RESUMO
Ion homeostasis plays a central role in polarisation and polar growth. In several cell types ion channels are controlled by reactive oxygen species (ROS). One of the most important cells in the plant life cycle is the male gametophyte, which grows under the tight control of both ion fluxes and ROS balance. The precise relationship between these two factors in pollen tubes has not been completely elucidated, and in pollen grains it has never been studied to date. In the present study we used a simple model - protoplasts obtained from lily pollen grains at the early germination stage - to reveal the effect of H2 O2 on cation fluxes crucial for pollen germination. Here we present direct evidence for two ROS-sensitive currents on the pollen grain plasma membrane: the hyperpolarisation-activated calcium current, which is strongly enhanced by H2 O2 , and the outward potassium current, which is modestly enhanced by H2 O2 . We used low concentrations of H2 O2 that do not cause an intracellular oxidative burst and do not damage cells, as demonstrated with fluorescent staining.
Assuntos
Canais de Cálcio/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Lilium/efeitos dos fármacos , Canais de Potássio/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Cálcio/metabolismo , Canais de Cálcio/metabolismo , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Citoplasma/metabolismo , Germinação/efeitos dos fármacos , Lilium/citologia , Lilium/fisiologia , Técnicas de Patch-Clamp , Pólen/citologia , Pólen/efeitos dos fármacos , Pólen/fisiologia , Tubo Polínico/citologia , Tubo Polínico/efeitos dos fármacos , Tubo Polínico/fisiologia , Potássio/metabolismo , Canais de Potássio/metabolismo , Protoplastos , Espécies Reativas de Oxigênio/análiseRESUMO
Pollen tube growth is a key step in the life cycle of seed plants, which defines the success of sexual reproduction. One of the most important contributions to this process is made by ion transport through plasmalemma, which is tightly coordinated in time and space. Different classes of signaling molecules are involved in the regulation of transmembrane ion transport including reactive oxygen species as it has been recently demonstrated. Here, using subprotoplasts isolated from pollen tubes, we have demonstrated a connection between hydrogen peroxide, on one side, and two groups of targets on the plasma membrane, on the other side: nifedipine-sensitive Ca(2+)-permeable channels and transport systems controlling membrane potential. H2O2 interaction with these targets causes the increase in cytoplasmic Ca2+ concentration and plasmalemma hyperpolarization. One of the consequences of target modification was acceleration of cell wall regeneration.
