of GLA gene in galactose metabolism after cadmium stress were the main reasons for the increase of stachyose content.The up-regulation of LYPLA2 and PLA2 G genes were the main reason for the increase of lysophosphatidylcholine content.The down-regulation of ggt and OXP1 genes were the main reasons for the decrease of glutamate content.These differential genes and differential metabolites may play a key role in Cd tolerance of winter wheat.