A role for ethylene signaling and biosynthesis in regulating and accelerating CO - and abscisic acid-mediated stomatal movements in Arabidopsis.

Little is known about long-distance mesophyll-driven signals that regulate stomatal conductance. Soluble and/or vapor-phase molecules have been proposed. In this study, the involvement of the gaseous signal ethylene in the modulation of stomatal conductance in Arabidopsis thaliana by CO /abscisic acid (ABA) was examined.

Stomatal CO/bicarbonate sensor consists of two interacting protein kinases, Raf-like HT1 and non-kinase-activity requiring MPK12/MPK4.

The continuing rise in the atmospheric carbon dioxide (CO) concentration causes stomatal closing, thus critically affecting transpirational water loss, photosynthesis, and plant growth. However, the primary CO sensor remains unknown. Here, we show that elevated CO triggers interaction of the MAP kinases MPK4/MPK12 with the HT1 protein kinase, thus inhibiting HT1 kinase activity.