The PATROL1 function in roots contributes to the increase in shoot biomass.

PATOL1 contributes to increasing biomass not only by effective stomatal movement but also by root meristematic activity. PATROL1 (PROTON ATPase TRANSLOCATION CONTROL 1), a protein with a MUN domain, is involved in the intercellular trafficking of AHA1 H-ATPase to the plasma membrane in guard cells. This allows for larger stomatal opening and more efficient photosynthesis, leading to increased biomass.

PECT1, a rate-limiting enzyme in phosphatidylethanolamine biosynthesis, is involved in the regulation of stomatal movement in Arabidopsis.

An Arabidopsis mutant displaying impaired stomatal responses to CO , cdi4, was isolated by a leaf thermal imaging screening. The mutated gene PECT1 encodes CTP:phosphorylethanolamine cytidylyltransferase. The cdi4 exhibited a decrease in phosphatidylethanolamine levels and a defect in light-induced stomatal opening as well as low-CO -induced stomatal opening.

Regulation of ppGpp Synthesis and Its Impact on Chloroplast Biogenesis during Early Leaf Development in Rice.

Guanosine tetraphosphate (ppGpp) is known as an alarmone that mediates bacterial stress responses. In plants, ppGpp is synthesized in chloroplasts from GTP and ATP and functions as a regulator of chloroplast gene expression to affect photosynthesis and plant growth. This observation indicates that ppGpp metabolism is closely related to chloroplast function, but the regulation of ppGpp and its role in chloroplast differentiation are not well understood.

Two independent cis-acting elements are required for the guard cell-specific expression of SCAP1, which is essential for late stomatal development.

Regulating the stomatal aperture to adapt to environmental changes is critical for plants as stomatal guard cells are responsible for gas exchange between plants and the atmosphere. We previously showed that a plant-specific DNA-binding with one finger (Dof)-type transcription factor, SCAP1, functions as a key regulator in the final stages of guard cell differentiation. In the present study, we performed deletion and gain-of-function analyses with the 5' flanking region of SCAP1 to identify the regulatory region controlling the guard cell-specific expression of SCAP1.

Cuticle permeability is an important parameter for the trade-off strategy between drought tolerance and CO uptake in land plants.

To protect against water loss, land plants have developed the cuticle; however, the cuticle strongly restricts CO uptake for photosynthesis. Controlling this trade-off relationship is an important strategy for plant survival, but the extent to which the changes in cuticle affects this relationship is not clear. To evaluate this, we measured CO assimilation rate and transpiration rate together in the mutant (), which exhibited marked evaporative water loss due to an increased cuticle permeability caused by a new allele of ().

Enhanced NRT1.1/NPF6.3 expression in shoots improves growth under nitrogen deficiency stress in Arabidopsis.

Identification of genes and their alleles capable of improving plant growth under low nitrogen (N) conditions is key for developing sustainable agriculture. Here, we show that a genome-wide association study using Arabidopsis thaliana accessions suggested an association between different magnitudes of N deficiency responses and diversity in NRT1.1/NPF6.

The Endoplasmic Reticulum Pathway for Membrane Lipid Synthesis Has a Significant Contribution toward Shoot Removal-Induced Root Chloroplast Development in Arabidopsis.

Chloroplast lipids are synthesized via two distinct pathways: the plastidic pathway and endoplasmic reticulum (ER) pathway. We previously reported that the contribution of the two pathways toward chloroplast development is different between mesophyll cells and guard cells in Arabidopsis leaf tissues and that the ER pathway plays a major role in guard cell chloroplast development. However, little is known about the contribution of the two pathways toward chloroplast development in other tissue cells, and in this study, we focused on root cells.

Increased Cuticle Permeability Caused by a New Allele of - Enhances CO Uptake.

Carbon dioxide (CO) is an essential substrate for photosynthesis in plants. CO is absorbed mainly through the stomata in land plants because all other aerial surfaces are covered by a waxy layer called the cuticle. The cuticle is an important barrier that protects against extreme water loss; however, this anaerobic layer limits CO uptake.

Improved stomatal opening enhances photosynthetic rate and biomass production in fluctuating light.

