Recent Selected Publications from the Geitmann Lab

For more publications and reprints in pdf format, please go to the IRBV web site.
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Chebli Y, Geitmann A. 2017. Cellular growth in plants requires regulation of cell wall biochemistry. Current Opinion in Cell Biology. in press
PDF is available upon request

Cell and organ morphogenesis in plants are regulated by the chemical structure and mechanical properties of the extracellular matrix, the cell wall. How the remodelling of this material is regulated to generate the morphological changes required during plant development is explored.

Geitmann A. 2017. Microfluidics and MEMS (microelectromechanical systems)-based platforms for experimental analysis of pollen tube growth behavior and quantification of cell mechanical properties. In: Obermeyer G, Feijó J (eds) Pollen Tube Tip Growth: From Biophysical Aspects to Systems Biology. Springer Verlag, in press
PDF is available upon request

Microfluidic technology can be used for the micromanipulation of single cells. Clever engineering has allowed for the measurement of single cell forces and the quantitative determination of biomechanical parameters. How these techniques have been exploited to study growing pollen tubes is summarized in this chapter.

Rakusova H, Geitmann A. 2017. Control of cellular morphogenesis through intracellular trafficking. In: Obermeyer G, Feijó J (eds) Pollen Tube Tip Growth: From Biophysical Aspects to Systems Biology. Springer Verlag, in press
PDF is available upon request

The pollen tube accomplishes invasive and directed behavior by manipulating the force and orientation of its cellular expansive growth. This in turn necessitates the orchestration ofits intracellular transport and secretory machinery. The molecular regulatory mechanisms involved in these processes are summarized in this contribution.

Geitmann A. 2016. Actuators acting without actin. Cell 166:15-17
PDF is available from the publisher or upon request

How do plant organs effect movement? Very differently from animal organs, that is for sure! Rather than employing actin-based contraction, movement in plant organs relies on water flux between cells or tissues, within cellular cytoplasm or cell wall. Understanding the mechanics requires quantitative experimentation and mechanical modeling at multiple scales. This Preview introduces an intriguing paper on the explosive seed dispersal by Hofhuis et al.

Agudelo CG, Packirisamy M, Geitmann A. 2016. Influence of electric fields and conductivity on pollen tube growth assessed via Electrical Lab-on-Chip. Scientific Reports 6:19812
PDF is available from the publisher or upon request

Elongating pollen tubes respond to the presence of electric fields. We designed a highly reproducible experimental setup based on Lab-on-Chip technology that allows researchers to assess the effect of electric field strengths and AC frequencies on single cells. Medium conductivity was found to be an important parameter determining the response of cells to the electric field.

Bidhendi AJ, Geitmann A. 2016. Relating the mechanics of the primary plant cell wall to morphogenesis. Journal of Experimental Botany 67: 449-461
PDF is available from the publisher or upon request

Regulation of the mechanical properties of the cell wall is a key parameter used by plants to control the growth behavior of individual cells and tissues. This review covers the major cell wall polysaccharides and their implication for plant cell wall mechanics.

Geitmann A, Nebenführ A. 2015. Navigating the plant cell: Intracellular transport logistics in the green kingdom. Molecular Biology of the Cell, 26 (19): 3373-3378
PDF is available from the publisher or upon request

All eukaryotic cells have to shuttle material between different compartments or between different subcellular regions. The logistics of actin and microtubule-mediated intracellular transport in plant cells is discussed.

Chebli Y, Geitmann A. 2015. Live cell and immuno-labeling techniques to study gravitational effects on single plant cells. In: Blancaflor E (ed) "Plant Gravitropism", Series "Methods in Molecular Biology", Humana Press, pp. 209-226
PDF is available upon request

Administering fluorescence label to single plant cells cultivated under micro- or hyper-gravity conditions requires specialized handling. This chapter provides detailed protocols and techniques.

