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Fleetwood SK, Kleiman M, Foster EJ. Preparation of isolated guard cells, containing cell walls, from Vicia faba. PLoS One 2024; 19:e0299810. [PMID: 38513160 PMCID: PMC10957180 DOI: 10.1371/journal.pone.0299810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 02/15/2024] [Indexed: 03/23/2024] Open
Abstract
Stomatal movement, initiated by specialized epidermal cells known as guard cells (GCs), plays a pivotal role in plant gas exchange and water use efficiency. Despite protocols existing for isolating GCs through proplasting for carrying out biochemical, physiological, and molecular studies, protocals for isolating GCs with their cell walls still intact have been lacking in the literature. In this paper, we introduce a method for the isolation of complete GCs from Vicia faba and show their membrane to remain impermeable through propidium iodide staining. This methodology enables further in-depth analyses into the cell wall composition of GCs, facilitating our understanding of structure-function relationship governing reversible actuation within cells.
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Affiliation(s)
- Sara K. Fleetwood
- Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, British Columbia, Canada
| | - Maya Kleiman
- Plant Sciences Institute, Agricultural Research Organization (Volcani Center), Rishon LeZiyyon, Israel
| | - E. Johan Foster
- Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, British Columbia, Canada
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2
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Wu Y, Wang Z, Zhang Z. Telescopic peristomes, hygroscopic movement and the spore release model of Regmatodon declinatus (Leskeaceae Bryophyta). AOB PLANTS 2023; 15:plad073. [PMID: 38028746 PMCID: PMC10656297 DOI: 10.1093/aobpla/plad073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Accepted: 11/01/2023] [Indexed: 12/01/2023]
Abstract
Moss peristome hygroscopic movement plays an important role in protecting and controlling spore release. Recent studies on the peristome's hygroscopic movement and spore release have focussed on mosses with 'perfect' peristomes, such as Brachytheciaceae, whereas the hygroscopic movement type and spore release pattern of 'specialized' peristomes, such as Regmatodon declinatus, are poorly understood. We investigated the relationship between the peristome's hygroscopic movement and spore release in the 'specialized' peristome of R. declinatus by the measurement of peristome hygroscopic movement parameters and the hygroscopic movement spore release test. It was found that: (i) Exostomes (EX) are significantly shorter than endostomes (EN), triggering the hygroscopic movement of telescopic peristomes, in which the EX rapidly elongate while closing in on the EN, and the teeth rapidly converge. (ii) Spore release was minimal when peristome movement was triggered alone. The number of spores released when exposed to wind was 124 times greater than in the absence of wind. Dry capsules released seven times more spores than wet capsules. The study reveals that the hygroscopic movement of 'telescopic' peristomes of R. declinatus did not contribute significantly to spore release. More spores were released when wind and hygroscopic movement acted synergistically. Dry capsules released the maximum number of spores. It was also revealed that structural damage to capsules can facilitate complete spore release. Finally, we modelled the release of R. declinatus spores from initiation to complete release, namely the coupled release model of wind-water-capsule structural damage.
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Affiliation(s)
- Yanzhi Wu
- School of Life Sciences, Guizhou Normal University, Guiyang 550001, China
| | - Zhihui Wang
- School of Life Sciences, Guizhou Normal University, Guiyang 550001, China
| | - Zhaohui Zhang
- Key Laboratory for Information System of Mountainous Area and Protection of Ecological Environment of Guizhou Province, Guizhou Normal University, Guiyang 550001, China
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3
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He Y, Bader MY, Li D, Stark LR, Li X, Liu X, Yuan Q, Guo S, Fang Z, Wang Z. Relationships among sporophytic and gametophytic traits of 27 subtropical montane moss species. AMERICAN JOURNAL OF BOTANY 2023; 110:e16253. [PMID: 37938812 DOI: 10.1002/ajb2.16253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 10/15/2023] [Accepted: 10/16/2023] [Indexed: 11/10/2023]
Abstract
PREMISE Moss sporophytes differ strongly in size and biomass partitioning, potentially reflecting reproductive and dispersal strategies. Understanding how sporophyte traits are coordinated is essential for understanding moss functioning and evolution. This study aimed to answer: (1) how the size and proportions of the sporophyte differ between moss species with and without a prominent central strand in the seta, (2) how anatomical and morphological traits of the seta are related, and (3) how sporophytic biomass relates to gametophytic biomass and nutrient concentrations. METHODS We studied the relationships between seta anatomical and morphological traits, the biomass of seta, capsule, and gametophyte, and carbon, nitrogen, and phosphorus concentrations of 27 subtropical montane moss species. RESULTS (1) Moss species with a prominent central strand in the seta had larger setae and heavier capsules than those without a prominent strand. (2) With increasing seta length, setae became thicker and more rounded for both groups, while in species with a prominent central strand, the ratio of transport-cell area to epidermal area decreased. (3) In both groups, mosses with greater gametophytic biomass tended to have heavier sporophytes, but nitrogen and phosphorus concentrations in the gametophyte were unrelated to sporophytic traits. CONCLUSIONS Our study highlights that the central strand in the seta may have an important functional role and affect the allometry of moss sporophytes. The coordinated variations in sporophyte morphological and anatomical traits follow basic biomechanical principles of cylinder-like structures, and these traits relate only weakly to the gametophytic nutrient concentrations. Research on moss sporophyte functional traits and their relationships to gametophytes is still in its infancy but could provide important insights into their adaptative strategies.
