Ubiquitination plays important roles in disease resistance in plants.
Lingmin Dai of Northwest A&F University in China identified and
characterized the RING-type ubiquitin ligase
[www.isaaa.org] gene,
VpUR9, from the powdery mildew resistant Chinese wild grapevine (Vitis
pseudoreticulata). The results are published in Plant Cell Tissue and Organ
Culture.

The gene was found to be induced in response to powdery mildew disease and
salicylic acid. VpUR9 gene was cloned and transformed into the
powdery-mildew susceptible grape (Vitis vinifera L.) variety Red Globe.
Twelve transgenic lines containing the gene were generated, but were found
to be susceptible to powdery-mildew. Furthermore, the expression of some
disease-resistant related genes of this variety also declined compared with
wild type grapes when inoculated with powdery mildew or salicylic acid.

These results suggest that the VpUR9 gene may have negatively regulated the
resistance of transgenic Red Globe to powdery mildew by changing the
SA-dependent and the MeJA-dependent defense pathways.

[link.springer.com]