Response Of Lotus To Heavy Metal Copper Stress And Transcriptomics Study

The lotus(Nelumbo nucifera)is one of the top ten famous flowers in China,and it is also the only aquatic flower among them.It has extremely high edible,medicinal and cultural values.Soil heavy metal pollution,as a current global economic and social problem,has posed a serious threat to agricultural production,meanwhile affected the living environment of lotus flowers.In order to explore the mechanism of heavy metals acting on the lotus,the variety "Yanyangtian" was used as the experimental material to study the effects of different concentrations of copper treatment on growth,physiology and transcriptome at different periods,which can provide some insights into lotus copper tolerance.The main findings are as follows:(1)Effects of copper stress on lotus growth.After 35 days of treatment with different concentrations of Cu,the average plant height of the lotus under different treatments showed a clear differentiation,and the overall trend of increasing first and then decreasing with the increase of Cu concentration,the strength of growth showed T3>T2 >T1>T0>T4>T5>T6>T7(T represents copper treatment concentration,the same below).The area of lotus leaf showed a phenomenon of increasing first and then decreasing.Low concentration of copper stress has little effect on the number of flowers,but high concentration of copper stress indicates that the number of flowers is reduced or even no flowers.In conclusion,the high concentration of copper stress seriously affected the normal growth and development of lotus.(2)Effects of copper stress on lotus physiology.The results showed that under copper stress,the total chlorophyll content of lotus leaves showed a trend of increasing firstly and then decreasing.Among them,copper stress mainly affects the synthesis of chlorophyll a(chlorophyll a,Chla),but has little effect on chlorophyll b(chlorophyll b,Chlb).The activities of the two antioxidant enzymes(SOD and POD)and the osmotic substances(soluble sugar,soluble protein and proline)were the highest under the T2 and T3 treatments,and the accumulation of soluble substances reached the highest,indicating that the lotus was under a certain concentration of Cu stress,which it can alleviate the toxicity of heavy metals by improving its own photosynthetic efficiency,enzyme activity and maintaining the intracellular and intracellular balance.(3)Effects of copper stress on lotus transcriptome.The transcriptome data betweenthe experimental group(Cu stress 7 days)and the control group were mainly determined.The results showed that 86,016 unigenes were annotated from the lotus transcriptome data,and 55 DEGs were screened,of which 54 genes were up-regulated and 1 gene was down-regulated.There are 34033 unigenes on the GO classification,of which the main functions in the molecular function are binding and catalytic activity,respectively 20313(46.09%)and 17974(40.78%)unigenes.Among them,cellular processes and metabolic processes account for the largest number,which are 20092(22.64%)and 17971(20.25%)unigenes respectively.Besides cells and cell components parts accounted for the largest number,which reached 22546(23.33%)and 22485(23.26%)unigenes in the cell composition.There are 6,806 unigenes annotations in the KEGG classification,which are divided into four major metabolic pathways,namely cellular processes,environmental information processing,genetic information processing,and metabolism.Among them,there are 2656 significant differential genes involved in metabolic signaling pathways,accounting for 39.02% of the total number with annotated differential genes in signaling pathways.It shows that lotus has produced more metabolic factors to cope with this stress after copper treatment.There are 15322 unigenes annotated in the KOG database,mainly involving signal transduction mechanisms(Signal transduction mechanisms),gene function prediction(General function prediction only),post-translational modification and protein update(Posttranslational modification,protein turnover,chaperones),ribose translation,ribosomal structure and biogenesis,carbohydrate transport and metabolism.Several key genes were selected for real-time fluorescence quantitative detection after the transcriptome analysis,and these data provide basic data on the transcriptome level and related genes and pathways that may be involved in Cu stress resistance for subsequent research.