IMG 4877 Strand group Dec 2018a 1920x1080Åsa Strand (first from left in the first row) and her group in December 2018 (photo: Anne Honsel)
[2018-12-13] The Swedish Research Council announced the new members of its board and of its scientific councils. Åsa Strand, professor at UPSC, is one of the nine members of the Scientific Council for Natural and Engineering Sciences. Her mandate is for three years (2019-2021).

The Swedish Research Council is a government agency within the Ministry of Education and Research that fund research and research infrastructure in all scientific disciplines. The council also has an advisory role to the Government on research policy issues and work to increase understanding of the long-term societal benefits of research.

The new members of the Scientific Councils are elected by an election assembly that is formed by representatives from the Swedish higher education institutions. In total, 165 electors are selected to appoint the new members of the three Scientific Councils and also the members of the board of the Swedish Research Council.

IMG 4900 AgriseraPrize2018 920x1080The Agrisera prize 2018 was presented to Sacha Escamez (middle) by Joanna Porankiewicz-Asplund (right) from Agrisera and by the chair of the UPSC board, Catherine Bellini (left). Photo: Anne Honsel

[2018-12-12] Sacha Escamez receives this year’s UPSC Agrisera Prize. The award was announced today during the traditional UPSC Christmas lunch. Sacha Escamez is awarded for his scientific achievements and engagement in scientific discussions at UPSC and for his valuable contribution in upgrading the UPSC microscopy platform. The prize values that Sacha Escamez’s diverse commitments helped to improve UPSC’s work and social environment.

Sacha Escamez successfully carried out research on the regulation of lignification and cell death during xylem development first as a PhD student and now as postdoc in Hannele Tuominen’s group. He actively participates in and encourages scientific discussions at UPSC and also promoted his research in a public science talk for the Swedish television last year.

This year, he invested a lot of time in upgrading the UPSC microscopy platform by collecting the requirements and wishes from his colleagues, testing out different systems and negotiating with the companies. He is taking on a key role in setting up single molecule detection methods that can be done with the new instrumentation at the UPSC microscopy platform, and he will help to introduce users to those new methods.

The UPSC Agrisera Prize is awarded every year to a PhD student, Postdoc or technician at UPSC for excellent scientific achievement and positive contributions to improve the UPSC working environment. Four nominations were sent in by Sacha Escamez’s colleagues for the UPSC Agrisera Prize this year. Sacha Escamez’s nomination stuck out because it emphasized not only his scientific achievement and encouragement for the microscopy platform but also his social engagement (e.g. by creating the UPSC innebandy team) to make UPSC a nice place to work at.


Link to the video of Sacha Escamez public science talk "How do plants make plumbing pipes from cells?"
Haas Julia 9594 170116 MPN 1920x1080Julia Haas; photo: Mattias Pettersson


Climate change will affect Norway spruce trees and also the bacteria and fungi that are living in symbiosis with the tree. Julia Haas showed in her PhD thesis that Norway spruce uses special strategies to adjust to cold and drought stress and that the microbial community living together with the trees is more diverse when the trees are fertilized. Her findings are important to predict how future boreal forests can cope with the changing environment. Julia Haas will defend her PhD thesis on Friday, 14th of December at Umeå University.

Higher temperatures, summer droughts and changes in the seasonal cycle with increasing late frost events in spring will not only compromise the productivity of Norway spruce forests but could threaten the existence of Norway spruce in boreal forests. Breeding for higher stress tolerance will help to adapt future tree generations to those challenges. Julia Haas identified genes that are involved in the regulation of drought and frost tolerance and therefore good targets for breeders to improve the tolerance against abiotic stresses in Norway spruce.

In her experiments, Julia Haas compared drought and frost responsive genes in Norway spruce seedlings with known changes in the herbaceous model plant Arabidopsis thaliana. Her results showed that well-known transcription factors that regulate the expression of a multitude of other genes in Arabidopsis under drought or frost were not expressed or lacking corresponding gene models in the Norway spruce genome.

