Abstract: 【Objective】 The cDNA sequence of cucumber S-adenosyl-L-homocysteine hydrolase（CsSAHH) gene was cloned and the gene expression patterns and protein structure were analyzed by bioinformatics methods to study the function of the gene. 【Method】 Based on selecting SSH of stem tips treated by ethrel, the cDNA sequence of cucumber SAHH gene (CsSAHH, GenBank accession, HQ444960) was obtained by RT-PCR and in silico cloning. The mRNA expressions of the gene in stem tips treated by ethrel and different tissues of male and female flowers were detected through semi-quantitative RT-PCR. And the protein structure was analyzed by bioinformatics methods.【Result】 The cDNA sequence of the gene was 1 545 bp, contained a predicted protein sequence of 485 amino acids, pI＝5.66, MW＝53.1 kD. The semi-quantitative RT-PCR results revealed that CsSAHH mRNA expression was increased by ethrel in stem tips and was lower in stamen than that in the other flower tissues. The physical and chemical properties of cucumber SAHH indicated that this protein has no clear signal peptid. The secondary structure of cucumber SAHH was mainly made of loops, α helixes and few β sheets. There were two S-adenosyl-L-homocysteine hydrolase active domains between positions 85-99 and 262-279. The speculated amino acids sequence of cucumber SAHH shared 63% homologies with Medicago truncatula and had low homologies with Oryza sativa, Zea mays and Arabidopsis thaliana.【Conclusion】 The full length of the CsSAHH cDNA were obtained. There are two S-adenosyl-L-homocysteine hydrolase active domains between positions 85-99 and 262-279. The CsSAHH mRNA expression was induced by ethrel in stem tips, and lowest in stamen. The expression of CsSAHH was stronger in female flower buds than small fruits and male flower buds at different development stages of untreated cucumber flowers.

Key words: cucumber (Cucumis stavius L.), CsSAHH gene, clone, expression pattern, protein function prediction