A novel papaya ACC oxidase gene (CP-ACO2) associated with late stage fruit ripening and leaf senescence

A novel 1-aminocyclopropane-1-carboxylate (ACC) oxidase cDNA clone (CP-ACO2, 1485 bp) was isolated from papaya for the first time. The deduced amino acid sequence shares 77% identity with the previously reported papaya CP-ACO1. Genomic Southern analysis with gene specific probes showed that CP-ACO2 is single copy in papaya genome. It was also identified to be ethylene and wounding inducible, an observation in agreement with the presence of ERE and WUN cis-acting elements in CP-ACO2 promoter region. Northern blot analysis revealed that CP-ACO2 was induced only at the late stage of fruit ripening and leaf senescence, while CP-ACO1 was induced before color break (mature) stage. These results suggest that CP-ACO2 is late stage associated, occurring during organ senescence, such as fruit ripening and leaf senescence; while AP-ACO1 is maturation associated are possible. Therefore, two distinct pathways for ACC oxidase regulated ripening, one is regular ripening associated, the other is late stage ripening associated. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.