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Heme oxygenase (HO, EC 1.14.99.3) is an important antioxidative enzyme in animals. Recently, it has been proven by many researches that HO was able to modulate plant tolerance against some abiotic stresses in planta. In the present report, HO system was brought into cytokinin-induced alleviation of senescence induced by darkness in detached wheat leaves, thus resulting in the full understanding of the possible mechanism related to the alleviation of plant leaf senescence conferred by cytokinin (CTK).In this study,6-BA was used to delay dark-induced senescence in detached wheat leaves. We also discovered that the HO activity, HO-1 transcript and HO-1 protein expression was induced by 6-BA, when it delay the degradation of chlorophyll and soluble protein content. Furthermore, ZnPPⅨ, the potent inhibitor of HO-1, was able to block 6-BA-induced responses, which were confirmed by the changes of chlorophyll, soluble protein, and TBARS cotent. Meanwhile, hemin, the HO-1 potent inducer, was able to delay senescence in detached wheat leaves under darkness treatment. Additionally, ZnPPⅨreversed the modulation of total catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) activities, isozyme activities and corresponding transcripts modulated by 6-BA. Additionally, hemin was able to up-regulate the total antioxidant enzymes activities, isozyme activities and corresponding transcripts to a certain extent.Overall, above results suggest that HO, at least partially, is involved in cytokinin-induced alleviation of senescence induced by darkness in detached wheat leaves.
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