The initiation of stomata, microscopic valves in the epidermis of higher plants that control of gas exchange, requires a co-ordinated sequence of asymmetric and symmetric divisions, which is under tight environmental and developmental control. Arabidopsis leaves grown under elevated photosynthetic photon flux density have a higher density of stomata. STOMAGEN encodes an epidermal patterning factor produced in the mesophyll, and our observations indicated that elevated photosynthetic irradiation stimulates STOMAGEN expression. Our analysis of gain and loss of function of STOMAGEN further detailed its function as a positive regulator of stomatal formation on both sides of the leaf, not only in terms of stomatal density across the leaf surface but also in terms of their stomatal index. STOMAGEN function was rate limiting for the light response of the stomatal lineage in the adaxial epidermis. Mutants in pathways that regulate stomatal spacing in the epidermis and have elevated stomatal density, such as stomatal density and distribution (sdd1) and too many mouth alleles, displayed elevated STOMAGEN expression, suggesting that STOMAGEN is either under the direct control of these pathways or is indirectly affected by stomatal patterning, suggestive of a feedback mechanism. These observations support a model in which changes in levels of light irradiation are perceived in the mesophyll and control the production of stomata in the epidermis by mesophyll-produced STOMAGEN, and whereby, conversely, stomatal patterning, either directly or indirectly, influences STOMAGEN levels.

• MeSH
• Arabidopsis genetika   růst a vývoj   metabolismus   účinky záření   MeSH
• fotosyntéza MeSH
• listy rostlin růst a vývoj   metabolismus   účinky záření   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• průduchy rostlin genetika   růst a vývoj   metabolismus   účinky záření   MeSH
• regulace genové exprese u rostlin účinky záření   MeSH
• signální transdukce MeSH
• světlo MeSH
• vývojová regulace genové exprese účinky záření   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• genové regulační sítě * MeSH
• proteiny huseníčku * genetika   MeSH
• průduchy rostlin genetika   MeSH
• sekvenční analýza RNA MeSH
• Publikační typ
• časopisecké články MeSH
• komentáře MeSH
• práce podpořená grantem MeSH

BACKGROUND AND AIMS: The idea that genome (size) evolution in eukaryotes could be driven by environmental factors is still vigorously debated. In extant plants, genome size correlates positively with stomatal size, leading to the idea that conditions enabling the existence of large stomata in fossil plants also supported growth of their genome size. We test this inductive assumption in drought-adapted, prostrate-leaved Cape (South Africa) geophytes where, compared with their upright-leaved geophytic ancestors, stomata develop in a favourably humid microclimate formed underneath their leaves. METHODS: Stomatal parameters (leaf cuticle imprints) and genome size (flow cytometry) were measured in 16 closely related geophytic species pairs from seven plant families. In each pair, representing a different genus, we contrasted a prostrate-leaved species with its upright-leaved phylogenetic relative, the latter whose stomata are exposed to the ambient arid climate. KEY RESULTS: Except for one, all prostrate-leaves species had larger stomata, and in 13 of 16 pairs they also had larger genomes than their upright-leaved relatives. Stomatal density and theoretical maximum conductance were less in prostrate-leaved species with small guard cells (<1 pL) but showed no systematic difference in species pairs with larger guard cells (>1 pL). Giant stomata were observed in the prostrate-leaved Satyrium bicorne (89-137 µm long), despite its relatively small genome (2C = 9 Gbp). CONCLUSIONS: Our results imply that climate, through selection on stomatal size, might be able to drive genome size evolution in plants. The data support the idea that plants from 'greenhouse' geological periods with large stomata might have generally had larger genome sizes when compared with extant plants, though this might not have been solely due to higher atmospheric CO2 in these periods but could also have been due to humid conditions prevailing at fossil deposit sites.

