Abstract: Total RNA was isolated from Betula platyphylla xylem by the method of modified CTAB which was more effective and simple. The primers of plant actins conserved coding region were designed and a full-length cDNA of actin was obtained using RT-PCR and RACE techniques. Its full length is 1 785 bp. The sequence analysis result revealed that it contained a coding region of 1 134 bp encoding a protein of 378 amino acids, a 5′-UTR of 157 bp and a 3′-UTR of 495 bp. Homologous alignment shows that it shares over 80% nucleotide sequence similarity and over 96% amino acid sequence similarity with actins in other plants. The full length cDNA sequence of actin was registered in GenBank with accession number EU588981.The phylogenetic tree reconstructed on the base of amino acid sequences suggests that the relationship of actin between B. platyphylla and Ricinus communis is most intimate and they might have the same differential time in evolution.

Key words: Betula platyphylla Suk., actin gene, gene clone, sequence analysis, evolution