Cytosolic calcium increases in response to a change in the positioning of gravisensors: results from space experiments.
Résumé
Plants are the ability to sense and to re-orient their growth in response to various stimuli including light, gravity, wind and humidity. The response of a plant organ to the change of gravity direction called gravitropism can be regarded as a crucial factor in the posture control of stems (Moulia and Fournier, 2009) and in the progression for roots into the soil (Roy and Basshamm, 2014). In roots, specialized sensory cells, called statocytes, located in the root apex, perceive signal gravity. Even if it is well known that amyloplasts (located in the statocytes) are considered as gravisensors, the role of these organelles on transduction pathways, is not clearly elucidated (Perbal and Driss-Ecole, 2003). Some studies have demonstrated that cytoplasmic free Ca2+ concentration ([Ca2+]cyt) is affected by environmental stimuli including gravity (for review, Tatsumi et al., 2014). The regulation of this homeostasis involves a series of transduction events such as the synthesis and activation of calcium binding and targeted proteins including calmodulin proteins.