Why Plants Usually Live Longer Than Animals

Stem cells are crucial for the continuous generation of new cells. Although the importance of stem cells in fuelling plant growth and development still many questions on their tight molecular control remain unanswered. Plant researchers at VIB and Ghent University discovered a new step in the complex regulation of stem cells.

 A root tip of the model plant Arabidopsis thaliana. The organizing cells are visualized by the green fluorescence and are surrounded by the stem cells (within the white frame). (Credit: © VIB, 2013)

Today, their results are published online in this week's issue of Science Express.
Lieven De Veylder said, "Our data suggest that certain organizing stem cells in plant roots are less sensitive for DNA-damage. Those cells hold an original and intact DNA copy which can be used to replace damaged cells if necessary. Animals rely on a similar mechanism but most likely plants have employed this in a more optimized manner. This could explain why many plants can live for more than hundreds of years, while this is quite exceptional for animals."
Quiescent organisers of plant growth
Plant growth and development depend on the continuous generation of new cells. A small group of specialized cells present in the growth axes of a plant is driving this. These so-called stem cells divide at a high frequency and have the unique characteristic that the original mother cell keeps the stem cell activity while the daughter cell acquires a certain specialization. Besides these stem cells, plant roots also harbor organizing cells. These organizing cells divide with a three- to ten-fold lower frequency, therefore often referred to as quiescent center cells. The organizing cells control the action of the surrounding stem cells and can replace them if necessary.
A new molecular network
For almost 20 years, scientists all over the world have been studying the action of the stem cells and that of their controlling organizing cells. Until now it was not known how quiescent and actively dividing cells could co-exist so closely and which mechanisms are at the basis of the quiescent character. Plant researchers at VIB and Ghent University have now identified a new molecular network that increases our understanding of stem cell regulation and activity.
Central in this process is the discovery of a new protein, the ERF115 transcription factor. The scientists demonstrated that the organizing cells barely divide because of the inhibition of ERF115 activity. When the organizing cells need to divide to replace damaged surrounding stem cells, ERF115 gets activated. ERF115 then stimulates the production of the plant hormone phytosulfokine which in turn activates the division of the organizing cells. Thus, the ERF115-phytosulfokine network acts as a back-up system during stress conditions which are detrimental for the activity of stem cells.
 

Journal Reference:

1. Jefri Heyman, Toon Cools, Filip Vandenbussche, Ken S. Heyndrickx, Jelle Van Leene, Ilse Vercauteren, Sandy Vanderauwera, Klaas Vandepoele, Geert De Jaeger, Dominique Van Der Straeten, and Lieven De Veylder. ERF115 Controls Root Quiescent Center Cell Division and Stem Cell Replenishment. Science, 24 October 2013 DOI: 10.1126/science.1240667

Courtesy: ScienceDaily

 

Making Hydrogen Cheaply by Imitating Bacteria? Unique Chemistry in Hydrogen Catalysts Revealed

Making hydrogen easily and cheaply is a dream goal for clean, sustainable energy. Bacteria have been doing exactly that for billions of years, and now chemists at the University of California, Davis, and Stanford University are revealing how they do it, and perhaps opening ways to imitate them.'

This hydrogen-generating cluster of iron (brown) and sulfur (yellow) atoms, with side groups of carbon monoxide (gray/red) and cyanide (gray/blue), could be a key to future fuel sources. (Credit: Protein Data Bank/courtesy graphic)

A study published Oct. 25 in the journal Science describes a key step in assembling the hydrogen-generating catalyst.
"It's pretty interesting that bacteria can do this," said David Britt, professor of chemistry at UC Davis and co-author on the paper. "We want to know how nature builds these catalysts -- from a chemist's perspective, these are really strange things."
The bacterial catalysts are based on precisely organized clusters of iron and sulfur atoms, with side groups of cyanide and carbon monoxide. Those molecules are highly toxic unless properly controlled, Britt noted.
The cyanide and carbon monoxide groups were known to come from the amino acid tyrosine, Britt said. Jon Kuchenreuther, a postdoctoral researcher in Britt's laboratory, used a technique called electron paramagnetic resonance to study the structure of the intermediate steps.
They found a series of chemical reactions involving a type of highly reactive enzyme called a radical SAM enzyme. The tyrosine is attached to a cluster of four iron atoms and four sulfur atoms, then cut loose leaving the cyanide and carbon monoxide groups behind.
"People think of radicals as dangerous, but this enzyme directs the radical chemistry, along with the production of normally poisonous CO and CN, along safe and productive pathways," Britt said.
Kuchenreuther, Britt and colleagues also used another technique, Fourier Transform Infrared to study how the iron-cyanide-carbon monoxide complex is formed. That work will be published separately.
"Together, these results show how to make this interesting two-cluster enzyme," Britt said. "This is unique, new chemistry."
Britt's laboratory houses the California Electron Paramagnetic Resonance center (CalEPR), the largest center of its kind on the west coast.
Other authors on the paper are: at UC Davis, postdoctoral researchers William Myers and Troy Stich, project scientist Simon George and graduate student Yaser NejatyJahromy; and at Stanford University, James Swartz, professor of chemical engineering and bioengineering. The work was supported by grants from the U.S. Department of Energy.
 

Journal Reference:

1. J. M. Kuchenreuther, W. K. Myers, T. A. Stich, S. J. George, Y. NejatyJahromy, J. R. Swartz, R. D. Britt. A Radical Intermediate in Tyrosine Scission to the CO and CN- Ligands of FeFe Hydrogenase. Science, 2013; 342 (6157): 472 DOI: 10.1126/science.1241859

Courtesy: ScienceDaily