| Potato (Solarium tuberosum L.),starchy, nutritious, and versatile, is one of the most important worldwide crops. The heavy metal contaminated soils are toxic to crops like potato and capable of accumulating in their products; and thus cause further processing products and food safety risks.The following researches were conducted to find the differences among StPCS genes of potato clones, and explore the role and mechanisms of potato PCS in resistance to heavy metals stress:Conserved sequences of StPCS were cloned from 4 potato clones and the sequence alignment were conducted; and the CDSs of StPCS of N5-08 and N5-48 were also cloned and analyzed for sequence alignments, and the amino acid sequence and structure of the protein coding by StPCS were predicted and analyzed; MDA and relative expression of StPCS of plantlets, treated by heavy metal (Cd, Pb, Cu, Zn), BSO, and GSH respectively for 12h, were detected; the relationship, among sequence and relative expression of StPCS, the level of Cd stress and plant damage were also associated.The main results and conclusions are:1. Conserved sequences of 4 potato clones were amplified, by PCR primers F1/R1 designed according to reference StPCS (AJ548472.1). Sequence alignments showed that there are a few different sites among sequences cloned from tested clones and AJ548472.1; but no amino acid difference.2. CDSs of StPCS of N5-08 and N5-48 were amplified, by PCR primers F2/R2 designed according to reference StPCS (AJ548472.1). The results of sequence alignments showed that both StPCS CDSs of N5-08 and N5-48 are highly homologous (>99%) to AJ548472.1; there is no different amino acid site in protein coding by StPCS of N5-08, and only one different site (328) in protein coding by StPCS of N5-48, referring to CAD68110.1 (coding by AJ548472.1). It is suggested that:the expression level rather than the structure of PCS responsible for the heavy metal resistance level of different potato clones.3. N-terminus of PCS was revealed to be highly conserved among potato and some other dicotyledons, containing Cys-56, His-162 and Asp-182 triplet. PCS of potato has the distinctive sites of dicotyledons PCS:Cys-56, Cys-90/91, Cys-109 and Cys-113; but has a much different C-terminus, containing 15 Cys residues; and 4 Cys-Cys elements (90-91,350-351,368-369,415-416) within it.4. MDA of 4 potato clones plantlets, treated by Cd 50 μmol/L for 12h, were detected; significant (P<0.01) differences were revealed by ANOVA among different clones and organs (root, stem and leaf). MDA contents of SY1 plantlets under Cu stress were the highest among different heavy metals (Cd, Pb, Cu and Zn) stress, and increased 233.22% and 146.62% compared with control in roots and stems respectively. While plantlet damage levels under essential elements (Cu and Zn) treatments are higher than nonessential elements (Pb and Cd) treatment; which needs further verification and research.5. The relative expression level of StPCS of 4 potato clones were significantly increased by Cd stress (12h); As for C5, the expression levels in entire plantlet and root are correlation with Cd concentration significantly, also the MDA level of entire plantlet is negative correlation with Cd concentration significantly. Thus StPCS expression of C5 might be induced by Cd, and play a protective role to plantlets under Cd stress. The relative StPCS expression level of N5-08 showed no significant among organs. It is suggested that N5-08 defers from C5 on StPCS expression regulation and Cd stress protection, and the two clones are capable of contrast material for further research.6. The relative expression level of C5 plantlets decreased by BSO+ Cd treatment significantly, while increased by GSH+ Cd treatment significantly. Those indicate that potato possesses the similar PCS SYnthesis pathway and regulating mechanisms with yeast and Arabidopsis. |
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