We work on many aspects of plant biology, so covering them all in a few pages is difficult. Selected projects are mentioned below
The ultimate goal of this project is to learn how to find the genetic differences that make trees different from each other. Forest trees are, in general, more genetically diverse than most other organisms and aspens are, in this respect, extreme. Gene sequences from two aspens are on average about as different genetically as human and chimpanzee sequences are.We have built many genomic resources for Populus in general and aspen (P. tremula) in particular, for example clone collections (the SwAsp and UmAsp collections), ESTs, DNA microarrays, genome sequence of poplar and aspen, small RNAs as well as bioinformatic tools and databases.We are also working on spruce, e g generated the spruce genome sequence.
Using these tools, we study how aspens acclimate and adapt to the environment. Particular attention is paid to the process of autumn senescence, trying to answer the question: How do trees know it is autumn? We are studying gene expression, hotosynthesis and metabolism of the leaves during autumn senescence. In these studies we use transgenic plants but, more importantly, natural variation.There is a steep cline in autumn senescence; trees from northern latitudes enter senescence much earlier than those from southern latitudes, and by using the aspen genome sequence, the collection of aspen clones and genetic tools like association mapping, we hope to understand the genetic basis of this important trait.The same strategies are also used to dissect other traits, including herbivory and other biotic interactions.
Photosynthetic light harvesting
In the photosynthetic apparatus of green plants, the light- harvesting chlorophyll a/b-binding (LHC) proteins serve as antennae for photosystems I and II. Members of the LHC protein family have three membrane-spanning regions and bind the majority of the photosynthetic pigments (chlorophyll and carotenoids), make the photosynthetic light reaction effi- cient and regulate the photosynthetic light reaction, for example by dissipating excess light and adjusting the excitation balance between the photosystems.There are a group of proteins that are more distant members of this protein family.This group consists of PsbS, ELIPs (early light-inducible proteins) and several smaller proteins, containing only one or two membrane anning regions. PsbS is necessary for a light dissipation process – the qE type of non-photochemical quenching (NPQ) or feedback de-excitation (FDE) - that operates when the plants is exposed to "excess light".
We are studying the family of LHC proteins using bio- chemical, reverse and forward genetic and molecular biological approaches. In Arabidopsis, over 30 genes encode proteins of this family and we are systematically producing (through T-DNA knockouts or artificial microRNAs) and analysing – also under field conditions - plants that lack different LHC proteins.The photosynthetic performance of these plants helps us understand the function of the individual proteins, the structure of the photosystems and energy transfer in the antenna.
|How does the tree know that it is autumn?||Field experiment with transgenic Arabidopsis.|
- Nystedt B, Street NR et al. (2013). The Norway spruce genome sequence gives insights into conifer genome evolution.Nature 497:579-584
- Tuskan GA, DiFazio S, Jansson S, et al. (2006). The genome of black cottonwood, Populus trichocarpa (Torr. & Gray) Science 313:1596-1604
- Sterky F, Bhalerao RR, Unneberg P, Segerman B, Nilsson P, Brunner AM, Campaa L, Jonsson Lindvall J, Tandre K, Strauss SH, Sundberg B, Gustafsson P, Uhlén M, Bhalerao RP, Nilsson O, Sandberg G, Karlsson J, Lundeberg J, Jansson S (2004). A Populus EST resource for plant functional genomics. PNAS 101 13951–13956
- Külheim C, Ågren J, Jansson S (2002). Rapid regulation of light harvesting is crucial for plant fitness in the field. Science 297:91-93
- Li, X-P, Björkman, O, Shih C, Grossman, AR, Rosenquist, M, Jansson, S, Niyogi, KK (2000). A pigment binding protein essential for regulation of photosynthetic light harvesting. Nature 40: 391-395