organisation - the Instituto Gulbenkian de Ciência

PLANT
GENOMICS
Jörg Becker Research Fellow
PhD in Biology, University of Bielefeld, Germany, 2001
Post-doc, IGC, Portugal
Head of IGC Gene Expression Unit
Research Fellow at the IGC since 2008
Our group is interested in the mechanisms underlying sexual reproduction and
early embryogenesis with a particular focus on the role of the male gametes.
Recent studies have shown that male gametes both in the plant and animal
kingdom carry complex sets of RNA molecules, including not only mRNAs but
also small RNAs. We are particularly interested in the role of these two RNA
classes before, during and after double fertilisation as it occurs in higher plants.
Using Arabidopsis thaliana as our primary experimental model we are addressing
specific questions like:
1. What are the functions of small RNA and DNA methylation pathways in
sperm cells?
2. Do sperm cell-derived RNAs play a role after fertilisation?
3. Do conserved core sets of genetic modules underlie common characteristics
of male gametes across kingdoms?
In addition we are interested in identifying gamete-expressed proteins with
functions in signalling events assuring double fertilisation and initiation of embryogenesis.
GROUP MEMBERS
Leonor Boavida (Post-doc)
Filipe Borges (External PhD student)
Patrícia Pereira (External PhD student)
Marcela Coronado (External PhD student, started in February)
Francisco Sousa (Trainee, started in June)
COLLABORATORS
Rob Martienssen (Cold Spring Harbor Laboratory, USA)
Keith Slotkin (Ohio State University, USA)
Ignacio Rubio Somoza (Max Planck Institute for Developmental Biology,
Germany)
Rui Gardner (IGC, Portugal)
José Feijó (IGC, Portugal)
Ji He (The Samuel Roberts Noble Foundation, USA)
Carlos Plancha (Cemeare Lda, Portugal)
Sheila McCormick (US Department of Agriculture/Agricultural Research
Service, USA)
Liam Dolan (Department of Plant Sciences; University of Oxford, England)
FUNDING
Fundação para a Ciência e a Tecnologia (FCT), Portugal
FP7 Marie Curie International Reintegration Grant, European Commission
FP7 Marie Curie Action: "Networks for Initial Training", European Commission
THE ROLE OF SPERM DERIVED microRNAs DURING DOUBLE FERTILISATION
IN ARABIDOPSIS
The world’s current food supplies rely almost exclusively on double fertilisation
as found in higher plants and characterised by the fusion of two male gametes
(sperm cells) with two female gametes (egg cell and central cell), giving rise
to the embryo and the endosperm. Thus a better molecular understanding of
double fertilisation will eventually provide the tools to improve crops. Micro-
RNAs (MiRs), as essential regulators in development processes and hormone
responses, are likely to play a role in sexual reproduction. Our deep sequencing
data of small RNAs from Arabidopsis sperm cells and pollen indicate that these
express MiRs belonging to dozens of microRNA families, with a number of them
showing higher expression levels in sperm cells than in pollen. We are analysing
the role these sperm cell MiRs might play for sperm cell viability and, if being
delivered to the female gametes upon fertilisation, for the regulation of early
embryogenesis and endosperm development.
We continued to address the potential role of MiRNAs in sperm cells using target
mimics and global inhibitors of small RNA pathways. Moreover, using a novel
FACS protocol (manuscript in prep), we isolated Arabidopsis microspores as well
as vegetative nuclei and sperm cells from mature pollen. By deep sequencing
of bisulphite converted genomic DNA from these three sample types we gained
important new insights into epigenetic changes occurring during microgametogenesis
(manuscript in prep).
IDENTIFICATION OF CONSERVED GERM CELL SPECIFIC MODULES
AS POTENTIAL PRECURSORS OF TOTIPOTENCY
Germ cell differentiation gave rise to all sexually reproducing organisms, but
along their evolution, several species developed distinct spatial and temporal
control over germline proliferation. The gametes are the end products of the
germ cell lineage, and transfer ultimately to the zygote their unique totipotent
potential, capable of giving rise to an entirely new organism. Despite the variety
of mechanisms distinguishing germ cell differentiation and fertilisation strategies
in plants and animals, the molecular pathways towards totipotency are
likely to remain conserved in form of a core set of genetic modules underlying
the totipotent potential of the gametes. This project focuses on the identification
of this conserved core set through the functional analysis of transcripts
encoding orthologue gene products in male gametes of plant, human and fly.
TRANSGENIC ARABIDOPSIS EXPRESSING GAMETE-SPECIFIC TETRASPANINS.
Upper panel - GFP localisation in the plasma membrane of sperm cells (sperm
nuclei mRFP). Bottom panel - Detail of GFP localisation in plasma membrane of
female gametophytic cells: egg cell (right) and synergid cells (left).
IGC ANNUAL REPORT ‘11
RESEARCH FELLOWS
71