Biology subjects

Traa, A.

Publications and source records attributed to Traa, A..

8 recordsLinked to original sources

bioRxiv2025

Impaired methyl recycling induces substantial shifts in sulfur utilization in Arabidopsis

The tight coordination of sulfur metabolism and growth regulation is predicated upon nutrient availability. Central to this balancing act is the utilization of cysteine (Cys) for the formation of methionine (Met) and S-adenosylmethionine (SAM). Plants that are severely deficient in regenerating Met due to reduced methylthioadenosine (MTA) nucleosidase activity experience numerous developmental abnormalities. Here, we assess the developmental, metabolic, and regulatory effects associated with decreased MTA recycling. We show that MTA over-accumulation predominantly occurs in reproductive tissues and leads to reduced levels of Cys, Met, and SAM, as well as elevated S-adenosylhomocysteine. These disruptions of primary sulfur utilization also lead to the misregulation of energy metabolism and altered cell cycle progression. RNA-seq experiments show a general down-regulation of many developmental and reproductive genes. Targeted metabolite analyses demonstrate clear impacts on the methyl index which are reflected in the results of bisulfite-sequencing experiments including global alterations in CG gene-body methylation levels and decreases of CHG and CHH methylation in transposable elements. Our findings demonstrate the broad impacts of MTA metabolism on plant development, sulfur utilization and the maintenance of the methyl index.

plant biology↗

bioRxiv2024

Mitochondrial superoxide acts in the intestine to extend longevity

Reactive oxygen species (ROS) are highly reactive oxygen containing molecules that are generated by normal metabolism. While ROS can cause damage to the building blocks that make up cells, these molecules can also act as intracellular signals that promote longevity. The levels of ROS within the cell can be regulated by antioxidant enzymes, such as superoxide dismutase (SOD), which converts superoxide to hydrogen peroxide. Interestingly, our previous work has shown that disruption of the mitochondrial SOD gene sod-2 results in increased lifespan, indicating that elevating levels of mitochondrial superoxide can promote longevity. To explore the molecular mechanisms involved, we determined the tissues in which disruption of sod-2 is necessary for lifespan extension and the tissues in which disruption of sod-2 is sufficient to extend lifespan. We found that tissue-specific restoration of SOD-2 expression in worms lacking SOD-2 could partially revert changes in fertility, embryonic lethality and resistance to stress, but did not inhibit the effects of sod-2 deletion on lifespan. Knocking down sod-2 expression using RNA interference specifically in the intestine, but not other tissues, was sufficient to extend longevity. Intestine-specific knockdown of sod-2 also increased resistance to heat stress and while decreasing resistance to oxidative stress. Combined, these results indicate that disruption of sod-2 in neurons, intestine, germline, or muscle is not required for lifespan extension, but that decreasing sod-2 expression in just the intestine extends lifespan. This work defines the conditions required for elevated mitochondrial superoxide to increase longevity.

genetics↗

bioRxiv2024

Developmental disruption of the mitochondrial fissiongene drp-1 extends the longevity of daf-2 insulin/IGF-1 receptor mutant

The dynamic nature of the mitochondrial network is regulated by mitochondrial fission and fusion, allowing for re-organization of mitochondria to adapt to the cells ever-changing needs. As organisms age, mitochondrial fission and fusion become dysregulated and mitochondrial networks become increasingly fragmented. Modulation of mitochondrial dynamics has been shown to affect longevity in fungi, yeast, Drosophila and C. elegans. While disruption of the mitochondrial fission gene drp-1 only mildly increases wild-type lifespan, it drastically increases the already long lifespan of daf-2 insulin/IGF-1 signaling (IIS) mutants. In this work, we determined the conditions required for drp-1 disruption to extend daf-2 longevity and explored the molecular mechanisms involved. We found that knockdown of drp-1 during development is sufficient to extend daf-2 lifespan, while tissue-specific knockdown of drp-1 in neurons, intestine or muscle failed to increase daf-2 longevity. Disruption of other genes involved in mitochondrial fission also increased daf-2 lifespan as did treatment with a number of different RNAi clones that decrease mitochondrial fragmentation. In exploring potential mechanisms involved, we found that deletion of drp-1 increases resistance to chronic stresses and slows physiologic rates in daf-2 worms. In addition, we found that disruption of drp-1 increased mitochondrial and peroxisomal connectedness in daf-2 worms, increased oxidative phosphorylation and ATP levels, and increased mitophagy in daf-2 worms, but did not affect their ROS levels or mitochondrial membrane potential. Overall, this work defined the conditions under which drp-1 disruption increases daf-2 lifespan and has identified multiple changes in daf-2;drp-1 mutants that may contribute to their lifespan extension.

