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Two novel types of plant hexokinases in the moss Physcomitrella patens
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Sveriges lantbruksuniversitet, Institutionen för växtbiologi och skogsgenetik.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Sveriges lantbruksuniversitet, Institutionen för Livsmedelsvetenskap, mjölkproduktlära.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Hexokinase catalyzes the phosphorylation of glucose and fructose, but it is also involved in sugar sensing in both fungi and plants. We have previously described two types of hexokinases in the moss Physcomitrella (Olsson et al., 2003, J. Biol. Chem. 278, 44439-44447). Type A, exemplified by the major Physcomitrella hexokinase PpHxk1, is a soluble protein that localizes to the chloroplast stroma. Type B, exemplified by PpHxk2, has an N-terminal membrane anchor. Both types are conserved also in seed plants, and localize to the chloroplast stroma and mitochondrial membranes, respectively. We have now characterized all eleven hexokinases encoded by the Physcomitrella genome. Based on their N-terminal sequences and intracellular localizations, three are type A hexokinases and four type B hexokinases. However, we also found two new types of hexokinases. Type C, encoded by a single gene, has neither transit peptide nor membrane anchor, and is found in the cytosol. Type D hexokinases, encoded by three genes, have membrane anchors and localize to mitochondrial membranes, but their sequences differ significantly from the type B hexokinases. Interestingly, all moss hexokinases are more similar to each other than to hexokinases from other plants. This suggests that the moss genes have undergone concerted evolution.

Keyword [en]
Hexokinase: Physcomitrella patens: subcellular localization
Identifiers
URN: urn:nbn:se:uu:diva-109192OAI: oai:DiVA.org:uu-109192DiVA: diva2:272024
Available from: 2009-10-13 Created: 2009-10-11 Last updated: 2010-01-14
In thesis
1. Studies of the Carbon and Energy Metabolism in the Moss Physcomitrella patens
Open this publication in new window or tab >>Studies of the Carbon and Energy Metabolism in the Moss Physcomitrella patens
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since a proper balance between anabolic and catabolic reactions is essential for all eukaryotes, the basic mechanisms for regulation of the energy and carbon metabolism have been conserved throughout evolution. The moss Physcomitrella patens, which belongs to one of the basal clades among land plants, has many unique properties that make it an excellent plant model system.

We have used a yeast two-hybrid system to identify novel possible regulators or targets of the moss Snf1-related kinases, previously shown to regulate energy homeostasis. The function of the identified interactors PpSki1 and PpSki2 was analyzed in order to better understand the biological role of plant Snf1-related kinases.

The recently completed genome sequence of Physcomitrella was used in a comparative approach to study to what extent key enzyme and gene families involved in transport and metabolism of sugars and in regulation of the energy and carbon metabolism are conserved between mosses and vascular plants.

It has long been known that transformed DNA can replicate episomally in Physcomitrella. We have now shown that such DNA can be rescued back into E. coli. Surprisingly, we found that the original plasmid can be recovered from moss transformants obtained with circular DNA. Plasmids rescued from transformants obtained with linearized DNA had been repaired either by homologous recombination or by cohesive end re-ligation. These findings suggest that methods using shuttle plasmids are feasible in Physcomitrella.

Hexokinase, a key enzyme in the carbon metabolism, catalyzes the first step in hexose metabolism, but is also involved in sugar sensing and signaling. We have now made an initial characterization of the complete hexokinase family in Physcomitrella which is encoded by 11 genes. Two new types of plant hexokinases, types C and D, were found in addition to the previously described types A and B.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 490
Keyword
Hexokinase, SnRK1, sugar signaling, carbon metabolism, Physcomitrella patens, shuttle vector, subcellular localization, model organism
National Category
Cell and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:uu:diva-109358 (URN)978-91-554-7631-1 (ISBN)
Public defence
2009-11-27, B41, Uppsala Biomedical Center (BMC), Husargatan 3, 75123 Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-11-05 Created: 2009-10-14 Last updated: 2009-11-05Bibliographically approved

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