Do Arabidopsis inflorescences twist in Space?
Résumé
Plant proprioception defines the ability of plant to perceive their curvature and to rectify it by the progressive establishment of straightening (1). This capacity to organ straightening needs a complex series of local growth adjustments, usually described as autotropism. Until recently, the signal behind this phenomenon of straightening has long been considered an integral mechanism of the gravitational responses and it remained poorly understood. Furthermore, the proprioceptive control could also be involved in straightening processes observed during phototropism (2), circumnutation (3) or other influences. Until now, to decorrelate this process from graviperception, it has been studied using mathematical modelling (4, 5) or using experiments performed in simulated-microgravity conditions such as those performed on clinostats (6). The overall aim of our space project is to decipher the contribution of multiple stresses induced by spaceflight conditions in the stem proprioceptive sensibilities. Plants grown on the International Space Station (ISS) will offer the unique opportunity to investigate the proprioception process in absence of graviperception. The experiments will be performed using Arabidopsis thaliana as a plant model, allowing the use of mutants or molecular tools targeted on specific molecular actors emerging as important in the proprioception process. The originality of the project lies in the use of a new generic phenotyping tool developed by the team and allowing the characterization of the dynamics of the gravi- and proprioceptive driving of plant curving/decurving movements, through image analysis associated with mathematical modelling using the facilities of the Advanced Plant Habitat. We propose to identify molecular mechanisms underlying simultaneously the curvature perception and the active control of growth in de-curvature. We will address this issue by investigating the function of F-actin organization and its dynamics in proprioceptive control of stem straightening. Our first on-Earth results, obtained using clinostat, on mutants affected in the cytoskeleton organization will be presented. Such knowledge will improve not only our ability to grow plants in space but will also feed research aiming at selecting plants on their straightening abilities for agriculture on earth. Thus, the data obtained within this project could be integrated in the models of plant development implemented within the framework of "a bioregenerative life support system” in space.
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