CONSTITUTIVE EXPRESSION OF PATHOGENESIS-RELATED GENES AS A STRATEGY FOR DISEASE RESISTANCE

THE PATHOGENESIS-RELATED (PR) PROTEINS OF HIGHER PLANTS HAVEBEEN POSTULATED AS CONSTITUTING A HOST DEFENSE MECHANISM WHICH IS EMPLOYED FOR COMBATING NATURAL PATHOGENS. THIS IS LARGELY BASE ON THE CONCOMITANT APPEARANCE OF THESE PROTEIN WITH THE DEVELOPMENT OF THE PATHOGEN-INDUCED HYPERSENSITIVE RESPONSE IN DISEASE RESESTANT PLANTS. WE WILL ATTEMPT TO ELUCIDATE THEIR ROLE IN PATHOGEN RESISTANCE BY GENETICALLY ENGINEERING THE CONSTITUTIVE EXPRESSION OF CLONED PR GENES IN A CULTIVAR OF TOBACCO (NICOTIANA TABACUM CV. XANTHI NN) WHICH IS SUSCEPTIBLE TO TOBACCO MOSAIC VIRUS AND NORMALLY FAILS TO ACCUMULATE PR PROTEINS. THE FUSION OF PR GENES TO AN EFFICIENT CONSTITUTIVE PLANT PROMOTER WILL ALLOW THEIR HIGH-LEVEL EXPRESSION AND THUS PROVIDE A SIMPLE MODEL SYSTEMWHEREBY THE PRESENCE OF PR PROTEINS CAN BE DIRECTLY CORREL- ATED TO THE PLANT'S CAPACITY TO ACQUIRE RESISTANCE FOLLOWINGVIRAL INFECTION.