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Affiliation(s)
- Yunyu He
- Shanghai Normal University, Shanghai, 200234, China
| | - Maaike Y Bader
- Ecological Plant Geography, Faculty of Geography, University of Marburg, Marburg, 35032, Germany
| | - Dandan Li
- Shanghai Normal University, Shanghai, 200234, China
| | - Lloyd R Stark
- School of Life Sciences, University of Nevada, Las Vegas, NV, 89154-4004, USA
| | - Xiaoming Li
- China-Croatia "Belt and Road" Joint Laboratory on Biodiversity and Ecosystem Services, CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Xin Liu
- China-Croatia "Belt and Road" Joint Laboratory on Biodiversity and Ecosystem Services, CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Qizhang Yuan
- Shanghai Normal University, Shanghai, 200234, China
| | | | - Zhiqiang Fang
- Sichuan Provincial Academy of Natural Resources Sciences, Chengdu, 610041, China
| | - Zhe Wang
- Shanghai Normal University, Shanghai, 200234, China
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4
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Montgomery SA, Berger F. The evolution of imprinting in plants: beyond the seed. PLANT REPRODUCTION 2021; 34:373-383. [PMID: 33914165 PMCID: PMC8566399 DOI: 10.1007/s00497-021-00410-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/12/2021] [Indexed: 05/14/2023]
Abstract
Genomic imprinting results in the biased expression of alleles depending on if the allele was inherited from the mother or the father. Despite the prevalence of sexual reproduction across eukaryotes, imprinting is only found in placental mammals, flowering plants, and some insects, suggesting independent evolutionary origins. Numerous hypotheses have been proposed to explain the selective pressures that favour the innovation of imprinted gene expression and each differs in their experimental support and predictions. Due to the lack of investigation of imprinting in land plants, other than angiosperms with triploid endosperm, we do not know whether imprinting occurs in species lacking endosperm and with embryos developing on maternal plants. Here, we discuss the potential for uncovering additional examples of imprinting in land plants and how these observations may provide additional support for one or more existing imprinting hypotheses.
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Affiliation(s)
- Sean A Montgomery
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr Gasse 3, 1030, Vienna, Austria
| | - Frédéric Berger
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr Gasse 3, 1030, Vienna, Austria.
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5
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Kubásek J, Hájek T, Duckett J, Pressel S, Šantrůček J. Moss stomata do not respond to light and CO 2 concentration but facilitate carbon uptake by sporophytes: a gas exchange, stomatal aperture, and 13 C-labelling study. THE NEW PHYTOLOGIST 2021; 230:1815-1828. [PMID: 33458818 DOI: 10.1111/nph.17208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 01/07/2021] [Indexed: 05/06/2023]
Abstract
Stomata exert control on fluxes of CO2 and water (H2 O) in the majority of vascular plants and thus are pivotal for planetary fluxes of carbon and H2 O. However, in mosses, the significance and possible function of the sporophytic stomata are not well understood, hindering understanding of the ancestral function and evolution of these key structures of land plants. Infrared gas analysis and 13 CO2 labelling, with supporting data from gravimetry and optical and scanning electron microscopy, were used to measure CO2 assimilation and water exchange on young, green, ± fully expanded capsules of 11 moss species with a range of stomatal numbers, distributions, and aperture sizes. Moss sporophytes are effectively homoiohydric. In line with their open fixed apertures, moss stomata, contrary to those in tracheophytes, do not respond to light and CO2 concentration. Whereas the sporophyte cuticle is highly impermeable to gases, stomata are the predominant sites of 13 CO2 entry and H2 O loss in moss sporophytes, and CO2 assimilation is closely linked to total stomatal surface areas. Higher photosynthetic autonomy of moss sporophytes, consequent on the presence of numerous stomata, may have been the key to our understanding of evolution of large, gametophyte-independent sporophytes at the onset of plant terrestrialization.
