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Yan Ji (left) and her supervisor Åsa Strand (right) after Yan Ji's defence (photo: Anne Honsel)
What are the first developmental steps when a cell turns green? This question was addressed by Yan Ji, PhD student in Åsa Strand’s group, who studied the development of chloroplasts, the sites in the cell where photosynthesis takes place. Chloroplast development is a very complex process involving a series of regulatory steps and Yan Ji could show that certain regulatory steps happen already earlier than previously assumed. She successfully defended her PhD thesis at Umeå University on Tuesday, 15th of December.
The greening process starts as soon as the cell receives light for example when a germinated seedling reaches the soil surface. The chloroplast originates from a cyanobacterium that was taken up by a eukaryotic cell. During evolution, some of the genetic information from the cyanobacterium has been transferred to the gene material of the host cell that is stored in the nucleus. Chloroplast development therefore requires a coordinated communication between the chloroplast and the nucleus. Yan Ji studied the early stages of chloroplast development in the plant Arabidopsis thaliana.
You studied chloroplast development during the greening process. What aroused your interest in this topic?
To understand photosynthesis is of course very important for plant research but I did not had very much background about the whole process of chloroplast development when I was applying for this position. However, when I started to work on this project and got to know more about it, I got more and more intrigued. And when I was then for the first time inducing the greening process in our cell culture system, I thought this is really cool.
What is the advantage of using a cell culture system to study chloroplast development?
Our project was focussing on early stages of chloroplast development. The cell culture system allowed us to better resolve these early stages temporally. When dark grown seedlings receive light, it takes about 12 to 24 hours until the chloroplasts are green and fully mature. In our cell culture system, it takes five days until the cells start to turn green after they receive light and the cells develop more synchronised. resembles the chloroplast development in true leaves, which are the leaves that develop after the seedling has reached the soil surface. The cell culture system is of course more artificial because the cells are isolated from their tissue context which plays also an important role for development. That is why we always complemented our cell culture experiments with experiments with seedlings to verify our results.
What was the most fascinating for you during your PhD? Have you experienced any unexpected surprises during your studies?
I focussed in my studies on the role of the plastid-encoded plastid RNA polymerase, called PEP. This is a multi-subunit protein complex in the chloroplast that is responsible for the activation of most of the genes needed for photosynthesis. It was thought that the fully assembled complex associated with additional proteins is only available in the light when the chloroplast is developing and becoming mature, while in the dark, PEP was thought to be mainly present in its core form consisting of just four core subunits. We wanted to study when the different subunits are recruited to the protein complex during chloroplast development and focussed on the time when the cells just started to become green. However, we realized that the fully assembled complex was already available both in our dark grown cells and in the dark grown seedlings. We could also indirectly show that the complex was already active at this stage. The difference to the more mature chloroplast was that the abundance of complexes available was much lower. There were some hints in this direction before from experiments with other plants, but we did not expect to find the fully assembled complex so early during chloroplast development in true leaves.
What was the biggest challenge you faced during your PhD?
The discovery that the full assembled PEP complex is already available much earlier than we thought was of course very fascinating but also quite challenging for me because I had to rethink and redesign my hypotheses and experiments as a whole. Some of the planned follow-up experiments did not make sense or were not feasible anymore. That was very challenging. I also faced some technical challenges when I wanted to isolate chloroplasts from the cell culture. This is a standard method for plants, but the established protocol did not work for cells from the cell culture because their cell walls seem to be stronger. We had big problems to break the cell walls which is needed to isolate the chloroplasts. We tried many different ways to get it done and this took very long time which was quite frustrating.
What are your plans for the future?
I definitely want to do a postdoc either back in China or somewhere here. During my PhD, I learned many lessons and I am really looking forward to starting a new project and applying my experiences from this time. Hopefully, I find a nice project in photobiology or photosynthesis research to be able to continue in this field. I would be very interested to study these topics in other species to see which processes and components are conserved among species.
