Such orientation of growth requires a guidance system relying on the detection of a directional environmental stimulus. In soil, the major environmental factors used as guidance stimuli are gravity and touch. The mechanisms by which a plant organ senses a gravity or touch stimulus, transduces the signal into physiological information and responds to that information are poorly understood.
Roots constitute a good model system to study such mechanisms.
We are studying the mechanisms involved in gravity and touch sensing, as well as the early stages of signal transduction in plant roots, using molecular genetic strategies. More specifically, we are using the T-DNA of Agrobacterium tumefaciens and various plant transposable elements as insertional mutagens to generate and characterize Arabidopsis thaliana mutants affected in their ability to respond to either a touch or a gravity stimulus. Additionally, we are developing a complementary molecular genetic strategy in the yeast Saccharomyces cerevisiae, aimed at identifying genes essential for touch sensing in eukaryotes. Yeast respond to hypotonic shock with a calcium pulse. Circadian oscillations of cytosolic and chloroplastic free calcium in plants.