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Affiliation(s)
- Jiří Kubásek
- Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, 1760/31, Czech Republic
| | - Tomáš Hájek
- Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, 1760/31, Czech Republic
| | - Jeffrey Duckett
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Silvia Pressel
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Jiří Šantrůček
- Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, 1760/31, Czech Republic
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6
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Guzmán-Delgado P, Laca E, Zwieniecki MA. Unravelling foliar water uptake pathways: The contribution of stomata and the cuticle. PLANT, CELL & ENVIRONMENT 2021; 44:1728-1740. [PMID: 33665817 DOI: 10.1111/pce.14041] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
Plants can absorb water through their leaf surfaces, a phenomenon commonly referred to as foliar water uptake (FWU). Despite the physiological importance of FWU, the pathways and mechanisms underlying the process are not well known. Using a novel experimental approach, we parsed out the contribution of the stomata and the cuticle to FWU in two species with Mediterranean (Prunus dulcis) and temperate (Pyrus communis) origin. The hydraulic parameters of FWU were derived by analysing mass and water potential changes of leaves placed in a fog chamber. Leaves were previously treated with abscisic acid to force stomata to remain closed, with fusicoccin to remain open, and with water (control). Leaves with open stomata rehydrated two times faster than leaves with closed stomata and attained approximately three times higher maximum fluxes and hydraulic conductance. Based on FWU rates, we propose that rehydration through stomata occurs primarily via diffusion of water vapour rather than in liquid form even when leaf surfaces are covered with a water film. We discuss the potential mechanisms of FWU and the significance of both stomatal and cuticular pathways for plant productivity and survival.
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Affiliation(s)
- Paula Guzmán-Delgado
- Department of Plant Sciences, University of California Davis, Davis, California, USA
| | - Emilio Laca
- Department of Plant Sciences, University of California Davis, Davis, California, USA
| | - Maciej A Zwieniecki
- Department of Plant Sciences, University of California Davis, Davis, California, USA
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7
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McAdam SAM, Duckett JG, Sussmilch FC, Pressel S, Renzaglia KS, Hedrich R, Brodribb TJ, Merced A. Stomata: the holey grail of plant evolution. AMERICAN JOURNAL OF BOTANY 2021; 108:366-371. [PMID: 33687736 PMCID: PMC8175006 DOI: 10.1002/ajb2.1619] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 09/10/2020] [Indexed: 05/11/2023]
Affiliation(s)
- Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
| | - Jeffrey G Duckett
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Frances C Sussmilch
- School of Natural Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
| | - Silvia Pressel
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Karen S Renzaglia
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, 62901, USA
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, D-97082, Germany
| | - Timothy J Brodribb
- School of Natural Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
| | - Amelia Merced
- USDA Forest Service, International Institute of Tropical Forestry, San Juan, PR, 00926, USA
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8
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Caine RS, Chater CCC, Fleming AJ, Gray JE. Stomata and Sporophytes of the Model Moss Physcomitrium patens. FRONTIERS IN PLANT SCIENCE 2020; 11:643. [PMID: 32523599 PMCID: PMC7261847 DOI: 10.3389/fpls.2020.00643] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 04/27/2020] [Indexed: 05/04/2023]
Abstract
Mosses are an ancient land plant lineage and are therefore important in studying the evolution of plant developmental processes. Here, we describe stomatal development in the model moss species Physcomitrium patens (previously known as Physcomitrella patens) over the duration of sporophyte development. We dissect the molecular mechanisms guiding cell division and fate and highlight how stomatal function might vary under different environmental conditions. In contrast to the asymmetric entry divisions described in Arabidopsis thaliana, moss protodermal cells can enter the stomatal lineage directly by expanding into an oval shaped guard mother cell (GMC). We observed that when two early stage P. patens GMCs form adjacently, a spacing division can occur, leading to separation of the GMCs by an intervening epidermal spacer cell. We investigated whether orthologs of Arabidopsis stomatal development regulators are required for this spacing division. Our results indicated that bHLH transcription factors PpSMF1 and PpSCRM1 are required for GMC formation. Moreover, the ligand and receptor components PpEPF1 and PpTMM are also required for orientating cell divisions and preventing single or clustered early GMCs from developing adjacent to one another. The identification of GMC spacing divisions in P. patens raises the possibility that the ability to space stomatal lineage cells could have evolved before mosses diverged from the ancestral lineage. This would have enabled plants to integrate stomatal development with sporophyte growth and could underpin the adoption of multiple bHLH transcription factors and EPF ligands to more precisely control stomatal patterning in later diverging plant lineages. We also observed that when P. patens sporophyte capsules mature in wet conditions, stomata are typically plugged whereas under drier conditions this is not the case; instead, mucilage drying leads to hollow sub-stomatal cavities. This appears to aid capsule drying and provides further evidence for early land plant stomata contributing to capsule rupture and spore release.
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Affiliation(s)
- Robert S. Caine
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
| | - Caspar C. C. Chater
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
| | - Andrew J. Fleming
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Julie E. Gray
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
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9
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Duckett J. Towards completing understanding of genome size characters in plants. A commentary on: 'Genome size and endopolyploidy evolution across the moss phylogeny'. ANNALS OF BOTANY 2020; 125:iv-v. [PMID: 32073607 PMCID: PMC7102991 DOI: 10.1093/aob/mcaa019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Major differences between moss and vascular plant genome sizes have major implications for stomatal biology whilst an absence of endopolyploidy in Sphagnum is most probably related to the unique development of the capitulum.
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Affiliation(s)
- Jeff Duckett
- Life Sciences, Plants Division, Natural History Museum, Cromwell Road, London, UK
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10
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Simkin AJ, Faralli M, Ramamoorthy S, Lawson T. Photosynthesis in non-foliar tissues: implications for yield. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:1001-1015. [PMID: 31802560 PMCID: PMC7064926 DOI: 10.1111/tpj.14633] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 11/16/2019] [Accepted: 11/25/2019] [Indexed: 05/19/2023]
Abstract
Photosynthesis is currently a focus for crop improvement. The majority of this work has taken place and been assessed in leaves, and limited consideration has been given to the contribution that other green tissues make to whole-plant carbon assimilation. The major focus of this review is to evaluate the impact of non-foliar photosynthesis on carbon-use efficiency and total assimilation. Here we appraise and summarize past and current literature on the substantial contribution of different photosynthetically active organs and tissues to productivity in a variety of different plant types, with an emphasis on fruit and cereal crops. Previous studies provide evidence that non-leaf photosynthesis could be an unexploited potential target for crop improvement. We also briefly examine the role of stomata in non-foliar tissues, gas exchange, maintenance of optimal temperatures and thus photosynthesis. In the final section, we discuss possible opportunities to manipulate these processes and provide evidence that Triticum aestivum (wheat) plants genetically manipulated to increase leaf photosynthesis also displayed higher rates of ear assimilation, which translated to increased grain yield. By understanding these processes, we can start to provide insights into manipulating non-foliar photosynthesis and stomatal behaviour to identify novel targets for exploitation in continuing breeding programmes.
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Affiliation(s)
- Andrew J. Simkin
- Genetics, Genomics and BreedingNIAB EMRNew Road, East MallingKentME19 6BJUK
| | - Michele Faralli
- School of Life SciencesUniversity of EssexWivenhoe ParkColchesterCO4 3SQUK
- Present address:
Department of Biodiversity and Molecular EcologyResearch and Innovation CentreFondazione Edmund Mach, via Mach 1San Michele all'Adige (TN)38010Italy
| | - Siva Ramamoorthy
- School of Bio Sciences and TechnologyVellore Institute of TechnologyVellore632014India
| | - Tracy Lawson
- School of Life SciencesUniversity of EssexWivenhoe ParkColchesterCO4 3SQUK
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11
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Renzaglia KS, Browning WB, Merced A. With Over 60 Independent Losses, Stomata Are Expendable in Mosses. FRONTIERS IN PLANT SCIENCE 2020; 11:567. [PMID: 32547571 PMCID: PMC7270291 DOI: 10.3389/fpls.2020.00567] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 04/16/2020] [Indexed: 05/22/2023]
Abstract
Because stomata in bryophytes are uniquely located on sporangia, the physiological and evolutionary constraints placed on bryophyte stomata are fundamentally different from those on leaves of tracheophytes. Although losses of stomata have been documented in mosses, the extent to which this evolutionary process occurred remains relatively unexplored. We initiated this study by plotting the known occurrences of stomata loss and numbers per capsule on the most recent moss phylogeny. From this, we identified 40 families and 74 genera that lack stomata, of which at least 63 are independent losses. No trends in stomata losses or numbers are evident in any direction across moss diversity. Extant taxa in early divergent moss lineages either lack stomata or produce pseudostomata that do not form pores. The earliest land plant macrofossils from 400 ma exhibit similar sporangial morphologies and stomatal distribution to extant mosses, suggesting that the earliest mosses may have possessed and lost stomata as is common in the group. To understand why stomata are expendable in mosses, we conducted comparative anatomical studies on a range of mosses with and without stomata. We compared the anatomy of stomate and astomate taxa and the development of intercellular spaces, including substomatal cavities, across mosses. Two types of intercellular spaces that develop differently are seen in peristomate mosses, those associated with stomata and those that surround the spore sac. Capsule architecture in astomate mosses ranges from solid in the taxa in early divergent lineages to containing an internal space that is directly connected to the conducing tissue and is involved in capsule expansion and the nourishment, hydration and development of spores. This anatomy reveals there are different architectural arrangements of tissues within moss capsules that are equally effective in accomplishing the essential processes of sporogenesis and spore dispersal. Stomata are not foundational to these processes.
