Elevated CO2-Induced Responses in Stomata Require ABA and ABA Signaling

Curr Biol. 2015 Oct 19;25(20):2709-16. doi: 10.1016/j.cub.2015.09.013. Epub 2015 Oct 8.

Abstract

An integral part of global environment change is an increase in the atmospheric concentration of CO2 ([CO2]) [1]. Increased [CO2] reduces leaf stomatal apertures and density of stomata that plays out as reductions in evapotranspiration [2-4]. Surprisingly, given the importance of transpiration to the control of terrestrial water fluxes [5] and plant nutrient acquisition [6], we know comparatively little about the molecular components involved in the intracellular signaling pathways by which [CO2] controls stomatal development and function [7]. Here, we report that elevated [CO2]-induced closure and reductions in stomatal density require the generation of reactive oxygen species (ROS), thereby adding a new common element to these signaling pathways. We also show that the PYR/RCAR family of ABA receptors [8, 9] and ABA itself are required in both responses. Using genetic approaches, we show that ABA in guard cells or their precursors is sufficient to mediate the [CO2]-induced stomatal density response. Taken together, our results suggest that stomatal responses to increased [CO2] operate through the intermediacy of ABA. In the case of [CO2]-induced reductions in stomatal aperture, this occurs by accessing the guard cell ABA signaling pathway. In both [CO2]-mediated responses, our data are consistent with a mechanism in which ABA increases the sensitivity of the system to [CO2] but could also be explained by requirement for a CO2-induced increase in ABA biosynthesis specifically in the guard cell lineage. Furthermore, the dependency of stomatal [CO2] signaling on ABA suggests that the ABA pathway is, in evolutionary terms, likely to be ancestral.

Keywords: ABA receptors; ABA signaling; NADPH oxidases; ROS; Rboh genes; [CO(2)] signaling; guard cells; signaling convergence; stomata; stomatal closure; stomatal density.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / metabolism*
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / metabolism*
  • Carbon Dioxide / metabolism*
  • Plant Stomata / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction*

Substances

  • Arabidopsis Proteins
  • Reactive Oxygen Species
  • Carbon Dioxide
  • Abscisic Acid