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, email@example.com
Robert Emmerich | Julius-Maximilians-Universität Würzburg
First time-lapse footage of cell activity during limb regeneration
25.10.2016 | eLife
Phenotype at the push of a button
25.10.2016 | Institut für Pflanzenbiochemie
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
25.10.2016 | Earth Sciences
25.10.2016 | Power and Electrical Engineering
25.10.2016 | Process Engineering