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Affiliation(s)
- Karen S. Renzaglia
- Plant Biology Department, Southern Illinois University, Carbondale, IL, United States
- *Correspondence: Karen S. Renzaglia,
| | - William B. Browning
- Plant Biology Department, Southern Illinois University, Carbondale, IL, United States
| | - Amelia Merced
- International Institute of Tropical Forestry, USDA Forest Service, San Juan, PR, United States
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12
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Sussmilch FC, Roelfsema MRG, Hedrich R. On the origins of osmotically driven stomatal movements. THE NEW PHYTOLOGIST 2019; 222:84-90. [PMID: 30444541 DOI: 10.1111/nph.15593] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 10/26/2018] [Indexed: 06/09/2023]
Abstract
Contents Summary 84 I. Introduction 84 II. Stomatal form and biomechanics 85 III. Stomatal function 86 IV. Evolution of guard cell ion channels 87 V. Conclusions 88 Acknowledgements 88 Author contributions 88 References 88 SUMMARY: Stomatal pores with apertures that can be adjusted by changes in guard cell turgor have facilitated plant success in dry environments. We explore their evolutionary origins, considering recent findings from bryophytes. Unlike vascular plant stomata, which close to prevent water loss, bryophyte stomata become locked open to promote spore desiccation. We find that the families of ion channels, known to control stomatal movements in angiosperms, are ancient and represented across extant land plants. However, although angiosperm guard cells express specific ion channel genes, none appear specifically expressed in stomata-bearing moss tissues. Given the evolutionary shift in stomatal function from promotion to prevention of water loss, we postulate that ion channels adopted guard cell-specific functions after the divergence of bryophytes.
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Affiliation(s)
- Frances C Sussmilch
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082, Würzburg, Germany
| | - M Rob G Roelfsema
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082, Würzburg, Germany
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082, Würzburg, Germany
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13
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Pressel S, Renzaglia KS, Dicky Clymo RS, Duckett JG. Hornwort stomata do not respond actively to exogenous and environmental cues. ANNALS OF BOTANY 2018; 122:45-57. [PMID: 29897395 PMCID: PMC6025193 DOI: 10.1093/aob/mcy045] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 03/14/2018] [Indexed: 05/22/2023]
Abstract
Backgrounds and Aims Because stomata in bryophytes occur on sporangia, they are subject to different developmental and evolutionary constraints from those on leaves of tracheophytes. No conclusive experimental evidence exists on the responses of hornwort stomata to exogenous stimulation. Methods Responses of hornwort stomata to abscisic acid (ABA), desiccation, darkness and plasmolysis were compared with those in tracheophyte leaves. Potassium ion concentrations in the guard cells and adjacent cells were analysed by X-ray microanalysis, and the ontogeny of the sporophytic intercellular spaces was compared with those of tracheophytes by cryo-scanning electron microscopy. Key Results The apertures in hornwort stomata open early in development and thereafter remain open. In hornworts, the experimental treatments, based on measurements of >9000 stomata, produced only a slight reduction in aperture dimensions after desiccation and plasmolysis, and no changes following ABA treatments and darkness. In tracheophytes, all these treatments resulted in complete stomatal closure. Potassium concentrations are similar in hornwort guard cells and epidermal cells under all treatments at all times. The small changes in hornwort stomatal dimensions in response to desiccation and plasmolysis are probably mechanical and/or stress responses of all the epidermal and spongy chlorophyllose cells, affecting the guard cells. In contrast to their nascent gas-filled counterparts across tracheophytes, sporophytic intercellular spaces in hornworts are initially liquid filled. Conclusions Our experiments demonstrate a lack of physiological regulation of opening and closing of stomata in hornworts compared with tracheophytes, and support accumulating developmental and structural evidence that stomata in hornworts are primarily involved in sporophyte desiccation and spore discharge rather than the regulation of photosynthesis-related gaseous exchange. Our results run counter to the notion of the early acquisition of active control of stomatal movements in bryophytes as proposed from previous experiments on mosses.
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Affiliation(s)
- Silvia Pressel
- Life Sciences Department, Natural History Museum, London, UK
| | - Karen S Renzaglia
- Plant Biology Department, Southern Illinois University, Carbondale, USA
| | - Richard S Dicky Clymo
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
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14
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Duckett JG, Pressel S. The evolution of the stomatal apparatus: intercellular spaces and sporophyte water relations in bryophytes-two ignored dimensions. Philos Trans R Soc Lond B Biol Sci 2018; 373:20160498. [PMID: 29254963 PMCID: PMC5745334 DOI: 10.1098/rstb.2016.0498] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2017] [Indexed: 11/12/2022] Open
Abstract
Cryo-scanning electron microscopy shows that nascent intercellular spaces (ICSs) in bryophytes are liquid-filled, whereas these are gas-filled from the outset in tracheophytes except in the gametophytes of Lycopodiales. ICSs are absent in moss gametophytes and remain liquid-filled in hornwort gametophytes and in both generations in liverworts. Liquid is replaced by gas following stomatal opening in hornworts and is ubiquitous in moss sporophytes even in astomate taxa. New data on moss water relations and sporophyte weights indicate that the latter are homiohydric while X-ray microanalysis reveals an absence of potassium pumps in the stomatal apparatus. The distribution of ICSs in bryophytes is strongly indicative of very ancient multiple origins. Inherent in this scenario is either the dual or triple evolution of stomata. The absence, in mosses, of any relationship between increases in sporophyte biomass and stomata numbers and absences, suggests that CO2 entry through the stomata, possible only after fluid replacement by gas in the ICSs, makes but a minor contribution to sporophyte nutrition. Save for a single claim of active regulation of aperture dimensions in mosses, all other functional and structural data point to the sporophyte desiccation, leading to spore discharge, as the primeval role of the stomatal apparatus.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.