About the public defence:
The public defence took place on Tuesday, 15th of December at Umeå University. Faculty opponent was Eevi Rintamäki, Department of Biochemistry at the University of Turku in Finland. Yan Ji's supervisor was Åsa Strand. The dissertation was live broadcasted via Zoom.
Title of the thesis: Regulation of chloroplast development during the greening process
Link to the thesis: urn:nbn:se:umu:diva-176773
For more information, please contact:
Yan Ji
Department of Plant Physiology
Umeå Plant Science Centre
Umeå University
Email:
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Kristoffer Jonsson (left) and Abdellah Lakehal (right)[2020-12-16] Last Friday, the Swedish Research Council announced their decision regarding the autumn call for the international postdoc grant. The projects from Kristoffer Jonsson and Abdellah Lakehal were among the approved projects. Both finished their PhD at UPSC in 2019 and are currently working as postdoc there. The grant offers them secure employment conditions for the next three years and allows them to work on their research projects abroad to acquire new competences and expand their international networks.
You are the first two postdocs bringing this research grant in this form to UPSC. How does it feel to receive this grant?
Abdellah Lakehal: I didn’t know that we were the first ones, it’s definitely an honour to bring such a prestigious grant to the institute that forged my career. I am very happy and excited at the same time.
Kristoffer Jonsson: It is a nice validation that my proposed project is of general interest, which makes me even more motivated to get started addressing my questions. Also, I’m happy that Abdellah also received this grant, since we started our PhD roughly at the same time, and followed each other throughout the years.
What are you planning to do in your project?
Kristoffer Jonsson: Within the framework of the grant, I want to examine the basis of self-organization in morphogenesis, and how endogenous mechanical cues instruct cellular growth decisions. The project is planned to involve three overall layers of methodology: cellular resolution growth tracking, mechanical measurements and 3D computational modelling.
Abdellah Lakehal: I’m interested in de novo lateral root organogenesis in plants. Lateral roots are the main determinant of root system architecture and they play crucial roles in plant productivity by ensuring an efficient uptake of water and nutrients. My project aims at uncovering the evolutionary history of the molecular networks that guide stem cell specification during lateral root organogenesis using an early divergent plant species as a model system. To achieve this goal, I will take advantage of the state-of-the-art technologies such as single-cell analysis and genome editing.
Where do you plan to go?
Abdellah Lakehal: I plan to perform my research in the lab of Prof. Tom Beeckman at VIB-UGent, Ghent, Belgium.
Kristoffer Jonsson: The plan is to join the lab of Anne-Lise Routier-Kierzkowska at the Plant Biology Research Institute (IRBV) at Montreal University, Montreal, Canada.
Why did you choose your host institution?
Kristoffer Jonsson: I mainly wanted the chance to work with Anne-Lise Routier-Kierzkowska, who is doing very exciting work in the field of plant biomechanics and computational modeling. Anne-Lise is a biophysicist, and perhaps therefore has a very different approach to biological questions from what I am used to, which I find very stimulating. Beyond my host lab, IRBV is a multidisciplinary institute, and Montreal is the home of two renowned plant research centers (IRBV and the Plant Science Dept at McGill University). Several international plant research meetings are regularly held in Montreal. Thus, I’m hoping to meet a dynamic environment.
Abdellah Lakehal: I chose VIB because it is one of the strongest and most influential research centres in the world. In one hand, VIB will provide me with easy access to all the facilities and services needed for the accomplishment of the project. On the other hand, I will have ample opportunities to develop new skills. I will be working under the guidance of Prof. Tom Beeckman, who is an internationally recognized expert in lateral root development and stem cell regulations. His lab made incredible contributions to this field. I will certainly learn a lot there. During my stay at VIB, I will also have the opportunity to establish collaborations with world-top experts in evolutionary biology.
How much time do you plan to spend at your host institution?
Abdellah Lakehal: At the moment, I plan to spend 3 years at VIB.
Kristoffer Jonsson: We haven’t decided the exact timeline yet. Besides the work situation, I also have my family to consider. I’m just starting to put this puzzle together now.
What are your next steps now?
