Sucrose delivers the carbon for cellulose biosynthesis. To make the carbon available, sucrose needs to be enzymatically cleaved. This can be done by two classes of enzymes, sucrose synthases and invertases. Umut Rende from Umeå Plant Science Centre (UPSC) investigated how these two enzyme classes contribute to cellulose biosynthesis in aspen wood. He will defend his PhD thesis at the Swedish University of Agricultural Science on Thursday, the 8th of December 2016.

Invertase TreesControl (WT) and different transgenic aspen lines with reduced invertase activity.Umut Rende has focussed specifically on sucrose synthases and cytosolic neutral invertases, enzymes that are active in developing aspen wood. By analysing transgenic aspen trees with reduced enzyme activity of either sucrose synthases or neutral invertases he could show that neutral invertases are important for cellulose biosynthesis. Sucrose synthase on the other hand is not delivering carbon specifically for synthesis of cellulose but also for other cell wall components like lignin and hemicellulose. 

The transgenic trees Umut Rende and his collegues created grew normally in the greenhouse without any visible differences to non-modified trees. “That was quite disappointing at first,” says Umut Rende. “The total neutral invertase activity in our invertase mutants was reduced by about 50%. We had to look deep into the chemistry and structure of the wood in these trees to see that the cellulose content and the diameter of the cellulose fibrils was reduced. This very specific cellulose defect demonstrated that neutral invertase activity is critical for cellulose formation in developing wood of hybrid aspen.”

Formas has recently granted two research projects from Umeå Plant Science Centre (UPSC) that both aim to analyse the specific role of carbohydrate metabolism for wood formation. Ewa Mellerowicz, coordinator of one project, will study the role of Carbohydrate Active Enzymes in wood formation. Totte Niitylä, who is leading the other project, aims to analyse how carbohydrates are transported and integrated into the wood. The two researchers from UPSC will each receive about three million SEK from Formas.  

A large proportion of the woody biomass arises from carbohydrates. The two projects will analyse the carbohydrate metabolism in developing wood in spruce and aspen. Both tree species are fully sequenced model species and important for the Swedish forest industry. The researchers aim to identify factors that control the mechanical and chemical properties of wood and that influence specific wood traits like volume and density which are interesting for forestry. The outcome of these projects will provide new insights into wood formation in trees and will be very interesting for spruce and aspen breeding programs in Sweden.  

Ewa Mellerowicz, Professor at the Swedish University of Mellerowicz Ewa 1150Agricultural Science (SLU), is focussing in her research on so called wood matrix polysaccharides. These are long-chained carbohydrates that interact with the other wood cell wall components, cellulose and lignin, to form a rigid structure. They are synthesized and modified by Carbohydrate Active Enzymes (CAZYmes) and affect the mechanical and chemical properties of cell walls in wood cells. In her project, Ewa Mellerowicz and her colleagues want to identify CAZYmes that are involved in wood formation in spruce where wood carbohydrate metabolism is so far not well studied.

The researchers specifically plan to characterize how the expression of the identified spruce CAZYme genes is changing during the day and how this influences the deposition of carbohydrates to the cell wall. In a further step, Ewa Mellerowicz and her team will test the function of the identified spruce genes in aspen. The identification and characterisation of spruce CAZYmes will be not only valuable for understanding wood formation in conifers. The enzymes might be also interesting tools for industrial use.

Totte NiittyläTotte Niittyla 1150, group leader at UPSC, is interested in the transport of carbohydrates from photosynthetic tissues to the wood and their metabolism in the wood. He and his team are developing carbon-13 isotope flux measurements for aspen. The researchers expose aspen plants for a short time to carbon dioxide that is labelled with the heavy isotope carbon-13. Then, they analyse how the label is transported to and metabolised in developing wood. By determining which compounds are labelled combined with enzyme activity measurements the researchers around Totte Niittylä aim to identify new genes that control carbon fluxes during wood formation.

Chemicals modifying plant development are commonly used to characterize the molecular basis of plant growth. In collaboration with the Laboratories for Chemical Biology Umeå (LCBU), Thomas Vain from Umeå Plant Science Centre (UPSC) has identified novel compounds that control plant development. He also contributed to develop workflows for processing digital images to quantify relevant biological information from these images. Thomas Vain will defend his PhD thesis at the Swedish University of Agricultural Science on Friday, the 25th of November 2016.   

Thomas Vain and his colleagues from LCBU, Umeå University, have screened about 8000 different compounds on their effects on plant development using the model plant Arabidopsis thaliana. Their special focus was on compounds that alter how plants perceive auxin, a phytohormone broadly regulating plant development. The identified molecules are useful tools to study fundamental aspects of plant development and might lead to the design of more specific agrochemicals. 

