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Doctoral thesis, 2022

Carbon allocation in aspen trees

Viljamaa, Sonja;


Trees allocate assimilated carbon between growth and storage. In this PhD thesis, I
investigated the regulation of carbon allocation during tree growth both at
transcriptional as well as whole-tree level, and with a focus on wood formation.
I performed a large-scale DNA affinity purification sequencing (DAP-seq)
screen on transcription factor proteins that regulate gene expression in developing
wood of aspen (Populus tremula). Together with bioinformaticians, I identified both
novel and previously reported interactions. The results were integrated into a
publicly available database, providing a novel resource for wood biology. We also
present a practical guide for the analysis of DAP-seq data to facilitate similar studies.
Next, I investigated carbon partitioning between growth and storage in aspen,
focusing on the role of starch as the major storage compound. We report that aspen
growth is not limited by starch reserves and suggest a passive starch storage
mechanism where sink tissues are the growth-limiting factor.
In a study on Arabidopsis (Arabidopsis thaliana), I address the debate on whether
sucrose synthase (SUS) enzymes are required in the biosynthesis of cellulose, the
most abundant component of wood. As mutants lacking all SUS isoforms grew
normally and their cellulose content was comparable to that of wild-type, I conclude
that SUS activity is not required for cellulose biosynthesis in Arabidopsis.
Taken together, the results of this PhD study fill key knowledge gaps in the field
and provide new starting points for future research projects on carbon allocation in


Wood formation; Secondary cell wall (SCW); Non-structural carbohydrates (NSC); Carbon allocation; Source-sink dynamics; Transcriptional regulation; Arabidopsis; Populus; DAP-seq

Published in

Acta Universitatis Agriculturae Sueciae

2022, number: 2022:58
ISBN: 978-91-7760-991-9, eISBN: 978-91-7760-992-6
Publisher: Swedish University of Agricultural Sciences

Authors' information

Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology

UKÄ Subject classification

Plant Biotechnology

URI (permanent link to this page)