THE PLANT CELL, Vol 4, Issue 8 961-969, Copyright © 1992 by American Society of Plant Biologists
Expression of an Outward-Rectifying Potassium Channel from Maize mRNA and Complementary RNA in Xenopus Oocytes
Y. Cao, M. Anderova, N. M. Crawford and J. I. Schroeder
Department of Biology and Center for Molecular Genetics, University of California at San Diego, La Jolla, California 92093-0116
Injection of Xenopus oocytes with poly(A)+ mRNA isolated from different
plants (maize, cucumber, and squash) results in the appearance of a
voltage- and time-dependent, potassium-selective, outward current that is
similar to the outward-rectifying potassium current recorded in many higher
plant cells. Maize shoots were found to be especially enriched in mRNA
encoding such activity. A cDNA library of maize shoot mRNA was constructed
in the vector [lambda]ZAPII and was used to synthesize RNA complementary to
the cDNA (cRNA). Injection of the cRNA gave rise to an outward-rectifying
potassium current with properties similar to the currents obtained by
poly(A)+ mRNA injection. These results demonstrate that higher plant mRNA
can be properly translated into a product that produces a voltage-regulated
potassium channel in the plasma membrane of Xenopus oocytes. Thus, Xenopus
oocytes can be used as a heterologous expression system for the functional
identification and isolation of plant ion channel genes as well as for the
study of structure-function relationship of plant ion channels.