Molecular Characterization of Pear 1-Aminocyclopropane-1-Carboxylate Synthase Gene Preferentially Expressed in Leaves

1-Aminocyclopropane-1-carboxylate (ACC) synthase catalyzes the conversion of S-adenosyl-L-methionine to ACC in the ethylene biosynthetic pathway. Lots of important ACC synthase genes have been isolated and characterized from the plant kingdom. In this study, a cDNA clone encoding putative ACC synthase was isolated from a cDNA library produced using mRNA from pear (Pyrus pyrifolia). The cDNA clone, designated PpACS1 (GenBank accession No. JQ284383), 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 techniques, a genomic clone corresponding to PpACS1 was isolated and shown to contain two introns with typical GT/AG boundaries defining the splice junctions. The PpACS1 gene product shared 97% identity with an ACC synthase from pear (Pyrus communis), and phylogenetic analyses clearly placed the gene product in the ACC synthase cluster of the plant ACS superfamily tree. RT-PCR analysis indicated that the PpACS1 gene was preferentially expressed in pear leaves. The transcript of PpACS1 gene was accumulated at relatively high levels in anthers. The expression signal was detected in shoot at relatively low levels, but none signal was detected in developing fruit of pear. These results suggested that the PpACS1 may participate in the regulation of ethylene production in pear leaves and anthers.