Specific objectives

The specific objectives of the project are as follows:

1. Identify rice genes differentially expressed in response to infection by Xoo and Xoc. The working hypothesis for this objective is that rice responds differently to these pathogens and the differential response is important in tissue-specific susceptibility.

2. Identify differences in gene content and expression between Xoo and Xoc by identifying and comparing type III secreted proteins; by identifying and comparing genes involved in disease through mutagenesis, virulence screening and reporter gene assays; and by genome comparison using either sequence data or suppressive, subtractive PCR. The working hypothesis is that Xoo and Xoc contain unique genes (or express genes uniquely) that account for their respective modes of pathogenicity.

3. Characterize functionally the differences between Xoo and Xoc in the context of their interactions with rice by mutagenesis, gene swapping, and, for effector proteins,in planta phenotypic screening, identification of potential plant targets, and characterization of rice gene expression changes in response to individual effectors. The working hypothesis is that discrete and discernible differences in gene content measurably affect tissue-specific susceptibility, and specifically, that different host molecular targeting or manipulation of rice gene expression by type III effector proteins of these two pathogens plays a major role.

4. Identify from rice deletion mutant and activation tagged libraries lines that show altered susceptibility or tissue-specificity for infection by Xoo and Xoc and determine differences in gene expression between these and wild type rice. The working hypothesis is that loss- or gain-of-function mutations will reveal rice genes that contribute to tissuespecific susceptibility. These genes could encode or affect expression of tissue-specific signals, targets, or defense response proteins.

5. Construct a Gateway® library of rice cDNAs generated from pooled samples of rice undergoing infection by Xoo or Xoc, Gateway® libraries of Xoo and Xoc type III effector genes, and new compatible vectors for expression in plants and pathogenic bacteria. These libraries and vectors will be valuable resources for further functional characterization of host and pathogen genes involved in susceptibility and tissue specificity. They will be valuable tools for genomics research in other areas as well.

6. Carry out activities to integrate research and education, increase participation by underrepresented groups, enhance infrastructure for research and education, and broadly disseminate research results to benefit society.

updated July 29, 2005