It has been reported that stomatal conductance often limits the steady-state photosynthetic rate. On the other hand, the stomatal limitation of photosynthesis in fluctuating light remains largely unknown, although in nature light fluctuates due to changes in sun position, cloud cover, and the overshadowing canopy. In this study, we analysed three mutant lines of Arabidopsis with increased stomatal conductance to examine to what extent stomatal opening limits photosynthesis in fluctuating light.

Increased stomatal conductance induces rapid changes to photosynthetic rate in response to naturally fluctuating light conditions in rice.

A close correlation between stomatal conductance and the steady-state photosynthetic rate has been observed for diverse plant species under various environmental conditions. However, it remains unclear whether stomatal conductance is a major limiting factor for the photosynthetic rate under naturally fluctuating light conditions. We analysed a SLAC1 knockout rice line to examine the role of stomatal conductance in photosynthetic responses to fluctuating light.

A phytochrome-B-mediated regulatory mechanism of phosphorus acquisition.

Phosphorus (P) is a key macronutrient whose availability has a profound effect on plant growth and productivity. The understanding of the mechanism underlying P availability-responsive P acquisition has expanded largely in the past decade; however, effects of other environmental factors on P acquisition and utilization remain elusive. Here, by imaging natural variation in phosphate uptake in 200 natural accessions of Arabidopsis, we identify two accessions with low phosphate uptake activity, Lm-2 and CSHL-5.

Involvement of S-type anion channels in disease resistance against an oomycete pathogen in Arabidopsis seedlings.

Pharmacological indications suggest that anion channel-mediated plasma membrane (PM) anion efflux is crucial in early defense signaling to induce immune responses and programmed cell death in plants. Arabidopsis SLAC1, an S-type anion channel required for stomatal closure, is involved in cryptogein-induced PM Cl efflux to positively modulate the activation of other ion fluxes, production of reactive oxygen species and a wide range of defense responses including hypersensitive cell death in tobacco BY-2 cells. We here analyzed disease resistance against several pathogens in multiple mutants of the SLAC/SLAH channels of Arabidopsis.

Eukaryotic lipid metabolic pathway is essential for functional chloroplasts and CO and light responses in guard cells.

Stomatal guard cells develop unique chloroplasts in land plant species. However, the developmental mechanisms and function of chloroplasts in guard cells remain unclear. In seed plants, chloroplast membrane lipids are synthesized via two pathways: the prokaryotic and eukaryotic pathways.

Structure-Based Chemical Design of Abscisic Acid Antagonists That Block PYL-PP2C Receptor Interactions.

In Arabidopsis, signaling of the stress hormone abscisic acid (ABA) is mediated by PYR/PYL/RCAR receptors (PYLs), which bind to and inhibit group-A protein phosphatases 2C (PP2Cs), the negative regulators of ABA. X-ray structures of several PYL-ABA and PYL-ABA-PP2C complexes have revealed that a conserved tryptophan in PP2Cs is inserted into a small tunnel adjacent to the C4' of ABA in the PYL-ABA complex and plays a crucial role in the formation and stabilization of the PYL-ABA-PP2C complex. Here, 4'-modified ABA analogues were designed to prevent the insertion of the tryptophan into the tunnel adjacent to the C4' of ABA in these complexes.

Contribution of the S-type Anion Channel SLAC1 to Stomatal Control and Its Dependence on Developmental Stage in Rice.

Rice production depends on water availability and carbon fixation by photosynthesis. Therefore, optimal control of stomata, which regulate leaf transpiration and CO2 absorption, is important for high productivity. SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1) is an S-type anion channel protein that controls stomatal closure in response to elevated CO2.

Differential Effects of Phosphatidylinositol 4-Kinase (PI4K) and 3-Kinase (PI3K) Inhibitors on Stomatal Responses to Environmental Signals.

Specific cellular components including products of phosphatidylinositol (PI) metabolism play an important role as signaling molecules in stomatal responses to environmental signals. In this study, pharmacological inhibitors of a set of cellular components, including PI4-kinase (PI4K) and PI3K, were used to investigate stomatal closure in response to CO, darkness, and abscisic acid (ABA). Treatment with PAO, a specific inhibitor of PI4K, specifically inhibited the stomatal response to CO compared with that to darkness and ABA.

Dominant and recessive mutations in the Raf-like kinase HT1 gene completely disrupt stomatal responses to CO2 in Arabidopsis.