Kristoffer Jonsson: I’m still involved in ongoing projects with the Bhalerao lab which I hope we can conclude shortly, so I will continue at UPSC/SLU at least until the summer 2021.
Abdellah Lakehal: It is hard to predict the future as goals are dynamic and change over time, however, my ultimate goal is to come back to Sweden and establish my independent research group. I plan to decode the secrets behind “stem cellness” in plants by adopting an evolutionary perspective. In other words, how and what was needed for the early divergent plant species to evolve this unique capacity allowing them to conquer land and adapt to the ever-changing environmental conditions. Acquiring such fundamental knowledge will certainly allow us to shed light on key aspects of lateral root organogenesis in the extant seed plants.
The Swedish Research Council approved 41 out of 169 project applications. The applicants must have received their PhD no more than 2 years before the call closes. The grant will be administered by a Swedish University or public organisation meaning that the applicants will be employed in Sweden while working abroad.
For questions, please contact:
Kristoffer Jonsson
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email:
Project title: Sensing yourself: Mechanical feedback between organ curvature and cell-based decisions
Host institution: Department of Plant Physiology, Umeå University
Visiting institution: Plant Biology Research Institute (Institut de Recherche en Biologie Végétale IRBV), Université de Montréal, Canada
Abdellah Lakehal
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email:
Project title: Decoding the molecular basis of lateral root stem cell specification in plants
Host institution: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
Visiting institution: Center for Plant Systems Biology, VIB-UGent, Belgium
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Pine tree in winter (Photo: Stefan Jansson & Pushan Bag)
[2020-12-15] How can conifers that are used for example as Christmas trees keep their green needles over the boreal winter when most trees shed their leaves? Science has not provided a good answer to this question but now an international team of scientists, including researchers from Umeå University, has deciphered that a short-cut in the photosynthetic machinery allows the needles of pine trees to stay green. The study was published today in the journal Nature Communications.
In winter, light energy is absorbed by the green chlorophyll molecules but cannot be utilized by the downstream reactions in the photosynthetic machinery as freezing temperatures stop most biochemical reactions. This is especially a problem in the early spring when temperatures can still be very low, but sunlight is already strong, and the excess light energy can damage the proteins of the photosynthetic machinery. The researchers showed that the photosynthetic apparatus is wired in a special way which allows pine needles to stay green all year long.
Under normal conditions, the two photosystems, the two functional units where light energy is absorbed and converted into chemical energy, are kept apart from each other to prevent a short-cut and allow efficient photosynthesis. In winter, the structure of the thylakoid membrane, where the two photosystems are located, is reorganized which brings the two photosystems in physical contact. The researchers showed that photosystem II donates energy directly to photosystem I and this short-cut mode protects the green chlorophyll and the needles when conditions become harsh.
“We have followed several pine trees growing in Umeå in northern Sweden over three seasons”, says Pushan Bag, PhD student at Umeå university, who has collected samples all around the year and made many of the analyses. “It was essential that we could work on needles “straight from outdoors” to prevent that they adjusted to the higher temperatures in the lab environment before we analysed them for example with electron microscopy which we used to visualize the structure of the thylakoid membrane.”
All plants have safety valves to deal with the excess light energy which is either dissipated as heat or as fluorescence light. However, only conifers seem to have such powerful valves that they can keep the photosynthetic apparatus intact over the extreme boreal winter. The research team combined biochemistry and ultrafast fluorescence analysis, a very sophisticated method that can resolve chlorophyll fluorescence light at a picosecond time scale. Like this, they could demonstrate how the pine needles deal with excess light energy to protect their sensitive photosynthetic apparatus from damage.
“We needed to adjust the equipment to study pine needles in cold temperatures in order to trap the unique mechanism”, explains Volha Chukhutsina from Vrije Universiteit Amsterdam, who has performed much of the ultrafast fluorescence analysis. “We also tried spruce needles but they were hard to fit in a good way into the equipment”. Alfred Holzwarth, who has developed the time-resolved fluorescence measurements adds: “The pine needles gave us the opportunity to study this shortcut mechanism - also called spill-over - as they really show an extreme adaptation.”
