SYT6: a newly identified protein involved in ER - trans-Golgi network Membrane Contact Sites

Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.SYT6 is a newly identified lipid transport protein from ER - trans-Golgi network Membrane Contact Sites. Our results show that: • SYT6 contacts trans-Golgi network vesicles through its coiled-coil domain. • SYT6 can efectively respond to Ca2+ using its terminal C2C domain. • SYT6-C2 domains preferentially bind to negatively charged membranes (with PI4P and PS) in presence of Ca2+.This research has been funded by AEI (PID2021-127649OB-I00 and PGC-2018-098789-B-I00) and FEDER-Junta de Andalucía (UMA18-FEDERJA-154). The attendance to this meeting was supported by Plan Propio de Investigación, Transferencia y Divulgación Científica de la Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech

NTMC2T5 protein family: newly identified ER-chloroplast contact site proteins involved in abiotic stress.

Plants are sessile organisms and therefore they have perfected a complex molecular signalling network to detect and respond to the different environmental stresses such as high temperatures, salinity, or drought. In plants, fatty acid synthesis takes place at chloroplasts, and they are assembled into glycerolipids and sphingolipids at the endoplasmic reticulum (ER). Then, the newly synthetized lipids in the ER are delivered to chloroplast via a non-vesicular pathway, likely through lipid transport proteins (LTP). These LTP would be localized in ER-chloroplast membrane contact sites (MCS). Synaptotagmin-like mitochondrial-lipid-binding (SMP) domain proteins are evolutionarily conserved LTP in eukaryotes that localize at MCS. They are involved in tethering of these MCS through interaction with other proteins/membrane lipids and in transferring of glycerolipids between these two membranes. We have studied the occurrence of SMP proteins in A. thaliana and S. lycopersicum by searching remote orthologs of human E-Syt1 (SMP protein). By using transient expression in N. benthamiana leaves and confocal microscopy, we have identified the NTMC2T5 family with two homologs in A. thaliana and only one in S. lycopersicum that are anchored to the chloroplast outer membrane and are interacting with the ER (at ER-chloroplast MCS). Our preliminary data have unequivocally demonstrated that NTMC2T5 proteins are anchored to the chloroplast, and they bind in trans the ER. Additionally, it is predicted that these proteins contain a SMP domain which is a lipid-transfer domain, indicating that these proteins could be responsible for some of the lipid transferring events at ER-chloroplast MCS that are still unknown. Our preliminary phenotypic analyses have shown that these proteins are involved in salt tolerance. Finally, we have observed that clustering of chloroplasts around the nucleus occurred when we overexpressed these proteins in Nicotiana benthamiana leaves.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Identification of NTMC2T5, a new lipid transfer protein family at ER-chloroplast contact sites involved in stress response

Plants are sessile organisms and they have perfected a complex molecular signalling network to detect and respond to different environmental stresses. In plants, fatty acid synthesis takes place at chloroplasts, and they are assembled into glycerolipids and sphingolipids at the ER. Then, the newly synthetized lipids in the ER are delivered to chloroplast via a non-vesicular pathway, likely through lipid transport proteins. These LTP would be localized in ER-chloroplast membrane contact sites (MCS), which are microdomains where membranes of these two different organelles are closely apposed but not fussing. SMP domain proteins are evolutionarily conserved LTP in eukaryotes that localize at MCS. We have studied the occurrence of SMP proteins in A. thaliana and S. lycopersicum. By using transient expression in N. benthamiana leaves and confocal microscopy, we have identified the NTMC2T5 family with two homologs in A. thaliana and only one in S. lycopersicum that are anchored to the chloroplast outer membrane and are interacting with the ER (at ER-chloroplast MCS. Our preliminary data have demonstrated that NTMC2T5 proteins are anchored to the chloroplast, and they bind in trans the ER. Additionally, it is predicted that these proteins contain a SMP domain which is a lipid-transfer domain, indicating that these proteins could be responsible for some of the lipid transferring events at ER-chloroplast MCS that are still unknown. We show the results of the lipidomic analysis we have performed in order to understand the role of these proteins. And our phenotypic analyses have shown that these proteins are involved in salt tolerance. Additionally, we have observed that clustering of chloroplasts occurred when we overexpressed these proteins. And Arabidopsis double knock-out mutant for these proteins showed less chloroplasts attached to the nucleus in epidermal cells, suggesting that these proteins could be involved in these chloroplast signalling events after stress.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech