Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2008
Publication Date: 2/2/2009
Citation: Ponce-Valdez, M., Moore-Fellman, S., Giovannoni, J.J., Gan, S., Watkins, C. 2009. Differential fruit gene expression in two strawberry cultivars in response to elevated CO2 during storage revealed by a heterologous fruit microarray approach. Postharvest Biology and Technology. 51:131-140. Interpretive Summary: In an effort to gain better understanding of the molecular mechanisms underlying postharvest storage characteristics of perishable fruits we have characterized differentially expressed genes in two strawberry cultivars distinguished by different responses to CO2: ‘Jewel’, which accumulates high amounts of ethanol and acetaldehyde in response to elevated concentrations of CO2, and ‘Cavendish’, which does not accumulate these fermentation products under the same conditions. While an important crop, strawberry is not a species for which many molecular tools are available and as such we used a tomato gene chip (microarray) to characterize gene expression in strawberry to further test the ability to take advantage of tools developed for one species on another. We show that a microarray approach involving heterologous DNA chips is useful for studying cross-species gene expression during ripening and postharvest storage when a species-specific chip for the specimen of interest is unavailable. Furthermore, the observed differences in gene expression provide new insight into the molecular basis of response to elevated CO2 in two different strawberry cultivars.
Technical Abstract: The use of a heterologous fruit microarray system to identify differentially expressed genes between strawberry cultivars with different responses to 20kPa CO2 (balance air) during storage has been evaluated. Specifically, a tomato cDNA microarray 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 48h, 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 to study a complex process in a crop of economic importance, for which genomic resources are limited, but also provides a foundation for investigating the molecular basis of responses to elevated CO2 during storage.