VIB researchers at Ghent University have discovered the substance that governs the formation of root offshoots in plants, and how it works. Root offshoots are vitally important for plants – and for farmers. Plants draw the necessary nutrients from the soil through their roots. Because they do this best with a well-branched root system, plants must form offshoots of their roots at the right moment. The VIB researchers describe how this process is controlled in the prominent professional journal Science. A key player in this process is a protein called ACR4. Depending on the signals that it receives from its environment, this protein triggers the formation of a root offshoot. Now that we know the control mechanism, we can begin to stimulate plant roots to form more, or fewer, offshoots. This can lead to a more ecological agriculture and to the production of better crops at the same time. An efficient network

It is difficult to overstate the importance of plants in our lives − they are responsible for our oxygen and for food, clothing, energy, and countless other things. And in turn, the importance of a plant’s roots is unquestionable: they provide the plant with necessary nutrients and moisture. The more the roots are subdivided, in breadth and depth, the better they can do their work. So, a well-coordinated, controlled formation of root offshoots is crucial to a plant. But, until now, how a plant determines when and where an offshoot should be formed was unknown.

Asymmetric cell division

The presence of stem cells is very important in the development of plants and animals. Stem cells are cells that can transform themselves into various types of cells. In animals, tissues and organs are formed before birth; but in fully-grown plants, stem cells continue to play a major role in the formation of new organs or tissues, such as root offshoots.

These stem cells are found inside the root, and several of them will induce the formation of an offshoot. These ‘root-founder’ cells undergo an asymmetric cell division. In contrast to the usual cell division, which gives rise to two identical cells, asymmetric cell division produces two different cells: a stem cell that is identical to the original cell, and a cell that is ready to become a specialized cell – in this case, a secondary root cell.

The decisive signal

With the aid of the mouse-ear cress (Arabidopsis thaliana), a frequently used model plant, Ive De Smet and Valya Vassileva in Tom Beeckman’s group have been studying how a plant determines which cells will trigger offshoots. To do this, the VIB researchers in Ghent have employed a special technology that makes it possible to make synchronous offshoots develop at different moments. This allowed them to isolate the cells that induce the formation of offshoots. They found out which genes are active in these cells and compared them with the genes that are crucial to normal cell division. In this way, the researchers identified a specific set of genes that control asymmetric cell division and send the signal for the formation of offshoots.

ACR4: control over asymmetric division

The researchers then examined one of these genes more closely. The ACR4 gene contains the DNA code for a receptor, a protein that is often located on the exterior of a cell to pick up signals from the outside and transmit them to the controlling mechanisms within the cell. When the researchers disrupted the function of ACR4 in plant cells, the precisely orchestrated asymmetric cell division was also disturbed. From this finding, De Smet and Vassileva inferred that ACR4 plays a key role in the creation of offshoots. Because the protein has a receptor function, triggering the formation of offshoots depends on its reaction to signals from the environment.

Desired or undesired

With this research, the scientists have discovered a fundamental mechanism − fundamental for the plant, and very important for plant-breeders as well. This new knowledge enables us to promote, or retard, the formation of offshoots − both activities are useful in a large number of applications.

Promoting an extensive root system helps plants absorb nutrients more readily, and thus they need less fertilizer. Such plants can also grow more easily in dry or infertile soils. Furthermore, plants with a well-developed root system are more firmly anchored in the soil and can be used to counteract erosion.

On the other hand, slowing down secondary root formation can be advantageous in tuberous plants, like potatoes or sugar beets. This enables these food crops to invest all their energy in the production of nutrients. Fewer root offshoots also makes it easier for farmers to harvest these crops.

Plant research with medical possibilities?

This plant research sheds light on the control of asymmetric cell division − and this kind of cell division is similar to the cell division of stem cells in animals, too. So, these results can also provide greater insight into how animal stem cells specialize.

For example, irregular cell division plays a role in the development of various types of cancer, and similar control mechanisms might underlie this process as well. This is clearly an important area for future research.

Just as a credit crunch is reshaping the global economic landscape, an often-unheralded shortage of clean water is confronting business and industry with a range of profound new challenges and opportunities, according to an article scheduled for the October 6 issue of Chemical & Engineering News, ACS’ weekly news magazine.

The cover story, written by C&EN Senior Business Editor Melody Voith, points out that big industrial companies, such as Dow Chemical, General Electric, Nalco, and Ashland, must manage day-to-day operations in ways that conserve and reuse water.  Once regarded as a cheap and inexhaustible resource, clean water increasingly is in short supply around the world, Voith explains, noting that lack of clean water is “a growing risk” to industry.

