Ultraviolet Light-induced Formation of Pisatin and Phenylalanine Ammonia Lyase

Abstract

The production of pisatin is induced3 in pea tissue by various plant pathogens (4, 8). This de novo synthesis can also be induced by an array of chemicals (9, 19, 22), most of which are known to have an affinity for double stranded DNA. Also, most of the inducers of pisatin or phenylalanine ammonia lyase (PAL)', EC 4.3.1.5 (a key enzyme in the biosynthesis of pisatin) have the potential to change the conformation of DNA. The induction of both pisatin and PAL is dependent on new RNA and protein synthesis (9, 22). We have proposed (9, 22) that the control of these cellular responses occurs at the gene transcription level and depends on the conformational state of the double stranded DNA (i.e., the DNA becomes more transcribable either by dissociating a repressor component or by assuming a more desirable conformation for transcription). If conformational changes in cellular DNA do, in fact, initiate this response, ultraviolet light which can dimerize thymidine bases and cause lesions in DNA (5, 23) should also influence this response. This paper describes the induced synthesis of pisatin and PAL by ultraviolet light.