The study was done with pine trees, but the researchers believe that the mechanism is probably similar for other conifer species – like the typical Christmas trees spruces and firs - because their photosynthetic apparatus is similar. “This remarkable adaptation not only enjoys us during Christmas but is in fact extremely important for mankind”, says Stefan Jansson from Umeå university. “Hadn´t conifers been able to survive in extreme harsh winter climates vast areas in the northern hemisphere may not have been colonized as conifers provided firewood, housing and other necessities. Still today they form the basis of the economy in most of the circumpolar taiga region”.
About the article:
Bag P., Chukhutsina V., Zhang Z., Paul S., Ivanov A.G., Shutova T., Croce R., Holzwarth A.R., Jansson S. (2020) Direct energy transfer from photosystem II to photosystem I confers winter sustainability in Scots Pine. DOI: 10.1038/s41467-020-20137-9
https://www.nature.com/articles/s41467-020-20137-9
For more information, please contact:
Professor Stefan Jansson
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
Email:
Phone +46-70-6772331
Text: Stefan Jansson & Pushan Bag
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Ioanna Antoniadi (left), winner of the UPSC Agrisera Prize 2020, and her group leader Karin Ljung (right) who is congratulating to the prize at the end of the UPSC Christmas Celebration on Zoom[2020-12-14] Ioanna Antoniadi is awarded with the UPSC Agrisera Prize 2020 to acknowledge her scientific achievements and her engagement to improve the work environment at UPSC. The UPSC Agrisera Prize is awarded every year to a person working at UPSC and was announced today during the virtual UPSC Christmas Celebration.
Ioanna Antoniadi works as a postdoc in Karin Ljung’s group at the Department of Forest Genetics and Plant Physiology at SLU. Since she started at UPSC, she contributed to several scientific publications, among others to a publication in Nature Communications in 2020. She is the expert for fluorescent-activated cell sorting (FACS) at UPSC - an advanced technique that allows to separate cells according to certain physical characteristics like for example different cell size – and was co-applicant for a successful grant application that allowed to purchase a new FACS instrument recently.
Besides her scientific contribution and her responsibility for supervising and training new users to the FACS instrument, Ioanna Antoniadi is part of the Departmental Common Laboratory Resources group that manages the laboratories at the Department of Forest Genetics and Plant Physiology. The nomination letter pointed out that “she is very engaged in improving the lab environment to make it work at its best” and that she spontaneously took over additional tasks besides her daily responsibilities to improve the work environment at UPSC.
The UPSC Agrisera Prize is awarded every year to a PhD student, a postdoc or a technician for excellent scientific achievement and great commitment to improve the UPSC work environment. It is sponsored by Agrisera but the members of the UPSC board select the winner of the prize. Everyone working at UPSC can nominate a colleague for the UPSC Agrisera Prize. This year, the UPSC Board received nine nominations, the highest number of nominations since 2014.
“The prize gives us the possibility to acknowledge great achievements and commitments and it is every year very difficult to choose one candidate out of many good suggestions”, says Catherine Bellini, chairmen of the UPSC Board who announced the winner of the prize today together with Joanna Porankiewicz-Asplund from Agrisera. “We were delight that we received this high number of nominations this year. It shows that people care about their workplace.”
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Bernadette Sztojka (right) and her supervisor Hannele Tuominen (left) chatting after Bernadette's defence
[2020-12-11] Lignin is the compound that makes plant cell walls waterproof and rigid. This allows plants to stand upright and transport water within their stem. Bernadette Sztojka, PhD student in Hannele Tuominen’s group, studied how lignin is synthesised and deposited in the cell walls, a process called lignification. She showed that cooperation between neighbouring cells is important for lignification of water-transporting vessel elements and identified three new regulators involved in this process. Bernadette Sztojka successfully defended her PhD thesis at Umeå University yesterday.
You did already your master thesis at UPSC but on a different topic. Why did you choose to switch topic and study lignification during your PhD thesis?