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Affiliation(s)
- Jeffrey G Duckett
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Silvia Pressel
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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15
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Sussmilch FC, Brodribb TJ, McAdam SAM. What are the evolutionary origins of stomatal responses to abscisic acid in land plants? JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:240-260. [PMID: 28093875 DOI: 10.1111/jipb.12523] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 01/15/2017] [Indexed: 05/20/2023]
Abstract
The evolution of active stomatal closure in response to leaf water deficit, mediated by the hormone abscisic acid (ABA), has been the subject of recent debate. Two different models for the timing of the evolution of this response recur in the literature. A single-step model for stomatal control suggests that stomata evolved active, ABA-mediated control of stomatal aperture, when these structures first appeared, prior to the divergence of bryophyte and vascular plant lineages. In contrast, a gradualistic model for stomatal control proposes that the most basal vascular plant stomata responded passively to changes in leaf water status. This model suggests that active ABA-driven mechanisms for stomatal responses to water status instead evolved after the divergence of seed plants, culminating in the complex, ABA-mediated responses observed in modern angiosperms. Here we review the findings that form the basis for these two models, including recent work that provides critical molecular insights into resolving this intriguing debate, and find strong evidence to support a gradualistic model for stomatal evolution.
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Affiliation(s)
- Frances C Sussmilch
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
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16
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Shtein I, Shelef Y, Marom Z, Zelinger E, Schwartz A, Popper ZA, Bar-On B, Harpaz-Saad S. Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups. ANNALS OF BOTANY 2017; 119:1021-1033. [PMID: 28158449 PMCID: PMC5604698 DOI: 10.1093/aob/mcw275] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 12/05/2016] [Indexed: 05/18/2023]
Abstract
Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns ( Asplenium nidus and Platycerium bifurcatum ) and angiosperms ( Arabidopsis thaliana and Commelina erecta ) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata ( Sorghum bicolor and Triticum aestivum ). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution.
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Affiliation(s)
- Ilana Shtein
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Yaniv Shelef
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Ziv Marom
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Einat Zelinger
- The Interdepartmental Equipment Unit, The Robert H. Smith Faculty of Agriculture, Food & Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Amnon Schwartz
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Zoë A. Popper
- Botany and Plant Science, Ryan Institute for Environmental, Marine and Energy Research, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Benny Bar-On
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Smadar Harpaz-Saad
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
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Qu X, Peterson KM, Torii KU. Stomatal development in time: the past and the future. Curr Opin Genet Dev 2017; 45:1-9. [PMID: 28219014 DOI: 10.1016/j.gde.2017.02.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 01/31/2017] [Accepted: 02/01/2017] [Indexed: 01/07/2023]
Abstract
Stomata have significantly diversified in nature since their first appearance around 400 million years ago. The diversification suggests the active reprogramming of molecular machineries of stomatal development during evolution. This review focuses on recent progress that sheds light on how this rewiring occurred in different organisms. Three specific aspects are discussed in this review: (i) the evolution of the transcriptional complex that governs stomatal state transitions; (ii) the evolution of receptor-ligand pairs that mediate extrinsic signaling; and (iii) the loss of stomatal development genes in an astomatous angiosperm.
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Affiliation(s)
- Xian Qu
- Department of Biology, University of Washington, Seattle, WA 98195-1800, USA
| | - Kylee M Peterson
- Department of Biology, University of Washington, Seattle, WA 98195-1800, USA
| | - Keiko U Torii
- Department of Biology, University of Washington, Seattle, WA 98195-1800, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195-1800, USA; Institute of Transformative Biomolecules, Nagoya University, Nagoya, Aichi 464-8601, Japan.
