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Steigerung der Phenylalaninammoniumlyase‐Aktivität, verursacht durch Plasmopara halstedii bei gegenüber Mehltau resistenten und empfindlichen Sonnenblumen‐Sämlingen
Author(s) -
TENA M.,
LOPEZ VALBUENA R.
Publication year - 1983
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/jph.1983.107.1.47
Subject(s) - biology , sunflower , helianthus annuus , downy mildew , phenylalanine ammonia lyase , inoculation , horticulture , enzyme assay , botany , helianthus , cultivar , phenylalanine , enzyme , biochemistry , amino acid
Plasmopara halstedii inoculation of the sunflower ( Helianthus annuus ) cultivars Peredovik (susceptible) and HA‐61 (resistant) caused an increase in phenylalanine ammonia‐lyase (PAL) activity. Although the initial rise in PAL activity was higher in HA‐61 than in Peredovik inoculated seedlings (values of 247 and 146 % above those of healthy controls, respectively), there was a relatively constant increase in PAL activity over basal level during the compatible interaction while, in the incompatible host, PAL increase declined with age. Increase in PAL activity was also observed in hypocothyl segments of Peredovik seedlings when incubated in a suspension of P. halstedii zoosporangia. Partially purified PAL from healthy seedlings exhibited negative cooperativity, the ratio of Km values obtained at high and low substrate concentrations (H : L ratio) was 8.3 and 12.8 for the enzymes from Peredovik and HA‐61, respectively. PAL activity in inoculated Peredovik and HA‐61 seedlings showed a lesser departure from a Michaelis‐Menten kinetics, the H : L ratios were of 2.9 and 2.2, respectively. In Peredovik, PAL activities, both constitutive and induced by infection, had the same optimum pH value (8.8), the same temperature for maximum activity (55 °C), and slightly different activation energy values (9,700 and 12,600 cal. mol −1 , respectively).