genetics↗

bioRxiv2023

Overexpression of mitochondrial fusion genes enhances resilience and extends longevity

The dynamicity of the mitochondrial network is crucial for meeting the ever-changing metabolic and energy needs of the cell. Mitochondrial fission promotes the degradation and distribution of mitochondria, while mitochondrial fusion maintains mitochondrial function through the complementation of mitochondrial components. Previously, we have reported that mitochondrial networks are tubular, interconnected and well-organized in young, healthy C. elegans, but become fragmented and disorganized with advancing age and in models of age-associated neurodegenerative disease. In this work, we examine the effects of increasing mitochondrial fission or mitochondrial fusion capacity by ubiquitously overexpressing the mitochondrial fission gene drp-1 or the mitochondrial fusion genes fzo-1 and eat-3, individually or in combination. We then measured mitochondrial function, mitochondrial network morphology, physiologic rates, stress resistance and lifespan. Surprisingly, we found that overexpression of either mitochondrial fission or fusion machinery both resulted in an increase in mitochondrial fragmentation. Similarly, both mitochondrial fission and mitochondrial fusion overexpression strains have extended lifespans and increased stress resistance, which appears to be at least partially due to the upregulation of multiple stress response pathways in these strains. Overall, our work demonstrates that increasing the expression of mitochondrial fission or fusion genes extends lifespan and improves biological resilience without promoting the maintenance of a youthful mitochondrial network morphology. This work highlights the importance of the mitochondria for both resilience and longevity.

developmental biology↗

bioRxiv2023

Endosomal trafficking protein TBC-2 isrequired for the longevity of long-livedmitochondrial mutants

Mutations that result in a mild impairment of mitochondrial function can extend longevity. Previous studies have shown that the increase in lifespan is dependent on stress responsive transcription factors, including DAF-16/FOXO, which exhibits increased nuclear localization in long-lived mitochondrial mutants. We recently found that the localization of DAF-16 within the cell is dependent on the endosomal trafficking protein TBC-2. Based on the important role of DAF-16 in both longevity and resistance to stress, we examined the effect of disrupting tbc-2 on lifespan and stress resistance in the long-lived mitochondrial mutants nuo-6 and isp-1 in C. elegans. Loss of tbc-2 markedly reduced the long lifespans of both mitochondrial mutants. Disruption of tbc-2 also decreased resistance to specific exogenous stressors in nuo-6 and isp-1 mutants. In contrast, tbc-2 inhibition had no effect on oxidative stress resistance or lifespan in isp-1 worms when DAF-16 is absent suggesting that the effect of tbc-2 on mitochondrial mutant lifespan may be mediated by mislocalization of DAF-16. However, this result is complicated by the fact that deletion of daf-16 markedly decreases both phenotypes in isp-1 worms. Surprisingly, disruption of tbc-2 did not prevent the upregulation of DAF-16 target genes in the long-lived mitochondrial mutants, suggesting the possibility that the effect of tbc-2 on lifespan and stress resistance in the long-lived mitochondrial mutants is at least partially independent of its effects on DAF-16 localization. Overall, this work demonstrates the importance of endosomal trafficking for the extended longevity and enhanced stress resistance resulting from mild impairment of mitochondrial function.

genetics↗

bioRxiv2022

Exercise preserves fitness capacity during aging through AMPK and mitochondrial dynamics

Exercise is a nonpharmacological intervention that improves health during aging, and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise transiently alters mitochondrial functionality and metabolism. Mitochondrial fission and fusion are critical effectors of mitochondrial plasticity, which allows a fine-tuned regulation of organelle connectiveness, size and function. Here we have investigated the role of mitochondrial dynamics during exercise in the genetically tractable model Caenorhabditis elegans. We show that in body wall muscle a single exercise session induces a cycle of mitochondrial fragmentation followed by fusion after a recovery period, and that daily exercise sessions delay the mitochondrial fragmentation and fitness capacity decline that occur with aging. The plasticity of this mitochondrial dynamics cycle is essential for fitness capacity and its enhancement by exercise training. Surprisingly, among longevity-promoting mechanisms we analyzed, constitutive activation of AMPK uniquely preserves fitness capacity during aging. As with exercise training, this benefit of AMPK is abolished by impairment of mitochondrial fission or fusion. AMPK is also required for fitness capacity to be enhanced by exercise, with our findings together suggesting that exercise enhances muscle function through AMPK regulation of mitochondrial dynamics. Our results indicate that mitochondrial connectivity and the mitochondrial dynamics cycle are essential for maintaining fitness capacity and exercise responsiveness during aging, and suggest that AMPK activation may recapitulate some exercise benefits. Targeting mechanisms to optimize mitochondrial fission and fusion balance, as well as AMPK activation, may represent promising strategies for promoting muscle function during aging. Significance StatementExercise is a powerful anti-aging intervention. In muscle exercise remodels mitochondrial metabolism and connectiveness, but the role of mitochondrial dynamics in exercise responsiveness has remained poorly understood. Working in Caenorhabditis elegans, we find that the mitochondrial dynamics cycle of fission and fusion is critical for fitness capacity, that exercise delays an aging-associated decline in mitochondrial connectiveness and fitness capacity, and that the mitochondrial dynamics cycle is required for the latter benefit. AMPK, which regulates mitochondrial dynamics, is needed for exercise to maintain fitness capacity with age and can recapitulate this exercise benefit. Our data identify the mitochondrial dynamics cycle as an essential mediator of exercise responsiveness, and an entry point for interventions to maintain muscle function during aging.