Sanati Nezhad A, Geitmann A. 2015. Tip growth in walled cells: Cellular expansion and invasion mechanisms. In: Cuerrier C, Pelling A (eds) Cells, Forces and the Microenvironment, CRC Press pp. 335-355
PDF will be available from the publisher or upon request

Plant cell morphogenesis is a process governed by a set of mechanical principles which determine how and into what shape the cell grows or how it deals with mechanical obstacles. In this review the individual concepts and vocabulary of plant cell growth in general and invasive growth in particular are explained.

Altartouri B, Geitmann A. 2014. Understanding plant cell morphogenesis requires real-time monitoring of cell wall polymers. Current Opinion in Plant Biology 23:76–82
PDF is available from the publisher or upon request

Plant developmental processes involve dynamic changes in the molecular architecture of the plant cell wall. Understanding these requires the live imaging of cell wall polysaccharides. This review summarizes recent technical advances that have made such observations possible.
 

Hamamura Y, Nishimaki M, Takeuchi H, Geitmann A, Kurihara D, Higashiyama T. 2014. Live imaging of calcium spikes during double fertilization in Arabidopsis. Nature Communications 5:4722
PDF is available from the publisher or upon request

The cells of the female gametophyte show distinct calcium spikes upon pollen tube discharge and fertilization by the sperm cells. These are the first observations of calcium profiles during in vivo fertilization in plants.
 

Sanati Nezhad A, Packirisamy M, Geitmann A. 2014. Dynamic, high precision targeting of growth modulating agents is able to trigger pollen tube growth reorientation. Plant Journal 80: 185-195
PDF is available from the publisher or upon request

The growing pollen tube apex represents a rapidly moving target making the local administration of drugs or proteins a challenge. We designed a microfluidic device with which we are able to target the growing region of the tube in tunable manner thus enabling its asymmetric exposure to chemical gradients with micrometer precision.
 

Geitmann A, Dyson R. 2014. Modeling of the primary plant cell wall in the context of plant development. In: "Cell Biology", Assman S, Liu B (eds), Series "The Plant Sciences", Tester M, Jorgensen RA (eds), Springer Verlag, New York, 1-17
PDF is available from the publisher or upon request

Understanding the structure and behavior of the plant cell wall has been aided by numerous quantitative and numerical approaches through modeling. In this review we explain various modeling approaches and point out the value of the different concepts used.
 

Ghanbari M, Sanati Nezhad A, Agudelo CG, Packirisamy M, Geitmann A. 2014. Microfluidic positioning of pollen grains in lab-on-a-chip for single cell analysis. Journal of Bioscience and Bioengineering 117: 504–511
PDF is available from the publisher or upon request

Playing pool billiard at micron-scale ..... this is what we try to achieve in the present paper. Our billiard balls are pollen grains and the pockets are the entrances of the microchannels in a microfluidic network. We haven't clarified how to identify the 8-ball yet, however.....
 

Sanati Nezhad A, Ghanbari M, Agudelo CG, Naghavi M, Packirisamy M, Bhat R, Geitmann A. 2014. Optimization of flow assisted entrapment of pollen grains in a microfluidic platform for tip growth analysis. Biomedical Microdevices 16: 23-33
PDF is available from the publisher or upon request

A key challenge in microfluidic design for single cell analysis is the positioning of the cells within the device. This is crucial in the TipChip in which pollen grains need to be placed in front of microchannels to enable the analysis of individual pollen tubes. Here we optimized fluid flow driven distribution of pollen grains over a series of traps that ensure identical experimental conditions for all cells.
 

Sanati Nezhad A, Geitmann A. 2013. The cellular mechanics of an invasive life style. Journal of Experimental Botany 64: 4709-4728
PDF is available from the publisher or upon request

Tip growing cells such as nuerons, fungal hyphae, root hairs and pollen tubes have the ability to invade living tissues and abiotic matrices. In this review article we examine the mechanical challenges associated with this way of life: the forces required to overcome mechanical impedance, as well as friction and pushback.
 

