Stimulation of phenylalanine ammonia-lyase in sorghum in response to inoculation with Bipolaris maydis

• Published in: Physiological and molecular plant pathology 1996, Vol.48 (1), p.55-64
• Main Authors: Orczyk, W., Hipskind, J., de Neergaard, E., Goldsbrough, P., Nicholson, R.L.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection
• ISSN: 0885-5765; 1096-1178
• DOI: 10.1006/pmpp.1996.0005

To determine whether the level of phenylalanine ammonia-lyase (PAL) activity in sorghum mesocotyl tissues is elevated in response to inoculation we used sorghum cultivars that differed in their ability to synthesize anthocyanins in response to light. These cultivars provided a means of distinguishing the light induced high background levels of PAL from increases in PAL that occur as a result of attempted infection. The induction of PAL as a response to both light and to attempted fungal infection was further confirmed by a time course study of RNA blot hybridizations with a barley PAL cDNA. Results showed that PAL transcripts in the cultivar that did not synthesize anthocyanins began to accumulate within 3h of exposure of the tissue to light but that the level of the transcript decreased rapidly thereafter. However, when the same cultivar was inoculated with the nonpathogen Bipolaris maydisthe intensity of the PAL transcript remained elevated throughout a period of 24h after inoculation. The results demonstrate that in this monocotyledonous host it is necessary to separate the naturally occurring high levels of PAL activity that are induced by light from the induction of PAL enzyme activity which occurs as a response to attempted fungal infection.