Browsing by Subject "stress response"

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  • Escamez, Sacha; Stael, Simon; Vainonen, Julia; Willems, Patrick; Jin, Huiting; Kimura, Sachie; Van Breusegem, Frank; Gevaert, Kris; Wrzaczek, Michael Alois; Tuominen, Hannele (2019)
    During plant vascular development, xylem tracheary elements (TEs) form water-conducting, empty pipes by genetically regulated cell death. Cell death is prevented from spreading to non-TEs by unidentified intercellular mechanisms, downstream of METACASPASE9 (MC9)-mediated regulation of autophagy in TEs. Here, we identified differentially abundant extracellular peptides in vascular-differentiating wild-type and MC9-down-regulated Arabidopsis cell suspensions. A peptide named Kratos rescued the abnormally high ectopic non-TE death resulting from either MC9 knockout or TE-specific overexpression of the ATG5 autophagy protein during experimentally induced vascular differentiation in Arabidopsis cotyledons. Kratos also reduced cell death following mechanical damage and extracellular ROS production in Arabidopsis leaves. Stress-induced but not vascular non-TE cell death was enhanced by another identified peptide, named Bia. Bia is therefore reminiscent of several known plant cell death-inducing peptides acting as damage-associated molecular patterns. In contrast, Kratos plays a novel extracellular cell survival role in the context of development and during stress response.
  • Pöntinen, Anna; Aalto-Araneda, Mariella; Lindström, Miia; Korkeala, Hannu (2017)
    Listeria monocytogenes is one of the most heat-resistant non-sporeforming food-borne pathogens and poses a notable risk to food safety, particularly when mild heat treatments are used in food processing and preparation. While general heat stress properties and response mechanisms of L. monocytogenes have been described, accessory mechanisms providing particular L. monocytogenes strains with the advantage of enhanced heat resistance are unknown. Here, we report plasmidmediated heat resistance of L. monocytogenes for the first time. This resistance is mediated by the ATP-dependent protease ClpL. We tested the survival of two wildtype L. monocytogenes strains-both of serotype 1/2c, sequence type ST9, and high sequence identity-at high temperatures and compared their genome composition in order to identify genetic mechanisms involved in their heat survival phenotype. L. monocytogenes AT3E was more heat resistant (0.0 CFU/ml log(10) reduction) than strain AL4E (1.4 CFU/ml log(10) reduction) after heating at 55 degrees C for 40 min. A prominent difference in the genome compositions of the two strains was a 58-kb plasmid (pLM58) harbored by the heat-resistant AT3E strain, suggesting plasmid-mediated heat resistance. Indeed, plasmid curing resulted in significantly decreased heat resistance (1.1 CFU/ml log(10) reduction) at 55 degrees C. pLM58 harbored a 2,115-bp open reading frame annotated as an ATP-dependent protease (ClpL)-encoding clpL gene. Introducing the clpL gene into a natively heat-sensitive L. monocytogenes strain (1.2 CFU/ml log(10) reduction) significantly increased the heat resistance of the recipient strain (0.4 CFU/ml log(10) reduction) at 55 degrees C. Plasmid-borne ClpL is thus a potential predictor of elevated heat resistance in L. monocytogenes. IMPORTANCE Listeria monocytogenes is a dangerous food pathogen causing the severe illness listeriosis that has a high mortality rate in immunocompromised individuals. Although destroyed by pasteurization, L. monocytogenes is among the most heat-resistant non-spore-forming bacteria. This poses a risk to food safety, as listeriosis is commonly associated with ready-to-eat foods that are consumed without thorough heating. However, L. monocytogenes strains differ in their ability to survive high temperatures, and comprehensive understanding of the genetic mechanisms underlying these differences is still limited. Whole-genome-sequence analysis and phenotypic characterization allowed us to identify a novel plasmid, designated pLM58, and a plasmid-borne ATP-dependent protease (ClpL), which mediated heat resistance in L. monocytogenes. As the first report on plasmid-mediated heat resistance in L. monocytogenes, our study sheds light on the accessory genetic mechanisms rendering certain L. monocytogenes strains particularly capable of surviving high temperatures-with plasmid-borne ClpL being a potential predictor of elevated heat resistance.
