Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/12/2005
Publication Date: N/A
Interpretive Summary: Pierce's disease is an economically serious disease of grapevines caused by the plant pathogenic bacterium Xylella fastidiosa. Currently there are no strategies available to effectively manage this disease. Accordingly, the most likely strategy to manage Pierce's disease is through genetic resistance. Although genetic resistance or tolerance to Pierce's disease occurs in some grape species, this resistance or tolerance has not been incorporated into commercial Vitis vinifera wine, table and grape cultivars. In this study, unique DNA sequences differentially expressed in stems, leaves and shoots of infected and non-infected Pierce's disease-susceptible and -resistant grapes were identified. This information will help define which metabolic pathways are involved in determining grape host susceptibility and resistance to Pierce's disease for developing commercially resistant grape cultivars.
Technical Abstract: The gram-negative bacterium Xylella fastidiosa (Xf) is the causal agent of Pierce's disease (PD) in grape as well as diseases of many fruit and ornamental plants. Twelve tissue specific subtractive suppression hybridization cDNA libraries were constructed from stem, leaf and shoot of PD resistant and susceptible sibling genotypes (V. rupestris x V. arizonica) in response to Xf infection. A total of 5,700 sequences were obtained from these cDNA libraries. The average size of the EST was 282 bp. Of them, 754 Expressed Sequence Tags (ESTs) showed BLASTX analysis (E<=0.00001) and 439 ESTs showed (E=0.0001-0.009) match to NCBI databases and the rest ~32 % of the sequences have not been previously described. Subsequent contiging of these ESTs help derive 993 contigs and 949 singletons. The percentage of unique sequences in each library varied from 19.3 to 74.5 %. Comparative analysis showed significant variation in EST expression levels between infected and non-infected PD resistant and PD susceptible grapes. Using Gene Ontology (GO) hierarchy the non-redundant sequences were classified into the three principal categories: molecular function (30%), cellular component (9%) and biological process (7%). Ten candidate genes, associated with host/pathogen interactions, were further selected for Taq-Man gene expression analysis. Currently we are designing genome-wide 60-mer oligonucelotide microarrays to dissect spatial and temporal differential expression. This approach will help define the transcriptional pathways involved in host susceptibility and resistance in grape.