Differential fruit gene expression in two strawberry cultivars in response to elevated CO2 during storage revealed by a heterologous fruit microarray approach

The use of a heterologous fruit microarray system to identify differentially expressed genes between strawberry cultivars with different responses to 20 kPa CO2 (balance air) during storage has been evaluated. Specifically, a tomato cDNA microarray containing approximately 12,000 ESTs (representing 8700 unigenes) was hybridized with strawberry cDNA populations to compare gene expression differences between two cultivars: ‘Jewel’, a cultivar that accumulates acetaldehyde and ethanol in response to elevated CO2 during storage, and ‘Cavendish’ that does not accumulate these compounds under the same storage conditions. A set of 80 tomato gene sequences gave differential hybridization signals between the two strawberry cultivar probes when they were stored in CO2 for 48 h, suggesting homologous strawberry genes with differential expression. Within each cultivar, when RNA from fruit stored in air was compared with that from fruit stored in CO2, 168 sequences suggested differential expression in ‘Jewel’, but only 51 were differentially expressed in ‘Cavendish’ fruit. Strawberry genes with putative homologies to enzymes involved in cell wall metabolism, ethylene action and stress were implicated by the tomato array. This research not only demonstrates the usefulness of using a heterologous microarray platform from a model species (tomato) to study a complex process in strawberry, a crop of economic importance, for which genomic resources are still limited, but also provides a foundation for investigating the molecular basis of responses to elevated CO2 during strawberry postharvest storage.