Phosphorylation of MAP Kinases crucially controls the response to environmental stress in Dunaliella viridis

The green unicellular microalga Dunaliella viridis has the ability to cope with a wide variety of environmental stressful conditions, such as thermal and osmotic shocks, high PAR, UV radiation and nitrogen deficiency. The lack of a rigid cell wall makes D. viridis an excellent model organism to study stress signaling in eukaryotic unicellular organisms. Mitogen-activated protein kinases (MAPKs) are highly conserved serine/threonine kinases that convert extracellular stimuli into a wide range of responses at both cellular and nuclear levels. In eukaryotic cells, MAPKs are involved in both cell proliferation and differentiation (ERK pathway) and stress responses (JNK and p38 pathways), through protein kinase cascades. Significantly lesser phosphorylation levels of ERK-like protein were observed in D. viridis cultures acclimated to high salinity (3-4 M NaCl). In contrast, JNK-like and p38-like proteins phosphorylation levels increased in stressed cells. Likewise, the efficacy of specific commercial inhibitors of the phosphorylation of ERK (PD98059), JNK (SP600125) and p38 (SB203580) revealed the importance of JNK-like proteins in the maintenance of cell viability, the highlighted participation of p38-like proteins and the non-direct implication of the ERK-like proteins in the acclimatization process. In summary, specific blockade of JNK- and p38-like cascades in stressed cells led to rapid cell death. The behavior of MAPK-like proteins in algae is not known in depth, so the analysis of their mechanism of action, as well as their function in this model microalga, will allow to estimate the fate of unicellular eukaryotic organisms in aquatic ecosystems subjected to environmental stress derived from the conditions prevailing within a framework of global climate change.Peer reviewe

Phosphorylation of MAP kinases crucially controls the response to environmental stress in Dunaliella viridis

El objetivo principal de este estudio fue analizar el papel que llevan a cabo las cascadas de las proteínas tipo MAPKs en la transducción de señales de estrés ambiental en el organismo modelo D. viridis. Se detectó la activación/desactivación y la función de las proteínas tipo MAPKs en este microalga adaptada a condiciones de alta salinidad, ante condiciones de hipersalinidad, alta irradiancia y UV.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Delineation of a lactococcal conjugation system reveals a restriction‐modification evasion system

Abstract Plasmid pUC11B is a 49.3‐kb plasmid harboured by the fermented meat isolate Lactococcus lactis subsp. lactis UC11. Among other features, pUC11B encodes a pMRC01‐like conjugation system and tetracycline‐resistance. In this study, we demonstrate that this plasmid can be conjugated at high frequencies to recipient strains. Mutational analysis of the 22 genes encompassing the presumed pUC11B conjugation cluster revealed the presence of several genes with essential conjugation functions, as well as a gene, trsR, encoding a putative transcriptional repressor of this conjugation cluster. Furthermore, plasmid pUC11B encodes an anti‐restriction protein, TrsAR, which facilitates higher conjugation frequencies when pUC11B is transferred into recipient strains containing Type II or Type III RM systems. These findings demonstrate how RM mechanisms can be circumvented when they act as a biological barrier for conjugation events