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TOPLESS re-dresses plants

We have finely analyzed [collaboration] the structure and function of the TOPLESS protein, which is involved in plant development. With potential opportunities in agronomy.

Published on 9 September 2017
The machinery that produce proteins from DNA is finely regulated. Activating or keeping inactive the right gene at the right moment is vital for a living organism. For example, when and how to choose the genes necessary for the production of roots, stems or leaves in the plant? "Co-repressors help to avoid the activation of genes at the wrong time," explains François Parcy, head of the Flower Development Regulators team in our laboratory. They allow to make a physical link between other actors of the regulation - the transcription factors - and remodeling proteins of the DNA ball. This ball, called chromatin, is decompacted to allow accessibility to the genes or is maintained in a dense form when the genes are silent.

Scientists have characterized the structure and function of one of these co-repressors, called TOPLESS. The latter is the founding member of a small family of co-repressors that are unique to plants and involved in many essential signaling pathways for the plant development and their response to stress. Its inactivation in the model plant Arabidopsis thaliana induces the formation of a plant where the stem is replaced by a root (which inspired the name of TOPLESS for the corresponding mutant).

More precisely, the researchers (BIG, ENS of Lyon, EMBL) analyzed the part of the TOPLESS protein involved in the interaction with its protein partners. They discovered a structure similar to the one of the rice protein that is even found in seaweed. Researchers have shown that the ability of interaction is kept isolated in an alga, thus demonstrating the age of this primordial function. "The comparison of the structure of TOPLESS with animal co-repressors has also revealed that these different co-repressors are made up of almost identical domains but assembled in different ways", says François Parcy. This study provides a good example of what the Nobel Prize François Jacob had called the "do it yourself of evolution for the construction of protein function". The study also provides keys for manipulating this essential function to responses to environmental stresses and also provides keys to enhance the adaptive potential of crop plants. This could allow the plants not to be all naked, roots in the air and stemless, because of stress!

Three-dimensional structure of the TOPLESS protein.

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