Sanati Nezhad A, Naghavi M, Packirisamy M, Bhat R, Geitmann A. 2013. Quantification of cellular penetrative forces using Lab-on-a-Chip technology and finite element modeling. PNAS 110: 8093–8098
PDF is available from the publisher or upon request

To reach an ovule, the pollen tube needs to invade the pistillar tissues of the receptive flower. This requires the exertion of invasive and dilating forces. To quantify these forces, we used the TipChip, a microfluidic platform, and exposed in vitro growing pollen tubes with mechanical obstacles. We found that pollen tubes often burst and release the sperm cells after having passed a narrow opening. Find more information about the project .
For media coverage check University of Montreal (English, French), Live Science, Phys.org, NBC News, Science Daily, Guokr.com, ChemFeeds.
 

Chebli Y, Kroeger J, Geitmann A. 2013. Transport logistics in pollen tubes. Molecular Plant 6: 1037–1052
PDF is available from the publisher or upon request

Intracellular transport over long distances as well as short term targeting and exchange with the outside of the cell are crucial processes during plant cell growth, particularly in the rapidly growing pollen tube. This review summarizes the biophysical underpinnings of intracellular transport processes and fluid mechanics in this tip growing cell.
 

Sanati Nezhad A, Packirisamy M, Bhat R, Geitmann A. 2013. In vitro study of oscillatory growth dynamics of Camellia pollen tubes in microfluidic environment. IEEE Transactions on Biomedical Engineering 60: 3185-3193
PDF is available from the publisher or upon request

Pollen tubes grow in oscillatory manner. We used the TipChip, a microfluidic experimental platform, to analyze these oscillations in detail and found that the growth dynamics is characterized by primary and secondary oscillation frequencies.
 

Chebli Y, Pujol L, Shojaeifard A, Brouwer I, van Loon JJWA, Geitmann A. 2013. Cell wall assembly and intracellular trafficking in plant cells are directly affected by changes in the magnitude of gravitational acceleration. PLoS One 8: e58246
PDF is available from the publisher or upon request
For some of the press coverage check UdeM Press Release, NBC, Fox News, Live Science, Huffington Post, Discover Magazine, Bioscience Technology Corriere della Sera, Daily Mail, Yahoo News, Guokr.com, Scientias.nl, CNET News, Latinos Post, ivoox (audio, Spanish), Radio Canada International (interview, French), Radio Suisse (interview, French)

Rapid and precisely targeted intracellular transport is a hallmark of tip growing cells such as neurons, pollen tubes and fungal hyphae. Life cell fluorescence imaging of pollen tubes exposed to hyper-gravity conditions in the Large Diameter Centrifuge of the European Space Agency showed that this process is affected by altered gravity acceleration. Similarly, both intracellular trafficking and cell wall assembly were disturbed by omnidirectional gravity applied in a Random Positioning Machine.
More information about the project and answers to questions raised by some of the media coverage.
 

Sanati Nezhad A, Naghavi M, Packirisamy M, Bhat R, Geitmann A. 2013. Quantification of the Young's modulus of the primary plant cell wall using Bending-Lab-On-Chip (BLOC). Lab on a Chip 13: 2599–2608
PDF is available from the publisher or upon request

The classical bending test used for the quantification of mechanical properties of rod shaped objects has been brought down to the microscopic scale with a test assay based on microfluidics technology. The device was used to quantify the Young's modulus of the pollen tube cell wall.
 

Sun XD, Feng ZH, Meng LS, Zhu J, Geitmann A. 2013. Arabidopsis ASL11/ LBD15 is involved in shoot apical meristem development and regulates WUS expression. Planta 237: 1367-1378
PDF is available from the publisher or upon request

Plant development is crucially influenced by processes occurring in the shoot apical meristem (SAM). We found that ASL11/LBD15, a member of the Arabidopsis thaliana AS2/LOB gene family, regulates cellular differentiation in the SAM. This new regulatory pathway acts via transcriptional control of WUSCHEL, a central regulator in the SAM.
 