cell biology↗

bioRxiv2021

Identification of novel therapeutic targets for polyglutamine toxicity disorders that target mitochondrial fragmentation

Huntingtons disease (HD) is one of at least nine polyglutamine toxicity disorders caused by a trinucleotide CAG repeat expansion, all of which lead to age-onset neurodegeneration. Mitochondrial dynamics and function are disrupted in HD and other polyglutamine toxicity disorders. While multiple studies have found beneficial effects from decreasing mitochondrial fragmentation in HD models by disrupting the mitochondrial fission protein DRP1, disrupting DRP1 can also have detrimental consequences in wild-type animals and HD models. In this work, we examine the effect of decreasing mitochondrial fragmentation in a neuronal C. elegans model of polyglutamine toxicity called Neur-67Q. We find that Neur-67Q worms have deficits in mitochondrial morphology in GABAergic neurons and decreased mitochondrial function. Disruption of drp-1 eliminates differences in mitochondrial morphology and rescues deficits in both movement and longevity in Neur-67Q worms. In testing twenty-four RNA interference (RNAi) clones that decrease mitochondrial fragmentation, we identified eleven clones that increase movement and extend lifespan in Neur-67Q worms. Overall, we show that decreasing mitochondrial fragmentation may be an effective approach to treat polyglutamine toxicity disorders and identify multiple novel genetic targets that circumvent the potential negative side effects of disrupting the primary mitochondrial fission gene drp-1. Significance StatementPolyglutamine toxicity disorders are caused by a trinucleotide CAG repeat expansion that leads to neurodegeneration. Both mitochondrial dynamics and function are disrupted in these disorders. In this work we use a simple genetic model organism, the worm C. elegans, to define the role of mitochondrial morphology in polyglutamine toxicity disorders. We show that CAG repeat expansion is sufficient to disrupt mitochondrial morphology and that genetic strategies that decrease mitochondrial fragmentation are beneficial in a neuronal model of polyglutamine toxicity. This work identifies multiple novel genes that are protective in worm models of polyglutamine toxicity, which may serve as potential therapeutic targets for Huntingtons disease and other polyglutamine toxicity disorders.

neuroscience↗

bioRxiv2021

Mitochondrial unfolded protein response transcription factor ATFS-1 increases resistance to exogenous stressors through upregulation of multiple stress response pathways

The mitochondrial unfolded protein response (mitoUPR) is an evolutionarily conserved pathway that responds to various insults to the mitochondria through transcriptional changes that restore mitochondrial homeostasis in order to facilitate cell survival. Gene expression changes resulting from the activation of the mitoUPR are mediated by the transcription factor ATFS-1/ATF-5. To further define the mechanisms through which the mitoUPR protects the cell during mitochondrial dysfunction, we characterized the role of ATFS-1 in responding to organismal stress. We found that activation of ATFS-1 is sufficient to cause upregulation of genes involved in multiple stress response pathways, including the DAF-16-mediated stress response pathway, the SKN-1-mediated oxidative stress response pathway, the HIF-mediated hypoxia response pathway, the p38-mediated innate immune response pathway, and antioxidant genes. Moreover, ATFS-1 is required for the upregulation of stress response genes after exposure to exogenous stressors, especially oxidative stress and bacterial pathogens. Constitutive activation of ATFS-1 increases resistance to multiple acute exogenous stressors, while disruption of atfs-1 decreases stress resistance. Although ATFS-1-dependent genes are upregulated in multiple long-lived mutants, constitutive activation of ATFS-1 in wild-type animals results in decreased lifespan. Overall, our work demonstrates that ATFS-1 serves a vital role in organismal survival of acute stresses through its ability to activate multiple stress response pathways, but that chronic ATFS-1 activation is detrimental for longevity.

genetics↗