Showing 191 - 200 of 274 Items
The EOL Enhancer Activates Eya Expression to Mediate Visual System Development in Drosophila melanogaster This record is embargoed.
- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Benjamin Sewell-Grossman
Access: Embargoed
A histological investigation of Arceuthobium pusillum infections in Picea rubens and Picea glauca
Date: 2024-01-01
Creator: Sade K. McClean
Access: Open access
- Arceuthobium pusillum is a hemiparasite that infects select Picea species. The hosts of A. pusillum do not experience the same symptoms of infection. A. pusillum infections are more fatal to P. marinara, and P. glauca. P. rubens, on the other hand, can survive longer with sustained infection. This presents itself as a contemporary issue because P. glauca, one of the parasite’s most vulnerable hosts, was untethered from ecological competition when old growth forests were subjected to large scale anthropogenic disturbances. These disturbances allowed P. glauca to proliferate, with A. pusillum following. A deeper understanding of the host-species specific responses to A. pusillum infection can broaden general knowledge of parasitic growth and development while also potentially inspiring conservation techniques. This study took advantage of the intrinsic differences between host and parasite to visualize infections in P. rubens and P. glauca, highlighting differences in infection outcome. By illuminating lignin and callose within cross sections of infected P. rubens and P. glauca branches, it was revealed that P. rubens forms dense bands of cells around the cortical strands of infection. These bands form more frequently in P. rubens than in P. glauca and are of a significantly larger area in P. rubens than in P. glauca (t(8), p=0.003, p=0.005). The discovery of the exterior bands is novel and exciting, as the bands are possibly made of callose and potentially facilitate P. rubens survival against A. pusillum infection. The foundational discoveries and results of this study should inspire, and warrant, further analysis.
Hybridization dynamics of a newly discovered parrotfish swarm in the Tropical Eastern Pacific
Date: 2017-05-01
Creator: Robert Barron
Access: Open access
- Hybrid zones and their dynamics are important in the understanding of the genetic basis of reproductive isolation and speciation. This study seeks to investigate the hybridization dynamics of a Scarus hybrid swarm within the Tropical Eastern Pacific (TEP) that includes four phenotypically distinct species: S. perrico, S. ghobban, S. rubroviolaceus, and S. compressus. Genetic and population structure analyses of four nuclear loci and a mitochondrial locus revealed that one of the four species, S. compressus, was the result of two different hybrid crosses: S. perrico ✕ S. rubroviolaceus and S. perrico ✕ S. ghobban. A NewHybrids model indicated that most of the S. compressus samples were F1 hybrids, but 21% of the S. compressus sample was classified as “parentals” which could also be explained by the presence of either F2 hybrids or backcrosses with S. compressus phenotypes, given the relatively low power of the nuclear data set (4 loci) to resolve complex hybrid genotypes. Significant mito-nuclear discordance in all three non-hybrid species is consistent with an evolutionary effect of backcrossing between F1 hybrids and “pure” species. This study reveals a relative ease of hybridization between parrotfish taxa separated by an estimated 4.5 million years of isolation and opens the door to further studies on the potential effects of gene flow across old species boundaries and perhaps the formation of new species by hybrid speciation in a diverse clade of tropical reef fish. Elucidating the nature of potentially “deep” F2 crosses and backcrosses within the TEP Scarus hybrid system will allow us to better understand the effects of hybridization on evolution and speciation on both a micro- and macro-ecological scale.
Some like it cold: the relationship between thermal tolerance and mitochondrial genotype in an invasive population of the European green crab, Carcinus maenas
Date: 2017-05-01
Creator: Aidan Fisher Coyle
Access: Open access
- Hybrid zones provide natural laboratories to study how specific genes, and interactions among genes, may influence fitness. On the east coast of North America, two separate populations of the European green crab (Carcinus maenas) have been introduced in the last two centuries. An early invasion from Southern Europe colonized New England around 1800, and was followed by a second invasion from Northern Europe to Nova Scotia in the early 1980s (Roman 2006). As these populations hybridize, new combinations of genes potentially adapted to different ends of a thermal spectrum are created in a hybrid zone. To test the hypothesis that mitochondrial and nuclear genes have effects on thermal tolerance, I measured response to cold stress in crabs collected from locations between southern Maine and northern Nova Scotia, and then genotyped the mitochondrial CO1 gene and two nuclear SNPs. Three mitochondrial haplotypes, originally from Northern Europe, had a strong effect on the ability of crabs to right themselves at a temperature of 4.5ºC. Crabs carrying these three haplotypes were 20% more likely to right compared to crabs carrying the haplotype from Southern Europe. The two nuclear SNPs, which were derived from transcriptome sequencing and were strong outliers between Northern and Southern European C. maenas populations, had no effect on righting response at low temperature. These results add C. maenas to the short list of ectotherms in which mitochondrial variation affects thermal tolerance, and suggests that natural selection is shaping the structure of the hybrid zone between the northern and southern populations This discovery of linkage between mitochondrial genotype and thermal tolerance also provides potential insight into the patterns of expansion for invasive populations of C. maenas around the world.