“There is just no replacement for good, clean water — and it is getting harder to come by,” Voith states.  At the same time, companies that supply water purification and conservation technology are taking advantage of new opportunities.  The articles explain how companies are investing in new technologies to meet the evolving demand for water treatment chemicals, services, and equipment.

Researchers in Norway report that injecting a special type of seawater called “smart water” into certain low-yield oil wells may help boost oil extraction by as much as 60 percent.  The study could help meet rising energy demands and provide consumers with some financial relief at the gas pump in the future, the scientists suggest.  Their findings are scheduled for the Sept. 10 issue of ACS’ Energy & Fuels, a bi-monthly journal.

In the new study, Tor Austad and colleagues note that more than 50 percent of the world’s oil reserves — billions of gallons of oil — are trapped in oil reservoirs composed of calcium carbonate, rocks that include chalk and limestone.  Scientists now inject seawater into chalk-based oil wells to boost oil extraction, but researchers do not know if the method will work for oil wells composed of limestone, a tough material known for its low oil-recovery rates — usually less than 30 percent, but in some cases less than 5 percent.

To find out, the scientists collected core samples from Middle East oil reservoirs composed of limestone and soaked them in crude oil for several weeks.  They then prepared batches of so-called “smart water,” seawater formulated with sulfate and other substances to improve seawater’s ability to penetrate limestone.  In laboratory studies, they showed that irrigating the limestone samples with “smart water” led to the same fundamental chemical reactions that occur in chalk.  Upcoming experiments will verify if the efficiency in oil recovery is comparable to the observations in chalk, the scientists note.

This year, the world and, in particular, developing countries and the poor have been hit by both food and energy crises.  As a consequence, prices for many staple foods have risen by up to 100%.  When we examine the causes of the food crisis, a growing population, changes in trade patterns, urbanization, dietary changes, biofuel production, and climate change and regional droughts are all responsible.  Thus we have a classic increase in prices due to high demand and low supply.  However, few commentators specifically mention the declining availability of water that is needed to grow irrigated and rainfed crops.  According to some, the often mooted solution to the food crisis lies in plant breeding that produces the ultimate high yielding, low waterconsuming crops.  While this solution is important, it will fail unless attention is paid to where the water for all food, fibre and energy crops is going to come from.

A few years ago, IWMI (the International Water Management Institute) demonstrated that many countries are facing severe water scarcity, either as a result of a lack of available fresh water, or due to a lack of investment in water infrastructure such as dams and reservoirs.  What makes matters worse is that this scarcity predominantly affects developing countries where the majority of the world’s under-nourished people-approximately 840 million -live.

The causes of water scarcity are essentially identical to those of the food crisis.  There are serious and extremely worrying factors that indicate water supplies are steadily being used up.  Essentially every calorie of food requires a liter of water to produce it.  Thus those of us on western diets, use about 2500-3000 liters per day.  A further 2.5 billion people by 2030 will mean that we have to find over 2000 more cubic kilometers of fresh water to feed them.  This is not any easy task given that current water usage for food production is 7500 cubic kilometers and supplies are scarce.  According to the recent report “Water for Food, Water for Life” of the Comprehensive Assessment of Water Management in Agriculture, which drew on the work of 700 scientists, unless we change the way we use water and increase “water productivity” (i.e. more crop per drop) we will not have enough water to feed the world’s growing population (This population is estimated to increase from 6 billion now to about 8.5 billion in 25 years.)  Compared with the lengthy agenda to combat climate change, this is a very short time indeed and yet the impacts of water scarcity will be profound.  However, very little is being done about it in most countries.

Since the formulation of the UN Millennium Goals in 2002, much of the water agenda has been focused around the provision of drinking water and sanitation.  This water comes from the same sources as agricultural water and as we urbanize and improve living standards there will be increasing competition for drinking water from domestic and other urban users, putting agriculture under further pressure.  While improving drinking water and sanitation is vital with respect to health and living standards, we cannot afford to neglect the provision and improved productivity of water for agriculture.