• MeSH
• délka genomu MeSH
• fylogeneze MeSH
• genom rostlinný genetika   MeSH
• listy rostlin MeSH
• průduchy rostlin genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Jihoafrická republika MeSH

Occurrence of stomata on both leaf surfaces (amphistomaty) promotes higher stomatal conductance and photosynthesis while simultaneously increasing exposure to potential disease agents in black cottonwood (Populus trichocarpa). A genome-wide association study (GWAS) with 2.2M single nucleotide polymorphisms generated through whole-genome sequencing found 280 loci associated with variation in adaxial stomatal traits, implicating genes regulating stomatal development and behavior. Strikingly, numerous loci regulating plant growth and response to biotic and abiotic stresses were also identified. The most significant locus was a poplar homologue of SPEECHLESS (PtSPCH1). Individuals possessing PtSPCH1 alleles associated with greater adaxial stomatal density originated primarily from environments with shorter growing seasons (e.g. northern latitudes, high elevations) or with less precipitation. PtSPCH1 was expressed in developing leaves but not developing stem xylem. In developing leaves, RNA sequencing showed patterns of coordinated expression between PtSPCH1 and other GWAS-identified genes. The breadth of our GWAS results suggests that the evolution of amphistomaty is part of a larger, complex response in plants. Suites of genes underpin this response, retrieved through genetic association to adaxial stomata, and show coordinated expression during development. We propose that the occurrence of amphistomaty in P. trichocarpa involves PtSPCH1 and reflects selection for supporting rapid growth over investment in immunity.

• MeSH
• alely MeSH
• celogenomová asociační studie MeSH
• druhová specificita MeSH
• fenotyp MeSH
• genotyp MeSH
• imunita rostlin genetika   MeSH
• jednonukleotidový polymorfismus genetika   MeSH
• kvantitativní znak dědičný MeSH
• podnebí MeSH
• Populus genetika   růst a vývoj   imunologie   fyziologie   MeSH
• průduchy rostlin genetika   fyziologie   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné geny MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• rozvržení tělního plánu * MeSH
• vývoj rostlin MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND AND AIMS: Genome size is known to affect various plant traits such as stomatal size, seed mass, and flower or shoot phenology. However, these associations are not well understood for species with very large genomes, which are laregly represented by geophytic plants. No detailed associations are known between DNA base composition and genome size or species ecology. METHODS: Genome sizes and GC contents were measured in 219 geophytes together with tentative morpho-anatomical and ecological traits. KEY RESULTS: Increased genome size was associated with earliness of flowering and tendency to grow in humid conditions, and there was a positive correlation between an increase in stomatal size in species with extremely large genomes. Seed mass of geophytes was closely related to their ecology, but not to genomic parameters. Genomic DNA GC content showed a unimodal relationship with genome size but no relationship with species ecology. CONCLUSIONS: Evolution of genome size in geophytes is closely related to their ecology and phenology and is also associated with remarkable changes in DNA base composition. Although geophytism together with producing larger cells appears to be an advantageous strategy for fast development of an organism in seasonal habitats, the drought sensitivity of large stomata may restrict the occurrence of geophytes with very large genomes to regions not subject to water stress.

• MeSH
• délka genomu MeSH
• DNA rostlinná analýza   genetika   MeSH
• ekologie MeSH
• ekosystém MeSH
• genom rostlinný MeSH
• molekulární evoluce MeSH
• průduchy rostlin anatomie a histologie   MeSH
• roční období MeSH
• rostliny anatomie a histologie   genetika   MeSH
• semena rostlinná anatomie a histologie   MeSH
• zastoupení bazí MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Stomatal ontogenesis, patterning, and function are hallmarks of environmental plant adaptation, especially to conditions limiting plant growth, such as elevated temperatures and reduced water availability. The specification and distribution of a stomatal cell lineage and its terminal differentiation into guard cells require a master regulatory protein phosphorylation cascade involving the YODA mitogen-activated protein kinase kinase kinase. YODA signaling results in the activation of MITOGEN-ACTIVATED PROTEIN KINASEs (MPK3 and MPK6), which regulate transcription factors, including SPEECHLESS (SPCH). Here, we report that acute heat stress affects the phosphorylation and deactivation of SPCH and modulates stomatal density. By using complementary molecular, genetic, biochemical, and cell biology approaches, we provide solid evidence that HEAT SHOCK PROTEINS 90 (HSP90s) play a crucial role in transducing heat-stress response through the YODA cascade. Genetic studies revealed that YODA and HSP90.1 are epistatic, and they likely function linearly in the same developmental pathway regulating stomata formation. HSP90s interact with YODA, affect its cellular polarization, and modulate the phosphorylation of downstream targets, such as MPK6 and SPCH, under both normal and heat-stress conditions. Thus, HSP90-mediated specification and differentiation of the stomatal cell lineage couples stomatal development to environmental cues, providing an adaptive heat stress response mechanism in plants.