“Norway spruce often grows in harsh environments and in extreme climates. This, together with the evolutionary distance to flowering plants can explain the observed differences”, explains Julia Haas. “It is not possible to just transfer knowledge from evolutionary younger but better studied agricultural crops or broad-leaved trees to Norway spruce. Breeding and genetic engineering of Norway spruce requires a special tool set making it more stress tolerant. My research provides a first insight into Norway spruce-specific mechanisms.”

The fitness of a tree is also influenced by microorganisms living in symbiosis with the tree. Bacteria and fungi can have beneficial effects on the growth and improve the abiotic stress tolerance of the plant host. However, climate change and human activities that increase the nutrient input in ecosystems can have both positive and negative effects on plant-associated microorganisms.

Julia Haas and her colleagues studied the diversity and composition of microorganisms in a Norway spruce forest that was fertilised over the last 25 years. Intriguingly, they found that the effect of fertilisation on the diversity of symbiotic fungi and bacteria was positive and that microbial communities with higher nutrient preferences established.

“Responses in this forest ecosystem are highly dynamic and processes involve complex interactions between fungi, bacteria and plants. But research has focussed for long time only on mycorrhizal fungi and trees. We need to start look at functions and the role other microorganisms play to fully comprehend how future changes will affect the whole ecosystem”, says Julia Haas. “Only then can we make reliable predictions about the robustness of the ecosystem to climate change.”

To identify beneficial plant microbiota is also interesting for the forest industry. The microorganisms can be applied in tree nurseries to improve the growth of the seedlings and this may help to secure tree production and growth in challenging climatic conditions in the future.

Julia Haas performed her graduate studies at the Umeå Plant Science Centre, Department of Plant Physiology, Umeå University. Her projects were in close collaboration with the Swedish forest company Holmen Skog AB.

Link to the thesis: http://umu.diva-portal.org/ 

About the thesis defence:

On Friday, the 14th of December, Julia Haas, Department of Plant Physiology, Umeå University, will defend her thesis, entitled ’ Abiotic stress and plant microbe interaction in Norway spruce’. The public defence will take place at 10:00am in Carl Kempe salen (KB.E3.03) in the KBC building, Umeå University. The faculty opponent will be Jennifer Baltzer, Associate Professor and Canada Research Chair in Forest and Global Change Department of Biology, Wilfrid Laurier University, Waterloo, Canada. Supervisor of the PhD thesis was Vaughan Hurry.

For more information, please contact:
Julia Haas
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Text: Julia Haas, Anne Honsel

KarinLjung T1A8799 ElisabethOhlsonWallin 1920x1080Photo: Elisabeth Ohlson Wallin

Clarivate Analytics published recently their list of world-class researchers in social sciences and sciences. Karin Ljung is again one of those. Her papers are highly cited and rank in the top one perscent in the field Plant & Animal Science in the years 2006-2016 in Web of Science.

Since 2014, Clarivate Analytics is publishing its Highly Cited Researchers list once a year based on citation analysis in Web of Science. In all five years, Karin Ljung was named in the list. This year, Clarivate Analytics extended their 21 field categories to a new category that considers researchers that publish across fields. About 6000 researchers are identified in the list as top researcher, 4000 in specific fields like Karin Ljung and 2000 in the new category “Cross-Field”.

The Clarivate Analytics list of Highly Cited Researchers 2018:
https://hcr.clarivate.com

Read more about the methodology how Clarivate Analytics selects Highly Cited Researchers:
https://hcr.clarivate.com/methodology/

Here you can find more about Karin Ljung's research and a publication list
HyPhOE applications logo 1920x1080

The HyPhOE project – Hybrid Electronics based on Photosynthetic Organisms – has held its start-up meeting. It provided an opportunity for the participating groups to share knowledge and plan common strategies.

The HyPhOE project is part of Horizon 2020, and is looking for ways to use plants, algae and bacteria to manufacture electronic materials and devices. The project is led by the Laboratory of Organic Electronics (LOE) at LiU, Campus Norrköping, and its Electronic Plants research group, with Eleni Stavrinidou as principal investigator.

In addition to researchers from LOE, the project has participants from the Umeå Plant Science Center in Sweden, the University of Bari in Italy, and two universities in France: Institut Polytechnique de Bordeaux and Université Paris Diderot. The involved researchers from UPSC are Totte Niittylä and Torgny Näsholm.

