Sowing the seeds: gene networks control germination

Arabidopsis
Plants, at all stages in their development, have the ability to sense many environmental cues and respond to these in various ways. This is essential because plants cannot get up and move like animals when the environment becomes challenging.
Professor Ian Graham
University of York biologists have gained key insights into the way regulatory gene networks control the germination of seeds…

Researchers at the University of York studying the influence of environmental factors on germination have gained new insights into the gene regulatory networks that are involved in the process. Their findings could have significant repercussions for agricultural science.

The research, which was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and the Garfield Weston Foundation, is reported in an online early edition of Proceedings of the National Academy of Sciences (PNAS) this week.

Lead author Professor Ian Graham, director of the Centre for Novel Agricultural Products (CNAP) in York’s Department of Biology, explained the significance of the research to ScienceOmega.com.

"Plants, at all stages in their development, have the ability to sense many environmental cues and respond to these in various ways," Professor Graham began. "This is essential because plants cannot get up and move like animals when the environment becomes challenging."

The most important decision
 

Although the majority of seeds are relatively robust and can survive for years in the soil, once they begin to germinate the young seedling is vulnerable to adverse environmental conditions. A seed which germinates in an early bout of warm weather may be wiped out by subsequent frosts, for example. In this respect, seed germination can be considered the most important ‘decision’ in the life of a plant; germinate at the wrong time and a vulnerable seedling will not establish and die.

"We are interested in the gene networks that control germination in plant seeds," Professor Graham continued. "Understanding them will provide new insight into how plants integrate multiple environmental signals to control whether or not a seed will germinate when it is provided with the right conditions of temperature, light, nutrients and water."

To some extent, the timing of germination is determined by the conditions to which the mother plant is exposed, as Professor Graham explained.

"While seeds are maturing on the mother plant, the environmental conditions that are experienced play an important role in influencing the seeds’ ability to germinate once they are shed from their parent," he said. "Some signals appear to be transmitted via the mother plant and others are received directly by the developing seed."

Warm conditions may induce the mother plant to produce fast-germinating, vigorous seedlings which have the chance to grow before the onset of winter, whereas cold conditions suggesting the arrival of wintery weather might cause a plant to produce more dormant seeds.

A finely tuned network
 

In their research on the model organism Arabidopsis, Professor Graham and his colleagues found that different varieties responded differently to disruptions of a network controlled by the regulator gene known as SPATULA. SPATULA controls the expression of five other regulatory genes, all of which promote dormancy. The different responses that the team observed reflect the finely tuned network in which these genes operate.

"What is fascinating is that SPATULA increases expression of two of these regulator genes but decreases expression of the other three," noted Professor Graham. "This gives an insight into the fine-tuning of dormancy versus germination which is going on in all seeds, even within a single population or the progeny of a single plant."

Some plants became more dormant and others less so when this network was manipulated by the scientists in ways indicative of environmental conditions in the regions that the varieties originated from.

The findings will no doubt have a role to play in the development of seeds for farming. Indeed, seed dormancy and seedling vigour are important agronomic traits and some of the first that need to be considered in selective breeding programmes for the domestication of new crops.

"Understanding the key genes that regulate this process should facilitate fast-track molecular breeding for these characteristics using either marker-assisted selection or transgenics," the professor commented.

To this end, there is an ongoing research programme in this area at CNAP, as Professor Graham told ScienceOmega.com.

"We are particularly interested in establishing how this gene network interacts with phytohormones and lipid-based signalling molecules such as OPDA (12-oxo-phytodienoic acid)."

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