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Funding Information: This work received funding support from Funda??o para a Ci?ncia e a Tecnologia (FCT), Portugal through the project PTDC/AGR-FOR/4218/2012, and the research units UID/Multi/04551/2013 (GREEN-IT), UIDB/00239/2020 (CEF) and UIDP/04035/2020 (GeoBioTec). C.A. acknowledges the FCT Investigator Program (IF/00376/2012/CP0165/CT0003). T.F.J. acknowledges FCT (PD/BD/113475/2015) and ITQB NOVA International PhD Program Plants for Life (PD/00035/2013). A.R.F. and S.A. are supported by the European Union?s Horizon 2020 research and innovation programme, project PlantaSYST (SGA-CSA No. 739582 under FPA No. 664620). Funding Information: Funding: This work received funding support from Fundação para a Ciência e a Tecnologia (FCT), Portugal through the project PTDC/AGR-FOR/4218/2012, and the research units UID/Multi/04551/2013 (GREEN-IT), UIDB/00239/2020 (CEF) and UIDP/04035/2020 (GeoBioTec). C.A. acknowledges the FCT Investigator Program (IF/00376/2012/CP0165/CT0003). T.F.J. acknowledges FCT (PD/BD/113475/2015) and ITQB NOVA International PhD Program Plants for Life (PD/00035/2013). A.R.F. and S.A. are supported by the European Union's Horizon 2020 research and innovation programme, project PlantaSYST (SGA-CSA No. 739582 under FPA No. 664620). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ; Actinorhizal plants have been regarded as promising species in the current climate change context due to their high tolerance to a multitude of abiotic stresses. While combined salt-heat stress effects have been studied in crop species, their impact on the model actinorhizal plant, Casuarina glauca, has not yet been fully addressed. The effect of single salt (400 mM NaCl) and heat (control at 26/22 °C, supra optimal temperatures at 35/22 °C and 45/22 °C day/night) conditions on C. glauca branchlets was characterised at the physiological level, and stress-induced metabolite changes were characterised by mass spectrometry-based metabolomics. C. glauca could withstand single salt and heat conditions. However, the harshest stress condition (400 mM NaCl, 45 °C) revealed photosynthetic impairments due to mesophyll and membrane permeability limitations as well as major stress-specific differential responses in C and N metabolism. The increased activity of enzymatic ROS scavengers was, however, revealed to be sufficient to control the plant oxidative status. Although C. glauca could tolerate single salt and heat stresses, their negative interaction enhanced the effects of salt stress. Results demonstrated that C. glauca responses to combined salt-heat stress could be explained as a sum of the responses from each single applied stress. ; publishersversion ; published

This work was supported by European Union, Program Horizon 2020, call H2020-SFS-2016-2, action RIA, and Portuguese national funds from Fundacao para a Ciencia e a Tecnologia (project PTDC/ASP-AGR/31257/2017; Funding from CNPq (fellowships to E. Campostrini, F.L. Partelli, and F.M. DaMatta) is also acknowledged. ; An unexpected heat resilience, and the mitigation of heat impacts by elevated [CO2] were recently reported in Coffea spp. Plants must maintain membrane fluidity and integrity to cope with temperature changes, which requires an adequate lipid dynamics. This work provides the lipid profile (galactolipids, GL; phospholipids, PL; sulfolipids, SL) of chloroplast membranes, and the expression of a set of genes related to lipid metabolism in Coffea arabica L. (cv. Icatu and IPR108) and C. canephora cv. Conilon CL153, under elevated [CO2] (380 or 700 μL L−1), heat (25/20, 31/25, 37/30 and 42/34 °C, day/night) and their interaction. Major membrane lipids alterations, different among genotypes, included: A) responsiveness of total fatty acids (TFAs) synthesis to [CO2] (except IPR108) and heat (except CL153); stronger remodeling (unsaturation degree) in the 700-plants from 37/30 °C to 42/34 °C, coordinated at transcriptional level with the down-regulation of fatty acid desaturase FAD3 gene (C. arabica) and up-regulation of lipoxygenase genes LOX5A (CL153 and Icatu) and LOX5B (Icatu) at the highest temperature; B) quantitative and qualitative modifications in GL (monogalactosyldiacylglycerol, MGDG; digalactosyldiacylglycerol, DGDG), PL (phosphatidylcholine, PC; phosphatidylglycerol, PG), and SL (sulfoquinovosyldiacylglycerol, SQDG) classes, prompted by heat, elevated [CO2], and, especially, the interaction, in CL153 and Icatu. Overall membrane enrichment with MGDG and DGDG as a result of heat and [CO2] interaction in these genotypes, but at the highest temperature only in Icatu the high [CO2] maintained greater contents and unsaturation values of these GLs than in the 380-plants. C) Among PL classes, PG seems to play an active role in heat acclimation of C. arabica genotypes, increasing in 700-plants at 42/34 °C. Globally, Icatu often showed changes closer to those of heat tolerant cv. CL153 than to cv. IPR108. Overall, lipid profile adjustments in chloroplast membranes, from TFAs bulk until FA unsaturation within each class, are expected to contribute to long-term acclimation to climate changes in coffee plant. ; publishersversion ; published