More information about the project can be found here:

News article about the project on the homepage of Linköping University:
https://liu.se/en/news-item/3-3-miljoner-euro-till-elektroniska-vaxter

Project information on the homepage from the European Commission:
https://cordis.europa.eu/project/rcn/216306_en.html

Information about electronic plants and the responsible group on the homepage of Linköping University:
Electronic Plants: https://liu.se/en/research/electronic-plants
Laboratory of Organic Electronics (LOE): https://liu.se/en/research/laboratory-of-organic-electronics

Formas2018 1920x1080From left to right: Carolin Seyfferth, Nathaniel Street, Xiao-Ru Wang and Hannele Tuominen; photo: Anne Honsel

Last week, Formas announced the decision for their annual open calls. Four projects affiliated with UPSC got granted. Carolin Seyfferth, postdoc in Hannele Tuominen’s group, received a mobility starting grant and the group leaders Nathaniel Street, Hannele Tuominen and Xiao-Ru Wang got funding for their research and development projects. All four projects focus on tree research.

Carolin Seyfferth will use her funding to search for genes that control chemical and physical wood properties like the content of cellulose and lignin, the density or the stiffness of the wood. She will use samples that were collected from aspen trees grown at different locations in Sweden. By comparing their genetic and transcriptomic differences with their biochemical wood properties, she hopes to find marker genes or gene networks that regulate respective wood properties. The mobility starting grant offers her to visit other labs with special expertise and resources that will help validating the most interesting gene sets.

Nathaniel Street will use data from the same collection of aspen trees as Carolin Seyfferth but he will focus on compounds that are produced by the trees for example to defend themselves against animal or fungi attacks. He wants to identify the genes that control the production of those compounds. Many of these compounds are of medicinal or commercial value and may also have an impact on the diverse communities of bacteria and fungi that are growing together with the tree in a beneficial way. To understand how the production of those compounds is controlled and can be reengineered will open up new possibilities for commercial forestry.

The project of Hannele Tuominen has the purpose to identify aspen genes that control tree features interesting for bioenergy or biofuel production. She will focus on a wide range of features including biomass production, wood chemistry and pathogen resistance. By comparing the genetic setup of a collection of different aspen variants, she wants to select marker genes that might help improve breeding for certain desired features. The best variants from the characterised collection can be directly used for example for short-rotation plantations of aspen that are used already now for bioenergy or biofuel production.

Xiao-Ru Wang, group leader at the Department of Ecology and Environmental Sciences and affiliated with UPSC, will work with another tree species, Scots pine. Her goal is to evaluate the genetic diversity in natural stands, breeding populations and production seed orchard crops in Sweden. She will compare the genetic variation in Scandinavia populations with other populations across the whole distribution range to understand the evolutionary history of Scots pine in Scandinavia, and how much of that diversity is captured in the breeding program for seedling production. This assessment will help to optimize current forest management for future challenges.

Link to the announcement from Formas:
http://www.formas.se/en/Press-News/News/Given-decisions-November-2018/

The projects:

Carolin Seyfferth (Mobility grant):
Title: Regulation of wood properties in aspen and birch through large-scale gene expression studies

Nathanial Street (Research and development project grants):
Title: Engineering specialised metabolism in aspen

 Hannele Tuominen (Research and development project grants):
Title: Harnessing natural variation in aspen for forest feedstock improvement

 Xiao-Ru Wang (Research and development project grants):
Title: Genetic diversity in Swedish conifer forests: are there reasons for concern?

 

For more information contact the project leader or have a look on their homepage:

Carolin Seyfferth
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Nathaniel Street
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
Phone: +46 (0)90 786 5473
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
www.upsc.se/nathaniel_street

Hannele Tuominen
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
Phone: +46 (0)90 786 9693
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
www.upsc.se/hannele_tuominen

Xiao-Ru Wang
Department of Ecology and Environmental Sciences
Umeå University
Phone: +46 90 786 99 55
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
https://www.upsc.se/xiao-ru_wang
http://www.emg.umu.se/english/about-the-department/staff/wang-xiao-ru/

181105 VRdecision picture

Two starting grants and two research project grants from researchers at UPSC were approved by the Swedish Research Council (Vetenskapsrådet). The four projects from Peter Kindgren, Karin Ljung, Alizée Malnoë and Ove Nilsson will examine how non-coding DNA can influence transcription of coding DNA, how nitrogen affects the formation of lateral roots, how plants protect themselves against too much light and how the annual growth cycle of trees is regulated.