Agudelo CG, Sanati Nezhad A, Ghanbari M, Naghavi M, Packirisamy M, Geitmann A. 2013. TipChip – a modular, MEMS (microelectromechanical systems)-based platform for experimentation and phenotyping of tip growing cells. Plant Journal 73:1057-1068
PDF is available from the publisher or upon request

The TipChip is an experimental platform that allows exposing pollen tubes to a variety of experimental assays such as chemical gradients, mechanical obstacles, fluid-air interface, and electrical fields.
 

Agudelo CG, Packirisamy M, Geitmann A. 2013 Lab-on-a-Chip for studying growing pollen tubes. In: Plant Cell Morphogenesis: Methods and Protocols, Series "Methods in Molecular Biology", eds. Žárský V, Cvrčková F, Springer. pp 237-248
PDF will be available from the publisher or upon request

The fabrication of the TipChip is explained in detail and numerous hints and tips are given for successful production and use of a microfluidic platform.
 

Kroeger JH, Geitmann A. 2013. Pollen tubes with more viscous cell walls oscillate at lower frequencies. Mathematical Modeling of Natural Phenomena 8: 25-34
PDF is available from the publisher or upon request

The addition of boron is thought to rigidify the cell wall and has been observed to reduce the oscillation frequency in pollen tubes. Our model attempts to explain this phenomenon by linking growth rate to a variety of cellular processes.
 

Chebli Y, van Loon JJWA, Geitmann A. 2012. Live cell imaging under hyper-gravity conditions. Bulletin of the Microscopical Society of Canada December: 8-13
PDF

Spinning a fluorescence microscope at 20g has its challenges. Here we explain how we monitored intracellular traffic in growing pollen tubes using ESA's Large Diameter Centrifuge.
 

Sanati Nezhad A, Ghanbari M, Agudelo CG, Packirisamy M, Bhat RB, Geitmann A. 2012. PDMS microcantilever-based flow sensor integration for lab-on-a-chip. IEEE Sensors Journal 13: 601-609
PDF is available from the publisher or upon request

To measure the speed of fluid flow within a microfluidic device a low cost and low-tec test assay was developed that relies on the flow-induced deformation of a calibrated PDMS cantilever. This test device allows for calibrated administration of fluid flow and shear stress.
 

Agudelo CG, Sanati Nezhad A, Ghanbari M, Packirisamy M, Geitmann A. 2012. A microfluidic platform for the investigation of elongation growth in pollen tubes. Journal of Micromechanics and Microengineering 22, 115009
PDF is available from the publisher or upon request

Studying pollen tubes one at a time is now possible using a microfluidic device that guides the elongating tubes through narrow microchannels where they can be exposed to experimental test assays.
 

Chebli Y, Kaneda M, Zerzour R, Geitmann A. 2012. The cell wall of the Arabidopsis thaliana pollen tube - spatial distribution, recycling and network formation of polysaccharides. Plant Physiology 160: 1940-1955
PDF is available from the publisher or upon request

The spatial distribution of the major cell wall polymers composing the Arabidopsis pollen tube cell wall is quantified and compared to the predictions of a mechanical model. Cellulose microfibrils were found to be oriented in near longitudinal orientation consistent with a linear arrangement of cellulose synthase CESA6 in the plasma membrane.
 

Kroeger JH, Geitmann A. 2012. The pollen tube paradigm revisited. Current Opinion in Plant Biology 15: 618–624
PDF is available from Elsevier or upon request

The pollen tube has become the object of numerous mathematical and physical modeling approaches. This review explains recent models in a way that is accessible to biologists. It points out the assumptions going into the respective models, the type of modeling, as well as the predictions and limitations of each approach.
 

Bou Daher F, Geitmann A. 2012. Actin Depolymerizing Factors ADF7 and ADF10 play distinct roles during pollen development and pollen tube growth. Plant Signaling & Behavior 7: 873-875
PDF is available from Landes Bioscience or upon request

Actin dynamics is regulated by actin binding proteins. We produced Arabidopsis lines expressing fluorescently labeled Actin Depolymerizing Factors ADF7 and ADF10 to monitor the behavior of these proteins during pollen germination and pollen tube growth. The two members of the ADF family show different subcellular localization profiles in elongating pollen tubes suggesting distinct functions.
 

