RICE, A STAPLE FOOD CROP FOR TWO THIRDS OF THE WORLD'S POPULATION, IS A PREMIER MODEL SPECIES FOR UNDERSTANDING HOST/MICROBE INTERACTIONS THAT INVOLVE CO-EVOLUTION OF NEW VIRULENCE STRATEGIES IN PATHOGENS AND COUNTERACTING RESISTANCE MECHANISM IN HOSTS. WE RECENTLY MADE A SURPRISING DISCOVERY IN OUR STUDIES OF THE BIOLOGY OF BACTERIAL TALES (TRANSCRIPTION ACTIVATOR-LIKE EFFECTORS). TALE PSEUDOGENES OF TWO PATHOVARS OF XANTHOMONAS ORYZAE FUNCTION AS BACTERIAL VIRULENCE DETERMINANTS BY INTERFERING WITH RESISTANCE IN RICE THAT IS MEDIATED BY A SUBFAMILY OF RESISTANCE (R) GENES IN RESPONSE TO ALL TESTED TALES. OUR PRELIMINARY RESULTS DEMONSTRATE THAT THE PREVIOUSLY ANNOTATED TALE PSEUDOGENES ARE NOT PSEUDOGENES; INSTEAD THEY ARE EXPRESSED AS TALE VARIANTS TO INTERFERE WITH THE PLANT RESISTANCE TRIGGERED BY THE PATHOGEN'S PROGENITOR TALES. WE, THEREFORE, RENAMED THESE VARIANTS AS ITALES (INTERFERING TALES). WE ALSO FOUND THAT THE RICE XA1, XA2 AND XA14 GENES FORM A NEW SUBFAMILY OF NBS-LRR R GENES WHOSE BROAD SPECTRUM OF TALE-TRIGGERED RESISTANCE CAN BE EFFECTIVELY LIMITED BY ITALES PREVALENT IN THE MAJORITY OF PATHOGEN ISOLATES. WE HYPOTHESIZE THAT RICE HAS EVOLVED A GROUP OF R GENES TO COUNTERACT TALES, WHILE PATHOGENS HAVE CO-EVOLVED VIRULENCE STRATEGIES BY MUTATING THE ELICITOR TALE GENES TO EVADE THE R GENE RECOGNITION/RESISTANCE IN HOST AND, THEREBY, SUPPRESS RESISTANCE TRIGGERED BY THE PROGENITOR TALES. IN THIS PROJECT, WE PROPOSE TO USE GENETIC, MOLECULAR AND BIOCHEMICAL APPROACHES TO THOROUGHLY CHARACTERIZE THE INTERACTIONS OF XA1 GENE SUBFAMILY MEMBERS WITH TALES THAT LEAD TO RESISTANCE AND ELUCIDATE HOW ITALES POTENTLY INTERFERE WITH SUCH RESISTANCE. SPECIFICALLY, WE WILL CHARACTERIZE THE UNIQUE STRUCTURES OF ITALES THAT ALLOW FOR SUPPRESSION OF XA1-RESISTANCE (AIM 1), DETERMINE THE PREVALENCE AND FUNCTION OF DIVERSE ITALE GENES AMONG A LARGE COLLECTION OF X. ORYZAE PV. ORYZAE AND X. ORYZAE PV. ORYZICOLA ISOLATES (AIM 2), CHARACTERIZE THE INTERACTION (DIRECT OR INDIRECT) BETWEEN TALES AND XA1 AS WELL AS ITALE AND XA1 THAT UNDERLIE RESISTANCE ELICITATION AND SUPPRESSION, RESPECTIVELY (AIM 3), AND PERFORM COMPARATIVE ANALYSES ON XA1, XA2 AND XA14 IN RESPONSE TO ITALE SUPPRESSION (AIM 4).