Collaboration between Leicester and South Korean scientists explains plants'
'double fertilisation' process
An enigma ? unique to flowering plants ? has been solved by researchers from
the University of Leicester (UK) and POSTECH, South Korea.

The discovery is reported in the journal Nature on 23 October 2008.

Scientists already knew that flowering plants, unlike animals require not
one, but two sperm cells for successful fertilisation.

The mystery of this ?double fertilization? process was how each single
pollen grain could produce ?twin? sperm cells. One to join with the egg cell
to produce the embryo, and the other to join with a second cell in the ovary
to produce the endosperm, a nutrient-rich tissue, inside the seed.

Double fertilisation is essential for fertility and seed production in
flowering plants so increased understanding of the process is important.

Now Professor David Twell, of the Department of Biology at the University of
Leicester and Professor Hong Gil Nam of POSTECH, South Korea report the
discovery of a gene that has a critical role in allowing precursor
reproductive cells to divide to form twin sperm cells.

Professor Twell said: ?This collaborative project has produced results that
unlock a key element in a botanical puzzle.

The key discovery is that this gene, known as FBL17, is required to trigger
the destruction of another protein that inhibits cell division. The FBL17
gene therefore acts as a switch within the young pollen grain to trigger
precursor cells to divide into twin sperm cells.

?Plants with a mutated version of this gene produce pollen grains with a
single sperm cell instead of the pair of sperm that are required for
successful double fertilization.

?Interestingly, the process employed by plants to control sperm cell
reproduction was found to make use of an ancient mechanism found in yeast
and in animals involving the selective destruction of inhibitor proteins
that otherwise block the path to cell division.

?Removal of these blocks promotes the production of a twin sperm cell cargo
in each pollen grain and thus ensures successful reproduction in flowering
plants.

?This discovery is a significant step forward in uncovering the mysteries of
flowering plant reproduction. This new knowledge will be useful in
understanding the evolutionary origins of flowering plant reproduction and
may be used by plant breeders to control crossing behaviour in crop plants.

?In the future such information may become increasingly important as we
strive to breed superior crops that maintain yield in a changing climate.
Given that flowering plants dominate the vegetation of our planet and that
we are bound to them for our survival, it is heartening that we are one step
closer to understanding their reproductive secrets.?

Researchers at the University of Leicester are continuing their
investigation into plant reproduction. Further research underway in
Professor Twell?s laboratory is already beginning to reveal the answers to
secrets about how the pair of sperm cells produced within each pollen grain
aquires the ability to fertilize.

Prof Twell?s work, in the Department of Biology at the University of
Leicester is financially supported by the UK Biotechnology and Biological
Research Council (BBSRC).
www.checkbiotech.org