Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Jeudi 26 avril 2012
Amphi 206 (Coeur d’Ecole) à 14h
Roles of plant K+ transporters and channels in K+acquisition and transpiration
CEBAS-CSIC. Campus de Espinardo. 30100 Murcia, Spain
K+ is an essential macronutrient required by plants to complete their life cycle. It fulfills important functions and it is widely used as a fertilizer to increase crop production. Plant roots are furnished with K+ transporters that secure the acquisition of K+ under a wide range of external concentrations. From Epstein’s pioneering work >40 years ago, K+uptake was considered to consist of a high- and a low-affinity component. The subsequent molecular approaches identified genes encoding K+ transport systems such as the high-affinity K+ transporter HAK1, (named HAK5 in some species), and the inward rectifier K+ channel AKT1, which could be involved in the first step of K+ uptake at the plant root. Studies in the model species Arabidopsis thaliana have allowed the demonstration that these two systems are crucial for K+ uptake from low concentrations. Nonetheless, in their absence, an unidentified system may mediate K+ uptake when external K+ is higher than 0.5 mM. Our recent results show that this unknown system is highly sensitive to external Ca2+ and putative candidates will be discussed. HAK5 and AKT1 activities are regulated for plant adaptation to different supplies of K+. Transcriptional regulation of HAK5 transporters is complex and responds to the supply of K+ and other nutrients such as NO3- and Pi. A preliminary deletion study of AtHAK5 promoter suggests the presence of CIS elements important for specific expression in epidermal root cells in response to low K+. On the other hand AKT1 has been shown to be activated in roots by the CIPK23-CBL1/9 complex. In addition, cipk23mutants showed increased drought tolerance because a hypersensitive response of their stomata to ABA. Recent results of our group show that the water-stress related phenotype of cipk23 plants is phenocopied in akt1 plants, suggesting that the regulation of AKT1 by CIPK23 takes place also in stomata to regulate plant transpiration.
Contact : Manuel Nieves Cordones