DIRECTING POTENTIAL ANTI-XYLELLA GENE PRODUCTSTO THE XYLEM OF TRANSGENIC GRAPEVINES Project Leaders:

One of our target genes is a pear pgip cloned in the Labavitch lab (Stotz et al. 1993). PGIPs are proteins containing a leucinerich repeat domain that are targeted to the plant cell wall and that specifically inhibit fungal polygalacturonases (PGs). By inhibiting PGs, PGIPs directly interfere with host cell wall degradation and may thus prevent degradation of pectic oligomeric elicitors that are inducers of the plant defense response. Their role in plant defense response suggests that they may be useful for engineering transgenic plants resistant to pathogen infection. Powell et al. (2000) showed that transgenic tomato plants transformed with the pear pgip gene exhibited reduced susceptibility to infection with Botrytis cinerea. The fact that Xylella fastidiosa, the causal agent of Pierce’s disease (PD) in grapevines, has genes putatively encoding PG and other cell walldegrading enzymes (Simpson et al. 2000) led us to hypothesize that PGIP could confer tolerance against Xylella in grapes. In order to test this hypothesis, proembryogenic calluses originating from anthers of Vitis vinifera cvs. Thompson Seedless and Chardonnay were co-cultivated with Agrobacterium tumefaciens strain EHA 101 harboring binary plasmid pDU94.0928 that contains the pear pgip gene under the control of the CaMV 35S promoter.