title: In vitro Arabidopsis pollen germination and characterization of the inward potassium currents in Arabidopsis pollen grain protoplasts.
abstract: The focus of this study is to investigate the regulatory role of K(+) influx in Arabidopsis pollen germination and pollen tube growth. Using agar-containing media, in vitro methods for Arabidopsis pollen germination have been successfully established for the first time. The pollen germination percentage was nearly 75% and the average pollen tube length reached 135 microm after a 6 h incubation. A decrease in external K(+) concentration from 1 mM to 35 microM resulted in 30% inhibition of pollen germination and 40% inhibition of pollen tube growth. An increase in external K(+) concentration from 1 mM to 30 mM stimulated pollen tube growth but inhibited pollen germination. To study how K(+) influx is associated with pollen germination and tube growth, regulation of the inward K(+) channels in the pollen plasma membrane was investigated by conducting patch-clamp whole-cell recording with pollen protoplasts. K(+) currents were first identified in Arabidopsis pollen protoplasts. The inward K(+) currents were insensitive to changes in cytoplasmic Ca(2+) but were inhibited by a high concentration of external Ca(2+). A decrease of external Ca(2+) concentration from 10 mM (control) to 1 mM had no significant effect on the inward K(+) currents, while an increase of external Ca(2+) concentration from 10 mM to 50 mM inhibited the inward K(+) currents by 46%. Changes in external pH significantly affected the magnitude, conductance, voltage-independent maximal conductance, and activation kinetics of the inward K(+) currents. The physiological importance of potassium influx mediated by the inward K(+)-channels during Arabidopsis pollen germination and tube growth is discussed.
authors.affiliation: Department of Plant Sciences, College of Biological Sciences, Key Research Laboratory in Plant Physiology and Biochemistry, China Agricultural University, Beijing 100094, China.
authors.forename: L M
authors.initials: LM
authors.lastname: Fan
authors.forename: Y F
authors.initials: YF
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: W H
authors.initials: WH
authors.lastname: Wu
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D001464:Barium / Q000378:metabolism; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D018525:Germination / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011058:Pollen / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D011523:Protoplasts / Q000502:physiology
chemical_list: D015221:Potassium Channels; D001464:Barium; D011188:Potassium; D002118:Calcium