RT Journal Article
SR Electronic
T1 Reconstitution of CO<sub>2</sub> regulation of SLAC1 anion channel and function of CO<sub>2</sub>-permeable PIP2;1 aquaporin as carbonic anhydrase 4 interactor
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 030296
DO 10.1101/030296
A1 Cun Wang
A1 Honghong Hu
A1 Xue Qin
A1 Brian Zeise
A1 Danyun Xu
A1 Wouter-Jan Rappel
A1 Walter F. Boron
A1 Julian I. Schroeder
YR 2015
UL http://biorxiv.org/content/early/2015/11/13/030296.abstract
AB Daily dark periods cause an increase in the leaf CO2 concentration (Ci) and the continuing atmospheric [CO2] rise also increases Ci. Elevated Ci causes closing of stomatal pores thus regulating gas exchange of plants. The molecular signaling mechanisms leading to CO2-induced stomatal closure are only partially understood. Here we demonstrate that high intracellular enhances currents mediated by the guard cell S-type anion channel SLAC1 when co-expressing either of the protein kinases OST1, CPK6 or CPK23 in Xenopus oocytes. Split-ubiquitin screening identified the PIP2;1 aquaporin as an interactor of the βCA4 carbonic anhydrase, which was confirmed in split luciferase, bimolecular fluorescence complementation and co-immunoprecipitation experiments. PIP2;1 exhibited CO2 permeability. Co-expression of βCA4 and PIP2;1 with OST1-SLAC1 or CPK6/23-SLAC1 enabled extracellular CO2 enhancement of SLAC1 anion channel activity. An inactive PIP2;1 point mutation was identified which abrogated water and CO2 permeability and extracellular CO2 regulation of SLAC1 activity in Xenopus oocytes. These findings identify the CO2-permeable PIP2;1 aquaporin as key interactor of carbonic anhydrases, show functional reconstitution of extracellular CO2 signaling to ion channel regulation and implicate SLAC1 as a bicarbonate-responsive protein in CO2 regulation of S-type anion channels.