HT1 (HIGH LEAF TEMPERATURE 1) is the first component associated with changes in stomatal aperture in response to CO2 to be isolated by forward genetic screening. The HT1 gene encodes a protein kinase expressed mainly in guard cells. The loss-of-function ht1-1 and ht1-2 mutants in Arabidopsis thaliana have CO2-hypersensitive stomatal closure with concomitant reductions in their kinase activities in vitro In addition to these mutants, in this study we isolate or obtaine five new ht1 alleles (ht1-3, ht1-4, ht1-5, ht1-6, and ht1-7).

The Transmembrane Region of Guard Cell SLAC1 Channels Perceives CO2 Signals via an ABA-Independent Pathway in Arabidopsis.

The guard cell S-type anion channel, SLOW ANION CHANNEL1 (SLAC1), a key component in the control of stomatal movements, is activated in response to CO2 and abscisic acid (ABA). Several amino acids existing in the N-terminal region of SLAC1 are involved in regulating its activity via phosphorylation in the ABA response. However, little is known about sites involved in CO2 signal perception.

CO2 Sensing and CO2 Regulation of Stomatal Conductance: Advances and Open Questions.

Guard cells form epidermal stomatal gas-exchange valves in plants and regulate the aperture of stomatal pores in response to changes in the carbon dioxide (CO2) concentration ([CO2]) in leaves. Moreover, the development of stomata is repressed by elevated CO2 in diverse plant species. Evidence suggests that plants can sense [CO2] changes via guard cells and via mesophyll tissues in mediating stomatal movements.

The HT1 protein kinase is essential for red light-induced stomatal opening and genetically interacts with OST1 in red light and CO2 -induced stomatal movement responses.

The question of whether red light-induced stomatal opening is mediated by a photosynthesis-derived reduction in intercellular [CO2 ] (Ci ) remains controversial and genetic analyses are needed. The Arabidopsis thaliana protein kinase HIGH TEMPERATURE 1 (HT1) is a negative regulator of [CO2 ]-induced stomatal closing and ht1-2 mutant plants do not show stomatal opening to low [CO2 ]. The protein kinase mutant ost1-3 exhibits slowed stomatal responses to CO2 .

Natural variation in stomatal responses to environmental changes among Arabidopsis thaliana ecotypes.

Stomata are small pores surrounded by guard cells that regulate gas exchange between plants and the atmosphere. Guard cells integrate multiple environmental signals and control the aperture width to ensure appropriate stomatal function for plant survival. Leaf temperature can be used as an indirect indicator of stomatal conductance to environmental signals.

Establishment of the chloroplast genetic system in rice during early leaf development and at low temperatures.

Chloroplasts are the central nodes of the metabolic network in leaf cells of higher plants, and the conversion of proplastids into chloroplasts is tightly coupled to leaf development. During early leaf development, the structure and function of the chloroplasts differ greatly from those in a mature leaf, suggesting the existence of a stage-specific mechanism regulating chloroplast development during this period. Here, we discuss the identification of the genes affected in low temperature-conditional mutants of rice (Oryza sativa).

Diversity in guanosine 3',5'-bisdiphosphate (ppGpp) sensitivity among guanylate kinases of bacteria and plants.

The guanosine 3',5'-bisdiphosphate (ppGpp) signaling system is shared by bacteria and plant chloroplasts, but its role in plants has remained unclear. Here we show that guanylate kinase (GK), a key enzyme in guanine nucleotide biosynthesis that catalyzes the conversion of GMP to GDP, is a target of regulation by ppGpp in chloroplasts of rice, pea, and Arabidopsis. Plants have two distinct types of GK that are localized to organelles (GKpm) or to the cytosol (GKc), with both enzymes being essential for growth and development.

Dynamics and environmental responses of PATROL1 in Arabidopsis subsidiary cells.

The Arabidopsis stomatal complex is composed of a pair of guard cells and surrounding anisocytic subsidiary cells. Subsidiary cells are thought to function as a supplier and receiver of bulk water and ions, and to assist turgor-driven stomatal movement, but the molecular mechanisms are largely unknown. In this work, we studied the dynamic behavior and environmental responses of PATROL1, which has been identified as a translocation factor of the plasma membrane proton pump ATPase (PM H(+)-ATPase) AHA1 in guard cells and subsidiary cells in Arabidopsis thaliana.