Identification and Characterisation of Two 1-Aminocyclopropane- 1-Carboxylate (ACC) Synthase cDNAs Expressed during Papaya (Carica papaya) Fruit Ripening

Abstract

The cloning and characterisation of two cDNAs (capacs1 and capacs2) encoding ACC synthase in papaya (Carica papaya L.) is described. capacs1 is 1104 bp long encoding 368 amino acids. capacs2 is 1098 bp long encoding 366 amino acids. The proteins encoded by both cDNAs contain the highly conserved active site of ACC synthases as well as 10 (capacs1) or 11 (capacs2) of the 12 amino acid residues conserved in most aminotransferases. Southern analyses indicate that capacs1 and capacs2 are present in the papaya genome as single copy genes. Both genes show very different expression patterns during fruit ripening. capacs1 mRNA levels are high in mature green fruits, decreasing steadily during ripening, whereas capacs2 mRNA levels are undetectable in mature green fruits but experience a dramatic increase with the onset of ripening and remain high throughout the various stages of ripening.