THE ROLE OF PKS1 MEDIATED SECONDARY METABOLISM IN HOST PENETRATION AND COLONIZATION DURING RICE BLAST DISEASE

Abstract

MAGNAPORTHE ORYZAE CAUSES DEVASTATING RICE BLAST DISEASES ALL OVER THE WORLD. THIS FUNGUS DIFFERENTIATES A SPECIALIZED INFECTION STRUCTURE, THE APPRESSORIUM, TO PENETRATE THE RICE LEAVES DURING INITIATION OF THE DISEASE. A LAYER OF CONDENSED MELANIN IS FORMED IN THE APPRESSORIUM TO MAINTAIN A HIGH TURGOR PRESSURE THEREIN TO FACILITATE THE HOST PENETRATION. HOWEVER, OTHER MECHANISMS THAT ARE RELATED TO THE APPRESSORIAL PENETRATION REMAIN ELUSIVE. IN THIS STUDY, WE DESCRIBE A PKS1 (POLYKETIDE SYNTHASE) CONTAINING GENE CLUSTER, WHICH IS ESSENTIAL FOR THE APPRESSORIAL FUNCTION. PKS1 DELETION MUTANT GENERATES NON-FUNCTIONAL APPRESSORIA THAT FAIL TO ELABORATE A PROPER PENETRATION PORE OR CONSEQUENTLY FAIL TO PENETRATE THE HOST SURFACE. THE PKS1-DELETION MUTANT ALSO SHOWED DEFECTS IN MELANIN DEPOSITION AND SEPTIN LOCALIZATION. THE ABC3 TRANSPORTER AND A SERINE HYDROLASE FSH1 SHARE THE AFOREMENTIONED GENE CLUSTER WITH PKS1. THESE GENES ARE CO-REGULATED WITH PKS1 AND ARE REQUIRED FOR THE PENETR