A Multi-Dimensional, Computational Analysis of Ultrasound-Induced Negative Phonotactic
Behavior in the Mediterranean Field Cricket Gryllus bimaculatus Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Ryan Minje Kang
Access: Access restricted to the Bowdoin Community
Associative color learning and foraging preferences of syrphid flies (Eristalis spp.) in an island plant-pollinator network Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Whitt Dodge
Access: Access restricted to the Bowdoin Community
Weather and Female Age Affect Reproductive Tradeoffs in Savannah Sparrow (Passerculus sandwichensis) Incubation Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Oscar Koziol Nigam
Access: Access restricted to the Bowdoin Community
Post-translational modification directs nuclear and hyphal tip localization of Candida albicans mRNA-binding protein Slr1
Date: 2017-05-01
Creator: Chaiyaboot Ariyachet, Christian Beißel, Xiang Li, Selena Lorrey, Olivia, Mackenzie, Patrick M. Martin, Katharine O'Brien, Tossapol Pholcharee, Sue Sim, Heike Krebber, Anne E. McBride
Access: Open access
- The morphological transition of the opportunistic fungal pathogen Candida albicans from budding to hyphal growth has been implicated in its ability to cause disease in animal models. Absence of SR-like RNA-binding protein Slr1 slows hyphal formation and decreases virulence in a systemic candidiasis model, suggesting a role for post-transcriptional regulation in these processes. SR (serine–arginine)-rich proteins influence multiple steps in mRNA metabolism and their localization and function are frequently controlled by modification. We now demonstrate that Slr1 binds to polyadenylated RNA and that its intracellular localization is modulated by phosphorylation and methylation. Wildtype Slr1-GFP is predominantly nuclear, but also co-fractionates with translating ribosomes. The non-phosphorylatable slr1-6SA-GFP protein, in which six serines in SR/RS clusters are substituted with alanines, primarily localizes to the cytoplasm in budding cells. Intriguingly, hyphal cells display a slr1-6SA-GFP focus at the tip near the Spitzenkörper, a vesicular structure involved in molecular trafficking to the tip. The presence of slr1-6SA-GFP hyphal tip foci is reduced in the absence of the mRNA-transport protein She3, suggesting that unphosphorylated Slr1 associates with mRNA–protein complexes transported to the tip. The impact of SLR1 deletion on hyphal formation and function thus may be partially due to a role in hyphal mRNA transport.
State of the Arg: Protein methylation at arginine comes of age
Date: 2001-07-13
Creator: Anne E. McBride, Pamela A. Silver
Access: Open access
Analysis of the yeast arginine methyltransferase Hmt1p/Rmt1p and its in vivo function. Cofactor binding and substrate interactions
Date: 2000-02-04
Creator: Anne E. McBride, Valerie H. Weiss, Heidi K. Kim, James M. Hogle, Pamela A., Silver
Access: Open access
- Many eukaryotic RNA-binding proteins are modified by methylation of arginine residues. The yeast Saccharomyces cerevisiae contains one major arginine methyltransferase, Hmt1p/Rmt1p, which is not essential for normal cell growth. However, cells missing HMT1 and also bearing mutations in the mRNA-binding proteins Np13p or Cbp80p can no longer survive, providing genetic backgrounds in which to study Hmt1p function. We now demonstrate that the catalytically active form of Hmt1p is required for its activity in vivo. Amino acid changes in the putative Hmt1p S-adenosyl-L-methionine-binding site were generated and shown to be unable to catalyze methylation of Np13p in vitro and in vivo or to restore growth to strains that require HMT1. In addition these mutations affect nucleocytoplasmic transport of Np13p. A cold- sensitive mutant of Hmt1p was generated and showed reduced methylation of Np13p, but not of other substrates, at 14 °C. These results define new aspects of Hmt1 and reveal the importance of its activity in vivo.