Primary Research On The Response Mechanism Of Cd Stress In Cotton

Cadmium pollution not only is adverse to agricultural production, but also damages the ecosystem. It is also a great harm to human health. Cotton is one of the most important economic crops in China. It is very important to repair Cd contaminated soil by growing cotton, which is significant to stabilize cotton production and reduce the pollution of farmland. C185, Xiangzamian 15 and Xiang 419 were used as studying materials, they are treated with different Cd concentrations around the whole growth period. Their agronomic traits, enzyme activity of functional leaves and Cd content in various organs were compared and analysized accurately and systematically. In addition, C185 was used as materials and RNA of seedling root was sequenced by Illumina sequencing method after growing in different Cd concentration. The main results are as follows:Firstly, Cadmium effects the growth and development of cotton plants. When the Cd concentration is low (about 1mg/L), it can promote the growth of cotton plants; When the Cd concentration increased to certain degree (about 5 mg/L), the growth and development of cotton plants are inhibited.Secondly, dry matter accumulation of cotton plants is affected by the Cd. The main effect is on root and boll and their dry matter weight will decrease when the concentration increases.Thirdly, enzyme activity of functional leaves is affected by the Cd. With the increase of cadmium concentration, protective enzyme system of leaves cell is broken and damaged more seriously. It is reflects mainly by decreased activity of two enzymes including superoxide dismutase (SOD) and peroxidase (POD) decreased, and increased content of malondialdehyde (MDA).Fourthly, the cadmium content of the cotton plant is directly affected by the cadmium concentration in external environment. When cadmium concentration in external environment is as low as 1 mg/L, cotton plants can absorb about 0.4 mg of cadmium from the matrix. But cotton plants can absorb 1.7mg of cadmium from the matrix. When the concentration of Cd in the soil is as high as 10 mg/L, cotton plants can absorb about 3.0mg of cadmium from the matrix.Fifthly, transcriptome analysis showed that, compared with the control,697 genes are up-regulated and 3388 genes are down-regulated in cotton seedling treated by 0.5mg/L of Cadmium.Sixthly, GO analysis of differentially expressed genes showed that all these genes are mainly involved in metabolic processes, cellular processes and single-organism process according to an assortment by their biological processes. They are mostly related to binding and catalytic activity clustered by their molecular function. In addition, these genes are mainly divides into cell, cell part and membrane if they are classified by their cellular components.Lastly, based pathway enrichment analysis of these differentially expressed genes, the study found that the maximum number of genes were rich in the metabolic pathways and secondary metabolites biosynthesis pathway, the most significant enrichment pathway were metabolic pathway, producing synthetic pathway and phenylpropanoid biosynthesis, and the pathway that with the largest enrichment degree are taurine and hypotaurine metabolism, phenylalanine metabolism, ascorbic acid metabolism and ganglion glycosphingolipid biosynthesis.