|Norelli, John (jay)|
|Farrell, JR., Robert - PENN STATE UNIV|
|Aldwinckle, Herb - CORNELL UNIV|
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.
Technical Abstract: 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.