Forschungsbericht:
Zellbiologie AG Maier
born September 20th 1957
1986 Diploma, Freiburg
1988 Promotion Freiburg
1993 Habilitation, Freiburg
1995 Heisenberg fellow
1995–1997 Associate Professor, Bayreuth
since 1997 Full Professor, Marburg
Research
projects:
Cryptomonads
Cryptomonads, unicellular flagellates, evolved by the enslavement and
intracellular reduction of a phototrophic eukaryote within another
eukaryote. This evolutionary strategy, secondary endosymbiosis, led to
plastids surrounded by three or four membranes. In the case of
cryptomonads, the plastid is surrounded by four membranes, but still
harbours a remnant cytoplasm of the enslaved alga including a pigmy
cell nucleus, the nucleomorph. In an international genome project we
have sequenced the nucleomorph genome of one cryptophyte, Guillardia
theta. Thereby we detected one of the smallest eukaryotic genomes
investigated so far, which is comprised of three little, linear
chromosomes. Interestingly the coding capacity of this genome is very
small as indicated by the fact that approximately 450 genes were
detected. Among these, only 30 encode proteins for plastid functions.
At the moment we are investigating several unusual aspects of the
nucleomorph and the cell biology of cryptophytes. One of our aims is to
elucidate the functions of proteins encoded by nucleomorph-specific
ORFs. For this, we have enlarged in our methodological repertoire by
using cyanobacteria and Arabidopsis other model organisms. Beside
functional aspects, we are interested in the phylogeny of the
proteins.
A further focus of our research is the intracellular protein transport
in cryptomonads. As the plastid of cryptomonads is surrounded by four
membranes and an additional remnant cytoplasm is present, a
sophisticated protein transport system evolved within cryptomonads. At
the moment we are studying how proteins are transported across the
second outermost membrane of the plastid and how they are further
distributed.
Diatoms
Similarly to cryptomonads, diatoms evolved in secondary endosymbiosis
and harbour a plastid, which is directly surrounded by four membranes.
At the moment we are studying one strain, Rhopalodia gibba. This
diatom harbours cell inclusions, which are called spheroid bodies. We
have shown that these spheroid bodies are intracellular cyanobacteria,
which have nitrogen fixation activity. Additionally, we have
investigated the phylogeny of the spheroid bodies in more detail and
identified a closely related free-living relative. Therefore it is now
possible to study genomic and physiological adaptations by changing
lifestyle from free-living to intracellular. For this, we have
initiated a comparative genome project dealing with the spheroid body
genome and that of the free-living relative. First results indeed
demonstrate early adaptations in the genomic composition of the
spheroid bodies.
Dinoflagellates (together with Dr. Stefan Zauner)
Ceratium horridum is an unusual dinoflagellate. This was shown
by its thylakoid organisation and by the localization of little
plasmids, the so-called minicircles. These circular molecules are
thought to represent the plastid genome of dinoflagellates. In C.
horridum the minicirlces are nucleus-encoded as shown by our recent
experiments. However, a plastid localization of a minor population of
these molecules cannot be ruled out. It was thought that RNA editing
acting on transcripts of genes of cyanobacterial origin is restricted
to higher plant plastids. In the case of C. horridum we
demonstrated for the first time that transcripts originating from
minicircle-encoded genes are substitutional edited. We observed an
unusual editing pattern, changing in most cases the encoded amino acid
or curing stop-codons. At the moment we are involved in the
characterization of editing of mitochondrial genes and in the isolation
of the mitochondrial genome.
Last, but not least, we are interested in the evolution of chloroplast
RNA editing. In order to explain this phenomenon, we have investigated
all known editing events and compared cis-acting sequences of editing
sites. This approach succeeded in the discovery of the evolution of
chloroplast RNA editing.
Publications: (U. Maier group only)
Original papers
Prechtl, J, Kneip, C, Lockhart, P, Wenderoth, K., Maier, UG (2004)
Intracellular sphaeroid bodies of Rhopalodia gibba have nitrogen fixing
apparatus of cyanobacterial origin. Mol. Biol. Evol. 21:
1477-1481.
Laatsch, T., Zauner, S, Stoebe-Maier, B, Kowallik, K.V, Maier, U.-G.
(2004) Plastid-derived single gene minicircles of the dinoflagellate
Ceratium horridum are localized in the nucleus. Mol. Biol. Evol. 21:
1318-1322.
Zauner, S., Greilinger, D., Laatsch, T., Kowallik, K, Maier, U.-G.
(2004) Substitutional editing of transcripts from genes of
cyanobacterial origin in the dinoflagellate Ceratium horridum. FEBS
Lett. 577: 535-538.
