A PhD studentship is available to study organelle dynamics during cell
division in the Arabidopsis root. If any of you have or know of
students who might be interested in this, would you please bring it to
their attention. Details are below. The full project description and
application procedure can be found on the Oxford Brookes University
PhD Research Studentship: Organellar fate during cytokinesis
Supervisors: Dr John Runions, Prof Chris Hawes, Dr David Evans
Eligibility: Applicants require a good Honours degree (2.1 or
equivalent) and either have been educated to degree level through the
medium of English or have TOEFL 600 (250) / IELTS 7 or equivalent
Value p.a. £11,500 bursary, & fees
Closing Date: 21st May
Interviews will be held on either June 6th, 7th or 8th
Background: Little is known about the mechanisms that determine
organellar fate during cytokinesis. As cells enter mitosis, the
nuclear envelope breaks down and rearrangements occur in the structure
of the cytoskeleton and endoplasmic reticulum (ER). In addition, Golgi
bodies, peroxisomes and mitochondria must re-duplicate so that
daughter cells are equally partitioned. We have in place techniques
for studying cell divisions at high resolution in a developmental
context. The arabidopsis root meristem is an ideal system in which to
study cell division in situ. Fluorescent protein marking of organelles
combined with confocal microscopy and image analysis of tissue 3D/4D
reconstructions will enable us to answer a number of questions about
organelle behaviour in the cell division zone. For example, i) what
role does the ER play in cell plate and nuclear envelope formation,
and ii) when do Golgi bodies re-duplicate and how are they partitioned
between daughter cells?
1) Cytokinesis in wild-type roots. Arabidopsis roots are ideal for
imaging when grown in coverslip-bottomed containers as they remain
healthy and continue to grow during observation. The student will
first learn high resolution live-cell imaging techniques by studying
cytokinesis in arabidopsis roots that have been stably transformed
with H2B-YFP which is a histone marker (Kurup et al, 2006) (fig.1).
This marker allows observation of nuclei during prophase and of
chromatin during other phases of the cell cycle. Co-Supervisor's
laboratories have fluorescent markers for other organelles. These will
be co-transformed into the nuclear-marking line in appropriate
combinations to describe the dynamics and disappearance / reappearance
of organelles during the cell cycle. We will concentrate on behaviour
of the ER, nuclear envelope and Golgi bodies during this phase. We
will use a cyclin marker that indicates entry into metaphase prior to
chromatin condensation for ease of targeting about-to-divide cells in
2) Photoactivation of organelles during mitosis. JR has developed a
technique for monitoring organelle development and dynamics using
photoactivatible fluorescent protein marking (Runions et al., 2006).
This technique utilises the short wavelength laser of the confocal
microscope system to either switch fluorescent proteins on or to
change their colour. The student will activate regions of ER both
proximal and distal to the site of cell-plate formation at different
phases of mitosis to monitor the contribution of existing ER into the
new cell plate and into the nuclear envelope. In addition, Golgi
bodies marked with the `kaede' fluorescent protein will be colour
photoswitched so that we can assess their dynamics during daughter
cell partitioning in later stages of mitosis.
3) Cytokinesis defective mutants. Several mutant lines of arabidopsis
have altered tissue morphology due to defects in cytokinesis (Jergens,
2005). These are distinct from cell-wall and cytoskeleton mutants and
seem to affect cell division because of defects in secretory pathway
function. Genes that play a role in cell division and that affect root
patterning include SCD1 (At1g49040), a homologue of the guanine
nucleotide exchange factors that regulate Rab GTPases and which affect
intracellular protein transport (Falbel et al., 2003), and several
including the KEULE-like loci which are Sec1p homologues that play a
role in membrane fusion (Sollner et al., 2002). Mutant arabidopsis
lines that are defective for these genes will be crossed with the
H2B-YFP nuclear marking line so that the role of the ER in defective
cytokinesis can be monitored using the techniques described above.
Ultimately, the student will report on the role of ER, and on the
behaviour of Golgi bodies and the nuclear envelope during normal and
defective cell division. This will be a significant contribution to
our understanding of cell function.
Falbel, TG et al. (2003) SCD1 is required for cytokinesis and
polarized cell expansion in Arabidopsis thaliana. Development 130:
Jergens, G (2005) Cytokinesis in higher plants. Annual Review of Plant
Biology 56: 281-299.
Kurup, K et al. (2006) Marking cell lineages in living tissues. Plant
Journal 42: 444-453.
Runions, J et al. (2006) Photoactivation of GFP reveals protein
dynamics within the endoplasmic reticulum membrane. Journal of
Experimental Botany 57: 43-50.
Sollner, R et al. (2002) Cytokinesis defective mutants of arabidopsis.
Plant Physiology 129: 678-690.
An opportunity to develop teaching skills in higher education may be
included in the training available with this studentship.
To discuss the project and for any other scientific queries contact
John Runions (jrunions from brookes.ac.uk).
To apply for this project, applicants should quote the title of the
studentship and include a letter of application, CV and the names and
addresses of two academic referees (one of whom can also comment on
the applicant's potential for teaching)
Applications will only be accepted by post, and not by email, to:
Ms Angela Robinson
School of Life Sciences
Oxford Brookes University
Tel: +44 (0) 1865 483295
Email: Ms Angela Robinson
C. John Runions, Ph.D.
School of Life Sciences
Oxford Brookes University
email: jrunions from brookes.ac.uk
phone: +44 (0) 1865 483 964
New - Oxford Brookes Master's in Bioimaging with Molecular
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