Cloning And Analysis StPCS Gene Of Potato(Solanum Tuberosum L.) And Effects Of Different Heavy Metals On Its Expression

Heavy metal stress affects the metabolic activities,growth and development of plant from the physiological,biological and genetic processes of the cell,resulting in the loss of yield and quality of plants.It was reported that there should be two types of the resistance and tolerance to heavy metal stress in plants:avoidance and tolerance.Phytochelatins(PCs)cysteine-rich polypeptides produced by phytochelatin synthase(PCS)-could alleviate the heavy metal poison by chelate,compartmentalized intracellular heavy metal ions.PCS expression was inducible to Cd2+,Pb2+ and some other heavy metals in Arabidopsis thaliana,Gramineae Cynodon,garlic,wheat,tomato and so on,with tissue specificity.Increased expression level of PCS led to higher synthesis of PCs and improved resistance and tolerance of plant to heavy metal.Previous studies showed that there were some sequence differences in StPCS-PCS of potato;the expression level of StPCS might be related to heavy metal treatments,and showed different resistance to heavy metal.In order to reveal functional difference among StPCS.s with different sequences,the inducibility of StPCS to some heavy metals,and its role in heavy metal resistance and tolerance,the SIPCS1 CDSs of four potato clones were cloned and analyzed;the expression levels of' StPCS in four potato clones were detected after treated by different heavy metals and levels for 12h.The main results and conclusions are as follows:1.Compared with the reference sequence(AJ548472.1),the StPCS CDSs of all four samples were different at site 979.The other differences sites are:C5 at 1233;SY1 at 674,1233;N5-08 at 1233,1300.All dif'ferent sites cause amino acid changes,except for site 1223.2.All four samples were different with the reference amino acid sequence(CAD68110.1)at amino acid site 327;the other different amino acid sites are:SY1 at 225,N5-08 at 434.Analysis of the predicted protein structure,with respect to their resistance to heavy metals in four samples,revealed that these StPCS structure differences may not cause functional and heavy metal resistance difference in potato plants.3.Under control conditions,the expression levels of S/PCS are:SY1>C5>N5-48>N5-08.The expression levels of C5 and SYl were close,and significantly higher than N5-08 and N5-48.After treatment with different heavy metals,the expression levels of StPCS in N5-08 increased mostly,followed by C5,SY1 and N5-48.It can be concluded that the resistance to heavy metals was mainly related to the increase of StPCS expression,and the expression level of StPCS was also affected-the higher expression level after induction and higher the original expression level,the better resistance to heavy metals.4.The StPCS expression levels of four sample were significantly increased under Cd treatment,and significantly higher than other metal treatments.The expression level of three samples reached the maximum at 100 ?pmol/L Cd,while SY1 at 50 ?mol/L.There were also significant increase of StPCS expression level under the Pb treatment,except for N5-48.The maximum expression level need higher Pb treatment level than those of Cd.The expression level were significantly increased by Cu treatment in C5 and N5-08,while not in N5-48 and SY1.Treatment of Zn significantly increased the expression level of three samples,except for N5-48,with different maximum level.5.It is revealed that the expression level of StPCS was inducible to Cd,Pb,Cu,Zn,in this experiment.The inducibility varied by genotypes of potato,heavy metals and their concentrations.There were extremely significant interaction effects between genotype x metal type,genotype x stress level,metal type x stress level and genotype x metal type x stress level.The StPCS expression was most significantly induced by Cd,and all four potato genotypes tested were inducible to Cd.