RAPID SCREENING OF GRAPE CDNA LIBRARIES AND FUNCTIONAL TESTING OF GENES CONFERRING RESISTANCE TO PIERCES DISEASE

• Author(s): Gilchrist, David; Lincoln, James; Lindow, Steven; Walker, Andrew;
• Abstract: Our overall objective is to identify novel genes from cDNA libraries of either grape or heterologous plants that, when expressed in grape, will disrupt infection, spread or symptom development of the xylem-limited bacteria, Xylella fastidiosa (Xf). Furthermore, we are specifically characterizing the effect of the genetic disruption of Pierces disease (PD) symptoms on the movement and establishment of the bacterium in the xylem of susceptible grape plants. Specific objectives are to: a) create cDNA libraries from several different grape backgrounds, including two with PD resistance; b) develop a functional A. rhizogenes-based cDNA screen in grape; c) examine the morphological and cytological features of cell death in symptomatic tissues; and d) investigate the potential of blocking PD symptom expression and disease impact with anti-apoptotic transgenes. To date we have developed a Agrobacterium. rhizogenes-based transformation procedure that results in the induction of transformed roots from infected or healthy vegetative tissue sections following co-cultivation with the transforming bacteria. Each emerging root is an independent transformation event. We then used this technique to develop a functional cDNA library screen (each root contains a different cDNA library member) for genes that block either bacterial multiplication, movement, or symptom expression. The only genes that will be identified will be those that directly affect the ability of the pathogen to cause disease and is not dependent on DNA sequence relationships. We have made excellent progress in creating an extensive library of full-length cDNAs from several resistant sources as well as susceptible Chardonnay and conducting initial screens of the libraries.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium