Calcium-dependent protein kinase CDPK16 phosphorylates serine-856 of glutamate receptor-like GLR3.6 protein leading to salt-responsive root growth in Arabidopsis.

Calcium-permeable channels in the plasma membrane play vital roles in plant growth, development, and response to environmental stimuli. Arabidopsis possesses 20 glutamate receptor-like proteins that share similarities with animal ionotropic glutamate receptors and mediate Ca influx in plants. Calcium-dependent protein kinases (CDPKs) phosphorylate serine (Ser)-860 of glutamate receptor-like (GLR)3.

Impacts of Mn, Fe, and Oxidative Stressors on MnSOD Activation by AtMTM1 and AtMTM2 in .

It has been reported that the mitochondrial carrier family proteins of AtMTM1 and AtMTM2 are necessary for manganese superoxide dismutase (MnSOD) activation in , and are responsive to methyl viologen (MV)-induced oxidative stress. In this study, we showed that MnSOD activity was enhanced specifically by Mn treatments. By using -overexpressing and -knockdown mutant plants treated with the widely used oxidative stressors including MV, NaCl, HO, and tert-butyl hydroperoxide (t-BH), we revealed that MnSOD was crucial for root-growth control and superoxide scavenging ability.

Guard Cell-Specific Pectin METHYLESTERASE53 Is Required for Abscisic Acid-Mediated Stomatal Function and Heat Response in .

Pectin is a major component of the plant cell wall, forming a network that contributes to cell wall integrity and flexibility. Pectin methylesterase (PME) catalyzes the removal of methylester groups from the homogalacturonan backbone, the most abundant pectic polymer, and contributes to intercellular adhesion during plant development and different environmental stimuli stress. In this study, we identified and characterized an Arabidopsis type-II , , which encodes a cell wall deposited protein and may be involved in the stomatal lineage pathway and stomatal functions.

Significance of AtMTM1 and AtMTM2 for Mitochondrial MnSOD Activation in .

The manganese (Mn) tracking factor for mitochondrial Mn superoxide dismutase (MnSOD) has been annotated as yMTM1 in yeast, which belongs to the mitochondrial carrier family. We confirmed that AtMTM1 and AtMTM2 are functional homologs of yMTM1 as they can revive yeast MnSOD activity in -mutant cells. Transient expression of AtMnSOD-3xFLAG in the and -double mutant protoplasts confirmed that AtMTM1 and AtMTM2 are required for AtMnSOD activation.

Coordination of ABA and Chaperone Signaling in Plant Stress Responses.

The abscisic acid (ABA) and chaperone signaling pathways are the central regulators of plant stress defense. Despite their significance and potential overlap, these systems have been described separately. In this review, we summarize information about mechanisms by which the ABA and chaperone signaling pathways might be coregulated.

Pectin Methylesterases: Cell Wall Remodeling Proteins Are Required for Plant Response to Heat Stress.

Heat stress (HS) is expected to be of increasing worldwide concern in the near future, especially with regard to crop yield and quality as a consequence of rising or varying temperatures as a result of global climate change. HS response (HSR) is a highly conserved mechanism among different organisms but shows remarkable complexity and unique features in plants. The transcriptional regulation of HSR is controlled by HS transcription factors (HSFs) which allow the activation of HS-responsive genes, among which HS proteins (HSPs) are best characterized.

Using Silicon Polymer Impression Technique and Scanning Electron Microscopy to Measure Stomatal Aperture, Morphology, and Density.

The number of stomata on leaves can be affected by intrinsic development programming and various environmental factors, in addition the control of stomatal apertures is extremely important for the plant stress response. In response to elevated temperatures, transpiration occurs through the stomatal apertures, allowing the leaf to cool through water evaporation. As such, monitoring of stomata behavior to elevated temperatures remains as an important area of research.

Pectin methylesterase is required for guard cell function in response to heat.

Pectin is an important cell wall polysaccharide required for cellular adhesion, extension, and plant growth. The pectic methylesterification status of guard cell walls influences the movement of stomata in response to different stimuli. Pectin methylesterase (PME) has a profound effect on cell wall modification, especially on the degree of pectic methylesterification during heat response.

PECTIN METHYLESTERASE34 Contributes to Heat Tolerance through Its Role in Promoting Stomatal Movement.

Pectin, a major component of the primary cell wall, is synthesized in the Golgi apparatus and exported to the cell wall in a highly methylesterified form, then is partially demethylesterified by pectin methylesterases (PMEs; EC 3.1.1.

The Heat Stress Factor HSFA6b Connects ABA Signaling and ABA-Mediated Heat Responses.

Heat stress response (HSR) is a conserved mechanism developed to increase the expression of heat shock proteins (HSPs) via a heat shock factor (HSF)-dependent mechanism. Signaling by the stress phytohormone abscisic acid (ABA) is involved in acquired thermotolerance as well. Analysis of Arabidopsis (Arabidopsis thaliana) microarray databases revealed that the expression of HSFA6b, a class A HSF, extensively increased with salinity, osmotic, and cold stresses, but not heat.

Regulation of transcription of nucleotide-binding leucine-rich repeat-encoding genes SNC1 and RPP4 via H3K4 trimethylation.

Plant nucleotide-binding leucine-rich repeat (NB-LRR) proteins serve as intracellular sensors to detect pathogen effectors and trigger immune responses. Transcription of the NB-LRR-encoding Resistance (R) genes needs to be tightly controlled to avoid inappropriate defense activation. How the expression of the NB-LRR R genes is regulated is poorly understood.

Chaperonin 20 might be an iron chaperone for superoxide dismutase in activating iron superoxide dismutase (FeSOD).

Activation of Cu/Zn superoxide dismutases (CuZnSODs) is aided by Cu incorporation and disulfide isomerization by Cu chaperone of SOD (CCS). As well, an Fe-S cluster scaffold protein, ISU, might alter the incorporation of Fe or Mn into yeast MnSOD (ySOD2), thus leading to active or inactive ySOD2. However, metallochaperones involved in the activation of FeSODs are unknown.

Oscillation regulation of Ca2+ /calmodulin and heat-stress related genes in response to heat stress in rice (Oryza sativa L.).

The Ca ( 2+) /calmodulin (CaM) signaling pathway mediates the heat stress (HS) response and acquisition of thermotolerance in plants. We showed that the rice CaM1-1 isoform can interpret a Ca ( 2+) signature difference in amplitude, frequency, and temporal-spatial properties in regulating transcription of nucleoplasmic small heat-shock protein gene (sHSPC/N) during HS. Ca ( 2+) and A23187 treatments under HS generated an intense and sustained increase in [Ca ( 2+) ]cyt and accelerated the expression of CaM1-1 and sHSPC/N genes, which suggests that HS-induced apoplastic Ca ( 2+) influx was responsible for the [Ca ( 2+) ]cyt transient and downstream HS signaling.

Models for the mechanism for activating copper-zinc superoxide dismutase in the absence of the CCS Cu chaperone in Arabidopsis.

Copper-zinc superoxide dismutase (CuZnSOD; CSD) is an important antioxidant enzyme for oxidative stress protection. To date, two activation pathways have been identified in many species. One requiring the CCS, Cu chaperone for SOD, to insert Cu and activate CSD (referred to as CCS-dependent pathway), and the other works independently of CCS (referred to as CCS-independent pathway).

Heat shock-induced biphasic Ca(2+) signature and OsCaM1-1 nuclear localization mediate downstream signalling in acquisition of thermotolerance in rice (Oryza sativa L.).

We investigated heat shock (HS)-triggered Ca(2+) signalling transduced by a Ca(2+) sensor, calmodulin (CaM), linked to early transcriptome changes of HS-responsive genes in rice. We observed a biphasic [Ca(2+) ](cyt) signature in root cells that was distinct from that in epicotyl and leaf cells, which showed a monophasic response after HS. Treatment with Ca(2+) and A23187 generated an intense and sustained increase in [Ca(2+) ](cyt) in response to HS.

Copper chaperone-dependent and -independent activation of three copper-zinc superoxide dismutase homologs localized in different cellular compartments in Arabidopsis.

Superoxide dismutases (SODs) are important antioxidant enzymes that catalyze the disproportionation of superoxide anion to oxygen and hydrogen peroxide to guard cells against superoxide toxicity. The major pathway for activation of copper/zinc SOD (CSD) involves a copper chaperone for SOD (CCS) and an additional minor CCS-independent pathway reported in mammals. We characterized the CCS-dependent and -independent activation pathways for three CSDs localized in different cellular compartments in Arabidopsis (Arabidopsis thaliana).

Characterization of copper/zinc and manganese superoxide dismutase in green bamboo (Bambusa oldhamii): Cloning, expression and regulation.

Bamboo is distinguished by its rapid growth, for growth more than 100 cm per day. Because of the rapid growth, tissues have significant ATP requirements, which results in intense reduction of oxygen and thus oxidative stress. For this reason, bamboo may have a special and efficient scavenger system to release the stress during fast cell division and elongation.

