Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 23 juin 2011
Amphi 2 à 14h

Calcium beyond the cytosol; regulation of apoplastic and vacuolar calcium is required for plant productivity and stress tolerance

Roger A. Leigh
Waite Research Institute, University of Adelaide, Glen Osmond, Australia

Calcium has key but diverse structural and signalling roles in plants. Structural roles include regulating cell wall stability, maintaining membrane integrity and contributing to turgor generation as a vacuolar osmoticum. Cytosolic calcium concentration ([Ca2+]cyt) is important in signal transduction pathways modulating developmental and environmental cues. Apoplastic and vacuolar repositories of Ca2+ are the major stores that shape [Ca2+]cyt transients and [Ca2+] in these non-cytosolic compartments must also be controlled to maximise productivity and responses to abiotic and biotic stress. Vacuolar [Ca2+] is differentially stored in different leaf cell-types: in the epidermis in grasses and the mesophyll in most dicots. We have sought to understand the role of vacuolar calcium using Arabidopsis as a model. Using in situ PCR and cryo-SEM we demonstrated a role for the tonoplast-localised Ca2+/H+ transporter CAX1 in this process. Furthermore, using a loss-of-function mutant of CAX1, we showed that compromising vacuolar calcium accumulation changed apoplastic [Ca2+] causing multiple leaf phenotypes including altered expression of cell wall modifying genes, expression of other Ca2+-transporters, increased cell wall thickness, decreased wall extensibility and reduced stomatal aperture. All phenotypes were conditionally suppressed by growth in a sufficient but reduced Ca supply and this provides a tool for the study of processes that are regulated by apoplastic [Ca2+]. Similar phenotypes and transcriptional responses occur following pathogen infection and using this mutant we can differentiate Ca2+– and pathogen-specific components. The importance of the tonoplast in controlling apoplastic [Ca2+] in general and in response to stress will be discussed.

Contact : Tracey Cuin

Contacts IBIP :
Sabine Zimmermann
Philippe Nacry
Christine Granier
Chantal Baracco