Shi, H., Zhang, Y. and Chen, L. 2013. Cloning, characterization and expression analysis of a 1-aminocyclopropane-1-carboxylate synthase gene from pear. Can. J. Plant Sci. 93: 465-471. In this study, a cDNA clone encoding putative 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) that catalyzes the conversion of S-adenosyl-L-methionine to ACC in ethylene biosynthetic pathway was isolated from a cDNA library produced using mRNA from pear (Pyrus pyrifolia). The cDNA clone, designated PpACS2, comprised an open reading frame of 1, 341 bp encoding a protein of 446 amino acids that shares high similarity with the known plant ACSs. Using PCR amplification technique, a genomic clone (GenBank accession number: KC146402) corresponding to PpACS2 was isolated and shown to contain two introns. The PpACS2 gene product shared 97% identity with an ACC synthase from pear (Pyrus communis). Phylogenetic analyses clearly placed the gene product in the ACC synthase cluster of plant ACS superfamily tree. Quantitative RT-PCR analysis indicated that the PpACS2 gene was preferentially expressed in young pear leaves and shoots. The transcript of PpACS2 gene was accumulated at relatively high levels in anthers, but no signal was detected in the petals and mesocarp of pear. These results suggest that the PpACS2 may participate in the regulation of ethylene production in pear leaves, shoots, and anthers.