Induction of a new Lipoxygenase Form in Cucumber Leaves by Salicylic Acid or 2,6‐Dichloroisonicotinic Acid*

Abstract

Changes in lipoxygenase (LOX) protein pattern and/ or activity were investigated in relation to acquired resistance of cucumber (Cucurnis sativus 1.) leaves against two powdery mildews. Sphoerotheca fuligineo (Schlecht) Salmon and Erysiphe cichoroceorurn DC et Merat. Acquired resistance was established by spraying leaves with salicylic acid (SA) or 2,6-dichloroisonicotinic acid (INA) and estimated in whole plants by infested leaf area compared to control plants. SA was more effective than INA. According to Western blots, untreated cucumber leaves contained a 97kDa LOX form, which remained unchanged for up to 48 h after pathogen inoculation. Upon treatment with SA alone for 24 h or with INA plus pathogen, an additional 95 kDa LOX form appeared which had an isoelectric point in the alkaline range. For the induction of this form, a threshold concentration of 1 mM SA was required, higher SA concentrations did not change LOX-95 expression which remained similar between 24 h and 96 h but further increased upon mildew inoculation. Phloem exudates contained only the LOX-97 form, in intercellular washing fluid no LOX was detected. Immunocytochemical localization revealed LOX protein in the cytosol of the mesophyll cells without differences between the forms.

Effect of 2,6‐dichloroisonicotinic acid, its formulation materials and benzothiadiazole on systemic resistance to alternaria leaf spot in cotton

“…Some of these proteins have in vitro activity against fungal pathogens ( Mauch et al ., 1988b ; Woloshuk et al ., 1991 ; Niderman et al ., 1995 ). Decreased susceptibility of cotton leaves to A. macrospora is likely to have been caused finally by the action of these and other products ( Uknes et al ., 1992 ; Wasternack et al ., 1994 ; Van Kan et al ., 1995 ; Feussner et al ., 1997 ; Schweizer et al ., 1997 ) of the process of systemic induction. The probable activation of all or some of these processes in addition to that of β‐1,3‐glucanase may explain why each component of formulated INA had more consistent effects in decreasing susceptibility ( Table 7) than in increasing β‐1,3‐glucanase activity ( Table 5).…”

A novel cucumber gene associated with systemic acquired resistance

“…In cucumber, induction of SAR by different pathogens as well as by SA, INA or BTH has been reported [15][16][17][18][19][20]. Infection of young cucumber plants with different pathogens can lead to broad spectrum SAR to at least 13 diseases and can protect plants from several pathogens for 4-6 weeks [21].…”

Ενζυμικές Δράσεις Στις Ελιές Και Το Ελαιόλαδο

“…Πάντως μετά τις πρώτες αναφορές που έγιναν στην αύξηση της δραστικότητας της LOX μετά από προσβολή από παθογόνο έχει γίνει ένας μεγάλος αριθμός εργασιών με παρόμοια αποτελέσματα (Galliard. 1978, Peever & Higgins 1988, Feussner et al 1997b.…”