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Summary: The evolution of adjustable stomatal pores, enabling CO2 acquisition, was one of the most significant events in the development of life on land. Here, we investigate how the guard cell signalling pathways that regulate stomatal movements evolved.We compare fern and angiosperm guard cell transcriptomes and physiological responses, and examine the functionality of ion channels from diverse plant species.We find that, despite conserved expression in guard cells, fern anion channels from the SLAC/SLAH family are not activated by the same abscisic acid (ABA) pathways that provoke stomatal closure in angiosperms. Accordingly, we find an insensitivity of fern stomata to ABA. Moreover, our analysis points to a complex evolutionary history, featuring multiple gains and/or losses of SLAC activation mechanisms, as these channels were recruited to a role in stomatal closure.Our results show that the guard cells of flowering and nonflowering plants share similar core features, with lineage‐specific and ecological niche‐related adaptations, likely underlying differences in behaviour. [ABSTRACT FROM AUTHOR]

Optimal stomatal regulation is important for plant adaptation to changing environmental conditions and for maintaining crop yield. The guard cell signal γ-aminobutyric acid (GABA) is produced from glutamate by glutamate decarboxylase (GAD) during a reaction that generates CO2 as a by-product. Here, we investigated a putative connection between GABA signalling and the more clearly defined CO2 signalling pathway in guard cells. The GABA-deficient mutant Arabidopsis lines gad2-1 , gad2-2 , and gad1/2/4/5 were examined for stomatal sensitivity to various CO2 concentrations. Our findings show a phenotypical discrepancy between the allelic mutant lines gad2-1 and gad2-2 —a weakened CO2 response in gad2-1 (GABI_474_E05) in contrast to a wild-type response in gad2-2 (SALK_028819) and gad1/2/4/5. Through transcriptomic and genomic investigation, we traced the response of gad2-1 to a deletion of full-length Mitogen-activated protein kinase 12 (MPK12) in the GABI-KAT line, thereafter renamed as gad2-1 *. Guard cell-specific complementation of MPK12 in gad2-1* restored the wild-type CO2 phenotype, which confirms the proposed importance of MPK12 in CO2 sensitivity. Additionally, we found that stomatal opening under low atmospheric CO2 occurs independently of the GABA-modulated opening channel ALUMINIUM-ACTIVATED MALATE TRANSPORTER 9 (ALMT9). Our results demonstrate that GABA has a role in modulating the rate of stomatal opening and closing, but not in response to CO2 per se. [ABSTRACT FROM AUTHOR]

For more than two decades, critical planning scholars have called for strategic spatial planning to cut its rational roots stemming from the 1960s–70s, and counter its tendency towards more incremental approaches of the 1980s–2000s. To truly address the core challenges of cities and regions in our times, spatial planning should plan for discontinuity. This paper explores how planning may embrace futuring practices to do so. Drawing on three materially oriented futuring approaches, 'Critical Future Studies', 'Sociology of Expectations', and 'Sociology of the Future', futuring practices may serve a threefold aim. First, exposing the power of 'normalisation', unlocking silenced futures. Second, providing a stage to exhibit and dramatise 'future expectations' (stories, images, artefacts) and their stakeholder connections. Third, letting urban materiality and corporeality truly speak for themselves to the present and the future, opening experiences of, and confrontations with, the technological, environmental and geographical unconscious. Consequently, we show how such futuring can take shape through the creation of an 'Archive of the Future', which we illustrate through Rotterdam as a case. [ABSTRACT FROM AUTHOR]

