Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Jeudi 9 décembre 2010
Amphi 208 (Cœur d’Ecole) à 14h
New strategies for imaging of Ca2+ and H2O2 in different subcellular compartments of plant cells
Dipartimento di Biologia, Università degli Studi di Padova, Padova, Italie
In order to gain insight into the roles played by Ca2+ and H2O2 in plant cells, it is necessary to have reliable, specific and non-invasive methodologies for their in vivodetection. In the last years a great development of new tools for the detection of such molecules has taking place. In particular new genetically-encoded probes for Ca2+(Cameleons) and H2O2 (HyPer) have been developed. Oxidative stress is a major challenge for all cells living in an oxygen-based world. Among reactive oxygen species, H2O2, is a well known toxic molecule and, nowadays, considered a specific component of several signalling pathways. Hence, the genetically-encoded H2O2 sensor HyPer was expressed in plant cells in different subcellular compartments. We demonstrated that the induction of cytoplasmic Ca2+ increase is followed by Ca2+ rise in the peroxisomal lumen. The analyses of HyPer fluorescence ratios were performed in leaf peroxisomes of tobacco and pre- and post-bolting Arabidopsis plants. These analyses allowed us to demonstrate that an intraperoxisomal Ca2+ rise in vivo stimulates catalase activity, increasing peroxisomal H2O2 scavenging efficiency. Ca2+ is a versatile second messenger involved in the control of a variety of physiological and pathological cellular processes. The use of genetically encoded Ca2+ indicators (e.g Cameleon) has greatly contributed to the study of Ca2+ handling in plant cells. Compared with mammalian cells, where a large set of data have been produced regarding the Ca2+ dynamics in different subcellular compartments, in plant cells there is still a poor comprehension of the role/s played by the organelles in the shaping of intracellular Ca2+ signals. Here the use of a new generation of Cameleon probes targeted to peroxisomes and mitochondria of plant cells will be presented.
Contact : Tou-Cheu Xiong