Poster: Plant-Pathogen Interactions

Abs # P15024: Genome-wide transcriptional response of grapes to Pierce's disease and water deficit

Presenter:	Choi, Hong-Kyu       Contact Presenter
Authors	Choi, Hong-Kyu  (A)   Iandolino, Alberto  (B)   Goes da Silva, Francisco  (A)   Cook, Douglas R.  (A)
Affiliations:	(A): University of California, Plant Pathology (B): Monsanto Inc.,

Pierce's disease (PD), caused by Xylella fastidiosa, is one of the most devastating diseases of cultivated grapes. To test the long-standing hypothesis that Pierce's disease results from pathogen-induced drought stress, we used the Affymetrix Vitis GeneChip to compare the transcriptional response of Vitis vinifera to Xylella infection, water deficit, or a combination of the two stresses. The results suggest a massive re-direction of gene transcription, involving 822 genes with a minimum 2-fold change (a < 0.01). Notable features of the transcriptional response were the up-regulation of transcripts for phenylpropanoid and flavonoid biosynthesis, pathogenesis related (PR) proteins, ABA/JA-responsive transcripts, and down-regulation of transcripts related to photosynthesis, growth and nutrition. The magnitude and directionality of pathogen-induced physiological changes related to photosynthesis and water relations were strongly correlated with suppression of transcripts involved with photosynthesis and other plastid-related activities. However, there was only limited overlap between pathogen-induced and water deficit-induced transcription, suggesting that Pierce's disease is not a simple function of pathogen-mediated drought stress. Interestingly, 138 of the pathogen-induced genes exhibited a significantly stronger transcriptional response when plants were simultaneously exposed drought stress. Real Time PCR analysis was used to validate microarray results, and allowed us to extend gene expression studies to field conditions involving a range of biotic and abiotic factors. Analysis of field samples confirmed the trends observed in the controlled Affymetrix experiment, and indicated that many of these transcripts respond generally to biotic stress.