Plants tightly control growth of their lateral organs, which led to the concept of apical dominance. However, outgrowth of the dormant lateral primordia is sensitive to the plant's nutritional status, resulting in an immense plasticity in plant architecture. While the impact of hormonal regulation on apical dominance is well characterized, the prime importance of sugar signaling to unleash lateral organ formation has just recently emerged. Here, we aimed to identify transcriptional regulators, which control the trade-off between growth of apical versus lateral organs. Making use of locally inducible gain-of-function as well as single and higher-order loss-of-function approaches of the sugar-responsive S1-basic-leucine-zipper (S1-bZIP) transcription factors, we disclosed their largely redundant function in establishing apical growth dominance. Consistently, comprehensive phenotypical and analytical studies of S1-bZIP mutants show a clear shift of sugar and organic nitrogen (N) allocation from apical to lateral organs, coinciding with strong lateral organ outgrowth. Tissue-specific transcriptomics reveal specific clade III SWEET sugar transporters, crucial for long-distance sugar transport to apical sinks and the glutaminase GLUTAMINE AMIDO-TRANSFERASE 1_2.1, involved in N homeostasis, as direct S1-bZIP targets, linking the architectural and metabolic mutant phenotypes to downstream gene regulation. Based on these results, we propose that S1-bZIPs control carbohydrate (C) partitioning from source leaves to apical organs and tune systemic N supply to restrict lateral organ formation by C/N depletion. Knowledge of the underlying mechanisms controlling plant C/N partitioning is of pivotal importance for breeding strategies to generate plants with desired architectural and nutritional characteristics. [ABSTRACT FROM AUTHOR]

Drought and salt exposure are among the most prevalent and severe abiotic stressors causing serious agricultural yield losses, alone and in combination. Little is known about differences and similarities in the effects of these two stress factors on plant metabolic regulation, particularly on nitrogen metabolism. Here, we studied the effects of water deprivation and salt exposure on water relations and nitrogen metabolites in leaves and roots of date palm seedlings. Both, water deprivation and salt exposure had no significant effects on plant water content or stable carbon (C) and nitrogen (N) isotope signatures. Significant effects of water deprivation on total C and N concentrations were only observed in roots, i.e. decreased total C and increased total N concentrations. Whereas salt exposure initially decreased total C and increased total N concentrations significantly in roots, foliar total C concentration was increased upon prolonged exposure. Initially C/N ratios declined in roots of plants from both treatments and upon prolonged salt exposure also in the leaves. Neither treatment affected soluble protein and structural N concentrations in leaves or roots, but resulted in the accumulation of most amino acids, except for glutamate and tryptophan, which remained stable, and serine, which decreased, in roots. Accumulation of the most abundant amino acids, lysine and proline, was observed in roots under both treatments, but in leaves only upon salt exposure. This finding indicates a similar role of these amino acids as compatible solutes in the roots in response to salt und drought, but not in the leaves. Upon prolonged treatment, amino acid concentrations returned to levels found in unstressed plants in leaves of water deprived, but not salt exposed, plants. The present results show both water deprivation and salt exposure strongly impact N metabolism of date palm seedlings, but in a different manner in leaves and roots. [ABSTRACT FROM AUTHOR]

Summary: Chenopodium quinoa uses epidermal bladder cells (EBCs) to sequester excess salt. Each EBC complex consists of a leaf epidermal cell, a stalk cell, and the bladder.Under salt stress, sodium (Na+), chloride (Cl−), potassium (K+) and various metabolites are shuttled from the leaf lamina to the bladders. Stalk cells operate as both a selectivity filter and a flux controller.In line with the nature of a transfer cell, advanced transmission electron tomography, electrophysiology, and fluorescent tracer flux studies revealed the stalk cell's polar organization and bladder‐directed solute flow.RNA sequencing and cluster analysis revealed the gene expression profiles of the stalk cells. Among the stalk cell enriched genes, ion channels and carriers as well as sugar transporters were most pronounced. Based on their electrophysiological fingerprint and thermodynamic considerations, a model for stalk cell transcellular transport was derived. [ABSTRACT FROM AUTHOR]