The projects I worked on before in the group of Rishikesh Bhalerao were more cell biology-oriented, related to vesicular trafficking. That was already quite a shift because my original background is horticulture. For my PhD, I wanted to further explore new territories this is why I applied for this PhD position, focusing on cell wall and wood formation.
You identified and characterised three new regulators involved in lignification. What do these regulators have in common and why are they peculiar?
The first regulator that we chose to work on was PIRIN2. A gene which is closely related to PIRIN2 was identified earlier in a cell culture system and shown to play a potential role in lignification. That is why we decided to characterise this gene in Arabidopsis. To better understand the molecular function of PIRIN2, we looked for proteins that interact with PIRIN2. That is how we came across the other two molecular players we studied, and this allowed us to expand the known molecular network. One of these two proteins has the opposite effect on lignin biosynthesis than PIRIN2. While PIRIN2 is suppressing the synthesis of certain types of monolignols, which are the basic modules of lignin, this protein is promoting it. The other protein we identified has no direct effect on lignin content or composition but connects lignin biosynthesis to diurnal timing.
Why does lignin biosynthesis need diurnal timing?
There have been a few previous studies that suggested that lignin-biosynthetic genes are activated in a diurnal pattern but there was never any upstream regulator found that controls these genes. Lignin is a very big carbon sink that means that a lot of carbon is required for its biosynthesis. That is why lignin biosynthesis has to be coordinated with resource availability and that brings in the diurnal regulation to connect lignin biosynthesis with carbon fixation during photosynthesis.
Which of your results is the most fascinating for you?
For me the first project, characterizing PIRIN2 and the non-cellautonomous lignification, was the most fascinating. PIRIN2 is a negative regulator of lignification but in a cell-type specific way. It is affecting the lignin composition of the cell walls of its neighbouring cells where it is not expressed. It is located in cells next to xylem vessels which form the water transporting “pipes”. We believe that the vessels need a specific lignin composition to allow for efficient water transport and PIRIN2 makes sure that they acquire the correct composition by suppressing the biosynthesis of certain monolignols which may not be optimal for water transport. I find these types of cooperative processes between cells really fascinating.
What was the biggest challenge you faced during your PhD?
It was hard sometimes to give up on ideas. We might have had a hypothesis and not necessarily showed that the hypothesis was proven right or wrong, but we realized that we did not had the means or time to follow up on this hypothesis. My original project that made me interested in the PhD topic became a bit squeezed in time because some other projects which I was supposed to finish quickly took over like for example the PIRIN2 project. It worked out fine for me in the end, but sometimes it was challenging to accept that I had to let a part of my project go unfinished.
Do you think your results might lead to practical applications in future?
I think especially PIRIN2 could be interesting for the forest industry. By manipulating PIRIN2 it might be possible to generate woody biomass with different lignin composition. Plants often get really sick when the lignin content is modified genetically but this is not the case when PIRIN2 is mutated. The effect on the chemical composition is not very strong in PIRIN2 mutants but those changes can still be beneficial for industrial use and they do not compromise the plant’s fitness.
What are your plans for the future? Do you want to continue with research?
I would like to transition towards more applied research, combining my background in horticulture with my PhD experience in plant molecular biology. This could be either in academia or industry. I am still curious to explore new territories and would like to change a bit the subject again.
About the public defence:
The public defence took place on Thursday, 10th of December at Umeå University. Faculty opponent was Simon Hawkins from the Department of Biology, University of Lille, France. Bernadette Sztojka's supervisor was Hannele Tuominen. The dissertation was live broadcasted via Zoom.
