Rapid depolarization and cytosolic calcium increase go hand-in-hand in mesophyll cells' ozone response.

Plant stress signalling involves bursts of reactive oxygen species (ROS), which can be mimicked by the application of acute pulses of ozone. Such ozone-pulses inhibit photosynthesis and trigger stomatal closure in a few minutes, but the signalling that underlies these responses remains largely unknown. We measured changes in Arabidopsis thaliana gas exchange after treatment with acute pulses of ozone and set up a system for simultaneous measurement of membrane potential and cytosolic calcium with the fluorescent reporter R-GECO1.

Combined action of guard cell plasma membrane rapid- and slow-type anion channels in stomatal regulation.

Initiation of stomatal closure by various stimuli requires activation of guard cell plasma membrane anion channels, which are defined as rapid (R)- and slow (S)-type. The single-gene loss-of-function mutants of these proteins are well characterized. However, the impact of suppressing both the S- and R-type channels has not been studied.

A role for calcium-dependent protein kinases in differential CO - and ABA-controlled stomatal closing and low CO -induced stomatal opening in Arabidopsis.

Low concentrations of CO cause stomatal opening, whereas [CO ] elevation leads to stomatal closure. Classical studies have suggested a role for Ca and protein phosphorylation in CO -induced stomatal closing. Calcium-dependent protein kinases (CPKs) and calcineurin-B-like proteins (CBLs) can sense and translate cytosolic elevation of the second messenger Ca into specific phosphorylation events.

Calcium signals in guard cells enhance the efficiency by which abscisic acid triggers stomatal closure.

During drought, abscisic acid (ABA) induces closure of stomata via a signaling pathway that involves the calcium (Ca )-independent protein kinase OST1, as well as Ca -dependent protein kinases. However, the interconnection between OST1 and Ca signaling in ABA-induced stomatal closure has not been fully resolved. ABA-induced Ca signals were monitored in intact Arabidopsis leaves, which express the ratiometric Ca reporter R-GECO1-mTurquoise and the Ca -dependent activation of S-type anion channels was recorded with intracellular double-barreled microelectrodes.

Rapid Responses to Abiotic Stress: Priming the Landscape for the Signal Transduction Network.

Plants grow and reproduce within a highly dynamic environment that can see abrupt changes in conditions, such as light intensity, temperature, humidity, or interactions with biotic agents. Recent studies revealed that plants can respond within seconds to some of these conditions, engaging many different metabolic and molecular networks, as well as rapidly altering their stomatal aperture. Some of these rapid responses were further shown to propagate throughout the entire plant via waves of reactive oxygen species (ROS) and Ca that are possibly mediated through the plant vascular system.

Natural Variation in Arabidopsis Cvi-0 Accession Reveals an Important Role of MPK12 in Guard Cell CO2 Signaling.

Plant gas exchange is regulated by guard cells that form stomatal pores. Stomatal adjustments are crucial for plant survival; they regulate uptake of CO2 for photosynthesis, loss of water, and entrance of air pollutants such as ozone. We mapped ozone hypersensitivity, more open stomata, and stomatal CO2-insensitivity phenotypes of the Arabidopsis thaliana accession Cvi-0 to a single amino acid substitution in MITOGEN-ACTIVATED PROTEIN (MAP) KINASE 12 (MPK12).

A Dominant Mutation in the HT1 Kinase Uncovers Roles of MAP Kinases and GHR1 in CO2-Induced Stomatal Closure.

Activation of the guard cell S-type anion channel SLAC1 is important for stomatal closure in response to diverse stimuli, including elevated CO The majority of known SLAC1 activation mechanisms depend on abscisic acid (ABA) signaling. Several lines of evidence point to a parallel ABA-independent mechanism of CO-induced stomatal regulation; however, molecular details of this pathway remain scarce. Here, we isolated a dominant mutation in the protein kinase HIGH LEAF TEMPERATURE1 (HT1), an essential regulator of stomatal CO responses, in an ozone sensitivity screen of Arabidopsis thaliana The mutation caused constitutively open stomata and impaired stomatal CO responses.

Guard cell SLAC1-type anion channels mediate flagellin-induced stomatal closure.

During infection plants recognize microbe-associated molecular patterns (MAMPs), and this leads to stomatal closure. This study analyzes the molecular mechanisms underlying this MAMP response and its interrelation with ABA signaling. Stomata in intact Arabidopsis thaliana plants were stimulated with the bacterial MAMP flg22, or the stress hormone ABA, by using the noninvasive nanoinfusion technique.

Closing gaps: linking elements that control stomatal movement.

Stomata are an attractive experimental system in plant biology, because the responses of guard cells to environmental signals can be directly linked to changes in the aperture of stomatal pores. In this review, the mechanics of stomatal movement are discussed in relation to ion transport in guard cells. Emphasis is placed on the ion pumps, transporters, and channels in the plasma membrane, as well as in the vacuolar membrane.