PLANT PHYSIOLOGY , Vol 115, Issue 4 1443-1451, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Constitutively Elevated Levels of Putrescine and Putrescine-Generating Enzymes Correlated with Oxidant Stress Resistance in Conyza bonariensis and Wheat
B. Ye, H. H. Muller, J. Zhang and J. Gressel
Department of Plant Genetics, Weizmann Institute of Science, Rehovot 76100, Israel (B.Y., J.Z., J.G.)
Oxidant stress resistance in Conyza bonariensis and wheat (Triticum
aestivum) has been correlated with high levels of antioxidant enzyme
activities. Additionally, external oxidant stresses can increase a plant's
levels of the enzymes of polyamine biosynthesis and polyamines, especially
putrescine. We investigated the constitutive relationships between
putrescine, putrescine-generating enzymes, and oxidant stress resistance in
wheat and C. bonariensis. Putrescine was Constitutively elevated (2.5- to
5.7-fold) in 2-week-old-resistant wheat and C. bonariensis biotypes, which
correlated with a 10- to 15-fold increase in paraquat oxidant resistance.
Arginine and ornithine decarboxylase activities doubled, along with higher
putrescine levels in resistant C. bonariensis. The variations in levels of
putrescine and arginine and ornithine decarboxylase activities paralleled
the constitutive variation of antioxidant enzymes, as well as oxidant
resistance. Higher levels of both putrescine and antioxidant enzyme
activities occurred during a peak of oxidant resistance at 10 weeks, when
paraquat resistance in C. bonariensis plants is >50-fold greater than in
the sensitive biotype. Application of 100 [mu]M putrescine can double
oxidant-stress resistance in the resistant C. bonariensis. Putrescine may
play an important role in contributing to the base level of oxidant
resistance found at the nonpeak period.