Hjorth, E., Hadfi, K., Zauner S., Maier, U.-G. (2005) Unique genetic
compartmentalization of the SUF system in cryptophytes and
characterization of a SufD mutant in Arabidopsis thaliana, FEBS Lett.
579:1129-1135
Kawach, O., Voß, C., Wolff, J., Hadfi K., Maier, U.-G., Zauner S.
(2005) Unique tRNA introns of an enslaved algal cell. Mol. Biol. Evol.
22:1694-1701
Gould, S., Sommer, M., Hadfi, K., Zauner, S., Maier, U.-G. (2005)
Protein Targeting into the Complex Plastid of Cryptophytes. J. Mol.
Evol., in press
Hauth, A.M. Maier, U.G., Lang, B.F., Burger, G. (2005) The
Rhodomonas salina mitochondrial genome: Compact gene arrangement
and extensive repeat region. Nucl. Acids Res., 33:4433-4442
Sineshchekov, O.A., Govorunova, E.G., Jung, K.H. , Zauner, S., Maier,
U.-G., Spudich, J.L. (2005) Rhodopsin-mediated Photoreception in
Cryptophyte Flagellates. Biophysical Journal, 89:4310-4319
S. Zauner, C. Klemme, K. Bolte and U.G. Maier (2005) Minicircles, genes
of mitochondrial origin and editing of transcripts in a
peridinin-containing dinoflagellate. submitted
Kawach, O., Prechtl, J., Nyadwhile, J., Maier, U.G. (2005)
Characterization of a cyanobacterial protein involved in coupling a
prosthetic group to β-phycocyanin. Under revision
Zauner, S., Stoebe-Maier, B., Gilson P, McFadden, G.I., Lockhart, P,
Maier, U.G. (2006) Differential gene transfers and gene duplications in
primary and secondary endosymbiosis. Under minor revision
Deschamps P., Haferkamp I., Dauvillée D., Haebel S., Steup M., Buléon
A., d’Hulst C., Gould S., Maier U., Neuhaus E., Ball S. (2006) The
nature of the periplastidial pathway of amylose synthesis in the
cryptophyte Guillardia theta. Euk. Cell, in press
Haferkamp, I., Deschamps, P., Ast, M., Jeblick, W., Maier, U., Ball,
S., Ekkehard Neuhaus, H.E. (2006) Molecular and biochemical analysis of
periplastidal starch metabolism in the cryptophyte Guillardia
theta. Euk. Cell, in press
Tillich M, Lewahrk P., Morton B.M., Maier U.G. (2006) Evolution of
Chloroplast RNA Editing. Submitted
Reviews
Hjorth, E., Hadfi, K., Gould, S.B., Kawach, O., Sommer, M.S., Zauner,
S., Maier, U.-G. (2004) Zero, one, two, three, and perhaps four.
Endosymbiosis and the gain and loss of plastids. Endocytobiol. Cell
Res. 15: 459-468.
Sommer, M.S., Gould, S.B., Kawach, O., Klemme, C., Voß, C., Zauner, S.,
Maier U.-G. (2005) Photosynthetic organelles and endosymbiosis. In:
Genome Evolution in Eukaryotic Microbes (Laura A. Katz and Debashish
Bhattacharya, eds.), accepted
Kawach, O., Sommer, M., Gould, S., Voß, C., Maier, U.-G., Zauner, S.
(2005) Nucleomorphs: remnant nuclear genomes. In: Genome Evolution in
Eukaryotic Microbes (Laura A. Katz and Debashish Bhattacharya, eds.),
accepted
Maier, U (2006) Vom Prokaryoten zum Eukaryoten. Nova Acta Leopoldina,
accepted
Diploma Theses
Wolf, Jonci (2004)
Rost, Martina (2004)
Voß, Christine (2004)
Klemme, Cornelia (2004)
Tim Ammon (2005)
Karin Jaschinski (2005)
Janine Büchel (2005)
Katrin Bolte (2005)
Sebastian Zoll (2006)
PhD theses:
Christoph Kneip (2004)
Elmar Hjorth (2005)
Funding
SFB Transregio 1
SFB 395
SFB 593
Graduate School, Intra- and inter-cellular transport and
communication
Members of the group
Uwe Maier, head
Stefan Zauner, Assistant Professor
Katrin Bolte, PhD student
Helena Funk, PhD student
Sven Gould, PhD student
Oliver Kawach, PhD student
Cornelia Klemme, PhD student
Peter Poltnigg, PhD student
Maik Sommer, PhD student
Christine Voß, PhD student
Franziska Hempel, Diploma student
Petra Lehmann, Diploma student
Marianne Johannsen, Technician
Christa Zimmermann, Technician
Prof. Dr. E. Mörschel
Dr. K. Wenderoth
Address
Laboratory for Cell Biology
Philipps-Universität Marburg
Karl-von-Firsch-Str.
D-35032 Marburg