Palin R, Geitmann A. 2012. The role of pectin in plant morphogenesis. BioSystems 109: 397–402
PDF is available from Elsevier or upon request

Pectin is a crucial component in the plant cell wall. Its molecular complexity and changing biochemical configuration make this component a key mediator of processes regulating plant development. In this review we discuss three experimental model systems in which the modulation of pectins play an important role: expansive growth in the root elongation zone, tip growth in the pollen tube, and organogenesis in the shoot apical meristem.
 

Kroeger JH, Geitmann A. 2012. Pollen tube growth: getting a grip on cell biology through modeling. Mechanics Research Communications 42: 32-39
PDF is available from Elsevier or upon request

You are an engineer or mathematician trying to figure out what seems to attract plant cell biologists to your discipline lately? In this review we provide an overview of recent analytical and computational models that have been developed to help explain various aspects of an intriguing biological phenomenon - tip growth as it occurs in pollen tubes and other cell types with polar elongation pattern. The underlying biological principles are explained for non-biologists.
 

Speranza A, Crinelli R, Scoccianti V, Geitmann A. 2012. Reactive oxygen species are involved in pollen tube initiation in kiwifruit. Plant Biology 14: 64–76
PDF is available from Elsevier or upon request

Plant cell growth and morphogenesis are associated with the production of reactive oxygen species (ROS). Here we show that ROS are involved in the germination and tube formation in pollen grains from kiwifruit. Inhibition of ROS production inhibited pollen germination and, inversely, inhibition of pollen germination by other means, reduced ROS production.
 

Pietruszka M, Lipowczan M, Geitmann A. 2012. Persistent symmetry frustration in pollen tubes. PLoS One 7: e48087
PDF will be available from the publisher or upon request

The shape of the pollen tube comprises two types of symmetry. The consequences for the behavior of the cell wall at the transition region between apex and shank are investigated from a mechanical point of view.


Chebli Y, Geitmann A. 2011. Gravity research on plants: Use of single cell experimental models. Frontiers in Plant Cell Biology 2, Article 56, 1-10
PDF is available from Frontiers or upon request

Numerous single cell systems have emerged as useful experimental systems to analyze the effect of altered gravity conditions on plant cell metabolism and functioning. In this review we summarize recent advances and point out the potential further exploitation of these systems. The review also provides an overview over the different mechanisms that have been proposed to be at the base of graviperception in plants.
 

Bou Daher F, Geitmann A. 2011. Actin is involved in pollen tube tropism through redefining the spatial targeting of secretory vesicles. Traffic 12: 1537–1551
PDF is available from Wiley Blackwell or upon request

Pollen tubes are able to follow chemical gradients by rapidly reorienting their growth. But how does the tube achieve this change in morphogenetic behavior mechanically? Here we exposed pollen tubes to precisely calibrated electrical fields and monitored their turning behavior to analyse vesicle delivery patterns and cytoskeletal dynamics leading up to the reorientation.
 

Kroeger J, Geitmann A. 2011. Modeling pollen tube growth: feeling the pressure to deliver testifiable predictions. Plant Signaling & Behavior 6: 1828-1830
PDF will be available from Landes Bioscience or upon request

If the Lockhart equation applies to pollen tubes, then why are growth rate and turgor seemingly uncoupled in oscillatory growth? In our theoretical model based on calcium triggered exocytosis we provide a possible explanation for the finding that at a high turgor regime the average growth rate in pollen tubes is rather insensitive to turgor changes.
 

Qi X, Kaneda M, Chen J, Geitmann A, Zheng H. 2011. A specific role for Arabidopsis TRAPPII in post-Golgi trafficking that is crucial for cytokinesis and cell polarity. Plant Journal 68: 234–248
PDF is available from Plant Journal or upon request

Cytokinesis and cell polarity are supported by membrane trafficking from the trans-Golgi network, but the molecular mechanisms that promote this process is poorly defined in plant cells. Here we show that TRAPPII (transport protein particle II, a complex consisting of several subunits) in Arabidopsis regulates post-Golgi trafficking that is crucial for assembly of the cell plate and cell polarity.
 

Bou Daher F, van Oostende C, Geitmann A. 2011. Spatial and temporal expression of Actin Depolymerizing Factors ADF7 and ADF10 during male gametophyte development in Arabidopsis thaliana. Plant and Cell Physiology 52: 1177–1192
PDF is available from Plant and Cell Physiology or upon request

The dynamics of the actin cytoskeleton is crucial for successful pollen germination and pollen tube growth. The regulation of this dynamical behavior lies with actin binding proteins. Here we show that two actin binding proteins, ADF7 and ADF10, are specifically expressed in pollen and using fluorescent label we demonstrate that their expression and cellular localization differ from each other.
 

Kroeger JH, Zerzour R, Geitmann A. 2011. Regulator or driving force? The role of turgor pressure in oscillatory plant cell growth. PLoS One 6: e18549
PDF is available from PLoS One or upon request

The role of turgor in the phenomenon of oscillatory growth in pollen tubes is intensely debated. Here we built a mathematical model that couples the Lockhart equation to dynamical equations for changes in material properties of the cell wall. The model shows that changes in turgor pressure are not necessary to explain the behavior of pollen tubes under different osmotic conditions. The predictions of the model are consistent with a series of experimental data and provides a framework for the conception of new experiments.
 

Winship LJ, Obermeyer G, Geitmann A, Hepler PK. 2011. Pollen tubes and the physical world. Trends in Plant Science 16: 353-355
PDF is available from Elsevier or upon request

Living beings have to obey physical laws and so do plant cells. Although plant cells are known to be able to control turgor, they generally do not use increases in turgor to grow but instead growth is triggered by a lowering in cell wall stiffness. Whether or not pollen tubes adhere to this principle has been debated in recent years and in the present paper we explore the physical principles involved.
 

Geitmann A. 2011. Generating a cellular protuberance - Mechanics of tip growth. In: Mechanical Integration in Plant Cells and Plants. edited by Wojtaszek P. Springer. pp 117-132
PDF is available upon request

Generating a tubular cell is not a trivial feat. In this review the initial steps of tube generation and the continuous elongation are analyzed from a mechanical point of view.

 

Geitmann A. 2011. Petunia. Evolutionary, developmental and physiological genetics. Book Review. Annals of Botany 107: vi-vii
PDF is available at Oxford Journals or upon request

Petunia is an important horticultural species but also a model for plant science. The article reviews the recent book edited by Tom Gerats and Judith Strommer.
 

Geitmann A. 2010. Mechanical modeling and structural analysis of the primary plant cell wall. Current Opinion in Plant Biology 13: 693–699
PDF is available from Elsevier or upon request

Modeling mechanical aspects of plant cell growth requires the integration of structural cell wall details with quantitative biophysical parameters. This review highlights recent advances in microscopic techniques and mechanical modeling that have made significant contributions to the field of cell wall biomechanics.
 

Fayant P, Girlanda O, Chebli Y, Aubin C-E, Villemure I, Geitmann A. 2010. Finite element model of polar growth in pollen tubes. Plant Cell 22: 2579–2593
PDF is available from ASPB or upon request
This article has been covered by the following editorial: Eckardt N. 2010. Modeling polar growth of plant cell walls. The Plant Cell 22: 2528. Link

To understand how intracellular, metabolic and signaling processes lead to cellular growth and shape generation we must understand the mechanical constraints governing the cellular growth process in plants. The generation of complex shapes can only be modeled with approximate methods. We use finite element modeling to demonstrate the usefulness of this engineering method for plant cell biology. Comparison between the predictions made by the model and the biochemical composition of the cell wall suggests an important structural role for the spatial distribution of methyl-esterified and acidic pectins in determining cell shape during pollen tube growth.
 

