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item Redinbaugh, Margaret - Peg
item CHEN, Z
item WILLIE, K
item LOUIE, R

Submitted to: Plant Molecular Biology International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/9/2003
Publication Date: 6/15/2003
Citation: Redinbaugh, M.G., Chen, Z., Willie, K., Louie, R. 2003. The maize resistance response to maize dwarf mosaic virus. Plant Molecular Biology International Conference Proceedings. S25-9.

Interpretive Summary:

Technical Abstract: The maize inbred Pa405 carries a high level of durable resistance to maize dwarf mosaic potyvirus (MDMV) conferred by a dominant gene (Mdml) on chromosome 6. The resistance response was previously suggested to be associated with a restriction of MDMV movement in vascular tissue. Although resistance in Pa405 is associated with a non-HR mechanism, there is no information about the response of resistant and susceptible maize to virus inoculation. Our objective was to begin to define MDMV resistance on the cellular and molecular level. In Pa405, no virus symptoms developed after leaf rub inoculation (LRI) with MDMV; however, the first five leaves of Pa405 developed mosaic symptoms after vascular puncture inoculation (VPI) of germinating maize kernels with MDMV. In the susceptible maize inbred Oh28 seedlings developed systemic mosaic symptoms after both LRI and VPI. Immunohistochemical analyses of embryo, leaf and stem tissues indicated that MDMV entered and replicated in all tissues of resistant (Pa405) and susceptible maize (Oh28), including vascular cells. Up to 10 days post-VPI there was little difference in virus distribution in the two lines. After longer periods, MDMV was localized in Pa405 tissues, but was distributed widely in Oh28. These results suggest that virus replication and, perhaps movement, may be blocked at some point after inoculation. PCR-Select (Clontech) was used to identify genes differentially expressed during the virus resistance response. In initial screens, cDNAs with homology to known defense genes were identified including phenylalanine ammonia lyase (PAL), subtilisin protease inhibitor (SPI), a proline rich protein, and a subtlisin chymotrypsin protease inhibitor. PAL and SPI were highly expressed in both resistant (Pa405) and susceptible (Oh28) maize after VPI and LRI with MDMV, but not in mock-inoculated tissue. To determine whether there is differential expression in resistant and susceptible maize, the timing of expression will be examined.