Darwin thinking

Student Talk Abstracts

Natural versus urban soil organic carbon stocks: a meta-analysis

Presenter: Shih-Chieh Chien | Advisor: Dr. Jennifer Krumins

Abstract: Soil is the largest organic carbon pool in terrestrial ecosystems to mitigate climate change impacts, but its ability to retain and store carbon varies, especially in urban ecosystems. We constructed a meta-analysis focusing on 30 cm soil depth by collecting data from over 191 prior studies measuring soil organic carbon (SOC) stocks across natural, urban green space, and urban intensive habitats. The SOC data are compared between different climatic zones, vegetation types, and human footprint index. The SOC stocks in natural habitats (98.22 ± 49.10 Mg ha-1) are significantly higher than urban green space (54.61 ± 22.02 Mg ha-1) and urban intensive habitats (65.88 ± 35.27 Mg ha-1). We find a significant and negative relationship between the human footprint and SOC stocks only in natural habitats. When compared across climatic zones or vegetation types, the capacity of natural soils to store C is variable and vulnerable to the human footprint. Carbon storage in urban soils is likely limited by persistent and stable anthropogenic influences keeping variability low, like urban green spaces where human management is likely high and SOC is low. A comprehensive understanding of C storage in soils is essential to land management and climate mitigation measures.

Determining the relationship between the tubulin code and microtubule-associated proteins in C. elegans

Presenter: Sasha Avrutis | Advisor: Dr. Bob O’Hagan

Additional Authors: Nicole Ross, Ellia Daniel

Abstract: Microtubules (MTs) are essential cytoskeletal elements that play diverse roles, such as intracellular transport of cargos, cell division, and maintenance of cell shape. Although all MTs are made by assembly of a and b tubulins, they are not uniform. MTs can be specialized for different structural and functional needs, but the mechanisms that specialize MTs are not completely understood. The Tubulin Code hypothesis suggests that MTs can be specialized by incorporating different a and b tubulin isoforms and by addition of reversible post-translational modifications (PTMs) such as glutamylation (addition of glutamate side chains to tubulin C-terminal tails). Non-motor microtubule-associated proteins (MAPs) act as another mechanism to regulate the MT cytoskeleton, but the function of many MAPs is not yet known. MT binding of some MAPs, such as mammalian Tau, has been found to be sensitive to MT glutamylation in vitro, suggesting that these two layers of MT regulation may interact. Both the Tubulin Code and MAPs are involved in neurodegenerative diseases in humans, suggesting that both of these mechanisms of MT regulation and specialization are essential for neurons.  For example, dysfunction of mammalian Tau protein, perhaps the most well-studied MAP, is involved in progressive neurodegenerative diseases such as Alzheimer’s Disease (AD) and other “tauopathies.” To further understand how the Tubulin Code and MAPs co-regulate MTs in neurons, we are using C. elegans to examine the interactions between the Tau homolog PTL-1 and mutations in genes encoding tubulins and enzymes that regulate MT glutamylation.  A PTL-1::mNeongreen endogenous CRISPR knock-in localized strongly to axons, weakly to dendrites, and, surprisingly, most strongly to sensory cilia in CEP neurons.  Although loss of enzymes that regulate glutamylation, such as CCPP-1, CCPP-6, TTLL-4, and TTLL-11, did not have strong effects, we found that a deletion allele of the a-tubulin TBA-9 virtually abolished ciliary PTL-1 localization. Our results support the hypothesis that the Tubulin Code and MAPs interact with one another to regulate and specialize neuronal and ciliary MTs, and suggest that PTL-1 plays an as yet unknown role in CEP cilia.

Arbacia punctulata preference for algal turf over kelp in a degraded forest ecosystem

Presentater: Ken Ham | Advisor: Dr. Colette Feehan

Additional Authors: Sophia Kelly, Carla A. Narvaez, Sean P. Grace

Abstract: Marine heatwaves and rising mean sea temperatures are causing community shifts from habitat forming kelp forests to opportunistic algal turfs. Biological interactions within turf-dominated reefs, including herbivory, remain poorly described, but likely have important implications for the stability of the collapsing kelp ecosystem. Here, we present field and laboratory findings from southern New England, documenting grazing preferences by the Atlantic purple sea urchin (Arbacia punctulata) in a degrading kelp forest ecosystem. We find that naturally grazed areas of reef have significantly lower turf cover as compared to ungrazed areas, but that grazing has no effect on the cover of the increasingly rare and previously dominant sugar kelp (Saccharina latissima). Diet preference for turf over kelp was confirmed with three laboratory feeding assays, wherein A. punctulata were offered kelp and/or turf under conditions where food choice was provided (choice feeding assay), where no choice was provided (no-choice feeding assay), and where choice was provided in a group of urchins (group feeding assay). In combination, these results indicate that there is potential for ecosystem managers to integrate A. punctulata grazing behavior into kelp forest conservation and restoration strategy.

The role of ICER in melanoma: A survival study in zebrafish

Presentater: Melissa Spigelman | Advisor: Dr. Carlos Molina

Additional Authors: James Reilly, Melissa Pallen

Abstract: Skin cancer is already the most common form of cancer in the United States and as we continue to damage and deplete our ozone layer we should expect skin cancer rates to continue increasing. Dr. Molina’s laboratory is seeking to find treatments for melanoma, a particularly aggressive and severe form of skin cancer highly prone to mutation, by using the protein ICER (inducible cAMP early repressor). ICER has been shown to inhibit the rapid division of cancer cells by blocking the cells in the G1 and G2 phases of the cell cycle. Additionally, ICER has been found to be abnormally repressed in cancer cells but when ICER is restored in those cancer cells they go into remission. To study the effects of ICER in vivo we created a line of genetically modified zebrafish which are genetically predisposed to melanoma and also express high levels of ICER. The focus of our research is measuring how the expression of ICER affects the melanoma free survival of these zebrafish using a survival study.