• MeSH
• Arabidopsis fyziologie   MeSH
• buněčná diferenciace MeSH
• buněčné dělení MeSH
• buněčný rodokmen MeSH
• epigeneze genetická MeSH
• fosforylace MeSH
• kotyledon cytologie   MeSH
• MAP kinasy kinas (kinas) genetika   metabolismus   MeSH
• mitogenem aktivované proteinkinasy kinas metabolismus   MeSH
• mitogenem aktivované proteinkinasy metabolismus   MeSH
• mutace MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• proteiny tepelného šoku HSP90 genetika   metabolismus   MeSH
• průduchy rostlin cytologie   růst a vývoj   metabolismus   MeSH
• reakce na tepelný šok * MeSH
• regulace genové exprese u rostlin MeSH
• signální transdukce MeSH
• transkripční faktory bHLH metabolismus   MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND AND AIMS: Stomatal density (SD) generally decreases with rising atmospheric CO2 concentration, Ca. However, SD is also affected by light, air humidity and drought, all under systemic signalling from older leaves. This makes our understanding of how Ca controls SD incomplete. This study tested the hypotheses that SD is affected by the internal CO2 concentration of the leaf, Ci, rather than Ca, and that cotyledons, as the first plant assimilation organs, lack the systemic signal. METHODS: Sunflower (Helianthus annuus), beech (Fagus sylvatica), arabidopsis (Arabidopsis thaliana) and garden cress (Lepidium sativum) were grown under contrasting environmental conditions that affected Ci while Ca was kept constant. The SD, pavement cell density (PCD) and stomatal index (SI) responses to Ci in cotyledons and the first leaves of garden cress were compared. (13)C abundance (δ(13)C) in leaf dry matter was used to estimate the effective Ci during leaf development. The SD was estimated from leaf imprints. KEY RESULTS: SD correlated negatively with Ci in leaves of all four species and under three different treatments (irradiance, abscisic acid and osmotic stress). PCD in arabidopsis and garden cress responded similarly, so that SI was largely unaffected. However, SD and PCD of cotyledons were insensitive to Ci, indicating an essential role for systemic signalling. CONCLUSIONS: It is proposed that Ci or a Ci-linked factor plays an important role in modulating SD and PCD during epidermis development and leaf expansion. The absence of a Ci-SD relationship in the cotyledons of garden cress indicates the key role of lower-insertion CO2 assimilation organs in signal perception and its long-distance transport.

• MeSH
• Arabidopsis cytologie   účinky léků   MeSH
• buk (rod) cytologie   účinky léků   MeSH
• dehydratace MeSH
• Helianthus cytologie   účinky léků   MeSH
• kotyledon účinky léků   fyziologie   MeSH
• Lepidium cytologie   účinky léků   MeSH
• oxid uhličitý farmakologie   MeSH
• počet buněk MeSH
• průduchy rostlin cytologie   účinky léků   MeSH
• životní prostředí MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Element content and expression of genes of interest on single cell types, such as stomata, provide valuable insights into their specific physiology, improving our understanding of leaf gas exchange regulation. We investigated how far differences in stomatal conductance (gs ) can be ascribed to changes in guard cells functioning in amphistomateous leaves. gs was measured during the day on both leaf sides, on well-watered and drought-stressed trees (two Populus euramericana Moench and two Populus nigra L. genotypes). In parallel, guard cells were dissected for element content and gene expressions analyses. Both were strongly arranged according to genotype, and drought had the lowest impact overall. Normalizing the data by genotype highlighted a structure on the basis of leaf sides and time of day both for element content and gene expression. Guard cells magnesium, phosphorus, and chlorine were the most abundant on the abaxial side in the morning, where gs was at the highest. In contrast, genes encoding H+ -ATPase and aquaporins were usually more abundant in the afternoon, whereas genes encoding Ca2+ -vacuolar antiporters, K+ channels, and ABA-related genes were in general more abundant on the adaxial side. Our work highlights the unique physiology of each leaf side and their analogous rhythmicity through the day.

