Cloning,Sequence Analysis and Expression of cDNA Encoding Plasma Aquaporins StPIP1 of Solanum tuberosum

Aquaporin belongs to a highly conserved group of membrane proteins called major intrinsic proteins that facilitate water transport across biological membranes.The gene encoding the Solanum tuberosum L.aquaporin(StPIP1)cDNA was cloned from leaf of S.tuberosum cv.Gannongshu No.2 under PEG6000 stress by RT-PCR.The StPIP1 cDNA was 867 bp in length,encoded a protein of 288 amino acids with a predicted molecular mass of 30.9 kD(GenBank Accessin No.DQ 999080).StPIP1 exhibited a typical structure with six membrane-spanning domains and an internal symmetry showing two highly conserved Asn-Pro-Ala(NPA)motifs,and possessing the MIP family signal consensus sequence SGXHXNPAVT and the higher plant PIP highly conservative sequence GGGANXXXXGY and TGI/TNPARSL/FGAAI/VI/VF/YN.The StPIP1 amino acids showed 92%～97% identity to other 14 plant species PIP1 subfamily,so StPIP1 should be a plasma membrane intrinsic proteins of PIP1 subfamily.The protein 3D structure was predicted by homology comparatvie modeling in Swiss-Model,the results from Swiss-Model showed that the 3D structure of StPIP1 was highly similitude with Spinacia oleracea(2B5F).Two plant expression vectors that schleped StPIP1 and GFP(green fluorencent protein)fusion genes were constructed,in which StPIP1 and GFP fusion genes were regulated by rd29A and CaMV35S promoters,respectively.Particle bombardment procedures were used to transfer StPIP1 and GFP fusion genes to onion(Allium cepa)epidermis cells,and transient expression was presented.The results showed that expression of StPIP1 was regulated by drought stress.