ALMT12 interacts with and inhibits SLAC1 to modulate stomatal movements and enhance plant biomass.

Stomata are pores that control carbon dioxide (CO2) and water exchange by modulating their aperture in response to different environmental and internal signals. The Slow-type SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1) and Rapid-type ALUMINUM-ACTIVATED MALATE TRANSPORTER 12 (ALMT12) anion channels mediate anion efflux in guard cells to promote stomatal closure. These channels were previously thought to function as 2 independent anion-permeable pores differing in their activation kinetics, voltage dependence, and anion selectivity. In this study, we found that ALMT12 interacts with and represses SLAC1 anion permeability in Xenopus oocytes and Arabidopsis (Arabidopsis thaliana) guard cells. This channel-channel regulatory mechanism modulates stomatal movements under high CO2 conditions and enhances plant biomass.