20161123 Vain Press release Figure1A. thaliana seedlings and the chemical structure of the phytohormone auxin
A chemical biology screen like the one performed by Thomas Vain and his colleagues consist normally of several steps. In the first round, a large amount of compounds was tested and the most effective compounds were selected. These compounds were characterised further using different, more specific approaches to understand their mode of action. They ended up with several interesting compounds that affect the auxin signalling pathway, which effects unravel in detail auxin perception and response. 

Thomas Vain and his colleagues from the UPSC went even further. They chose one of their most affective compounds and performed a genetic screen with it. They used a population of randomly mutagenized Arabidopsis seedlings and screened for mutants that were resistant to the selected compound. The mutation in the resistant mutants will tell the researchers more about possible mediators of the effect of the selected compound. This will increase the understanding about how auxin is perceived and how responses to auxin are regulated. 

Vetenskapsrådet decided to fund the research projects of Rishikesh P. Bhalerao, Stefan Jansson, Stéphanie Robert and Åsa Strand, all researchers at the Umeå Plant Science Center (UPSC). They will receive about three million SEK each for their research projects over four years. In total, Vetenskapsrådet has granted 340 from 1767 applications in the field of natural and engineering sciences.

VR2016Photo: Anne Honsel The four granted projects cover different research areas within plant science. Rishikesh P. Bhalerao will analyse how aspen trees reactivate their growth in spring. Two different temperature signals are necessary for this. First low temperatures in winter are needed to break the dormancy whereas subsequent warm temperatures in spring induce bud burst after dormancy has been released. Rishikesh Bhalerao will focus in his project on elucidating the molecular basis of temperature mediated dormancy break and bud burst.

The aim of Stefan Jansson’s project is to understand how trees survive the winter. He plans to compare deciduous trees like aspen with evergreen needle trees like spruce. Deciduous trees degrade and recycle their photosynthetic components in autumn before they shed their leaves. Evergreen trees in contrast keep their photosynthetic machinery during the winter and stay green. Stefan Jansson wants to analyse how these different strategies to survive the winter are regulated.

Stéphanie Robert will examine how cell shapes are determined. Cell walls have been suggested to be heterogeneous in their mechanical and chemical properties. These properties determine the stiffness and elasticity of the cell wall, which control cell growth and overall cell shape. Stéphanie Robert will analyse which cell wall components are influencing the properties of the cell wall and how these properties control the shape of the cell.

Åsa Strand will investigate which regulatory mechanisms control the development of chloroplasts, the photosynthetic centre of the plant cell. Photosynthetic activity is established during chloroplast development and as a consequence this leads to drastic changes in the metabolism of the cell. Åsa Strand wants to understand how these metabolic changes interconnected to chloroplast development are communicated within the cell. The focus of her project will be on the communication between the chloroplast and the nucleus.

Plants continuously have to decide how to invest their resources. If they invest more into growth, they might become more susceptible against diseases or easier attacked by herbivores. On the other hand, a strong investment into their defence system will be at the expense of growth. Vicki Huizu Guo Decker from Umeå University has found that certain defence chemicals, influence the decision making process in Aspen trees. Vicki Huizu Guo Decker has successfully defended her thesis on Friday the 4th of November.   

The production of defense chemicals is costly for a plant. Vicki Huizu Guo Decker has worked with Aspen trees that have evolved different strategies to invest their resources. Those trees produce different levels of tannins and salicinoids which are phenolic defence compounds. Vicki Huizu Guo Decker wanted to know how these genetically different Aspen trees (also called Aspen genotypes) react to additional nitrogen nutrition and how this affects the plant associated microorganisms.   

image006The soil nitrogen content influences the plant's decision to grow or to defend. 
Nitrogen nutrition normally promotes plant growth and inhibits the synthesis of tannins in the tree leaves. Vicki Huizu Guo Decker found that there is a connection between the genetically inherited level of tannins and the trees’ strategy to deal with limited nitrogen availability. Aspen trees with low tannin levels grew better on poor soils with low nitrogen levels than trees that contain a lot of tannins. “Trees with high levels of tannins invest more energy to keep these levels high”, says Huizu Vicki Guo Decker. “That is why they grow less when nitrogen is limited. This strategy can be of advantage for the tree when it is for example attacked by insects.”

