MPK12 in stomatal CO signaling: function beyond its kinase activity.

Protein phosphorylation is a major molecular switch involved in the regulation of stomatal opening and closure. Previous research defined interaction between MAP kinase 12 and Raf-like kinase HT1 as a required step for stomatal movements caused by changes in CO concentration. However, whether MPK12 kinase activity is required for regulation of CO -induced stomatal responses warrants in-depth investigation.

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.

Mitogen-activated protein kinases MPK4 and MPK12 are key components mediating CO -induced stomatal movements.

Respiration in leaves and the continued elevation in the atmospheric CO concentration cause CO -mediated reduction in stomatal pore apertures. Several mutants have been isolated for which stomatal responses to both abscisic acid (ABA) and CO are simultaneously defective. However, there are only few mutations that impair the stomatal response to elevated CO , but not to ABA.

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.

Fluorescent protein-based reporters of the actin cytoskeleton in living plant cells: fluorophore variant, actin binding domain, and promoter considerations.

Genetically encoded filamentous actin (F-actin) reporters designed based on fluorescent protein fusions to F-actin binding domains of actin regulatory proteins have emerged as powerful tools to decipher the role of the actin cytoskeleton in plant growth and development. However, these probes could interfere with the function of endogenous actin binding proteins and in turn impact actin organization and plant growth. We therefore surveyed F-actin labeling and compared organ growth in Arabidopsis thaliana lines expressing a variety of F-actin markers.

Overexpression of Fatty Acid Amide Hydrolase Induces Early Flowering in Arabidopsis thaliana.

N-acylethanolamines (NAEs) are bioactive lipids derived from the hydrolysis of the membrane phospholipid N-acylphosphatidylethanolamine (NAPE). In animal systems this reaction is part of the "endocannabinoid" signaling pathway, which regulates a variety of physiological processes. The signaling function of NAE is terminated by fatty acid amide hydrolase (FAAH), which hydrolyzes NAE to ethanolamine and free fatty acid.

Ozone-triggered rapid stomatal response involves the production of reactive oxygen species, and is controlled by SLAC1 and OST1.

The air pollutant ozone can be used as a tool to unravel in planta processes induced by reactive oxygen species (ROS). Here, we have utilized ozone to study ROS-dependent stomatal signaling. We show that the ozone-triggered rapid transient decrease (RTD) in stomatal conductance coincided with a burst of ROS in guard cells.

Overexpression of a fatty acid amide hydrolase compromises innate immunity in Arabidopsis.

N-acylethanolamines are a group of lipid mediators that accumulate under a variety of neurological and pathological conditions in mammals. N-acylethanolamine signaling is terminated by the action of diverse hydrolases, among which fatty acid amide hydrolase (FAAH) has been well characterized. Here, we show that transgenic Arabidopsis lines overexpressing an AtFAAH are more susceptible to the bacterial pathogens Pseudomonas syringae pv.

Improved imaging of actin filaments in transgenic Arabidopsis plants expressing a green fluorescent protein fusion to the C- and N-termini of the fimbrin actin-binding domain 2.

The role of the actin cytoskeleton in plant development is intimately linked to its dynamic behavior. Therefore it is essential to continue refining methods for studying actin organization in living plant cells. The discovery of green fluorescent protein (GFP) has popularized the use of translational fusions of GFP with actin filament (F-actin) side-binding proteins to visualize in vivo actin organization in plants.

Differential expansion and expression of alpha- and beta-tubulin gene families in Populus.

Microtubule organization is intimately associated with cellulose microfibril deposition, central to plant secondary cell wall development. We have determined that a relatively large suite of eight alpha-TUBULIN (TUA) and 20 beta-TUBULIN (TUB) genes is expressed in the woody perennial Populus. A number of features, including gene number, alpha:beta gene representation, amino acid changes at the C terminus, and transcript abundance in wood-forming tissue, distinguish the Populus tubulin suite from that of Arabidopsis thaliana.

N-Acylethanolamine metabolism interacts with abscisic acid signaling in Arabidopsis thaliana seedlings.

