PM H+-ATPase is a potential target of hormone signaling during pollen tube growth in petunia
Aim. Pollen tube growth is the best known example of highly polarized plant cell expansion. This process is known to require intensive exocytosis at the tip which is supported by dynamic cytoskeleton, vesicle trafficking, and functioning of ion transporters in pollen tube plasma membrane (PM). We have attempted to test the possibility of plant hormones functioning as signal molecules in progamic phase of fertilization. Methods. The effects of exogenous plant hormones, indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellin A3 (GA3), and cytokinin (kinetin) on the growth, PM polarization of in vitro germinating petunia (Petunia hybrida L.) pollen tubes were investigated. Results. Growth-stimulated effects of IAA, ABA and GA3 were accompanied by orthovanadate-sensitive hyperpolarization of PM suggesting possible involvement of PM H+-ATPase activation in this process. Fluorescent labeling the enzyme with H+-ATPase antibodies exhibited IAA- and ABA-induced lateral membrane redistribution of it into the subapical zone of pollen tube PM. Conclusions. All these results, taken together, indicate the potential target of hormone signaling in pollen tubes, PM H+-ATPase, related to the hormone-induced modulation of the above mentioned characteristics of this proton pump.
Keywords: Petunia hybrida, Pollen tube, PM H+-ATPase, phytohormones.
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