USING FUNCTIONAL AND APPLIED GENOMICS TO IMPROVE STRESS AND DISEASE RESISTANCE IN FRUIT TREES
Location: Appalachian Fruit Research Laboratory: Innovative Fruit Production, Improvement and Protection
Title: Rapid transcriptional response of apple to fire blight disease revealed by cDNA suppression subtractive hybridization analysis
Submitted to: Tree Genetics & Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2007
Publication Date: March 19, 2008
Citation: Norelli, J.L., Farrell, Jr., R.E., Bassett, C.L., Baldo, A.M., Lalli, D., Aldwinckle, H.S., Wisniewski, M.E. 2008. Rapid transcriptional response of apple to fire blight disease revealed by cDNA suppression subtractive hybridization analysis. Tree Genetics & Genomics. 5: p. 27-40.
Interpretive Summary: Fire blight is a destructive disease of apple and pear trees that is estimated to cost the U.S. fruit industry over $100 million a year in crop losses and disease control. A technique known as 'suppression subtractive cDNA hybridization' was used to identify genes in apple that respond to fire blight infection. A total of 468 apple genes were identified that responded to the disease between 1 and 72 hours after challenge with the fire blight pathogen. The DNA sequence of these genes was deposited in a publicly accessible database maintained by the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov). This genetic information will be used by biologists, horticulturalists, and plant breeders to develop new strategies for improving plant resistance to fire blight disease.
Fire blight, caused by the bacterium Erwinia amylovora (Ea), is a destructive disease of many tree and shrub species of the Rosaceae. Suppression subtractive cDNA hybridization (SSH) was used to identify genes that are differentially up- and down- regulated in apple (Malus X domestica) in response to challenge with Ea. cDNA libraries were constructed from Ea- and mock- challenged apple leaf tissue at various time intervals after challenge treatment ranging from 0.25 hours post inoculation (hpi) to 72 hpi and utilized in SSH. Gel electrophoresis of PCR-amplified SSH cDNAs indicated a greater quantity and size diversity in reverse SSH samples (down-regulated genes) collected at 1 hpi and 2 hpi, in comparison to forward SSH samples (up-regulated) or in comparison to reverse SSH samples (down-regulated) at 24 hpi and 48 hpi. A total of 468 non-redundant apple ESTs that responded to Ea challenge were identified by SSH. In analyzing the probable biological process associated with the SSH-ESTs, the reliability of BLASTX comparisons was improved by first identifying the Malus EST assembly most similar to the SSH-EST by BLASTN analysis and then using the most similar Malus EST assembly for BLASTX analysis. Many of SSH-ESTs identified following Ea-challenge of apple were similar to genes known to respond to bacterial challenge in the A. thaliana. The result indicated that there is a transcriptional response in apple to fire blight disease within 1hpi and that the transcriptional response can vary over time.