Monday October 29 2007
CEA
The role of copper in detecting stress
Nature Genetics (2007) 39, 792-796
CEA
The Plant Development Biology Laboratory (IBEB, Cadarache) has identified two copper oxidases that arrest growth in Arabidopsis thaliana roots when the root tips reach a low-phosphate environment. Strangely enough, this response depends on the metal content of the culture medium. A better understanding of this phenomenon could lead to applications in agronomy and phytoremediation.
In contrast with animals which can range over vast areas to find food, plants have to source the nutrient materials they require, such as water and minerals, from the soil surrounding their root systems. While it has long been known that plant root systems are able to modify their architecture in order to preferentially explore the most nutrient-rich soil environments, there is still uncertainty over how roots manage to identify which areas are the most favourable. The Plant Development Biology Laboratory has focused on this question, using phosphate as the mineral and Arabidopsis thaliana as the plant model.
Following a lengthy search based on quantitative genetics (ref. 1), two copper oxidases (LPR1 and LPR2), which play a critical role in detecting low-phosphate environments, were discovered. Mutant roots continue to grow in this nutrient-poor environment while non-mutant roots abruptly arrest their growth. Furthermore, simply placing the root tip in contact with this unfavourable environment is sufficient to arrest growth suggesting that the 'cap', tissue located at the root's exploratory tip, is the organ used to detect the physico-chemical condition of the soil environment. Surprisingly, this phenomenon depends on the metal content of the culture medium (Fe, Cu, Mn).
While it is a long-established fact that roots can sense the earth's gravitational force, this is the first time it has been demonstrated that root caps play a role in detecting environmental stress. These results open up new perspectives in developmental biology with potential applications in the agricultural sciences, such as nutrition and phytoremediation.
References
1 - Matthieu Reymond, Sergio Svistoonoff, Olivier Loudet, Laurent Nussaume and Thierry Desnos. Identification of QTL controlling root growth response to phosphate starvation in Arabidopsis thaliana Plant, Cell and Environment 29:115-125 (2006).
Caption: Arabidopsis seedlets in which the root tip shows a lesser
expression of the LPR1 gene (LPR1-) are unresponsive to
low-phosphate environments (Pi): root growth is no
longer inhibited.