What happens to plant seeds during germination? Researchers led by Dr. Gerhard Leubner from the University of Freiburg in collaboration with six international groups of researchers will be jointly looking into these processes. The virtual Seed (vSEED) consortium took first place in a field of 54 contestants in the European Research Era-Net Plant Genomics competition. What makes the scientists’ project so special is that they are planning to explain the molecular, physiological and mechanical processes of plant seeds in their entirety and bring these three levels together using mathematical models.
Plant seeds have a key status in the life cycle of plants. One of the main functions of seeds is to enable plants to spread into new environments, for example via birds or the wind. In addition, the seed stage of a plant's life cycle is the point at which it is best protected against drought. Embryos are still able to survive in the seeds if they dry out and are left with a water content as low as five to ten per cent of the normal water content. The sleep-like stage, also referred to as dormancy, can last for many years, enabling the embryos to wait for optimal conditions for germination. Detailed insights into the biology of seeds is not only of great interest for basic scientists, but also for the agricultural and food industry. With a participation of around 20 billion euros, the seed industry makes a considerable contribution to the world economy.
What exactly happens inside germinating seeds? How are embryos that are awakening from dormancy able to overcome the resistance of seed coats and grow a root? “This phenomenon can only be understood by looking at the molecular and mechanical processes in their entirety,” said Dr. Gerhard Leubner, head of the plant physiology research group at the Institute of Biology II at the University of Freiburg. “This requires biologists and mathematicians to work in close cooperation in order to produce an integrative and comprehensive view of the various levels of these processes by means of systems biology modelling. And, in a nutshell, that is the precise goal of the interdisciplinary virtual Seed project.”
Over the next three years, the consortium, which consists of four European partners, will take on the task of creating a mathematical description of the dynamic processes involved in the germination of seeds of the closely related plant species Arabidopsis thaliana (thale cress) and Lepidium sativum (garden cress). The researchers' concept won the European Research Area-Net Plant Genomics (ERA-PG) competition, outpacing 53 other contestants. The research consortium, led by Prof. Dr. Michael Holdsworth from the University of Nottingham (Great Britain), will receive 1.7 million euros in funding for the next three years for four laboratories and several postdoctoral positions. "We were delighted with our success," said Leubner who coordinates the Freiburg sub-projects. "It is very special to compete against so many excellent teams in a competition like this and win first place."
The starting point for the researchers’ interdisciplinary research is biomechanics. In cooperation with the Plant Biomechanics group led by Prof. Dr. Thomas Speck in Freiburg, Leubner’s team has developed an apparatus that enables the measurement of mechanical changes in the seed coat as the seeds germinate. The researchers prepare the coats, clamp them into a rack, and press a metal rod with a controlled amount of force against the coats in order to discern the force required for the root tip to break through the coat. Leubner’s group is also investigating the molecular conditions underlying this process. They have already found that the germination process is initiated by the softening of the coat tissues, a process triggered by enzymes that degrade the cell walls of the seed coats. Another important aspect of germination is the interactions between plant hormones. In addition to projects funded under vSEED, there is a postdoc in Leubner’s team, Dr. Krystyna Oracz, who is looking into the role of hormones and cell wall changes during germination. Oracz has a grant from the Alexander-von-Humbold Foundation.
Leubner and his team also know from previous experiments that environmental influences such as temperature play a decisive role during germination. Molecular signalling networks need to integrate information about the environment. In order to identify and understand these networks, the scientists will use transcriptome analyses and modern imaging methods to obtain a comprehensive picture of the genes that are activated in the different tissues of germinating plant seeds and that mediate the germination process. Besides the Freiburg researcher groups, teams from the University of Nottingham, the University of Leeds (Great Britain) and the University of Wageningen (Netherlands) are contributing their molecular genetic, biochemical and material scientific know-how.
“The project will throw up a large amount of information from different types of experiments,” said Leubner. “All this information will eventually have to be brought together and simulated in multidimensional models. This is how we hope to get an overall picture of the germination process.” In order to cope with the flood of data, complex mathematical methods and suitable software programmes are required. Two other teams from Nottingham are in charge of the statistical analyses. The recently opened Centre for Biosystems Analysis at the University of Freiburg, with whom Leubner’s team will work closely, also has similar know-how. The vSEED project is the first attempt to understand the biology of germinating plant seeds in its entirety.
PD Dr. Gerhard Leubner
Institute of Biology II, Botany/Plant Physiology
University of Freiburg
Tel.: +49 (761) 203 2936
Fax: +49 (761) 203 2612