More than half a century has passed since the first use of models in urban planning. Most urban planners have agreed on using models either to simplify complicated systems or to make simulations of such systems in order to predict their future. There is, however, disagreement on how far such simplifications and simulations have worked toward the planners' goals and objectives. In this paper, through historical analysis, we placed the model-theory interaction into the broader scope of scientific modeling to develop guidelines applicable to the narrow field of urban modeling. Here, we developed an argument that models' applicability and meaningfulness in urban planning are primarily dependent on planning theories, that is, models and theories should move parallel to achieve all the functions and capabilities claimed by models. Thus, an interactive process shapes the model as the mediator between the theory and the phenomenon: (a) the theory explains an abstract phenomenon, (b) the model provides an understanding of that phenomenon, and (c) the original abstract explanation is revisited and made more practical. This evolutionary process is our view of the "mediator model," that is, a new definition of the urban model. [ABSTRACT FROM AUTHOR]

Inward-rectifying [K.sup.+] channels serve as a major pathway for [Ca.sup.2+]-sensitive [K.sup.+] influx into guard cells. Arabidopsis thaliana guard cell inward-rectifying [K.sup.+] channels are assembled from multiple [K.sup.+] channel subunits. Following the recent isolation and characterization of an akt2/3-1 knockout mutant, we examined whether the AKT2/3 subunit carries the [Ca.sup.2+] sensitivity of the guard cell inward rectifier. Quantification of RT-PCR products showed that despite the absence of AKT2 transcripts in guard cells of the knockout plant, expression levels of the other [K.sup.+] channel subunits (KAT1, KAT2, AKT1, and AtKC1) remained largely unaffected. Patch-clamp experiments with guard cell protoplasts from wild type and akt2/3-1 mutant, however, revealed pronounced differences in [Ca.sup.2+] sensitivity of the [K.sup.+] inward rectifier. Wild-type channels were blocked by extracellular [Ca.sup.2+] in a concentration-and voltage-dependent manner. Akt2/3-1 mutants lacked the voltage-dependent [Ca.sup.2+] block, characteristic for the [K.sup.+] inward rectifier. To confirm the akt2/3-1 phenotype, two independent knockout mutants, akt2-1 and akt2::En-1 were tested, demonstrating that the loss of AKT2/3 indeed affects the [Ca.sup.2+] dependence of guard cell inward rectifier. In contrast to AKT2 knockout plants, AKT1, AtKC1, and KAT1 loss-of-function mutants retained [Ca.sup.2+] block of the guard cell inward rectifier. When expressed in HEK293 cells, AKT2 channel displayed a pronounced susceptibility toward extracellular [Ca.sup.2+], while the dominant guard cell [K.sup.+] channel KAT2 was [Ca.sup.2+] insensitive. Thus, we conclude that the AKT2/3 subunit constitutes the [Ca.sup.2+] sensitivity of the guard cell [K.sup.+] uptake channel. KEY WORDS: Arabidopsis * guard cells * potassium channel * calcium sensitivity * AKT2/3

Climate change is increasing the frequency and intensity of warming and drought periods around the globe, currently representing a threat to many plant species. Understanding the resistance and resilience of plants to climate change is, therefore, urgently needed. As date palm (Phoenix dactylifera) evolved adaptation mechanisms to a xeric environment and can tolerate large diurnal and seasonal temperature fluctuations, we studied the protein expression changes in leaves, volatile organic compound emissions, and photosynthesis in response to variable growth temperatures and soil water deprivation. Plants were grown under controlled environmental conditions of simulated Saudi Arabian summer and winter climates challenged with drought stress. We show that date palm is able to counteract the harsh conditions of the Arabian Peninsula by adjusting the abundances of proteins related to the photosynthetic machinery, abiotic stress and secondary metabolism. Under summer climate and water deprivation, these adjustments included efficient protein expression response mediated by heat shock proteins and the antioxidant system to counteract reactive oxygen species formation. Proteins related to secondary metabolism were downregulated, except for the P. dactylifera isoprene synthase (PdIspS), which was strongly upregulated in response to summer climate and drought. This study reports, for the first time, the identification and functional characterization of the gene encoding for PdIspS, allowing future analysis of isoprene functions in date palm under extreme environments. Overall, the current study shows that reprogramming of the leaf protein profiles confers the date palm heat- and drought tolerance. We conclude that the protein plasticity of date palm is an important mechanism of molecular adaptation to environmental fluctuations. [ABSTRACT FROM AUTHOR]