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oai:riuma.uma.es:10630/376012026-02-03T11:08:37Zcom_10630_2254col_10630_37953

Type II Metacaspases are involved in cell stress but not in cell death in the unicellular green alga Dunaliella tertiolecta. Mata, Maria Teresa Palma, Armando López Parages, María Vázquez, Victor Cheng-Sánchez, Iván Sarabia-García, Francisco Ramón López-Figueroa, Félix Jiménez-Gámez, Carlos Segovia-Azcorra, María Muerte celular Ultraviolet radiation (UVR; 280–400 nm) has a great impact on aquatic ecosystems by affecting ecophysiological and biogeochemical pro-cesses as a consequence of the global change scenario generated by anthro-pogenic activities. We studied the effect of PAR (P)+UVA (A)+UVB (B) i.e. PAB, on the molecular physiology of the unicellular green alga Dunaliella tertio-lecta for six days. We assessed the relationship between the triggered UVR stress response and metacaspases and caspase-like (CL)activities, which are proteases denoted to participate in cell death (CD) in phytoplankton. UVR inhibited cell growth and in vivo chlorophyll a fluorescence but did not cause cell death. Western blot analyses reflected that Type-II metacaspases (MCs) are present and appear to be involved in UVR induced-cell stress but not in dark-induced CD in D. tertiolecta. Enzyme kinetics revealed that cleavage of the MCs-reporter substrates RVRR, QRR, GRR, LKR, HEK, and VLK was 10-fold higher than WEHD, DEVD, IETD, and LETD CLs-substrates. The lowest apparent Michaelis-Menten constants (KMap) corresponded to RVRRase (37.5 μM) indi-cating a high affinity by the RVRR substrate. The inhibition of enzymatic activ-ities by using inhibitors with different target sites for hydrolyses demonstrat-ed that from all of the R/ Kase activities only RVRRase was a potential candi-date for being a metacaspase. In parallel, zymograms and peptide-mass fin-gerprinting analyses revealed the identities of such Rase activities suggesting an indirect evidence of possible natural physiological substrates of MCs. We present evidence of type II-MCs not being involved in CD in D. tertiolecta, but rather in survival strategies under the stressful irradiance conditions applied in this study. 2025-02-03T09:39:38Z 2025-02-03T09:39:38Z 2019 journal article Mata MT, Palma A, García-Gómez C, López-Parages M, Vázquez V, Cheng-Sánchez I, Sarabia F, López-Figueroa F, Jiménez C, Segovia M. Type II-Metacaspases are involved in cell stress but not in cell death in the unicellular green alga Dunaliella tertiolecta. Microb Cell. 2019 Oct 7;6(11):494-508. doi: 10.15698/mic2019.11.696. PMID: 31799323; PMCID: PMC6859423 https://hdl.handle.net/10630/37601 10.15698/mic2019.11.696 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Shared Science Publishers OG