Effects of chitosan andaspergillus flawson isozymes related to phenouc compound synthesis and protein profiles of peanut seeds

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Abstract
Changes in isozymes and peanut protein molecular weights were determined in mature peanuts treated with chitosan and/or Aspergillus flavus. Enzymes involved with the synthesis of phenolic compounds were analyzed. Cinnamyl alcohol dehydrogenase (CAD), glutamate dehydrogenase (GDH), and glucose‐6‐phosphate dehydrogenase (G6PDH) were resolved by native‐PAGE using gradient gels containing 8–25% polyacrylamide while polyphenoloxidases (PPO) were resolved with 10–15% polyacrylamide. Anodic peroxidase (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 promoted GDH (Rf=0.14; Rf=0.20; Rf=0.25) and SKD (pl=4.56; pl=4.04) activities. 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 after inoculation of mature seeds with A. flavus, an early change in protein composition of moderately susceptible cultivar of peanuts, Starr, was detected by non‐denaturing gel electrophoresis. Resistant cultivar J‐11 exhibited a delay in alteration of protein composition until 72 h. Manipulation of specific enzyme activities could help elucidate biochemical mechanisms in elicitor‐host interaction and control contamination by aflatoxin‐producing fungi.

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