Reciprocal regulation of Ca2+-activated outward K+ channels of Pyrus pyrifolia pollen by heme and carbon monoxide
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- •The regulation of plant potassium (K+) channels has been extensively studied in various systems. However, the mechanism of their regulation in the pollen tube is unclear.
- •In this study, the effects of heme and carbon monoxide (CO) on the outward K+ (K+out) channel in pear (Pyrus pyrifolia) pollen tube protoplasts were characterized using a patch-clamp technique.
- •Heme (1 μM) decreased the probability of K+out channel opening without affecting the unitary conductance, but this inhibition disappeared when heme was co-applied with 10 μM intracellular free Ca2+. Conversely, exposure to heme in the presence of NADPH increased channel activity. However, with tin protoporphyrin IX treatment, which inhibits hemeoxygenase activity, the inhibition of the K+out channel by heme occurred even in the presence of NADPH. CO, a product of heme catabolism by hemeoxygenase, activates the K+out channel in pollen tube protoplasts in a dose-dependent manner. The current induced by CO was inhibited by the K+ channel inhibitor tetraethylammonium.
- •These data indicate a role of heme and CO in reciprocal regulation of the K+out channel in pear pollen tubes.