In the photosynthesis apparatus of green plants, the light-harvesting chlorophyll a/b-binding (LHC) proteins serve as antenna for photosystem I and photosystem II. Members of the LHC protein family bind the majority of the photosynthetic pigments (chlorophyll and carotenoids), make the photosynthetic light reaction efficient and regulate the photosynthetic light reaction, for example by dissipating excess light and adjusting excitation balance between the photosystems. A tight regulation of the light reaction is necessary to prevent production of oxygen radicals. We are studying the large family of LHC proteins using biochemical, genetic and molecular biological approaches. In Arabidopsis, 31 genes encode proteins of this family and we are systematically producing and analysing plants that lack different LHC proteins. We have produced a large number of transgenic Arabidopsis lines that each completely lack one of the LHC proteins (by means of anti-sense inhibition), and studies of the photosynthetic performance of these plants have helped us understand the function of the individual proteins and the structure of the photosystems. We are also studying different mutants that are impaired in light harvesting or light dissipation, and have for example identified the protein (PsbS) that work as the safety valve of the photosynthetic light reaction.

Functional genomics of aspen leaves

 

Functional genomics give us tools to look at the total pattern of gene expression in a tissue. We have sequenced over 10 000 EST clones from Populus leaves, annotated the sequences using a novel, semiautomatic procedures and are now studing the total pattern of gene expression in Populus leaves over the whole growing season using DNA microarrays. A database (PopulusDB) has also been created that should serve as the node in the Populus EST program. This is the fundament for studies when the effects on different environmental factors (both biotic and abiotic) on gene expression in aspen leaves in nature is be studied. Particular attention is paid to the process of autumn senescence. We are studying the gene expression during the senescence process in order to understand how the process is regulated at the molecular level and finally to manipulate it.

Selected publications:

 

Jansson, S. () The light-harvesting chlorophyll a/b-binding proteins. Biochem. Biophys Acta : 1-19

 

Jansson, S. () A guide to the LHC genes and their relatives in Arabidopsis. Trends in Plant Sciences 4: 236-240.    Abstract     Full text (pdf)

 

Jansson, S., Andersson, J., Kim, S.J. & Jackowski, G. () An Arabidopsis thaliana protein homologous to cyano-bacterial high light-inducible proteins. Plant Molecular Biology 42: 345-351   Abstract

 

Li, X-P., Björkman, O., Shih, C., Grossman, A.R., Rosenquist, M., Jansson, S. & Niyogi, K.K. () A pigment binding protein essential for regulation of photosynthetic light harvesting. Nature 40: 391-395   Abstract    Full text (pdf)

 

Andersson, J., Walters, R.G., Horton, P. & Jansson, S. () The photosynthetic antenna proteins CP29 and CP26 are not necessary for protective energy dissipation. Plant Cell 13:     Abstract   Full text (pdf)

 

Ganeteg, U., Strand, Å., Gustafsson, P. & Jansson, S. () The properties of the chlorophyll a/b-binding proteins Lhca2 and Lhca3 studied in vivo using antisense inhibition. Plant Physiol. 127: 150-158   Abstract   Full text (pdf)

 

Külheim, C., Ågren, J. & Jansson, S. () Rapid regulation of light harvesting and plants fitness in the field. Science 297: 91-93   Abstract    Full text (pdf)