PSC Frontier Seminar Series
Title: Synaptotagmins at endoplasmic reticulum-plasma membrane contact sites mediate diacylglycerol homeostasis after abiotic stress
Speaker: Prof. Miguel A. Botella, Department of Biochemistry and Molecular Biology, University of Malaga (Spain)
Time: 10:00 am
Day/Date: November 1st, 2018 (Thursday)
Host PI: Prof. Alberto Macho
Venue: No.1 meeting room
Production at the plasma membrane of signaling lipids such as diacylglycerol and phosphatidic acid are early plant responses to multiple stresses. Maintaining low levels of these lipids at the plasma membrane is essential not only to provide signaling specificity but also to avoid membrane damage due to their structural characteristics. The Arabidopsis Synaptotagmin 1 (SYT1) protein is localized at endoplasmic reticulum-plasma membrane contact sites (ER-PM CS) and a loss-of-function mutant of SYT1 exhibits decreased PM integrity under different abiotic stresses such freezing, salt or mechanical damage although the molecular basis is not understood. Here we show that the constitutively expressed SYT1 and the cold inducible SYT3 have a role in freezing tolerance and function as PtdIns4P-dependent tethers of the ER-PM CS. SYT1 is a lipid transport protein that preferentially binds in vivo saturated diacylglycerol (DAG) while show little affinity for unsaturated DAG or glycerolipids with polar heads. This suggests that SYT1 role is to shuttle the excess of saturated DAG from the plasma membrane to the ER that is produced under stress-activation of protein kinase C. Consistent with this role, cold treatment increase the localization of SYT1 and SYT3 to contact sites and the massive induction of genes related with membrane damage in the syt1/syt3 double mutant. In addition, we show that SYT1 interacts with diacylglycerol kinase 2 (DGK2) in ER-PM CS and a double syt1/dgk2 mutant show decreased freezing tolerance that single mutants. Taken together, we propose a model in which SYT1 and SYT3 prevent the accumulation of DAG at the PM through removal of saturated DAG but also through controlling the conversion of DAG to phosphatidic acid by DGK2 activity at the PM.
The seminar will be delivered in English.