Niittylä, Totte - Cell Wall Biosynthesis and Carbohydrate Metabolism

My lab investigates plant cell wall biosynthesis and carbohydrate metabolism in Arabidopsis, aspen and Norway spruce. We are interested in the molecular mechanisms responsible for sucrose transport to secondary cell wall forming cells, and the subsequent production of cell wall polymer precursors.

Totte Niittylä behind aspen trees (photo taken by Fredrik Larsson)

Photo: Fredrik Larsson

Transcriptional regulation plays an important role in these processes, and we are applying different genomics tools to identify transcription factors involved in woody biomass accumulation. We also work on carbohydrate active enzymes involved in the biosynthesis of arabinogalactan proteins (AGPs), which form a diverse group of cell surface- and wall-associated glycoproteins. We are interested in AGP’s role in cell wall biosynthesis, and the relationship between AGP glycosylation and AGP functionality.

A) Light microscopy picture of aspen wood fibers and vessels; B) Cross section of Arabidopsis stem. Lignified cell walls are shown in red and non-lignified in blue; C) Cross section of aspen stem; D) Siliques of wild type Arabidopsis and opnr-1 showing the seed abortion phenotype (left). Elongated zygotes of wild type and opnr-1 (middle). Confocal microscopy images showing the dual localisation of OPNR in nuclear envelope and mitochondria labelled with PHB3-mCherry (right).

In addition to wood biology we also explore novel fundamental cellular processes. One third of the genes in the model plant Arabidopsis remain of unknown function. Our ambition is to push new inroads to this unknown gene space. We are interested in identifying essential genes, which are indispensable for the function of a plant cell and constitute the minimum gene set required for cellular life.

Siliques of wild type Arabidopsis and opnr-1 showing the seed abortion phenotype (left). Elongated zygotes of wild type and opnr-1 (middle). Confocal microscopy images showing the dual localisation of OPNR in nuclear envelope and mitochondria labelled with PHB3-mCherry (right)

Our approach is to investigate evolutionarily-conserved single copy Arabidopsis genes of unknown function with predominant expression in meristematic cells. Evolutionarily-conserved single copy genes in flowering plants have been shown to be enriched in essential housekeeping functions. This exploratory project has led us to new areas of cell biology, and provide an adventure for those who do not fear the unknown.

Recently we identified an essential gene named OPENER (OPNR) in this project. opnr mutants show zygotic lethality and endosperm arrest, and intriguingly OPNR localizes to both nuclear envelope and mitochondria pointing to an uncharacterized essential process occurring in both nucleus and mitochondria in dividing plant cells.

Svensk sammanfattning

Key Publications
CV Dr. Totte Niittyla

Key Publications
CV Dr. Totte Niittyla

Key Publications

Mahboubi A, Linden P, Hedenström M, Moritz T, Niittylä T (2015). Carbon-13 tracking after 13CO2 supply revealed diurnal patterns of wood formation in aspen. Plant Physiology 168: 478-489.
Gerber L, Zhang B, Roach M, Rende U, Gorzsás A, Kumar M, Burgert I, Niittylä T and Sundberg B (2014). Deficient sucrose synthase activity in developing wood does not specifically affect cellulose biosynthesis, but causes an overall decrease in cell wall polymers. New Phytologist 203: 1220 – 1230.
Mahboubi A, Ratke C, Gorzsás A, Kumar M, Mellerowicz EJ, Niittylä T (2013). Aspen SUCROSE TRANSPORTER 3 allocates carbon into wood fibers. Plant Physiology 163, 1729-1740.
Nystedt et al. (2013). The Norway spruce genome sequence gives insights into conifer genome evolution. Nature, 497, 579-584.
Roach M, Gerber L, Sandquist D, Gorzsas A, Hedenström M, Kumar M, Steinhauser MC, Feil R, Daniel G, Stitt M, Sundberg B and Niittylä T (2012). Fructokinase is required for carbon partitioning to cellulose in aspen wood. Plant Journal, 70, 967 – 977.