Abstract: C-8,7 sterol isomerase plays a vital role in the sterol biosynthesis pathway. UsingA rabidopsis C-8, 7 sterol isomerase (GenBank accession No. AAD03489) amino acid sequence as a querying probe,many highly homologous EST sequenceswere obtained from GenBank and a putative cDNA sequence of potato C-8, 7 sterol isomerase was assembled. Futhermore, a putative C-8, 7 sterol isomerase gene cDNA, named StSI1 (GenBank accession No. EU103613 ) was cloned from potato (Solanum tuberosum L. ). StSI1 was 886 bp in full length, including a 5′untranslated region of 59 bp, 3′untranslated region of 161 bp with poly A, and a 666 bp length open reading frame (ORF) encoding 221 amino acids with the molecular weight of 25 kD. Software prediction results showed that StSI1 contained a 35 amino acid lenghth signal pep tide at the N terminal. Homology analysis showed that the deduced amino acid sequence of StSI1 shared 32.9% - 61.3% identity with sterol isomerase from other organisms. RT2PCR analysis showed that the StSI1 was highly expressed in skin and eyes of potato stem tuber. The exp ression profiling also showed that StSI1 mRNA was up regulated intensively both by temperature and light.

Key words: potato, gene cloning, expressing analysis