Breakthrough study solves plant sex mystery

Posted by er134 at Jun 06, 2014 10:50 AM |
University of Leicester team undresses the genetic hierarchy in plant sperm cell formation

Issued by University of Leicester Press Office on 6 June 2014

An artist’s impression and caption/ credit are available below:

DUO1
Image credit: Jerome Twell; Artist’s interpretation of the genetic circuit directing the production of twin sperm in each pollen grain - in which the master control gene DUO1 switches on the DAZ1 and DAZ2 proteins to control cell division to allow twin sperm production to proceed.


A team of biologists from the University of Leicester has solved a mystery surrounding how plants have sex.

The researchers have discovered a pair of proteins made by flowering plants that are vital for the production of the sperm present within each pollen grain.

Scientists already knew that flowering plants, in contrast to animals, require not one, but two sperm cells for successful fertilisation: one to join with the egg cell to produce the embryo and one to join with a second cell to produce the nutrient-rich endosperm inside the seed.

The mystery of this 'double fertilization' process is how each single pollen grain is able to produce twin sperm cells.

This breakthrough study from the Twell Laboratory at the University of Leicester, published in the prestigious academic journal The Plant Cell, has found a pair of genes called DAZ1 and DAZ2 that are essential for making twin sperm cells. Plants with mutated versions of DAZ1 and DAZ2 produce pollen grains with a single sperm that is unable to fertilize.

The researchers show that DAZ1 and DAZ2 are controlled by the protein DUO1 that acts as a ‘master switch’ - so that DUO1 and the DAZ1/DAZ2 genes work in tandem to control a gene network that ensures a pair of fertile sperm is made inside each pollen grain.

Interestingly, DAZ1 and DAZ2 perform their role by cooperating with a well-known ‘repressor’ protein called TOPLESS that acts as a brake on unwanted gene activity that would otherwise halt sperm and seed production. Although TOPLESS has many roles in plants it has not previously been linked sperm production.

Professor David Twell at the University of Leicester’s Department of Biology, who led the study, said: “We often take for granted sexual reproduction in plants and its role in our lives. It is a complex process that has been studied scientifically for over a century, but it is only recently that we are beginning to get a grip on the underlying mechanisms.

“We hope to use our discovery to decipher the origins of sexual reproduction and to further demystify the fascinating process - of how plants make the fertile sperm inside the pollen grains - that are essential for the vast majority of our food crop production.”

Given their important role in male fertility, the discovery of DAZ1 and DAZ2 has the potential to be applied in the development of new plant breeding techniques to prevent the unwanted passing of genes – or ‘horizontal gene transfer’ - between crops or from crops to wild species.

This new knowledge also generates genetic tools and new ways of thinking about, and monitoring the effects of, environmental stresses on the reproductive process. In future such information may become increasingly important as we strive to breed superior crops that maintain yield in a changing climate.

The study, ‘An EAR-Dependent Regulatory Module Promotes Male Germ Cell Division and Sperm Fertility in Arabidopsis’, is published in the May 2014 issue of The Plant Cell and can be read here: http://www.plantcell.org/content/early/2014/05/29/tpc.114.124743.short?keytype=ref

ENDS


Notes to Editors:

For interviews and further information contact Professor David Twell, Department of Biology, University of Leicester via email twe@le.ac.uk

http://www2.le.ac.uk/departments/biology/people/twell

Full text of the study is available here: http://www.plantcell.org/content/early/2014/05/29/tpc.114.124743.short?keytype=ref


Further information on the study and the Twell Lab:

The research, which was funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC), is the culmination of over 5 years of work. The research was a team effort from the Twell Lab involving the work of Dr Michael Borg, together with PhD students Nicholas Rutley and Mihai Gherghiniou, who were funded by BBSRC and Ugur Sari, who was funded by the Turkish Ministry of National Education.

The team from the Twell Lab collaborated on the study with experts in plant fertilization, Dr Yuki Hamamura (Okayama University) and Professor Tetsuya Higashiyama (Nagoya and Okayama Universities), and with TOPLESS protein experts, Dr Kevin Rozwadowski and Dr Sateesh Kagale from Agriculture and Agri-food Canada.

The Twell Lab was the first to discover genes, such as DUO1, that are dedicated to the role of sperm cell production in plants in research on the common weed Arabidopsis thaliana - thale or mouse ear cress – in 2005. This was done by extensive genetic screening of flowers from over 10,000 plants to look for mutants that produced pollen grains containing one instead of two sperm cells. The Twell Lab remains at the forefront in the field of pollen development and sexual plant reproduction.

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