Hormonal regulation, and intracellular localization of a 33-kD cationic peroxidase in excised cucumber cotyledons
1989
Abeles, F.B. | Hershberger, W.L. | Dunn, L.J.
Ethylene enhanced chlorosis and levels of 33-kilodalton cationic peroxidase (33-CPO) in excised cucumber (Cucumis sativus L. cv 'Poinsett 76') cotyledons. Compared to other hormones, such as kinetin, indoleacetic acid, gibberellic acid, and abscisic acid, ethylene was the only effective promoter of 33-CPO synthesis. The hypothesis that peroxidase plays a role in chlorophyll degradation was tested by comparing levels of 33-CPO in cotyledons treated with compounds thought to either retard (kinetin, indoleacetic acid and gibberellic acid), or promote (abscisis acid and methyl jasmonate [MJ] senescence. It was concluded that 33-CPO did not play a role in senescence since no direct correlation between chlorophyll content and 33-CPO was observed. MJ was as effective as ethylene in inducing senescence. However, ethylene did not appear to be involved in the action of MJ. Using immunocytochemistry, 33-CPO was found to be located primarily around starch grains and near the plasmalemma. High levels of 33-CPO were also found in cells destined to be vascular tissue.
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