Synaptotagmins at the endoplasmic reticulum-plasma membrane contact sites maintain diacylglycerol homeostasis during abiotic stress

23 pags., 6 figs.
Endoplasmic reticulum–plasma membrane contact sites (ER–PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER–PM protein tether synaptotagmin1 (SYT1) exhibit decreased PM integrity under multiple abiotic stresses, such as freezing, high salt, osmotic stress, and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER–PM tether that also functions in maintaining PM integrity. The ER–PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild-type while the levels of most glycerolipid species remain unchanged. In addition, the SYT1-green fluorescent protein fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work
This work was supported by the Ministerio de Economıa y Competitividad, co-financed by the European Regional Development Fund (grant no. BIO2017-82609-R to M.A.B.), the Ministerio de Ciencia, Innovacion y Universidades (grant no. PGC2018-098789-B-I00 to N.R.-L.) UMA-FEDER (grant UMA18-FEDERJA-154 to N.R.-L.), and the Marie SkłodowskaCurie actions (grant no. H2020-655366-IIF- PLICO to M.A.B. and N.R.-L.). N.R.L. was supported by the Ramon y Cajal program RYC-2013-12699 (MINECO, Spain). J.P.-S. and S.G.-H. were funded by the Ministerio de Economıa y Competitividad in Formacion del Personal Investigador Fellowship (grant no. BES-2012-052324) and (PRE2018- 085284), respectively. R.P.H. and J.A.N. received support from the Biotechnology and Biological Sciences Research Council (BBSRC, UK) in the form of an Institute Strategic Programme Grant (grant no. BBS/E/C/000I0420). J.L. is supported by the Program of Introducing Talents of Discipline to Universities (111 Project, grant no. B13007). A.P.M. and J.P.-S. were supported by the Shanghai Center for Plant Stress Biology (Chinese Academy of Sciences), Chinese 1000 Talents Program. A.R. was supported by the Natural Sciences and Engineering Research Council of Canada (NSERCDiscovery Grant no. RGPIN-2019-05568). Support was also provided by AEI/FEDER, UE (grant nos. BIO2016-79187-R and PID2019-106987RB-I00 to J.P.-S.) and by the European Research Council under the European Union’s Seventh Framework Programme (grant no. FP7/2007-2013)/ERC grant agreement no. 742985 to J.F. and T-Rex (project number 682436 to D.V.D.).