• MeSH
• genotyp MeSH
• komplementární DNA genetika   izolace a purifikace   MeSH
• listy rostlin genetika   metabolismus   MeSH
• mikroanalýza elektronovou sondou MeSH
• období sucha MeSH
• Populus klasifikace   genetika   metabolismus   MeSH
• protonové ATPasy genetika   metabolismus   MeSH
• průduchy rostlin genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• RNA rostlin genetika   izolace a purifikace   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• stromy genetika   metabolismus   MeSH
• transpirace rostlin fyziologie   MeSH
• voda fyziologie   MeSH
• vývoj rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND AND AIMS: Cytokinins are positive regulators of shoot development. However, it has previously been demonstrated that efficient activation of the cytokinin biosynthesis gene ipt can cause necrotic lesions and wilting in tobacco leaves. Some plant pathogens reportedly use their ability to produce cytokinins in disease development. In response to pathogen attacks, plants can trigger a hypersensitive response that rapidly kills cells near the infection site, depriving the pathogen of nutrients and preventing its spread. In this study, a diverse set of processes that link ipt activation to necrotic lesion formation were investigated in order to evaluate the potential of cytokinins as signals and/or mediators in plant defence against pathogens. METHODS: The binary pOp-ipt/LhGR system for dexamethasone-inducible ipt expression was used to increase endogenous cytokinin levels in transgenic tobacco. Changes in the levels of cytokinins and the stress hormones salicylic, jasmonic and abscisic acid following ipt activation were determined by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS). Trends in hydrogen peroxide content and lipid peroxidation were monitored using the potassium iodide and malondialdehyde assays. The subcellular distribution of hydrogen peroxide was investigated using 3,3'-diaminobenzidine staining. The dynamics of transcripts related to photosynthesis and pathogen response were analysed by reverse transcription followed by quantitative PCR. The effects of cytokinins on photosynthesis were deciphered by analysing changes in chlorophyll fluorescence and leaf gas exchange. KEY RESULTS: Plants can produce sufficiently high levels of cytokinins to trigger fast cell death without any intervening chlorosis - a hallmark of the hypersensitive response. The results suggest that chloroplastic hydrogen peroxide orchestrates the molecular responses underpinning the hypersensitive-like response, including the inhibition of photosynthesis, elevated levels of stress hormones, oxidative membrane damage and stomatal closure. CONCLUSIONS: Necrotic lesion formation triggered by ipt activation closely resembles the hypersensitive response. Cytokinins may thus act as signals and/or mediators in plant defence against pathogen attack.

• MeSH
• alkyltransferasy a aryltransferasy genetika   MeSH
• buněčná smrt MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty genetika   metabolismus   MeSH
• cytokininy genetika   metabolismus   MeSH
• dexamethason farmakologie   MeSH
• fotosyntéza genetika   MeSH
• geneticky modifikované rostliny MeSH
• interakce hostitele a patogenu * MeSH
• listy rostlin cytologie   genetika   fyziologie   MeSH
• nekróza genetika   MeSH
• oxidační stres genetika   MeSH
• peroxid vodíku metabolismus   MeSH
• peroxidace lipidů MeSH
• průduchy rostlin fyziologie   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• regulátory růstu rostlin genetika   metabolismus   MeSH
• tabák genetika   mikrobiologie   fyziologie   MeSH
• umlčování genů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Abscisic acid (ABA) play a crucial role in plant acclimation to heavy-metals stresses. Nevertheless, the effects of ABA on long-distance transport and its consequences for cadmium (Cd) accumulation are insufficiently understood. Here, we investigated the effects of ABA on the development of the whole-plant water transport pathway and implications for Cd uptake and transport to the shoot of Sedum alfredii. Exposure to Cd stimulated the production of endogenous ABA levels in the non-hyperaccumulating ecotype (NHE), but not in the hyperaccumulating ecotype (HE). Increased ABA levels in NHE significantly reduced aquaporin expressions in roots, the number of xylem vessel in stem, dimensions and densities of stomata in leaves, but induced leaf osmotic adjustment. Furthermore, the ABA-driven modifications in NHE plants showed typically higher sensitivity to ABA content in leaves compared to HE, illustrating ecotype-specific responses to ABA level. In NHE, the ABA-mediated modifications primarily affected the xylem transport of Cd ions and, at the cost of considerable water delivery limitations, significantly reduced delivery of Cd ions to shoots. In contrast, maintenance of low ABA levels in HE failed to t limit transpiration rates and maximized Cd accumulation in shoots. Our results demonstrated that ABA regulates Cd hyperaccumulation of S. alfredii through specific modifications in the water transport continuum.

• MeSH
• kadmium MeSH
• kořeny rostlin MeSH
• kyselina abscisová MeSH
• Sedum * MeSH
• voda MeSH
• Publikační typ
• časopisecké články MeSH