Researchers discover secret of plants’ ‘double fertilisation’ mystery

An enigma, unique to flowering plant, has been solved by a team of researchers from the UK and South Korea, reports Science Daily.

It was already known that flowering plants, unlike animals require not one, but two sperm cells for successful fertilisation.

However, how the “double fertilisation” was achieved from a single pollen grain, which then led to “twin” sperm cells, remained a mystery.

The process results in one sperm cell joining with the egg cell to produce the embryo, while the other to joins 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, writing in the Journal Nature, 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,” he added.

“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 fertilisation.

“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 fertilise.

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).

Source: Science Daily

Date: 23/10/2008

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