Title of the thesis: New regulators of xylem lignification in Arabidopsis
Link to the thesis: http://umu.diva-portal.org/smash/record.jsf?pid=diva2%3A1500629
For more information, please contact:
Bernadette Sztojka
Department of Plant Physiology
Umeå Plant Science Centre
Umeå University
Email:
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Tree phenotyping platform at UPSC (photo: Anne Honsel)
[2020-12-08] Stefan Jansson and Ove Nilsson were interviewed by the Swedish TV about CRISPR/CAS9, the technique for which discovery Emmanuelle Charpentier and Jennifer A. Doudna received the Nobel Prize in Chemistry this year. Several reports are broadcasted this week by the Swedish TV to highlight this year’s Nobel Prizes which are officially celebrated on Thursday, the 10th of December. The interviews with the two researchers from UPSC were broadcasted yesterday in “Vetenskapens värld” on Swedish Television (SVT) and in the news on TV4.
CRISPR/CAS9 is already now broadly used in plant research and also at UPSC several plants have been already genetically modified using this technique. This is presented in the reports done by the Swedish TV channels. In “Vetenskapens värld”, a popular science programme on SVT, Stefan Jansson explains how he uses CRISPR/CAS9 in his research and in TV4 News, Ove Nilsson presents the phenotyping platform at UPSC and describes the advantages of CRISPR/CAS9 for plant research. The two reports are online available and contain also a lot of footage from the plant material at UPSC.
Links to the video clips (both in Swedish):
“Vetenskapens värld” on SVT
Footage from UPSC is shown between minute 05:12 and 06:37 and between 10:02 and 10:24
https://www.svtplay.se/video/29350256/vetenskapens-varld/vetenskapens-varld-sasong-33-nobelpristagarna-2020?position=1765&id=e4zWnox
TV4 News from the 7th of December at 22:00 o’clock
Footage from UPSC is shown between minute 18:46 and 21:21
https://www.tv4play.se/program/nyheterna/13308076
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Ondřej Novák (left) and Karin Ljung (right) at the Swedish Metabolomics Facility in Umeå (photo: Carolin Rebernig)
On Wednesday last week, Clarivate published its annual list of Highly Cited Researchers 2020. Karin Ljung and Ondřej Novák are again under the top one percent of the world’s most highly cited researchers in the field of “Plant & Animal Science”. This is the third time that Ondřej Novák is on Clarivate’s list and the seventh time for Karin Ljung.
The methodology behind Clarivate’s list is based on citation analyses that determines the top one percent of Highly Cited Researchers using the Web of Science database. More than 6,000 researchers, in 21 fields of the sciences and social sciences, and cross field categories were selected based on the number of highly cited papers they produced over an 11-year period from January 2009 to December 2019.
More information and the full list of Highly Cited Researchers can be found here:
https://recognition.webofscience.com/awards/highly-cited/2020/
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Twelve PhD students presented their research projects with short pre-recorded video pitches during the KBC DAYS 2020 last week. The video pitches were the outcome of a course in science communication that the students participated in before. An evaluation committee evaluated all pitches and awarded Lill Eilertsen, PhD student in Judith Lundberg-Felten’s group at UPSC, with the prize for the best presentation.
Every year, the best PhD student presentation is awarded during the KBC DAYS but normally they are presenting their research with a scientific poster. Due to the online format of the KBC DAYS 2020, the organisation committee decided against a poster presentation but instead asked for short pre-recorded video pitches and offered in combination with this a course in science communication. Twelve PhD students affiliated with KBC took the chance and participated in the course. Their video-pitches were evaluated during the KBC DAYS by an evaluation committee of six people and the best presentation was awarded with a travel voucher sponsored by Agrisera AB.
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Photos of Rishikesh Bhalerao (top left), Stéphanie Robert (top middle), Åsa Strand (top right), Hannele Tuominen (bottom left) and Stéphane Verger (bottom right) whos project proposals were granted by the Swedish Research Council in 2020.
On Thursday last week, the Swedish Research Council announced which project proposals in the field of natural and engineering sciences receive financial support in 2020. Five projects from UPSC were approved. Stéphane Verger receives a starting grant and Rishikesh Bhalerao, Stéphanie Robert, Åsa Strand and Hannele Tuominen project grants.
The topics of the five projects from UPSC deal with seasonal growth, cell shape, cell internal communication, lignin biosynthesis and cell-to-cell adhesion. The focus is for all on the molecular level but using different plant model organisms and applying a wide range of different methods. In total, the Swedish Research Council approved this year 324 of 1668 applications in the field of natural and engineering sciences including research project grants and starting grants.