Heat shock-triggered Ca2+ mobilization accompanied by pectin methylesterase activity and cytosolic Ca2+ oscillation are crucial for plant thermotolerance.

Apoplastic Ca(2+) concentration controls membrane permeability, cell wall stabilization, and cell integrity; however, little is known about its role in thermotolerance in plants. Here, we report that the acquired thermotolerance of etiolated rice seedlings (Oryza sativa) was abolished by an exogenously supplied Ca(2+) chelator, EGTA, related to increased cellular content leakage during heat shock (HS) treatment. Thermotolerance was restored by the addition of Ca(2+) during EGTA incubation.

AtHSBP functions in seed development and the motif is required for subcellular localization and interaction with AtHSFs.

In Arabidopsis thaliana, heat shock factor binding protein (AtHSBP) is a negative regulator of the heat shock response (HSR), and defective AtHSBP leads to seed abortion. We found that the wild-type and AtHSBP-knockout plants did not differ in ovule phenotypes at flower position 3, which indicates that the seed abortion occurs after fertilization and during embryogenesis. The conserved residues of the hydrophobic heptad repeat (HR) domains in AtHSBP were mutated and examined for their subcellular localization and interacting ability with heat shock factors (AtHSFs).

Recovery of heat shock-triggered released apoplastic Ca2+ accompanied by pectin methylesterase activity is required for thermotolerance in soybean seedlings.

Synthesis of heat shock proteins (HSPs) in response to heat shock (HS) is essential for thermotolerance. The effect of a Ca(2+) chelator, EGTA, was investigated before a lethal HS treatment in soybean (Glycine max) seedlings with acquired thermotolerance induced by preheating. Such seedlings became non-thermotolerant with EGTA treatment.

Cytosol-localized heat shock factor-binding protein, AtHSBP, functions as a negative regulator of heat shock response by translocation to the nucleus and is required for seed development in Arabidopsis.

Heat shock response (HSR) is a universal mechanism in all organisms. It is under tight regulation by heat shock factors (HSFs) and heat shock proteins (HSPs) after heat shock (HS) to prevent stress damage. On the attenuation of HSR, HSP70 and HSF Binding Protein1 (HSBP1) interact with HSF1 and thus dissociate trimeric HSF1 into an inert monomeric form in humans.

Regulation of floral organ abscission in Arabidopsis thaliana.

Abscission is a developmental program that results in the active shedding of infected or nonfunctional organs from a plant body. Here, we establish a signaling pathway that controls abscission in Arabidopsis thaliana from ligand, to receptors, to downstream effectors. Loss of function mutations in Inflorescence Deficient in Abscission (IDA), which encodes a predicted secreted small protein, the receptor-like protein kinases HAESA (HAE) and HAESA-like 2 (HSL2), the Mitogen-Activated Protein Kinase Kinase 4 (MKK4) and MKK5, and a dominant-negative form of Mitogen-Activated Protein Kinase 6 (MPK6) in a mpk3 mutant background all have abscission-defective phenotypes.

A copper chaperone for superoxide dismutase that confers three types of copper/zinc superoxide dismutase activity in Arabidopsis.

The copper chaperone for superoxide dismutase (CCS) has been identified as a key factor integrating copper into copper/zinc superoxide dismutase (CuZnSOD) in yeast (Saccharomyces cerevisiae) and mammals. In Arabidopsis (Arabidopsis thaliana), only one putative CCS gene (AtCCS, At1g12520) has been identified. The predicted AtCCS polypeptide contains three distinct domains: a central domain, flanked by an ATX1-like domain, and a C-terminal domain.

Characterization of the genomic structures and selective expression profiles of nine class I small heat shock protein genes clustered on two chromosomes in rice (Oryza sativa L.).

The cytosolic class I small heat shock proteins (sHSP-CI) represent the most abundant sHSP in plants. Here, we report the characterization and the expression profile of nine members of the sHSP-CI gene family in rice (Oryza sativa Tainung No.67), of which Oshsp16.

Azetidine-induced accumulation of class I small heat shock proteins in the soluble fraction provides thermotolerance in soybean seedlings.

Accumulation of class I small heat shock proteins (sHSPs) is induced by the proline analog, azetidine-2-carboxylic acid (Aze) in soybean seedlings to a level similar to that induced by exposure to 40 degrees C. However, only the treatment with 10 mM Aze for 6 h and subsequently with 10 mM proline for 24 h protected the seedlings from damage during subsequent exposure to 45 degrees C as assessed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. A chaperone activity assay showed that the purified class I sHSPs induced by Aze were functional in vitro and protected proteins from thermal denaturation.