Winship LJ, Obermeyer G, Geitmann A, Hepler PK. 2010. Under pressure, cell walls set the pace. Trends in Plant Science 15: 363-369
PDF is available from Elsevier or upon request

Pollen tubes in vitro typically display regular oscillations in growth rate. Studies of these oscillating cells have shown that underlying processes such as ion fluxes and cell wall properties also vary rhythmically, with a high degree of regularity and stability. The oscillatory changes in growth rate have been purported to be controlled by oscillations in the turgor pressure in the apical region of the tube. Here we explain that turgor is unlikely to oscillate significantly in growing pollen tubes, and that spatial and temporal control of the growth process is governed by the dynamic mechanical properties of the cell wall. 
 

Geitmann A. 2010. How to shape a cylinder - Pollen tube as a model system for the generation of complex cellular geometry. Sexual Plant Reproduction 23: 63–71
Preprint (accepted manuscript)
PDF available from Springer or upon request

In this review article mechanical aspects of pollen tube germination and growth are analyzed. What allows the germinating pollen grain to form a tubular protuberance? Does the exine play a role in determining the tube diameter? What adaptations in the growth pattern allow the pollen tube to invade a stiff matrix? Why is tip growth advantageous for the invasive and target-oriented life style of the pollen tube?
 

Aouar L, Chebli Y, Geitmann A. 2010. Morphogenesis of complex plant cell shapes - the mechanical role of crystalline cellulose in growing pollen tubes. Sexual Plant Reproduction 23: 15–27  
Preprint (accepted manuscript)
PDF available from Springer or upon request

Cellulose is an important structural component in the plant cell wall. Cellulose microfibrils confer resistance to tensile stress. Their preferential orientation therefore directs cell expansion. In most cylindrical plant cells, cellulose  is oriented in transverse direction to the long axis. We found that this is not the case in pollen tubes and we relate the mechanics of cellulose to the invasive life style of this cell type. 
 

Zerzour R, Kroeger JH, Geitmann A. 2009. Polar growth in pollen tubes is associated with spatially confined dynamic changes in cell mechanical properties. Developmental Biology 334: 437-446  
Preprint (accepted manuscript)
PDF available from Elsevier or upon request

Expansive growth in a plant cell relies on the interplay between the internal turgor and the forces in the cell wall opposing deformation. Which of the two parameters controls the dynamics of growth has been controversial in the case of pollen tube growth. We now show that both the initiation of polar growth and the rapid growth phases during oscillatory growth in pollen tubes are preceded by a softening of the cell wall. Our micro-indentation experiments also showed that cellular turgor pressure does not undergo changes during these repeated, accelerated growth phases. This points to an important role for the cell wall mechanical properties in controlling the dynamics of pollen tube growth.
 

Kroeger JH, Bou Daher F, Grant M, Geitmann A. 2009. Microfilament orientation contrains vesicle flow and spatial distribution in growing pollen tubes. Biophysical Journal 97: 1822-1831 
Preprint (accepted manuscript)
PDF available from Biophysical Society or upon request

How come the secretory vesicles in the apical region of the pollen tube move in a precisely defined pattern if there is no filamentous actin to guide them? We answer this question with a theoretical model based on the spatial configuration of the subapical actin fringe. The model reveals fundamental principles governing the logistics of intracellular transport processes and the dynamics of the cytoskeleton in rapidly growing plant cells.
 

Geitmann A, Ortega JKE. 2009. Mechanics and modeling of plant cell growth. Feature Review. Trends in Plant Science 14: 467-478  
Preprint  (accepted manuscript)
PDF available from Elsevier or upon request

A fundamental underpinning of plant development is expansive cellular growth. Understanding the biophysical principles of plant cell growth is therefore crucial for the analysis of mutant phenotypes. In this feature review we provide an overview of the state-of-the-art of the biomechanics of primary plant cell growth. We discuss recently developed conceptual and mechanical models explaining plant cell growth. The mechanics of overall plant cell expansion versus spatially confined growth events leading to complex cellular geometries are elaborated. We propose new terms to precisely identify different types of cellular growth. 
 

Geitmann A, Dumais J. 2009. Not-so-tip-growth. Plant Signaling & Behavior 4: 136-138   PDF

Tip growth is a spatially confined growth process that occurs in certain cell types with an invasive life style. In these cells all growth activity occurs at the extreme end of the cell, resulting in a continuously elongating cylinder. However, quantification of surface deformation patterns and localization of exocytosis events has revealed that cellular expansion in some of the cell types exhibiting tip growth might actually be in an annular region around the pole of the cell. In this addendum paper we explore the principles governing tip growth in root hairs and pollen tubes.
 

Bou Daher F, Chebli Y, Geitmann A. 2009. Optimization of conditions for germination of cold-stored Arabidopsis thaliana pollen. Plant Cell Reports 28: 347-457  
Preprint (accepted manuscript) 
PDF
available from Springer or upon request

Does your Arabidopsis pollen germinate well and reproducibly in vitro? Does it store well in the freezer? If not, try our optimized protocols adapted for a wide range of experimental setups.

 

Chebli Y, Bou Daher F, Sanyal M, Aouar L, Geitmann A. 2008. Microwave assisted processing of plant cells for optical and electron microscopy. Bulletin of the Microscopical Society of Canada 36(3): 15-19   PDF

Do you want to reduce the bench time for sample preparation for fluorescence and electron microscopy? Do you need to reduce fixation-induced artifacts and increase antigenicity? All you need is a (science grade) microwave to accelerate all sample preparations steps, from fixation to dehydration and labeling. Try our optimized protocols adapted for single plant cells.
 

Bove J, Vaillancourt B, Kroeger J, Hepler PK, Wiseman PW, Geitmann A. 2008. Magnitude and direction of vesicle dynamics in growing pollen tubes using spatiotemporal image correlation spectroscopy (STICS) and fluorescence recovery after photobleaching (FRAP). Plant Physiology 147: 1646-1658   PDF

Secretory vesicles deliver the cell wall material required for the assembly of the elongating pollen tube tip. Their precise movement pattern and the location of exocytosis are important parameters for the understanding of the principles governing the logistics of intracellular material transport. However, because of their small size, it is difficult to quantitatively determine the movement pattern of vesicles in the optical microscope. We used high temporal resolution confocal microscopy in combination with spatio-temporal image correlation spectroscopy to determine the intracellular streaming of these organelles. These studies, in combination with the results of FRAP (fluorescence recovery after photobleaching) experiments reveal that the intracellular transport mechanism is optimized for efficient material delivery to the growing cell surface.
 

Kroeger JH, Geitmann A, Grant M. 2008. Model for calcium dependent oscillatory growth in pollen tubes. Journal of Theoretical Biology 253: 363-374   PDF

Many pollen tubes grow in an oscillatory manner. Concomitantly to the dynamic alterations in growth rate, a number of cellular parameters undergo oscillatory changes. We established a theoretical model for this growth pattern. It is based on feedback mechanisms involving the mechanics of the cell wall and the secretion of new cell wall material controlled by the intracellular calcium concentration.
 

Chebli Y, Geitmann A. 2007. Mechanical principles governing pollen tube growth. Functional Plant Science and Biotechnology 1: 232-245   PDF

Numerous scientific papers have identified cellular parameters that influence the growth rate of the pollen tube. In this review article we provide a compilation of those parameters that have been shown to undergo changes during oscillatory growth. We develop a conceptual model of the pollen tube growth dynamics that is centered around the mechanics of the growing cell. Cell wall physical properties and the turgor pressure have pivotal functions since they represent the downstream parameters of all cellular signaling events.
 

Geitmann A, Palanivelu R. 2007. Fertilization requires communication: Signal generation and perception during pollen tube guidance. Floriculture and Ornamental Biotechnology 1:77-89   PDF

The interaction between the male gametophyte and the female tissues forming the pistil requires the ability of both partners to perceive and respond to the signals emitted by the other partner. In this review article we summarize the state-of-the-art of the signaling mechanisms involved in pollination and pollen tube growth, two crucial steps in sexual plant reproduction.
 

For a complete list of publications and reprints in pdf format, please go to the IRBV web site.