ABA‐mediated regulation of stomatal density is OST1‐independent

Peer reviewe

Large Scale Detonation Testing: New Findings in the prediction of DDTs at large scales

PresentationA large vapor cloud explosion (VCE) followed by a fire is one of the most dangerous and high-consequence events that can occur at petrochemical facilities. As the size and complexity of facilities increase, designs must consider the potential adverse effects associated with vapor cloud explosions in large congested areas and understand the potential for more devastating deflagration-to-detonation transitions (DDTs) on these facilities. While the likelihood of DDTs is lower than deflagrations, they have been identified in some of the most recent large-scale explosion incidents including: 2005 Buncefield explosion, 2009 San Juan explosion, and 2009 Jaipur event. The consequences of DDTs can be orders of magnitude larger than deflagration because they have the ability to self-propagate outside the region of high congestion/confinement. Hence, it is critical to understand how a facility’s geometry or equipment layout can affect explosion consequences and assist in their mitigation and/or prevention. Due to the inability to predict such devastating phenomena on the large scale, owners and designers cannot evaluate installations for risk of DDTs and provide “inherently safer” layout or mitigation measures to significantly reduce or eliminate such hazards. However, there is a lack of data at the large scale to validate the necessary design tools used to predict the risk of DDT. One of the main goals of this research project is to provide large scale DDT explosion data and validate the tools necessary to predict vapor cloud explosions in early design phase. This paper will present the results of large scale testing being conducted in a newly developed test rig of 50,000 ft3 (1,500 m3 ) gross volume under award Subcontract 12121-6403-01 provided by the Research Partnership to Secure Energy for America (RPSEA). These tests involve evaluation of deflagrations and DDTs involving stoichiometric, lean and rich mixtures, with propane and methane fuels. The effectiveness of mitigation techniques such as solid inhibitors or deluge is evaluated for preventing DDTs

Õpilaste õpistrateegiate arendamine sekkumisprogrammi "Õpime mõttega" toel ja nende vanemaid kaasates

Õpioskuste teadlik arendamine, kus õpetajad lastevanematega õpilasi süsteemselt juhendavad, on distantsõppe kogemuse valguses saanud tähenduslikumaks kui kunagi varem. Uuringu eesmärk oli selgitada, kuidas süsteemsel juhendamisel muutub õpilaste raporteeritud strateegiate kasutamine ja teadlikkus õpistrateegiatest ning kuivõrd õpilaste ja lastevanemate sekkumisjärgsed hinnangud õpistrateegiate tõhususele on seotud. Teadlikkus õpistrateegiatest tähendab õpilaste oskust hinnata strateegiate tõhusust ning teha valikuid tõhusamate strateegiate kasutamise kasuks. Sekkumisuuringul kasutati kolmanda klassi õpilastega programmi "Õpime mõttega". Sekkumisuuringu eel ja järel koguti andmeid õpilaste õpistrateegiate kasutamise ning hinnangute kohta, kasutades õpi- ja enesemääratluspädevuse teste. Lastevanematega korraldati vestlusringid õpistrateegiate teadlikkuse tõstmiseks ja hinnati nende teadlikkuse muutust sekkumise jooksul. Tulemused näitavad, et juba lühiajalise sekkumise tulemusena hindasid õpilased tõhusaid strateegiaid kõrgemalt. Lastevanemate teadlikkus tõhusatest õpistrateegiatest paranes ja ilmnes seos lastevanemate ja laste hinnangutes vähetõhusatele strateegiatele.  Summar

The Role of ENHANCED RESPONSES TO ABA1 (ERA1) in Arabidopsis Stomatal Responses Is Beyond ABA Signaling

Proper stomatal responses are essential for plant function in an altered environment. The core signaling pathway for abscisic acid (ABA)-induced stomatal closure involves perception of the hormone that leads to the activation of guard cell anion channels by the protein kinase OPEN STOMATA1. Several other regulators are suggested to modulate the ABA signaling pathway, including the protein ENHANCED RESPONSE TO ABA1 (ERA1), that encodes the farnesyl transferase beta-subunit. The era1 mutant is hypersensitive to ABA during seed germination and shows a more closed stomata phenotype. Using a genetics approach with the double mutants era1 abi1-1 and era1 ost1, we show that while era1 suppressed the high stomatal conductance of abi1-1 and ost1, the ERA1 function was not required for stomatal closure in response to ABA and environmental factors. Further experiments indicated a role for ERA1 in blue light-induced stomatal opening. In addition, we show that ERA1 function in disease resistance was independent of its role in stomatal regulation. Our results indicate a function for ERA1 in stomatal opening and pathogen immunity.Peer reviewe

The PYL4 A194T mutant uncovers a key role of PYL4-PP2CA interaction for ABA signaling and plant drought resistance

