Premium
Alternaria cassiae Alters Phenylpropanoid Metabolism in Sicklepod ( Cassia obtusifolia )
Author(s) -
Hoagland R. E.
Publication year - 1990
Publication title -
journal of phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 60
eISSN - 1439-0434
pISSN - 0931-1785
DOI - 10.1111/j.1439-0434.1990.tb01166.x
Subject(s) - cassia , biology , phenylalanine ammonia lyase , phenylpropanoid , shoot , inoculation , spore , botany , pathogen , horticulture , alternaria , weed , phenylalanine , microbiology and biotechnology , biosynthesis , enzyme , biochemistry , medicine , alternative medicine , amino acid , pathology , traditional chinese medicine
Phenylpropaniod metabolism has been implicated in plant defence mechanism(s) against pathogen attack. In this study, phenylpropanoid metabolism was examined over a 72 h time course in the weed sicklepod ( Cassia obtusifolia ) in relation to pathogenic effects of the fungus Alternaria cassiae. When 3‐ to 4‐week old seedlings were challenged by the pathogen, extrable phenylalanine ammonia‐lyase (PAL, E.C. 4.3.1.5) activity was dramatically increased above that in uninfected plants severalhours after inoculation and exposure to dew. Greatest increases of enzyme activity (3‐fold, specific activity basis) occurred at ca 15–23 after treatment with fungal spores. After this peak of activity, PAL activity declined with time in infectedtissue, but remained greater than in uninfected plants through 65 h after treatment. Total methanol‐soluble hydroxyphenolic compound levels (PAL products) were higher in shoots (stems and leaves) of infected plants at 48–72 h. Leaves contained a higherconcentration (per gram fresh weight) of hydroxyphenolic compounds than did stems, and infected leaves exhibited a phenolic content greater than that of uninfected leaves at ca 27–72 h. Increased soluble phenolic compound production correlated with the appearance of lesions and necrotic spots on leaves and stems. UV irradiation examination and spectrofluorometric analysis of thin layer chromatographic separations of methanolic exatracts revealed a substantial increase of several components ininfected tissue 48 h after inoculation. Results support the view that PAL activity increases correlate with increased phenolic compound production in this host/pathogen interaction.