Another factor that is thought to influence the fitness of the tree are endophytic fungi. These are plant associated microorganisms that co-exist with the tree but do not cause any disease symptoms. Instead, their presence might improve the fitness of the tree against plant attacking insects. Vicki Huizu Guo Decker found that the composition of the fungal community on Aspen leaves is strongly related to the level of phenolic compounds. Especially salicinoids influence the structure of the fungal community.

The relationship between endophytic fungi and the host plants get image005Treatment with the Aspen leaf beetles and resulting deeding damages. even more complex when additional environmental factors are added like plant attacking insects. Huizu Vicki Guo Decker worked with Aspen leaf beetles. This specialised beetles and their larvae feed on Aspen trees and the larvae even use the phenolic compounds from the tree for their own defence. Guo Decker showed that the fungal composition becomes less specific to the respective respective genetic Aspen genotype when the Aspen leaf beetles are attacking the tree.

[2016-10-05] The Knut and Alice Wallenberg Foundation grants two research projects from the Umeå Plant Science Centre with together SEK 76 million. One project focuses on understanding how plants control the time to flower in changing environmental conditions, while the other aims to identify key genes controlling tree growth and environmental adaption. 

The project “Epigenetic and Metabolic Control of Flowering Time” is led by Markus Schmid, since 2015 professor at Umeå University and the Umeå Plant Science Centre (UPSC). He will receive, together with his co-applicants Johannes Hanson, Ove Nilsson and Karin Ljung, SEK 28 million. The project leader of the project “UPSC Forest Biology and Biotechnology” is Ove Nilsson, director of the UPSC and professor at the Swedish University of Agricultural Sciences (SLU). This project involves 40 research groups from the UPSC and will be funded with SEK 48 million.

187238 schmid markus 7682 150904 mpn originalPhoto: Mattias PetterssonMarkus Schmid focuses in his research on how plants control their flowering time. The induction of flowering is a central event in the life cycle of plants. Only when plants flower at the right time their reproduction, and therefore their survival, is ensured. The underlying regulatory mechanisms are very complex including regulation on epigenetic (i.e. the modification of the genome without changing the DNA sequence), genetic, hormonal and metabolic levels. 
“The decision if a plant starts to flower is made in a very small subset of cells”, explains Markus Schmid. “Within this project, we will isolate those specific cells and analyse the molecular mechanisms that control the induction of flowering. This will help us to predict the ecological consequences of future climate changes and to select plant varieties that are well adapted to their particular environment.” 

The basis of the second project is the long standing expertise OveNilssonPhoto: Anne Honselof the UPSC in a broad range of plant biology related research areas. “This is a large joint project from the UPSC and we are very delighted that we received the funding,” says Ove Nilsson. “We will develop a large scale gene-mining program based on data that we have been collecting at the UPSC for more than 20 years. Our aim is to identify key regulators of tree growth and wood development.”

A central point of the project will be the establishment of a tree phenotyping platform. This platform will be part of a new greenhouse that will be built at the UPSC. It will allow to continuously monitor the growth and development of trees under highly standardized conditions. Trees in which the identified key genes are modified will be analysed in order to understand how they control tree growth, climate adaptation and wood properties. The most promising candidates will be further studied in field trials.

[2016-09-29] Humans adjust to weather changes by changing their clothes or changing their location. Plants have developed other strategies to adapt to a changing environment. Louise Norén Lindbäck from Umeå Plant Science Centre has detected new ways how plants sense changes in their environment and how they communicate these changes within the plant cell. She will defend her findings on the 6th of October. 

Louise Norén LindbäckPhoto: Carole DubreuilLouise Norén Lindbäck has identified a new mechanism that is controlled by signaling molecules of the chlorophyll biosynthesis. These molecules are called tetrapyrroles. They can activate a signal transmitted from the chloroplast, the place where chlorophyll is synthesized in the cell and photosynthesis takes place, to the nucleus. This signal from the chloroplast informs the nucleus about which genes need to be turned on or off to adapt the cell machinery to changes in the environment.

”This new signaling pathway is important both under normal conditions for fine-tuning the protein synthesis during the day as well as under extreme conditions to protect the plant against for instance too much light”, says Louise Norén Lindbäck. ”We humans can go inside or take on/off our clothes to adapt to changes of the weather. Plants do it by producing special proteins that can help to protect their cells against excessive sunlight”.

The chloroplast is talking constantly with the nucleus of the cell but this is not a one-way communication. Signals go back and forth all the time. Like this the two cell compartments discuss which proteins are needed when and where to adapt best to changes in the environment. The sunlight is a key factor in this communication. It does not only deliver the energy which is driving photosynthesis. The sunlight informs the plant also about e.g. the time of the day or the season of the year.