N-Acylethanolamines (NAEs) are bioactive acylamides that are present in a wide range of organisms. In plants, NAEs are generally elevated in desiccated seeds, suggesting that they may play a role in seed physiology. NAE and abscisic acid (ABA) levels were depleted during seed germination, and both metabolites inhibited the growth of Arabidopsis thaliana seedlings within a similar developmental window.

Organization and function of the actin cytoskeleton in developing root cells.

The actin cytoskeleton is a highly dynamic structure, which mediates various cellular functions in large part through accessory proteins that tilt the balance between monomeric G-actin and filamentous actin (F-actin) or by facilitating interactions between actin and the plasma membrane, microtubules, and other organelles. Roots have become an attractive model to study actin in plant development because of their simple anatomy and accessibility of some root cell types such as root hairs for microscopic analyses. Roots also exhibit a remarkable developmental plasticity and possess a delicate sensory system that is easily manipulated, so that one can design experiments addressing a range of important biological questions.

Manipulation of Arabidopsis fatty acid amide hydrolase expression modifies plant growth and sensitivity to N-acylethanolamines.

In vertebrates, the endocannabinoid signaling pathway is an important lipid regulatory pathway that modulates a variety of physiological and behavioral processes. N-Acylethanolamines (NAEs) comprise a group of fatty acid derivatives that function within this pathway, and their signaling activity is terminated by an enzyme called fatty acid amide hydrolase (FAAH), which hydrolyzes NAEs to ethanolamine and their corresponding free fatty acids. Bioinformatic approaches led to the identification of plant homologues of FAAH that are capable of hydrolyzing NAEs in vitro.

Differential effects of two phospholipase D inhibitors, 1-butanol and N-acylethanolamine, on in vivo cytoskeletal organization and Arabidopsis seedling growth.

Plant development is regulated by numerous chemicals derived from a multitude of metabolic pathways. However, we know very little about the biological effects and functions of many of these metabolites in the cell. N-Acylethanolamines (NAEs) are a group of lipid mediators that play important roles in mammalian physiology.

The potato virus X TGBp2 movement protein associates with endoplasmic reticulum-derived vesicles during virus infection.

The green fluorescent protein (GFP) gene was fused to the potato virus X (PVX) TGBp2 gene, inserted into either the PVX infectious clone or pRTL2 plasmids, and used to study protein subcellular targeting. In protoplasts and plants inoculated with PVX-GFP:TGBp2 or transfected with pRTL2-GFP:TGBp2, fluorescence was mainly in vesicles and the endoplasmic reticulum (ER). During late stages of virus infection, fluorescence became increasingly cytosolic and nuclear.

Green fluorescent protein fusions to Arabidopsis fimbrin 1 for spatio-temporal imaging of F-actin dynamics in roots.

The visualization of green fluorescent protein (GFP) fusions with microtubule or actin filament (F-actin) binding proteins has provided new insights into the function of the cytoskeleton during plant development. For studies on actin, GFP fusions to talin have been the most generally used reporters. Although GFP-Talin has allowed in vivo F-actin imaging in a variety of plant cells, its utility in monitoring F-actin in stably transformed plants is limited particularly in developing roots where interesting actin dependent cell processes are occurring.

The promotion of gravitropism in Arabidopsis roots upon actin disruption is coupled with the extended alkalinization of the columella cytoplasm and a persistent lateral auxin gradient.

The actin cytoskeleton has been implicated in regulating plant gravitropism. However, its precise role in this process remains uncertain. We have shown previously that disruption of the actin cytoskeleton with Latrunculin B (Lat B) strongly promoted gravitropism in maize roots.

Expression of a glycine decarboxylase complex H-protein in non-photosynthetic tissues of Populus tremuloides.

The Gly decarboxylase complex (GDC) is abundant in mitochondria of C3 leaves and functions in photorespiratory carbon recovery. However, expression of GDC component proteins has generally been less evident in non-green tissues. Here we report an aspen (Populus tremuloides Michx.