  • Olkkonen, Emmi (Helsingin yliopisto, 2021)
    Long non-coding RNAs (lncRNAs) are over 200 bp long RNA molecules that are not translated into protein. LncRNAs can regulate the expression of protein coding genes, and studies have indicated their role in stress response. Stress response has also been associated with differences in the structure of the myelin sheaths in the mouse brain cortex. Myelin is produced by mature oligodendrocytes (OLGs), and therefore, OLGs are likely to play a role in stress response. The aim of this thesis was to find lncRNAs differentially expressed in the oligodendrocytes and myelin on the medial prefrontal cortex of stressed mice in comparison to controls. Mice of strains C57/6NCrl and DBA/2NCrl, differing in stress response, were exposed to chronic social defeat stress. After the stress paradigm, the mice were assigned as stress-susceptible or stress-resilient, the susceptible mice exhibiting anxiety-like behavior. RNA from OLGs and myelin from the medial prefrontal cortex of the mice was sequenced, and I compared the lncRNA expression levels between stressed and control mice and stress-susceptible and resilient mice using bioinformatic methods. I also assessed modules formed by lncRNAs and protein coding genes correlating in expression in both datasets. I used RT-qPCR to investigate if results from two differentially expressed lncRNAs, Gm37885 and Neat1, replicate in a stress hormone-treated oligodendrocyte cell line. Three hundred and seventy lncRNAs were differentially expressed between stressed mice and controls or stress-susceptible and resilient mice in the OLG dataset and 132 in the myelin dataset. Two hundred and 87 of them overlapped with a protein coding gene in the OLG and myelin datasets, respectively. Sixty-one percent of the differentially expressed lncRNAs were specific to comparisons in the OLG dataset and 73 % in the myelin dataset, but 39 % of the differentially expressed lncRNAs in the OLG dataset and 27 % in the myelin dataset were shared between them. No module of genes with correlating expression levels was associated with stress, but the expression levels of two correlation modules from each dataset differed between strains. The results for one of the differentially expressed lncRNAs, Gm37885, replicated in stressed Oli-neu cells in RT-qPCR. The results of my thesis indicate that multiple lncRNAs are involved in the mouse stress response, as many were differentially expressed and shared between phenotype comparisons. Additionally, significant gene expression differences were observed between strains, which could contribute to the previously reported strain differences in stress susceptibility. The results also suggest a specific role of Gm37885 in GR-mediated stress response. However, the function of Gm37885 remains unknown, and further studies regarding Gm37885 and the other differentially expressed lncRNAs should be carried out to draw conclusions of their contribution to the OLG-mediated stress response.
  • Grabsztunowicz, Magda; Rantala, Marjaana; Ivanauskaite, Aiste; Blomster, Tiina; Koskela, Minna M.; Vuorinen, Katariina; Tyystjarvi, Esa; Burow, Meike; Overmyer, Kirk; Mähönen, Ari P.; Mulo, Paula (2021)
    In Arabidopsis, two leaf-type ferredoxin-NADP(+) oxidoreductase (LFNR) isoforms function in photosynthetic electron flow in reduction of NADP(+), while two root-type FNR (RFNR) isoforms catalyse reduction of ferredoxin in non-photosynthetic plastids. As the key to understanding, the function of RFNRs might lie in their spatial and temporal distribution in different plant tissues and cell types, we examined expression of RFNR1 and RFNR2 genes using beta-glucuronidase (GUS) reporter lines and investigated accumulation of distinct RFNR isoforms using a GFP approach and Western blotting upon various stresses. We show that while RFNR1 promoter is active in leaf veins, root tips and in the stele of roots, RFNR2 promoter activity is present in leaf tips and root stele, epidermis and cortex. RFNR1 protein accumulates as a soluble protein within the plastids of root stele cells, while RFNR2 is mainly present in the outer root layers. Ozone treatment of plants enhanced accumulation of RFNR1, whereas low temperature treatment specifically affected RFNR2 accumulation in roots. We further discuss the physiological roles of RFNR1 and RFNR2 based on characterization of rfnr1 and rfnr2 knock-out plants and show that although the function of these proteins is partly redundant, the RFNR proteins are essential for plant development and survival.