More information about the individual approved projects:
Project: Unravelling the genetic network mediating temperature control of dormancy release and bud break in hybrid aspen
Bud break in perennial trees starts in spring after trees have been exposed to extended period of cold temperatures that release dormancy, followed by a period of increasing temperatures that signal spring onset. The exact timing of bud break is very crucial for the trees to prevent damage to young leaves and meristems enclosed in the buds from sudden late frosts. Rishikesh Bhalerao is researching on how temperature regulates the release of the dormant state to allow bud break in spring. In the approved project, he plans to identify the genetic framework that controls these temperature-mediated processes in the model tree hybrid aspen.
Contact:
Rishikesh Bhalerao
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email:
https://www.upsc.se/rishikesh_bhalerao
Project: Molecular mechanisms regulating shape acquisition in plants
How does a cell receive its final shape? Stéphanie Robert wants to answer this question focusing on leaf epidermal pavement cells. These cells form the outer layer of the leaf and have a very specific jigsaw puzzle shape. The mechanical and chemical properties of the cell wall but also cell internal factors like the plant growth regulator auxin determine the final shape of a cell. In her project, Stéphanie Robert aims at finding new molecular players involved in the development of cell shape and at looking deeper into the interactions between the different factors involved in this development.
Contact:
Stéphanie Robert
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email:
http://www.upsc.se/stephanie_robert
Project: Establishment of Photosynthesis, a Tale of Two Genomes
Åsa Strand focusses in her project on cell internal communication, specifically on the communication between the chloroplast and the nucleus. The chloroplast is the place were photosynthesis is conducted. Some of the genetic information that is needed for chloroplast development is stored in the nucleus. That is why a synchronised exchange of information between the chloroplast and the nucleus is indispensable for proper chloroplast development. Åsa Strand wants to understand in more detail how this communication between the chloroplast and the nucleus is regulated.
Contact:
Åsa Strand
Department of Plant Physiology
Umeå Plant Science Centre
Umeå University
Email:
http://www.upsc.se/asa_strand
Project: Cell-type specific lignification in plant vasculature
Lignin is used by plants to increase stability and provide a water repellent surface in the water transporting system. However, for industrial applications, it often reduces the accessibility of the favoured cellulose. Hannele Tuominen aims on identifying the molecular mechanisms behind lignin biosynthesis and on characterising lignin composition in different cell types. To understand how and why cell-type specific lignification is established might help to improve the properties of lignocellulosic raw material for bioprocessing.
Contact:
Hannele Tuominen
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email:
http://www.upsc.se/hannele_tuominen
Project: Mechanics and dynamics of cell-to-cell adhesion in plants
Stéphane Verger focusses in his research on how neighbouring cells in a tissue interact and attach to each other, a dynamic process called cell adhesion. To maintain cell adhesion despite changes in the surrounding is very important to keep a tissue functioning and Stéphane Verger wants to reveal the dynamic mechanisms that are involved in this process. He plans to apply genetical, pharmaceutical but also mechanical and microscopic approaches to understand how cell adhesion is maintained in plants.
Contact:
Stéphane Verger
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email:
http://www.upsc.se/stephane_verger
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Pieter Nibbering and his PhD supervisor Totte Niittylä after the successful defence (photo: Anne Honsel)
[2020-10-30] Plant cell walls need to be flexible and at the same time rigid to give stability but also allow growth. Glycoproteins, proteins with attached carbohydrates, are only a minor component of the cell wall which consists mainly of cellulose, hemicellulose, pectin and lignin. Nevertheless, modifications of such glycoproteins can have a strong impact on the properties of the plant cell wall. This was shown by Pieter Nibbering, PhD student in Totte Niittylä’s group, who studied cell wall formation in the herbal plant Arabidopsis and in poplar. Pieter Nibbering successfully defend his PhD thesis at the Swedish University of Agricultural Sciences on Friday, 30th of October.
