Carbon allocation in aspen trees

Sammanfattning: Trees allocate assimilated carbon between growth and storage. In this PhD thesis, Iinvestigated the regulation of carbon allocation during tree growth both attranscriptional 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 developingwood of aspen (Populus tremula). Together with bioinformaticians, I identified bothnovel and previously reported interactions. The results were integrated into apublicly available database, providing a novel resource for wood biology. We alsopresent 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 aspengrowth is not limited by starch reserves and suggest a passive starch storagemechanism where sink tissues are the growth-limiting factor.In a study on Arabidopsis (Arabidopsis thaliana), I address the debate on whethersucrose synthase (SUS) enzymes are required in the biosynthesis of cellulose, themost abundant component of wood. As mutants lacking all SUS isoforms grewnormally and their cellulose content was comparable to that of wild-type, I concludethat SUS activity is not required for cellulose biosynthesis in Arabidopsis.Taken together, the results of this PhD study fill key knowledge gaps in the fieldand provide new starting points for future research projects on carbon allocation intrees.