Peter Kindgren and Alizée Malnoë received starting grants to establish their research groups at UPSC. Peter Kindgren is currently still working at the University of Copenhagen but he will move in the end of 2019 to Umeå and then start setting up his own research group. He wants to understand how DNA that does not contain protein information (non-coding DNA) affects the transcription of protein encoding DNA, especially under stress conditions like cold. Alizée Malnoë started her research group at UPSC in January 2018. She is working on molecular mechanisms of photoprotection in plants, i.e. molecular processes that prevent the damage of a plant by an excess of light.

Karin Ljung and Ove Nilsson, both professors at the Swedish University of Agricultural Sciences and group leaders at UPSC, got research project grants. Karin Ljung will examine how different sources of nitrogen affect the initiation and development of lateral roots and influence the structure of the root system. Ove Nilsson’s project addresses how bud set, bud break and flowering are regulated in trees like aspen. His focus is on the genetic mechanisms that control the annual growth cycle.


The projects:

Peter Kindgren:
ImPaCT – Implications of Polymerase Collision caused by Transcription

Karin Ljung:
Nitrogen modulation of lateral root initiation in Arabidopsis

Alizée Malnoë:
Molecular Mechanisms of Photoprotection in Plants

Ove Nilsson:
The Role of FT-like Genes in the Regulation of the Annual Growth Cycle in Trees


Link to the announcement from the Swedish Research Council:
https://www.vr.se/english/calls-and-decisions/grant-decisions/decisions/2018-09-06-natural-and-engineering-sciences.html


For more information contact the project leader or have a look on their homepage:

Peter Robert Kindgren
Section for Molecular Plant Biology
Department of Plant and Environmental Sciences
University of Copenhagen
Phone: +45 35 33 46 39
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
https://plen.ku.dk/english/employees/?pure=en%2Fpersons%2Fpeter-robert-kindgren(525289c6-db78-4032-8942-ade2c82c3792).html

Karin Ljung
Umeå Plant Science Centre
Department of Forest Genetics and Plant Physiology
Swedish University of Agricultural Sciences
Phone: +46 (0)90 786 8355
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
www.upsc.se/karin_ljung

Alizée Malnoë
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
Phone: +46 (0)90 786 5459
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
www.upsc.se/alizee_malnoe

Ove Nilsson
Umeå Plant Science Centre
Department of Forest Genetics and Plant Physiology
Swedish University of Agricultural Sciences
Phone: +46 (0)90 786 8487
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
www.upsc.se/ove_nilsson

asp bearb 1920x1080 StefanJanssonAspen tree which genome is now mapped; photo: Stefan Jansson

This week, a team of researchers from Sweden, Belgium, England, Italy, Norway and South Korea published the genomes of two species of aspen trees. The project has taken close to ten years to complete and proved to be more complicated than thought as well as significantly expanding in scope.

"At last! We really had a moving target as we wanted to develop a resource that will be of maximum use to all researchers in tree biology, which led us to expand the project and keep trying to improve the work", says Nathaniel Street, Umeå University, who has shifted from being a postdoctoral researcher at the start of the position to assistant professor and, currently, university lecturer, and who eventually led the project.

Charting the set of genes present in a species provides perhaps the most important piece of the puzzle for all kinds of biology studies that, once available, enables virtually any type of study. The mapping of the human genome (published in 2001) was the foundation for a broad range of breakthroughs in medicine in the 21st century. Swedish tree researchers were early comers to this area, with work starting in 1998 that provided a first mapping for a subset of the aspen genes as well as contributing to the first complete mapping of a tree genome – black cottonwood (Populus trichocarpa) in 2006. This was only the third plant genome to be published, with only thale cress (Arabidopsis) and rice being available earlier.

In 2008-2009, a small group of Swedish researchers at the Umeå Plant Science Centre took on the challenge of mapping the aspen (Populus tremula) genome. Despite the fact that no such extensive genome project had been carried out in Sweden, they were optimistic; new, cheaper and more powerful techniques had just become available and pilot studies using these had shown that, among other things, the genetic variation in aspen was enormous. Indeed, in some respects, two aspen trees are, on average, as genetically different as a human and a chimpanzee. The project received a total of one million kronor from the Centre for Metagenomic Sequence Analysis - a precursor to SciLife Lab, which was formed in 2010 - and the Kempe Foundation and Nathaniel Street, a postdoc at the Umeå Plant Science Centre, started the practical work.

The tree selected for mapping grows on the Umeå University / SLU campus and had been studied since 1999. The researchers rapidly generated promising results, but it also became clear that the genome of the closely related black cottonwood could not be used as a reference, which made the project substantially more challenging. The project expanded, and more people and research groups became involved, with 27 researchers from six countries contributing to the results that are now published in the journal Proceedings of the National Academy of Sciences, PNAS. As well as mapping the genome, 24 individuals of European trembling aspen, 22 of the American quaking aspen (Populus tremuloides) and, as a reference, 24 black cottonwood poplars were analysed, which made it possible to understand how the species have evolved and adapted to different environments.

"The biggest challenge for the work, apart from the project lacking a long-term budget, was to deal with those parts of the genome that do not contain genes" says Nathaniel Street.

The genes themselves were mapped very early in the project, but the DNA sequence between genes differs so extensively in aspen between the two copies of the genome that each individual has - one inherited from the mother and one from the father - that methods developed to study other genomes such as humans, which are very inbred compared to aspen, did not work.

"We have now been able to show, for example, which genes appear to be the most important for the adaptation of aspen to our Nordic climate. This and much of our other work in the last five years has been made possible by this project" says Pär Ingvarsson, who, during the long journey, moved to SLU in Uppsala. This is a real milestone, the huge variation in aspen is a great resource for understanding evolution and the genome sequence gives us the tools needed to unlock this information.

"While it took a long time to finally map the whole genome, the project has produced multiple spin-offs along the way. Without this project, the gigantic work of sequencing Norway spruce, published in 2013, would not have been started. The databases of plant genomes we have produced and updated are used worldwide today, says Stefan Jansson, professor at Umeå University, who started the project in 2009.

The article:

Functional and evolutionary genomic inferences in Populus through genome and population sequencing of American and European aspen, Yao-Cheng Lin, Jing Wang, Nicolas Delhomme, Bastian Schiffthaler, Görel Sundström, Andrea Zuccolo, Björn Nystedt, Torgeir R. Hvidsten, Amanda de la Torre, Rosa M. Cossu, Marc P. Hoeppner, Henrik Lantz, Douglas G. Scofield, Neda Zamani, Anna Johansson, Chanaka Mannapperuma, Kathryn M. Robinson, Niklas Mähler, Ilia J. Leitch, Jaume Pellicer, Eung-Jun Park, Marc Van Montagu, Yves Van de Peer, Manfred Grabherr, Stefan Jansson, Pär K. Ingvarsson, and Nathaniel R. Street
Proceedings of the National Academy of Sciences (PNAS) October 29, 2018

Link to the publication: https://doi.org/10.1073/pnas.1801437115


For further information, please contact:

Nathaniel Street, UPSC, Fysiologisk botanik, Umeå universitet, This email address is being protected from spambots. You need JavaScript enabled to view it., tel +46 72-537 20 03

Pär K Ingvarsson, UPSC, Department of Plant Biology, Swedish University of Agricultural Sciences, This email address is being protected from spambots. You need JavaScript enabled to view it., tel +46 70-8485977

Stefan Jansson, UPSC, Department of Plant Physiology, Umeå universitet, This email address is being protected from spambots. You need JavaScript enabled to view it., tel +46 70-677 23 31

More information:
Link to the Swedish press release at Umeå University

Eureka Alert Photo TKTP AT1.03 3d Seedling V4 1920x1080Live images of a plastid-localized ATP sensor in an Arabidopsis seedling. Read more 


Photosynthesis generates adenosine triphosphate (ATP), which is the universal molecular fuel in living organisms. An international research team led by Dr Boon Leong Lim from the School of Biological Sciences of The University of Hong Kong could visualize ATP concentrations in chloroplasts and cytosol of living plants. The team included research groups from Sweden, USA and Germany. The Swedish participant was professor Per Gardeström from UPSC, Department of Plant Physiology at Umeå University. The results highlight how different parts of the photosynthetic cell are interconnected in order to optimize the efficiency of photosynthesis and is of interest for future crop breeding. The study is now presented by the journal PNAS.

All life on earth ultimately relies on energy from the sun and photosynthesis in plants is the vital link. The researchers around Boon Leong Lim showed that in mature plants the chloroplastic ATP pool is separated from the rest of the cell. A surplus of reducing equivalents can be exported from the chloroplast and used by mitochondria to supply ATP to the cytosol but the rate of ATP import into mature chloroplasts to support CO2 fixation was negligible. Only chloroplasts of very young developing leaves of Arabidopsis thaliana could import ATP from the cytosol to support their development. This developmental transition could be important in order to restrict futile ATP consumption at night when photosynthesis is not operating.

“We saw a significantly lower concentration of ATP in the chloroplast than in the cytosol of mature photosynthetic cells,” said study lead author Dr Boon Leong Lim. “Although the chloroplast is the key energy harvester and producer in a plant cell, its demand for ATP is also extremely high. Illumination increases chloroplast ATP concentration instantly, but it drops to a basal level very quickly after illumination stops. Our results suggest that there was a need to restrict ATP consumption in mature chloroplasts in the dark. A primary job of mature mesophyll chloroplasts is to harvest energy and export sugar to support plant growth in the light. Nevertheless, wasteful energy consumption must be avoided in the dark.”

Co-authors Dr Wayne K. Versaw and Abira Sahu of Texas A&M University stated: “Live imaging of intact plants provided the spatial and temporal resolution to reveal important changes in how different cell compartments collaborate to manage photosynthesis and overall cellular energy.”

The results also have important implications for the understanding of energy flow in plant cells. Using energy harvested from sunlight, water molecules are split into protons, oxygen and electrons. The electrons pass through photosystems to reduce NADP+ to NADPH that acts as a carrier for the electrons. Together with water splitting, this so called linear electron flow (LEF) also creates a pH gradient across the thylakoid membrane, the inner membrane of the chloroplast. This pH gradient is the driving force for ATP synthesis. To fix one CO2 molecule in a chloroplast, 3 ATP and 2 NADPH molecules are consumed. However, only 2.57 ATP molecules per 2 NADPH are generated by LEF. The shortfall of ATP must be met for photosynthesis to operate efficiently.

A paper published in Nature in 2015 (524:366–369) showed that chloroplasts in unicellular diatoms can import cytosolic ATP to support carbon fixation. Chiapao Voon, who joined the lab as a PhD student, explained: “Unlike unicellular diatoms, mature plant chloroplasts are unable to import ATP from the cytosol to supplement the demand for CO2 fixation. Rather, the export of reducing equivalents is the key to maintaining the optimal ATP/NADPH ratio required for photosynthesis. Otherwise, the build-up of NADPH in chloroplasts will impede photosynthesis”.

“The ability to study metabolism in the living cell with a spatial resolution between the different cellular compartments is a big step forward and will significantly increase our understanding on how the cell is operating. I have in particular been interested in the implications for mitochondrial contributions to photosynthetic metabolism” complements co-author Prof. Per Gardeström from Umeå University.

Co-author Prof. Markus Schwarzländer of Münster University added: “The study brings us a step closer to understanding how carefully cells optimize the operating conditions in their different organelles. I find it particularly intriguing how efficiency of plant energy metabolism can be maintained, and how this appears to be dynamically adjusted.”

