When during evolution did plants learn to conserve water? The first attempts in this regard have been discovered by an international research team with a moss. The findings also revealed how evolution affects molecules.
The first plants to venture out of the sea and onto land 500 million years ago were green algae. They had to cope with the fact that they were no longer constantly surrounded by water. This meant that they ran the serious risk of withering slowly in the event of a drought.
The moss Physcomitrella patens was a pioneer in water conservation matters during evolution.
(Photo: Pirex / Wikimedia Commons)
A later generation of terrestrial plants, mosses, resolved this problem quite cleverly: If water is in short supply, they do dry out slowly but as soon as they come into contact with water once more their photosynthesis starts up again and they continue to grow. Mosses manage to do this because they acquired a tolerance to dessication during their evolution as a land dweller.
Enzyme OST1 has a key function
Mosses, like all other plants, produce the stress hormone abscisic acid (ABA) when a water shortage occurs. This in turn boosts the production of special proteins that protect it from drying out, known as dehydrins. These ensure that the mosses survive a period of drought without any major loss of function. The production of these dehydrins is particularly reliant on, among other things, the enzyme OST1.
Even with more highly evolved plants, this enzyme ensures that excessive water loss is avoided. However, it does not just do that here via anti-dessication proteins, but using a second path as well: It activates the anion channel SLAC1 of the guard cells in the plant’s epidermis. Thereupon, the guard cells close the pores through which vital carbon dioxide flows into the plant, but through which water is also lost to the environment.
When did guard cells first appear during evolution? The first land-dwelling algae and also the relatively simple liverwort do not yet possess any. It is only with the more highly evolved mosses that guard cells appear, albeit only sparsely still: They are only located on a pinhead-like structure that the moss uses to disseminate its spores.
Results published in “Current Biology”
When during evolution did plants learn to control the production of dehydrins using the enzyme OST1? And when did they begin to use this enzyme to activate the anion channel of the guard cells? These questions have been answered by Würzburg plant biologists Dietmar Geiger and Rainer Hedrich with counterparts from Freiburg, Madrid, Riyadh, Uppsala, Kyoto, and West Lafayette. Their findings have been published in the journal “Current Biology”.
The researchers compared OST1 enzymes and SLAC1 channels from four different highly evolved plants: They examined the terrestrial alga Klebsormidium nitens, the common liverwort Marchantia polymorpha, the moss Physcomitrella patens, and the thale cress Arabidopsis thaliana as a representative of more highly evolved plants.
Structure of the anion channel proved decisive
It emerged that all OST1 variants do not differ markedly in their gene sequence and that they can all boost the production of dehydrins. Likewise, all OST1 variants can activate the anion channel of the thale cress. Yet, they failed with the channels of the alga and liverwort. The key to water conservation must therefore lie in the structure of the channel.
With the moss examined, which is younger in developmental history terms than the liverwort, the scientists discovered something unusual: It possesses two forms of anion channel, and one of them reacts already to OST1 – albeit very weakly. If the second, fully inactive channel is modified based on the model of the OST1-sensitive channels, it becomes increasingly active.
As a result, the research team has shown that even very early on during evolution OST1 had matured to such an extent that it is able to control dehydrin production. On the other hand, the channel SLAC1 did not acquire the ability to react to OST1 until moss emerged. “Evolution played with the structure of the channel and with its function until such time as it could be controlled by the existing ABA dehydrin signalling pathway and could assume the task of being a water conservation button,” says Hedrich.
Search for a further evolutionary playground
Does this mean that the question of the evolution of water conservation has been answered? Not yet, believes the Würzburg professor: “The guard cells of the mosses and of the later ferns react only weakly, if at all, to the water stress hormone ABA. We therefore need to examine yet when, on the path to becoming a highly evolved flowering plant, all the functional components of the ABA-dependent signalling pathway gathered in the guard cells. We presume that the playground for the optimization of this path lies in the transition from ferns to early flowering plants.”
Stomatal Guard Cells Co-opted an Ancient ABA-Dependent Desiccation Survival System to Regulate Stomatal Closure, Christof Lind, Ingo Dreyer, Enrique J. López-Sanjurjo, Katharina von Meyer, Kimitsune Ishizaki, Takayuki Kohchi, Daniel Lang, Yang Zhao, Ines Kreuzer, Khaled A.S. Al-Rasheid, Hans Ronne, Ralf Reski, Jian-Kang Zhu, Dietmar Geiger, and Rainer Hedrich, Current Biology, published online on March 19, 2015, http://www.cell.com/current-biology/abstract/S0960-9822%2815%2900131-1
Prof. Dr. Rainer Hedrich, Department of Botany I (Plant Physiology and Biophysics), University of Würzburg, T +49 (0)931 31-86100, firstname.lastname@example.org
Robert Emmerich | Julius-Maximilians-Universität Würzburg
Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory
Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine