Browsing by Subject "Longevity"

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Interplay between nutrition, senescence and cytosine methylation in Arabidopsis thaliana
(2023) Vatov, Emil; Ludewig, Uwe
In monocarpic plants, senescence is the last stage of leaf development and usually leads to the death of the organism. Systematic degradation of leaf components provides nutrients for the newly developing flowers and seeds. The physiology and transcriptional changes that occur in A. thaliana during this process are very well documented. However, the involvement of epigenic mechanisms remains to be established. In this study, the role of cytosine methylation in the regulation of monocarpic leaf senescence was examined in A. thaliana. Hypomethylated ddc (drm1/2 cmt3) and hypermethylated ros1 mutants showed consistent senescence-specific phenotypes. Disrupted de-novo methylation resulted in delayed, while disrupted demethylation resulted in earlier flowering and appearance of first symptoms of senescence. Both genotypes executed the senescence program faster than Col-0, with lower leaf:seed and higher C:N ratios. During nitrogen, or phosphorus withdrawal and resupply, nutrient remobilization was not inhibited in the two mutants. However, the plant’s response in terms of changes in shoot and root growth was delayed, or non existent. Furthermore, the impact of N withdrawal on delay of the flowering time was inhibited in the two mutants. These results support involvement of cytosine methylation in stress response signaling and downstream effects on organ development and flowering times. The stress response and senescence specific phenotypes of ddc could be partially due to disrupted WRKY signaling, as loss of methylation in W-box binding sites was prevalent, specifically near the transcription start sites of ORFs, and WRKY18, 25 and 53 appeared to be sensitive towards cytosine methylation. Overall decrease in cytosine methylation levels was observed, as early as the opening of the first flowers, together with a decrease in chlorophyll concentrations and an increase in H2O2 and glucose levels in the wild type Col-0. Inhibition in maintenance methylation in the early stages of reproductive growth is consistent with these observations. A complex interaction between four cytokinins was present as early as flower induction, followed by a mass turnover of bound auxin (IAA) at flower opening, that resulted in near doubling of free IAA at seed development. Plant defense responses were induced thereafter, as an increase in salicylic acid (SA) and camalexin occurred, followed by an increase in jasmonic acid (JA) and abscisic acid (ABA). Active RNA-dependent DNA methylation (RdDM) was indicated by a moderate overrepresentation of hypermethylated CHG and CHH loci, together with partial recovery of total methylation levels at the latest stages during seed maturation. Considering the delayed senescence phenotype of ddc, de-novo methylation via RdDM appears to be involved in initiation and execution of the senescence program. Furthermore, hypomethylation at ROS1 gene regulatory region was related to down regulation of gene expression. As an antagonist of RdDM, together with the early senescence phenotype of ros1, these results strengthen the importance of de-novo methylation for senescence, while active demethylation gets down regulated. Overall, methylation changes were little related to known gene expression changes that are associated with senescence. Limited targeting of WRKY and bZIP binding sites hinders conclusions about senescence specific effects of cytosine methylation in signal transduction networks. Altogether, the present work shines light on the importance of proper maintenance of cytosine methylation for flowering time, nutrient remobilization and senescence, and identifies defined cytosine methylation changes during senescence in a comprehensive physiological framework.
Uncovering the relationship between selenium status, age, health, and dietary habits: Insights from a large population study including nonagenarian offspring from the MARK-AGE project
(2023) Giacconi, Robertina; Piacenza, Francesco; Aversano, Valentina; Zampieri, Michele; Bürkle, Alexander; Villanueva, María Moreno; Dollé, Martijn E.T.; Jansen, Eugène; Grune, Tilman; Gonos, Efstathios S.; Franceschi, Claudio; Capri, Miriam; Weinberger, Birgit; Sikora, Ewa; Toussaint, Olivier; Debacq-Chainiaux, Florence; Stuetz, Wolfgang; Slagboom, Pieternella Eline; Bernhardt, Jürgen; Fernández-Sánchez, Maria Luisa; Provinciali, Mauro; Malavolta, Marco
An inadequate selenium (Se) status can accelerate the aging process, increasing the vulnerability to age-related diseases. The study aimed to investigate plasma Se and Se species in a large population, including 2200 older adults from the general population (RASIG), 514 nonagenarian offspring (GO), and 293 GO Spouses (SGO). Plasma Se levels in women exhibit an inverted U-shaped pattern, increasing with age until the post-menopausal period and then declining. Conversely, men exhibit a linear decline in plasma Se levels with age. Subjects from Finland had the highest plasma Se values, while those from Poland had the lowest ones. Plasma Se was influenced by fish and vitamin consumption, but there were no significant differences between RASIG, GO, and SGO. Plasma Se was positively associated with albumin, HDL, total cholesterol, fibrinogen, and triglycerides and negatively associated with homocysteine. Fractionation analysis showed that Se distribution among plasma selenoproteins is affected by age, glucometabolic and inflammatory factors, and being GO or SGO. These findings show that sex-specific, nutritional, and inflammatory factors play a crucial role in the regulation of Se plasma levels throughout the aging process and that the shared environment of GO and SGO plays a role in their distinctive Se fractionation.