[2016-09-23] PNAS has published this week at the same time three articles that focus on one enzyme, the dioxygenase for auxin oxidation 1 (DAO1). This enzyme catalyses the oxidation and thereby inactivation of auxin, a plant hormone important for the regulation of plant growth and development. Researchers from Umeå Plant Science Centre contributed to two of these articles while the third is published by a separate research group.

The plant hormone auxin is very crucial for regulating plant growth and development. The shape of the plant as well as the function of tissues and cells is controlled by auxin. It acts on cell division, elongation and differentiation and directs like this for example the growth of a plant towards the light. The spatial distribution of auxin within the plant is very inhomogeneous to allow this directed growth. It is regulated by complex interactions between different pathways for auxin transport, signalling and metabolism.

Three mechanisms control auxin metabolism: auxin biosynthesis, degradation and conjugation, i.e. the binding of auxin to amino acids or sugars. Enzymes involved in biosynthesis and conjugation of auxin are already well characterised but little was known about the enzyme which catalyses the degradation of auxin by oxidation. The three PNAS articles show for the first time that DAO1 (dioxygenase for auxin oxidation 1) is the functional auxin oxidising enzyme in Arabidopsis and they provide altogether a very detailed characterisation of this enzyme.

Ljung KarinPhoto: Mattias Pettersson
The team around Karin Ljung from the Umeå Plant Science Centre (UPSC) could show that mutants with reduced DAO1 activity have increased levels of auxin conjugates. These conjugates are considered to be storage forms of auxin with low biological activity. The researchers concluded that the missing function of DAO1 for inactivating auxin is compensated by an increased activity of auxin conjugating enzymes. This is important for keeping the auxin homeostasis balanced.

The groups of Markus Owen and Malcolm Bennett from Nottingham University chose a systems biology approach. They developed in cooperation with Karin Ljung’s group a mathematical model of auxin metabolic pathways based on experimental data. The researchers predicted with the help of their model that the auxin concentration in the DAO1 mutant is elevated in a special zone in the root tip. The root hairs in this mutant were longer than normal and the prediction gave the explanation for these findings.

This summer, Stefan Jansson has grown (probably for the first time) gene-edited cabbage plants in his garden. Together with the journalist Gustaf Klarin from Radio Sweden, he has harvested and lunched the plants that were modified using the “genetic scissors” CRISPR-Cas9. This news motivated even the prestigious journal Science to write a news message about it.

Since several years, Stefan Jansson, professor at the Umeå Plant CRISPR middag Bild 17 IG WebbScience Centre (UPSC) and at Umeå University, is very active in discussing questions about GMO (genetically modified organisms). The recent development of gene editing methods like CRISPR-Cas9 breathed new life into this GMO discussion.  

CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 allows either to exchange one part of a gene by another DNA fragment or to cut a segment out. The cabbage plant grown this summer in Stefan’s garden was modified in the latter way, i.e. a segment of the DNA was removed but no “foreign DNA” introduced.  

The Swedish Board of Agriculture decided in November 2015 that plants modified with this new technique by which defined parts of the DNA are cut out of the genome are not considered to fall under the GMO-legislation. This decision allowed Stefan Jansson to grow the modified cabbage plants legally in his garden. He has blogged about his unique summer gardening experiences in the “Forskarbloggen” at Umeå University. 

[2016-08-26] The UPSC PhD and Postdoc Retreat 2016 took place last week in Skeppsvik Herrgård, close to Umeå. During two days the PhD students and Postdocs discussed their research, learned about advanced scientific techniques and had some career training. The feedback was overall very positive and the interest is high to make it to an annually repeating event. 

One intention for initiating a UPSC PhD and Postdoc Retreat was to offer training related to career development. The emphasis this year was on exercising the job interview situation. HR officer and job coach Maria Rönnholm discussed with the participants what is important before, during and after a job interview and she simulated a job interview situation. 

UPSC Retreat2016 smallPhoto: Anne Honsel The other main focus of this year’s retreat was to strengthen the PhD and Postdoc network within the UPSC. The organisers created a program that consisted not only of scientific sessions but also included team building activities and some free time for social activities and discussions. About 35 people participated and their responses were throughout positive: “It was a really good mix of technical, scientific and career training and fun”, as one of the participants summarised the two exciting days. 

The first day started with the presentation of the individual research projects. Every participant got two minutes’ time to explain his/her project to the others using a hand-drawn poster. “Many of us were first very sceptical when we heard what we were supposed to do”, said another participant. “But then it turned out to be really interesting and the time passed by very fast.”