The article:
ATP compartmentation in plastids and cytosol of Arabidopsis thaliana revealed by fluorescent protein sensing
Chia Pao Voon, Xiaoqian Guan, Yuzhe Sun, Abira Sahu, May Ngor Chan, Per Gardeström, Stephan Wagner, Philippe Fuchs, Thomas Nietzel, Wayne K. Versaw, Markus Schwarzländer, Boon Leong Lim
Proceedings of the National Academy of Sciences (PNAS) Oct 2018, 201711497; DOI: 10.1073/pnas.1711497115
Link to the publication


Photo description:

Live images of a plastid-localized ATP sensor in an Arabidopsis seedling. Red and green panels show the emission of the ATP sensor at 470 nm – 507 nm, and 526 nm – 545 nm, in a 3-day-old seedling. The ratio between both emission channels is represented in a rainbow color scale in the lower left panel, which corresponds to ATP concentration (higher levels in red and lower levels in green). The lower right panel shows a brightfield image of the same seedling.

For questions please contact:
Professor Per Gardeström
Department of Plant Physiology
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Photo: Chia Pao Voon
Text: Boon Leong Lim, Chia Pao Voon, Wayne K. Versaw, Per Gardeström, Markus Schwarzländer

Lifting response of hybrid aspen: Time-lapse video showing 28 days of the tension wood response of a wild type hybrid aspen (Populus tremula x P. tremuloides). Video created by Bernard Wessels.


When a tree is placed horizontally, it starts to bend to lift itself back upright towards the light. A special type of wood, called tension wood, is formed in the bending region and works like a contracting muscle to lift the tree up. Bernard Wessels showed in his PhD thesis that the plant hormone ethylene is required for the up-lifting response in hybrid aspen. He also identified new components that are involved in the regulation of this process. He defended his PhD thesis at Umeå University on the 5th of October. 

“We analysed genetically modified hybrid aspen trees that were altered in their response to ethylene”, says Bernard Wessels. “These trees were placed horizontally to induce the up-lifting response and so the formation of tension wood. Over a period of four weeks, we took pictures in regular intervals to monitor how the trees lift themselves up. We combined all pictures into a time-lapse video and compared the up-lifting response of the mutants with a non-modified control. Mutants that lost the ability to sense the ethylene signal struggled to lift themselves up from the surface of the table while mutants that were more sensitive to ethylene lifted themselves up faster.”

Bernard Wessels also found that ethylene influences the frequencies of the different xylem cell types in the tension wood. Hybrid aspen wood consists mainly of two cell types; the vessel elements and the fibers, and ethylene was shown here to favour the formation of the fibers over the vessel elements. “We think that the mechanical strength of the fibres is needed to lift the tree up”, explains Bernard Wessels.”

In another approach, Bernard Wessels and his colleagues used a large dataset that contains information about which genes are active during different stages of wood formation. They screened for genes that are involved in the communication of the ethylene signal. In all different stages of wood formation, they found genes that were related to ethylene, and they identified and characterized new genes that are involved in the communication of the ethylene signal.

Bernard Wessels has performed his graduate studies at the Umeå Plant Science Centre, Department of Plant Physiology, Umeå University. His results help to understand how wood develops in trees that are displaced from their original position due to mechanical stimulus such as wind. This knowledge is very interesting for the forestry industry and might be needed to select for trees that can deal better with extreme variations in weather.

Link to the thesis: urn:nbn:se:umu:diva-151724

What is ethylene?
Did you ever experience that your green bananas ripened faster when you placed them next to an apple? This is caused by the plant hormone ethylene that is produced by the ripening apple. Ethylene is a colourless gas with a faint sweet odour that acts as a hormone in plants. It stimulates fruits to ripe but it is also involved in many other aspects of plant development, e.g. like germination of seeds, senescence, reaction to environmental stresses or mechanical wounding. Ethylene is of high commercial interest because it fastens the ripening process of fruits and vegetables and the senescence of cut flowers.

 

About the thesis defence:

On Friday, the 5th of October, Bernard Wessels, Department of Plant Physiology, Umeå University, defended his thesis, entitled ’The significance of ethylene and ETHYLENE RESPONSE FACTORS in wood formation of hybrid aspen’. The public defence took place at 9:00 am in Lilla hörsalen ( KB.E3.01) in the KBC building, Umeå University. The faculty opponent was Prof. Kurt Fagerstedt, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland. Supervisor of the PhD thesis was Hannele Tuominen.

For more information, please contact:

Bernard Wessels, Department of Plant Physiology, Umeå University
Telephone +4670 0130923
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.