Ethylene biosynthesis in banana fruit: Isolation of a genomic clone to ACC oxidase and expression studies

In this paper we present the expression studies and structural analysis of one genomic sequence isolated from banana. Using a RNA-based PCR amplification of ACC oxidase cDNAs from ripe banana, we obtained a product of 800 bp which after sequence analysis was found to code for a protein highly homologous to ACC oxidase proteins. This PCR product was used as probe for screening a genomic library and three different groups of clones were obtained as indicated by restriction mapping. One clone (ACO1) was selected for further study and fully sequenced. Comparison of this sequence with the PCR products and other cloned ACC oxidase genes, revealed that ACO1 encoded the transcript in four exons interrupted by three introns. Southern blot analysis showed a major band hybridizing to the PCR probe suggesting that the ACC oxidase gene is present in a single copy or that the genes are clustered as is the case in tomato and carnation. By northern blot analysis it was found that the ACC oxidase transcript appears in the pulp earlier than in the peel but that exogenous ethylene alters this pattern and the transcript is expressed in the peel first. (C) 1997 Elsevier Science Ireland Ltd.