EFFECTS OF CHITOSAN AND ASPERGILLUS-FLAVUS ON ISOZYMES RELATED TO PHENOLIC COMPOUND SYNTHESIS AND PROTEIN PROFILES OF PEANUT SEEDS

Changes in isozymes and peanut protein molecular weights were determin ed in mature peanuts treated with chitosan and/or Aspergillus flavus. Enzymes involved with the synthesis of phenolic compounds were analyze d. Cinnamyl alcohol dehydrogenase (CAD), glutamate dehydrogenase (GDH) , and glucose-6-phosphate dehydrogenase (G6PDH) were resolved by nativ e-PAGE using gradient gels containing 8-25% polyacrylamide while polyp henoloxidases (PPO) were resolved with 10-15% polyacrylamide. Anodic p eroxidase (PRX) and shikimate dehydrogenase (SKD) were detected by IEF -PAGE (pi range of 4.0-6.5). Chitosan induced enzyme activities of PPO (Rf=0.34) and SKD (pl=5.22; pl=4.85) in viable seeds while A. flavus enhanced activities of G6PDH (Rf=0.44),;GDH (Rf=0.14), PRX (pl=4.00), PPO (Rf=0.27), and SKD (pl=4.56; pl=4.27). Chitosan + A. flavus promot ed GDH (Rf=0.14; Rf=0.20; Rf=0.25) and SKD (pl=4.56; pl=4.04) activiti es. SKD with five isozyme bands was a better marker for comparing the effects of elicitors. Chitosan and chitosan + A. flavus treated seeds did not have any protein molecular weight changes over 72 h. By 48 h a fter inoculation of mature seeds with A. flavus, an early change in pr otein composition of moderately susceptible cultivar of peanuts, Starr , was detected by non-denaturing gel electrophoresis. Resistant cultiv ar J-11 exhibited a delay in alteration of protein composition until 7 2 h. Manipulation of specific enzyme activities could help elucidate b iochemical mechanisms in elicitor-host interaction and control contami nation by aflatoxin-producing fungi.