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18
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Chater CC, Caine RS, Tomek M, Wallace S, Kamisugi Y, Cuming AC, Lang D, MacAlister CA, Casson S, Bergmann DC, Decker EL, Frank W, Gray JE, Fleming A, Reski R, Beerling DJ. Origin and function of stomata in the moss Physcomitrella patens. NATURE PLANTS 2016; 2:16179. [PMID: 27892923 PMCID: PMC5131878 DOI: 10.1038/nplants.2016.179] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 10/20/2016] [Indexed: 05/02/2023]
Abstract
Stomata are microscopic valves on plant surfaces that originated over 400 million years (Myr) ago and facilitated the greening of Earth's continents by permitting efficient shoot-atmosphere gas exchange and plant hydration1. However, the core genetic machinery regulating stomatal development in non-vascular land plants is poorly understood2-4 and their function has remained a matter of debate for a century5. Here, we show that genes encoding the two basic helix-loop-helix proteins PpSMF1 (SPEECH, MUTE and FAMA-like) and PpSCREAM1 (SCRM1) in the moss Physcomitrella patens are orthologous to transcriptional regulators of stomatal development in the flowering plant Arabidopsis thaliana and essential for stomata formation in moss. Targeted P. patens knockout mutants lacking either PpSMF1 or PpSCRM1 develop gametophytes indistinguishable from wild-type plants but mutant sporophytes lack stomata. Protein-protein interaction assays reveal heterodimerization between PpSMF1 and PpSCRM1, which, together with moss-angiosperm gene complementations6, suggests deep functional conservation of the heterodimeric SMF1 and SCRM1 unit is required to activate transcription for moss stomatal development, as in A. thaliana7. Moreover, stomata-less sporophytes of ΔPpSMF1 and ΔPpSCRM1 mutants exhibited delayed dehiscence, implying stomata might have promoted dehiscence in the first complex land-plant sporophytes.
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Affiliation(s)
- Caspar C. Chater
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Mexico
| | - Robert S. Caine
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Marta Tomek
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany
| | - Simon Wallace
- Royal College of Veterinary Surgeons, Belgravia House, 62-64 Horseferry Rd, London SW1P 2AF, UK
| | - Yasuko Kamisugi
- Centre for Plant Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Andrew C. Cuming
- Centre for Plant Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Daniel Lang
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany
| | - Cora A. MacAlister
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, 48109-1048, USA
| | - Stuart Casson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | | | - Eva L. Decker
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany
| | - Wolfgang Frank
- Plant Molecular Cell Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, LMU Biocenter, Großhaderner Straße 2, 82152 Planegg-Martinsried, Germany
| | - Julie E. Gray
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Andrew Fleming
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Ralf Reski
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany
- BIOSS – Centre for Biological Signalling Studies, 79104 Freiburg, Germany
| | - David J. Beerling
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
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Cullen E, Rudall PJ. The remarkable stomata of horsetails (Equisetum): patterning, ultrastructure and development. ANNALS OF BOTANY 2016; 118:207-18. [PMID: 27268485 PMCID: PMC4970360 DOI: 10.1093/aob/mcw094] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 02/18/2016] [Accepted: 03/31/2016] [Indexed: 05/21/2023]
Abstract
BACKGROUND AND AIMS The stomata of Equisetum - the sole extant representative of an ancient group of land plants - are unique with respect to both structure and development, yet little is known about details of ultrastructure and patterning, and existing accounts of key developmental stages are conflicting. METHODS We used light and electron microscopy to examine mature stomata and stomatal development in Equisetum myriochaetum, and compared them with other land plants, including another putative fern relative, Psilotum We reviewed published reports of stomatal development to provide a comprehensive discussion of stomata in more distantly related taxa. KEY RESULTS Stomatal development in Equisetum is basipetal and sequential in strict linear cell files, in contrast with Psilotum, in which stomatal development occurs acropetally. In Equisetum, cell asymmetry occurs in the axial stomatal cell file, resulting in a meristemoidal mother cell that subsequently undergoes two successive asymmetric mitoses. Each stomatal cell complex is formed from a single precursor meristemoid, and consists of four cells: two guard cells and two mesogene subsidiary cells. Late periclinal divisions occur in the developing intervening cells. CONCLUSIONS In addition to the unique mature structure, several highly unusual developmental features include a well-defined series of asymmetric and symmetric mitoses in Equisetum, which differs markedly from Psilotum and other land plants. The results contribute to our understanding of the diverse patterns of stomatal development in land plants, including contrasting pathways to paracytic stomata. They add to a considerable catalogue of highly unusual traits of horsetails - one of the most evolutionarily isolated land-plant taxa.
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Affiliation(s)
- Erin Cullen
- Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
| | - Paula J Rudall
- Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
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Merced A, Renzaglia KS. Patterning of stomata in the moss Funaria: a simple way to space guard cells. ANNALS OF BOTANY 2016; 117:985-94. [PMID: 27107413 PMCID: PMC4866314 DOI: 10.1093/aob/mcw029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 11/15/2015] [Accepted: 01/11/2016] [Indexed: 05/18/2023]
Abstract
BACKGROUND AND AIMS Studies on stomatal development and the molecular mechanisms controlling patterning have provided new insights into cell signalling, cell fate determination and the evolution of these processes in plants. To fill a major gap in knowledge of stomatal patterning, this study describes the pattern of cell divisions that give rise to stomata and the underlying anatomical changes that occur during sporophyte development in the moss Funaria. METHODS Developing sporophytes at different stages were examined using light, fluorescence and electron microscopy; immunogold labelling was used to investigate the presence of pectin in the newly formed cavities. KEY RESULTS Substomatal cavities are liquid-filled when formed and drying of spaces is synchronous with pore opening and capsule expansion. Stomata in mosses do not develop from a self-generating meristemoid as in Arabidopsis, but instead they originate from a protodermal cell that differentiates directly into a guard mother cell. Epidermal cells develop from protodermal or other epidermal cells, i.e. there are no stomatal lineage ground cells. CONCLUSIONS Development of stomata in moss occurs by differentiation of guard mother cells arranged in files and spaced away from each other, and epidermal cells that continue to divide after stomata are formed. This research provides evidence for a less elaborated but effective mechanism for stomata spacing in plants, and we hypothesize that this operates by using some of the same core molecular signalling mechanism as angiosperms.
