Articles
ISOLATION OF GENES AFFECTING PEACH FRUIT RIPENING
One step in this process is to isolate appropriate genes.
To this end we have isolated a collection of cDNA clones that represent genes whose mRNAs are regulated during fruit ripening.
Ten clones were isolated using RNA from various stages of softening and RNA from phenotypically different fruit through differential screens.
Four clones were isolated using homology to genes believed to be involved in the ripening process.
To determine which of these clones would be most appropriate to manipulate, three sets of experiments were performed to determine the following: 1) the time in fruit developmentsa at which the corresponding mRNA accumulated; 2) whether this level of accumulation was associated with defined traits such as softening or texture; and 3) whether the DNA sequence allowed us to identify their product by comparison to other sequenced genes.
The clones fell into four patterns of RNA accumulation: decrease during fruit development; increase during embryo development; increase during ripening; and an increase that correlated with the narrower window of softening.
When accumulation was examined in cultivars with different phenotypes, the patterns and amounts of RNA accumulation did not correlate with phenotype with the exception that none of the ripening related RNAs accumulated in a non-softening peach-almond hybrid (the fruit desiccate without the final swell and softening seen in peach fruit). Sequencing resulted in the tentative identification of one clone as ACC oxidase or the ethylene forming enzyme.
This gene is our first choice for manipulation through antisense constructs with the goal of retarding peach fruit softening.