Virus-resistant squash

Squash resistant to infection by Cucumber mosaic cucumovirus (CMV), Zucchini yellow mosaic potyvirus (ZYMV) and Watermelon mosaic potyvirus 2 (WMV-2) through incorporation of virus-derived sequences that encode the coat proteins (CPs) from each of these viruses.

CMV73/ZYMV72/WMBN22

All three coat protein genes were fused to the 5' untranslated sequence from CMV to enhance translation of the transgene mRNA.

Southern blot analysis of genomic DNA from CZW-3 indicated the presence of a single copy of the T-DNA containing intact sequences corresponding to the CP encoding genes form CMV, ZYMV, and WMV2, integrated at a single site. Additional analyses verified the presence of a single copy of the NPTII encoding neo antibiotic resistance marker gene, and no incorporation of plasmid backbone sequences outside of the T-DNA region.

The CZW-3 squash line was developed using recombinant DNA techniques to resist infection by CMV, ZYMV, and WMV2 by inserting virus-derived sequences that encode the coat proteins (CPs) from each of these viruses. The introduced viral sequences do not result in the formation of any infectious particles, nor does their expression result in any disease pathology.

This transgenic squash exhibits "pathogen-derived resistance" to infection and subsequent disease caused by CMV, ZYMV, and WMV2 through a process that is related to viral cross-protection. Although the exact mechanism by which the viral protection occurs is unknown, most evidence suggests that expression of viral CP by a plant interferes with one of the first steps in viral replication, uncoating (removal of CP) from the incoming virus. Other modes of action of cross-protection have also been suggested.