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Affiliation(s)
- Amelia Merced
- Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901, USA
| | - Karen S Renzaglia
- Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901, USA
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Merced A. Novel insights on the structure and composition of pseudostomata of Sphagnum. AMERICAN JOURNAL OF BOTANY 2015; 102:329-35. [PMID: 25784466 DOI: 10.3732/ajb.1400564] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
PREMISE OF THE STUDY The occurrence of stomata on sporophytes of mosses and hornworts is congruent with a single origin in land plants. Although true stomata are absent in early-divergent mosses, Sphagnum has specialized epidermal cells, pseudostomata, that partially separate but do not open to the inside. This research examined two competing hypotheses that explain the origin of pseudostomata: (1) they are modified stomata, or (2) they evolved from epidermal cells independently from stomata.• METHODS Capsule anatomy and ultrastructure of pseudostomata were studied using light and electron microscopy, including immunolocalization of pectins.• KEY RESULTS Cell walls in pseudostomata are thin, two-layered, and rich in pectins, similar to young moss stomata, including the presence of cuticle on exterior walls. Outer and ventral walls have a thick cuticle that suggests that initial separation of ventral walls involves cuticle deposition as in true stomata. Further mechanical separation between ventral walls does not form a pore and occurs as the capsule dries.• CONCLUSIONS As in moss stomata, pseudostomata wall architecture and behavior facilitate capsule dehydration, shape change, and dehiscence, supporting a common function. The divergent structure and fate of pseudostomata may be explained by the retention of Sphagnum sporophytes within protective leaves until nearly mature. Ultrastructural and immunocytological data suggest that pseudostomata are related to stomata but do not conclusively support either hypothesis. Solving the relationship of early land plants is critical to understanding stomatal evolution. Pseudostomata are structurally and anatomically unique, but their relationship to true stomata remains to be determined.
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Affiliation(s)
- Amelia Merced
- Department of Plant Biology, Southern Illinois University, Carbondale, Illinois 62901 USA
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Merced A, Renzaglia K. Developmental changes in guard cell wall structure and pectin composition in the moss Funaria: implications for function and evolution of stomata. ANNALS OF BOTANY 2014; 114:1001-10. [PMID: 25129633 PMCID: PMC4171074 DOI: 10.1093/aob/mcu165] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 06/30/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND AND AIMS In seed plants, the ability of guard cell walls to move is imparted by pectins. Arabinan rhamnogalacturonan I (RG1) pectins confer flexibility while unesterified homogalacturonan (HG) pectins impart rigidity. Recognized as the first extant plants with stomata, mosses are key to understanding guard cell function and evolution. Moss stomata open and close for only a short period during capsule expansion. This study examines the ultrastructure and pectin composition of guard cell walls during development in Funaria hygrometrica and relates these features to the limited movement of stomata. METHODS Developing stomata were examined and immunogold-labelled in transmission electron microscopy using monoclonal antibodies to five pectin epitopes: LM19 (unesterified HG), LM20 (esterified HG), LM5 (galactan RG1), LM6 (arabinan RG1) and LM13 (linear arabinan RG1). Labels for pectin type were quantitated and compared across walls and stages on replicated, independent samples. KEY RESULTS Walls were four times thinner before pore formation than in mature stomata. When stomata opened and closed, guard cell walls were thin and pectinaceous before the striated internal and thickest layer was deposited. Unesterified HG localized strongly in early layers but weakly in the thick internal layer. Labelling was weak for esterified HG, absent for galactan RG1 and strong for arabinan RG1. Linear arabinan RG1 is the only pectin that exclusively labelled guard cell walls. Pectin content decreased but the proportion of HG to arabinans changed only slightly. CONCLUSIONS This is the first study to demonstrate changes in pectin composition during stomatal development in any plant. Movement of Funaria stomata coincides with capsule expansion before layering of guard cell walls is complete. Changes in wall architecture coupled with a decrease in total pectin may be responsible for the inability of mature stomata to move. Specialization of guard cells in mosses involves the addition of linear arabinans.
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Affiliation(s)
- Amelia Merced
- Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901, USA
| | - Karen Renzaglia
- Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901, USA
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