There are potential solutions.  Better water storage has to be considered.  Ethiopia, which is typical of many sub-Saharan African countries, has a water storage capacity of 38 cubic meters per person.  Australia has almost 5000 cubic meters per person, an amount that in the face of current climate change impacts may be inadequate.  While there will be a need for new large and medium-sized dams to deal with this critical lack of storage in Africa, other simpler solutions are also part of the equation.  These include the construction of small reservoirs, sustainable use of groundwater systems including artificial groundwater recharge and rainwater harvesting for smallholder vegetable gardens.  Improved yearround access to water will help farmers maintain their own food security using simple supplementary irrigation techniques.  The redesign of both the physical and institutional arrangements of some large and often dysfunctional irrigation schemes will also bring the required productivity increases.  Safe, risk free reuse of wastewater from growing cities will also be needed.  Of course these actions need to be paralleled by development of droughttolerant crops, and the provision of infrastructure and facilities to get fresh food to markets.

Current estimates indicate that we will not have enough water to feed ourselves in 25 years time, by when the current food crisis may turn into a perpetual crisis.  Just as in other areas of agricultural research and development, investment in the provision and better management of water resources has declined steadily since the green revolution.  I and my water science colleagues are raising a warning flag that significant investment in both R&D and water infrastructure development are needed, if dire consequences are to be avoided.

A new analysis of the Martian rock that gave hints of water on the Red Planet — and, therefore, optimism about the prospect of life — now suggests the water was more likely a thick brine, far too salty to support life as we know it.The finding, by scientists at Harvard University and Stony Brook University, is detailed this week in the journal Science.

“Liquid water is required by all species on Earth and we’ve assumed that water is the very least that would be necessary for life on Mars,” says Nicholas J. Tosca, a postdoctoral researcher in Harvard’s Department of Organismic and Evolutionary Biology. “However, to really assess Mars’ habitability we need to consider the properties of its water. Not all of Earth’s waters are able to support life, and the limits of terrestrial life are sharply defined by water’s temperature, acidity, and salinity.”

Together with co-authors Andrew H. Knoll and Scott M. McLennan, Tosca analyzed salt deposits in four-billion-year-old Martian rock explored by NASA’s Mars Exploration Rover, Opportunity, and by orbiting spacecraft. It was the Mars Rover whose reports back to Earth stoked excitement over water on the ancient surface of the Red Planet.

The new analysis suggests that even billions of years ago, when there was unquestionably some water on Mars, its salinity commonly exceeded the levels in which terrestrial life can arise, survive, or thrive.

“Our sense has been that while Mars is a lousy environment for supporting life today, long ago it might have more closely resembled Earth,” says Knoll, Fisher Professor of Natural Sciences and professor of Earth and planetary sciences at Harvard. “But this result suggests quite strongly that even as long as four billion years ago, the surface of Mars would have been challenging for life. No matter how far back we peer into Mars’ history, we may never see a point at which the planet really looked like Earth.”

Tosca, Knoll, and McLennan studied mineral deposits in Martian rock to calculate the “water activity” of the water that once existed on Mars. Water activity is a quantity affected by how much solute is dissolved in water; since water molecules continuously adhere to and surround solute molecules, water activity reflects the amount of water that remains available for biological processes.

The water activity of pure water is 1.0, where all of its molecules are unaffected by dissolved solute and free to mediate biological processes. Terrestrial seawater has a water activity of 0.98. Decades of research, largely from the food industry, have shown that few known organisms can grow when water activity falls below 0.9, and very few can survive below 0.85.

Based on the chemical composition of salts that precipitated out of ancient Martian waters, Tosca and his colleagues project that the water activity of Martian water was at most 0.78 to 0.86, and quite possibly reaching below 0.5 as evaporation continued to concentrate the brines, making it an environment uninhabitable by terrestrial species.

“This doesn’t rule out life forms of a type we’ve never encountered,” Knoll says, “but life that could originate and persist in such a salty setting would require biochemistry distinct from any known among even the most robust halophiles on Earth.”

The scientists say that the handful of terrestrial halophiles — species that can tolerate high salinity — descended from ancestors that first evolved in purer waters. Based on what we know about Earth, they say that it’s difficult to imagine life arising in acidic, oxidizing brines like those inferred for ancient Mars.

“People have known for hundreds of years that salt prevents microbial growth,” Tosca says. “It’s why meat was salted in the days before refrigeration.”

Tosca and Knoll say it’s possible there may have been more dilute waters earlier in Mars’ history, or elsewhere on the planet. However, the area whose rocks they studied — called Meridiani Planum — is believed, based on Mars Rover data, to have been one of the wetter, more hospitable areas of ancient Mars.