molecular biology learning from legumes€¦ · structure and the internal deformation of...
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N°!" I QUARTERLY I APRIL !#$! ! wLive from the Labs |
BY MARK REYNOLDS
w! Mollusk shells, metallic wire, cell phones... Nanocrystals are all around us. Understanding their structure is crucial for improving our ability to build nanodevices.
Yet until now, microscopy techniques for the study of these materials were insufficiently precise, or required the destruction of the sample. A new method developed by Virginie Chamard’s team at the Institut Fresnel" in collaboration with the ESRF# now gives researchers the ability to see nanocrystals in high-resolution, and in three dimensions.$ According to the researchers, it will allow “quantitative imaging,” which reveals the structure and the internal deformation of nanocrystals.
In theory, the structure of bulk crystals is well understood, but “models cannot always account for changes that happen inside a crystal’s structure at the nanoscale,” Chamard explains. “When reaching the nanometer size range for crystals, additional strain results from how the material interacts with different surfaces and interfaces in its environment.”
These forces can alter the material from within—the atoms will shift slightly from their
Crystal-Clear View at the Nanoscale position in an ideal bulk crystal, modifying its properties.”
The new technique relies on focusing a synchrotron-generated coherent X-ray beam on the sample. As the beam scans the sample, a detector captures the intensity of the diffracted X-rays and provides a series of “diffraction patterns.” These are processed by a specific algorithm that generates a $D image at a resolution of just a few nanometers.
This powerful new method should allow scientists to examine the structural integrity of nanocrystals, whether from microelectronic nanocomponents, or from the complex and unique crystal organization of sea shells. %". Institut Fresnel (CNRS / Ecole centrale de Marseille / Université
Aix-Marseille). %#. European Synchrotron Radiation Facility.%$. P. Godard et al., “Three-dimensional high-resolution quantitative
microscopy of extended crystals,” Nat. Commun., #%"". #: &'( | DOI: "%."%$(/ncomms"&'!.
Physics
CONTACT INFORMATION% LIPM, Toulouse. Frédéric Debellé > [email protected]
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BY MARIE&HÉLÈNE TOWHILL
w! Among all cultivated plants, legumes have developed a unique ability over the course of their evolution: that of fixing atmospheric nitrogen through symbiosis with the soil bacteria called rhizobium. This characteristic bears significant interest for agronomic and environmental purposes. Indeed, le-gumes do not require nitrogen fertilizers, which reduces both cost and pollution.
At what point did they develop this ability, and which specific genes are at work in rhizobial symbiosis? To try to answer these questions, an international consortium sequenced the genome of the model legume Medicago truncatula (Mt), also known as barrel medic." “The decoding took almost six years,” ex-
plains Frédéric Debellé, from the LIPM# in Toulouse, who participated in the study. “We now have a draft sequence covering approximately !&% of Mt’s genes.”
The sequence analysis revealed that a whole-genome duplication occurred around &( million years ago, at a time when the legume family underwent im-portant diversification. The capacity to establish symbiosis with rhizobia proba-bly arose before this duplication, and in-volved the recruitment of genes control-ling a pre-existing symbiotic association between the root of a plant and a fungus, called endomycorrhizal association. The whole-genome duplication allowed the further specialization of rhizobial symbi-osis-related gene functions in legumes.
“A better understanding of this sym-biotic process will help improve it in
legumes, and in the future, it could even be transferred to other cultivated plants,” says Debellé.
“More generally, since Medicago truncatula is very close to many European crop legumes, such as pea, field bean, lentil, alfalfa, and clover, obtaining its genome sequence represents a decisive step for the development of new resources for the breeding of these important crops,” he concludes.%". N. D. Young et al., “The Medicago genome provides
insight into the evolution of rhizobial symbioses,” Nature,)#%"". *(%: &#%-*.
%#. Laboratoire des interactions plantes-microorganismes (CNRS / INRA).
Learning from LegumesMolecular Biology
CONTACT INFORMATION% Institut Fresnel, Marseille. Virginie Chamard > [email protected]
q The model legume Medicago truncatula.
#' Albatross visiting a scientist on the Crozet Islands.
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