Plants and stress; key players on the thin line between life and death revealed

Our crops are not doing well these days: too much water, too little sunlight... In short, they are suffering from stress. Scientists from VIB, associated with the Katholieke Universiteit Leuven (K.U.Leuven), have revealed a new mechanism demonstrating the intricate ways in which plants deal with stress. The newly discovered control system has a remarkable way of orchestrating the activity of hundreds of genes, forcing the plant into ‘safety mode’; the consumption of energy is contained while the organism is stimulated to mobilize reserves. This may have a negative impact on growth, but it allows the plant to temporarily safeguard itself against pernicious stress conditions. These findings also may prove to be useful beyond the case of plants, for the results are likely to be valuable in understanding disorders such as cancer and diabetes.

Life thanks to plants
Plants catch sunlight and use it as an energy source to produce sugars from CO2 and water. In doing so, they are at the very basis of the food chain. Ultimately, all life on earth depends upon this biochemical process: photosynthesis. Without plants, life as we know it today would simply not be possible. But what if things go wrong? When there is too little sunlight, for example? And what with other stressful conditions for plants? Environmental changes can compromise photosynthesis and exhaust energy supplies.

Plants control their own energy balance
Fortunately, plants have developed different mechanisms to detect and cope with 'stress’. Together with his American colleagues at Harvard Medical School (Boston, USA), VIB scientist Filip Rolland, associated with the Katholieke Universiteit Leuven, is uncovering a new system of detection and control. It is driven by KIN10 and KIN11. These ‘kinases’ – which are also found in human beings – react to energy shortages, when, for example, there is too little sunlight or too little sugar production. They control the activity of a broad network of genes, promoting the release of energy (catabolism) from alternative sources and blocking its assimilation (anabolism). In this way, the plant protects itself against stress conditions; like a really bad summer.

The key players: KIN10 & KIN11
The model organism for this study was Arabidopsis thaliana or thale cress. For decades, this small weed has been used as a model in molecular and genetic plant research. The scientists have tested numerous stress conditions that affect photosynthesis and energy production, such as darkness, herbicide treatment and flooding (lack of oxygen). By overexpressing the KIN10 gene, causing the plant to produce more of this protein, stress tolerance is increased and plants survive longer. By switching off these genes, their control function is eliminated.

With this research, the Flemish and American scientists have succeeded for the first time in attributing KIN10 and KIN11 a key role in the control of the plant energy budget and metabolism and thus the fragile balance between growth and survival; in short, the choice between life and death.

Are humans similar to plants?
The new insights gained by this study are not limited to the functioning of plants; they may also be important for human beings. KIN10 and KIN11, as ’fuel gauges’ controlling the expression of a whole set of genes, are also found in mammals. The results with plants, therefore, may play a pioneering role in discovering new functions of these proteins in disorders such as diabetes, cancer, obesitas, and aging.

Relevant scientific publication
The research findings are published in the leading scientific journal Nature (Baena-González et al., A central integrator of transcription networks in plant stress and energy signalling, Nature, 2007).

New light-sensing ability discovered in disease-causing bacteria

The bacteria that cause brucellosis can sense light and use the information to regulate their virulence, according to a study in the August 24 issue of the journal Science. The discovery comes after 120 years of research into the disease, which causes abortions in livestock and fevers in humans. Researchers found that two other bacteria, including a species that attacks plants, sense light using the same type of protein structure, and at least 94 more species possess the code for it in their DNA.

"These bacteria have been very well studied for years, and no one knew they could sense light," said lead author Trevor Swartz, who initiated the study as a research scientist at the University of California, Santa Cruz. "Now it seems like it's a common thing rather than being an anomaly."

The ubiquity of the structure suggests that light may play a much more important role in bacterial life than has previously been recognized. And because the recurrent structure can be paired with a variety of signaling proteins, it gives organisms immense versatility in the ways they use light, Swartz said.

"We have bumped into an entirely new family of light receptors in nature," said coauthor Roberto Bogomolni, professor of chemistry and biochemistry at UCSC.

The receptor molecule contains a light-sensing region known as an LOV domain because it resembles similar units in other proteins that sense light, oxygen, or voltage, said coauthor and longtime collaborator Winslow Briggs, of the Carnegie Institution of Washington. The structure crops up in a variety of proteins, where it lends its light-sensing ability to the whole molecule. The light-sensing structure is very different from either the light-harvesting molecules of photosynthesis or the light-gathering pigments in our own eyes.

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