Scientists observe earliest steps in seed germination

Dec. 27 (UPI) -- Several studies have highlighted the roles hormones play in enabling seed germination, the sprouting of a seedling, or small plant, from a seed, but much less is known about how energy metabolism is jump-started at the outset of the germination process -- until now.

Using a new kind of fluorescent biosensor, researchers were able to watch energy metabolism and a sulfur-powered process called redox metabolism. The new observations, described this week in the journal PNAS, showed energy metabolism is kick-started just minutes after a seed is exposed to water. In no time, the cells' energy centers, or mitochondria, began facilitating respiration.

Researchers were also able to watch the activation of molecular switches, including thiol-redox switchers, that allow for energy to be efficiently released.

"By looking into the very early processes of germination control, we can gain a better understanding of the mechanisms driving seed germination," study leader Markus Schwarzländer, professor at the University of Münster in Germany, said in a news release. "In future we could think about how such switches could be used in crop biotechnology."

What's remarkable about seed germination is that the timing of the processes that turn seed into seedling are not fixed. In fact, the seeds of many plants, especially those of desert species, must remain dormant for years, even decades, until conditions are just right. As soon as conditions are suitable, the germination process must begin in haste.

Understanding the early steps of the germination process, including those related to metabolism, could help scientists design better crop seeds -- seeds that maintain their germination potential, or vigor, for longer periods of time, but which can germinate with great efficiency.

During lab tests, fluorescent biosensors helped scientists track two forms of cellular energy, microscope adenosine triphosphate, ADP, and Nicotinamide adenine dinucleotide phosphate, NADPH, during the germination process. Scientists also silenced genes related to the proteins that power redox switches and observed the affect on the germination process. Seeds with silenced redox switches were less active during germination than unedited seeds.

During another round of tests, scientists used a combination of biochemical and mass spectrometry methods to isolate and observe the interactions between redox proteins and mitochondria. Scientists were able to identify several cysteine-peptides that play a role in facilitating the efficient release of energy produced by mitochondria.

"The process could be likened to the traffic control system of a large city," said Thomas Nietzel, a postdoctoral researcher at the University of Münster. "Before the rush hour -- i.e. germination -- starts, which puts large quantities of metabolites 'on the road', the traffic light and routing systems need to be switched on in the morning; and here this is done by the thiol redox switches."