[EN] Because abscisic acid (ABA) is recognized as the critical hormonal regulator of plant stress physiology, elucidating its signaling pathway has raised promise for application in agriculture, for instance through genetic engineering of ABA receptors. PYRABACTIN RESISTANCE1/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS ABA receptors interact with high affinity and inhibit clade A phosphatases type-2C (PP2Cs) in an ABA-dependent manner. We generated an allele library composed of 10,000 mutant clones of Arabidopsis (Arabidopsis thaliana) PYL4 and selected mutations that promoted ABA-independent interaction with PP2CA/ABA-HYPERSENSITIVE3. In vitro protein-protein interaction assays and size exclusion chromatography confirmed that PYL4(A194T) was able to form stable complexes with PP2CA in the absence of ABA, in contrast to PYL4. This interaction did not lead to significant inhibition of PP2CA in the absence of ABA; however, it improved ABA-dependent inhibition of PP2CA. As a result, 35S: PYL4(A194T) plants showed enhanced sensitivity to ABA-mediated inhibition of germination and seedling establishment compared with 35S:PYL4 plants. Additionally, at basal endogenous ABA levels, whole-rosette gas exchange measurements revealed reduced stomatal conductance and enhanced water use efficiency compared with nontransformed or 35S:PYL4 plants and partial up-regulation of two ABA-responsive genes. Finally, 35S:PYL4(A194T) plants showed enhanced drought and dehydration resistance compared with nontransformed or 35S:PYL4 plants. Thus, we describe a novel approach to enhance plant drought resistance through allele library generation and engineering of a PYL4 mutation that enhances interaction with PP2CA.Pizzio Bianchi, GA.; Rodriguez, L.; Antoni-Alandes, R.; Gonzalez Guzman, M.; Yunta, C.; Merilo, E.; Kollist, H.... (2013). The PYL4 A194T mutant uncovers a key role of PYL4-PP2CA interaction for ABA signaling and plant drought resistance. Plant Physiology. 163(1):441-455. doi:10.​1104/​pp.​113.​224162S441455163

The role of Arabidopsis ABA receptors from the PYR/PYL/RCAR family in stomatal acclimation and closure signal integration

Stomata are microscopic pores found on the surfaces of leaves which act to control CO2 uptake and water loss. By integrating information derived from endogenous signals with cues from the surrounding environment the guard cells, that surround the pore, ‘set’ stomatal aperture to suit the prevailing conditions. Much research has concentrated on understanding the rapid intracellular changes that result in immediate changes to stomatal aperture. In this study we look instead at how stomata acclimate to longer timescale variations in their environment. We show that the closure-inducing signals ABA, increased CO2, decreased relative air humidity (RH), and darkness each access a unique gene network made up of clusters (or modules) of common cellular processes. However, within these some gene clusters are shared among all four stimuli. All stimuli modulate the expression of members of the PYR/PYL/RCAR family of ABA receptors, however these are modulated differentially in a stimulus-specific manner. Of the six members of the PYR/PYL/RCAR family expressed in guard cells, PYL2 is sufficient for guard cell ABA-induced responses. Whereas, in the responses to CO2 PYL4 and PYL5 are essential. Overall our work shows the importance of ABA as a central regulator and integrator of long-term changes in stomatal behaviour, including sensitivity, elicited by external signals. Understanding this architecture may aid breeding of crops with improved water and nutrient efficiency

Structure-guided engineering of a receptor-agonist pair for inducible activation of the ABA adaptive response to drought

Strategies to activate abscisic acid (ABA) receptors and boost ABA signaling by small molecules that act as ABA receptor agonists are promising biotechnological tools to enhance plant drought tolerance. Protein structures of crop ABA receptors might require modifications to improve recognition of chemical ligands, which in turn can be optimized by structural information. Through structure-based targeted design, we have combined chemical and genetic approaches to generate an ABA receptor agonist molecule (iSB09) and engineer a CsPYL1 ABA receptor, named CsPYL15m, which efficiently binds iSB09. This optimized receptor-agonist pair leads to activation of ABA signaling and marked drought tolerance. No constitutive activation of ABA signaling and hence growth penalty was observed in transformed Arabidopsis thaliana plants. Therefore, conditional and efficient activation of ABA signaling was achieved through a chemical-genetic orthogonal approach based on iterative cycles of ligand and receptor optimization driven by the structure of ternary receptor-ligand-phosphatase complexes

A ligand-independent origin of abscisic acid perception

Land plants are considered monophyletic, descending from a single successful colonization of land by an aquatic algal ancestor. The ability to survive dehydration to the point of desiccation is a key adaptive trait enabling terrestrialization. In extant land plants, desiccation tolerance depends on the action of the hormone abscisic acid (ABA) that acts through a receptor-signal transduction pathway comprising a PYRABACTIN RESISTANCE 1-like (PYL)–PROTEIN PHOSPHATASE 2C (PP2C)–SNF1-RELATED PROTEIN KINASE 2 (SnRK2) module. Early-diverging aeroterrestrial algae mount a dehydration response that is similar to that of land plants, but that does not depend on ABA: Although ABA synthesis is widespread among algal species, ABA-dependent responses are not detected, and algae lack an ABA-binding PYL homolog. This raises the key question of how ABA signaling arose in the earliest land plants. Here, we systematically characterized ABA receptor-like proteins from major land plant lineages, including a protein found in the algal sister lineage of land plants. We found that the algal PYL-homolog encoded by Zygnema circumcarinatum has basal, ligand-independent activity of PP2C repression, suggesting this to be an ancestral function. Similarly, a liverwort receptor possesses basal activity, but it is further activated by ABA. We propose that co-option of ABA to control a preexisting PP2C-SnRK2-dependent desiccation-tolerance pathway enabled transition from an all-or-nothing survival strategy to a hormone-modulated, competitive strategy by enabling continued growth of anatomically diversifying vascular plants in dehydrative conditions, enabling them to exploit their new environment more efficiently