Planta

, Volume 211, Issue 2, pp 209–217

Increases in cytosolic Ca2+ are not required for abscisic acid-inhibition of inward K+ currents in guard cells of Vicia faba L.

  • Lisa A. Romano
  • Tobias Jacob
  • Simon Gilroy
  • Sarah M. Assmann

DOI: 10.1007/s004250000286

Cite this article as:
Romano, L., Jacob, T., Gilroy, S. et al. Planta (2000) 211: 209. doi:10.1007/s004250000286

Abstract.

 The inward K+ channels (IKin) of guard cells are inhibited upon application of abscisic acid (ABA). It has been postulated that IKin inhibition requires an elevation in cytosolic free Ca2+ levels ([Ca2+]c) because: (i) experimental increases in [Ca2+] c can mimic the ABA effect, and; (ii) ABA can trigger an elevation of [Ca2+]c in guard cells. However, not all guard cells respond to ABA with a [Ca2+]c increase, and the magnitude of the increases that do occur is variable. Therefore, an obligate role for Ca2+ in the regulation of downstream effectors of ABA response, such as the IKin channels, remains in question. In this study, we developed a methodology for simultaneous patch clamping and confocal ratiometric Ca2+ imaging of Vicia faba L. guard-cell protoplasts. This allowed us to directly assess the relationship between ABA-induced changes in [Ca2+]c and IKin inhibition. In the presence of extracellular Ca2+, the extent of [Ca2+]c elevation correlated with the extent of IKin inhibition. However, upon chelation of either extracellular Ca2+, [Ca2+]c, or both, extracellular Ca2+ and [Ca2+]c, [Ca2+]c elevation did not occur in response to ABA yet IKin currents were still strongly inhibited. These data illustrate that Ca2+-independent regulation is involved in ABA-inhibition of stomatal opening processes.

Key words: Abscisic acidCytosolic calciumGuard cellK+ channelsVicia (K+ channels)

Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Lisa A. Romano
    • 1
  • Tobias Jacob
    • 1
  • Simon Gilroy
    • 1
  • Sarah M. Assmann
    • 1
  1. 1.Department of Biology, Penn State University, University Park, PA, 16802, USAUS