CLONING AND FUNCTIONAL EXPRESSION OF A PLANT VOLTAGE-DEPENDENT CHLORIDE CHANNEL

Plant cell membrane anion channels participate in basic physiological functions, such as cell volume regulation and signal transduction. How ever, nothing is known about their molecular structure. Using a polyme rase chain reaction strategy, we have cloned a tobacco cDNA (CIC-Nt1) encoding a 780-amino acid protein with several putative transmembrane domains. CIC-Nt1 displays 24 to 32% amino acid identity with members o f the animal voltage-dependent chloride channel (CIC) family, whose ar chetype is CIC-0 from the Torpedo marmorata electric organ. Injection of CIC-Nt1 complementary RNA into Xenopus oocytes elicited slowly acti vating inward currents upon membrane hyperpolarization more negative t han -120 mV. These currents were carried mainly by anions, modulated b y extracellular anions, and totally blocked by 10 mM extracellular cal cium. The identification of CIC-Nt1 extends the CIC family to higher p lants and provides a molecular probe for the study of voltage-dependen t anion channels in plants.