Your thesis focuses on plant cell wall formation in Arabidopsis and aspen. What was interesting you about doing research on cell walls?
I find cell walls very interesting because they so complex. It is very challenging to work with them and I wanted to take on this new challenge. Another reason why I decided for this PhD project was that you cannot just use one or two methods when studying cell walls but need to use many different tools like e.g. molecular cloning, chemistry and protein expression to come closer to an answer of your questions. This diversity was also very interesting for me because it allowed me to learn a lot of different techniques.
You worked with certain glycoproteins that are lesser known components of the cell wall. Why are these glycoproteins important?
That is actually the question we tried to answer during my PhD. We do not know yet why they are important. The difficulty is that approximately 1200 proteins in Arabidopsis are predicted to have this kind of carbohydrates called arabinogalactan glycans attached - not only those ones we worked with. The attached glycans fulfil many different functions. They can e.g. stabilize the protein to make sure that the protein can perform the right function, they can interact directly with the cell wall or with cell wall components or they can bind salts for instance calcium and be involved in signal transduction. For our experiments, we used mutants in which the biosynthesis of some glycoproteins is impaired meaning that the glycans are not added properly to the proteins. The mutants clearly showed growth defects and/or defects in stress response and this let us conclude that the impaired glycoproteins are important for normal growth and stress responses.
Which of your results is the most fascinating for you?
Some of our mutants only showed an obvious difference to our control plants when they were grown under stressful conditions. This is rather what you expect if you modify minor components of the cell wall. However, the growth of other mutants was strongly affected also under optimal growth conditions. This was really unexpected for me because I did not think that a modification of a protein that is adding glycans to some of the 1200 predicted glycoproteins has such a severe effect on the cell wall. We still do not fully understand this result, but we have some ideas and are hopefully close to figure out what the cause is.
What was the biggest challenge you faced during your PhD?
The biggest challenge in my whole PhD was to transfer those proteins to bacteria or tobacco which allows to multiply and isolate these proteins and do functional studies. They need a very specific environment to be active which made the full procedure very challenging. We are still struggling with this, but I will continue on optimizing the process in the next couple of weeks.
Do you think your results might lead to practical applications in future?
We still need to do more research before we come closer to practical applications. When we understand better how modifications of the glycoproteins affect cell wall properties, we might be able to alter the interaction between cell wall components and like this change the properties of the cell wall. We could for example make cellulose or hemicellulose easier to extract which could be interesting for the pulp and paper industry or make the cell walls a bit more bendable or allow that it can expand more. Beside of the mutant studies with Arabidopsis, we also performed a bioinformatic analysis where we predicted which proteins in poplar are glycoproteins and where these proteins are expressed in the wood. Also this study does not result in direct applications but it is groundwork for future research in poplar and closely related species there is the potential for possible future applications.
Do you plan to continue doing research on cell wall or do you have already other plans for your future?
My plan is to go back to the Netherlands, and I am currently searching a postdoc there. It is quite difficult now during the Corona crisis because not many positions open up. I would like to continue doing research on cell walls. There is still a lot to uncover. Unfortunately, not many research groups in the Netherlands are working on cell walls. That is why I am also thinking to write my own postdoc proposal focusing on the role of the cell wall in abiotic stress responses in Arabidopsis but also in crops. I have never worked with crops before and I would like to start with that. On the long run, I would like to do research in a breeding company and working with crops hopefully will help me to come closer to that.
About the public defence:
The public defence took place on Friday, 30th of October at SLU in Umeå. Faculty opponent was Grégory Mouille, Institut Jean-Pierre Bourgin, UMR 1318 INRAE-AgroParisTech, France. Pieter Nibbering's supervisor is Totte Niittylä. The dissertation was live broadcasted on SLU Play: https://play.slu.se.
Title of the thesis: The role and synthesis of β1,3-galactans in plant cell wall formation
Link to the thesis: https://pub.epsilon.slu.se/17817/
For more information, please contact:
Pieter Nibbering
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences (SLU)
Email: