Biology subjects

Atherton, K. F.

Publications and source records attributed to Atherton, K. F..

3 recordsLinked to original sources

bioRxiv2023

Symbiosis modulates gene expression of symbionts, but not hosts, under thermal challenge

Increasing ocean temperatures are causing dysbiosis between coral hosts and their symbionts. Previous work suggests that coral host gene expression responds more strongly to environmental stress compared to their intracellular symbionts; however, the causes and consequences of this phenomenon remain untested. We hypothesized that symbionts are less responsive because hosts modulate symbiont environments to buffer stress. To test this hypothesis, we leveraged the facultative symbiosis between the scleractinian coral Oculina arbuscula and its symbiont Breviolum psygmophilum to characterize gene expression responses of both symbiotic partners in and ex hospite under thermal challenges. To characterize host and in hospite symbiont responses, symbiotic and aposymbiotic O. arbuscula were exposed to three treatments: 1) control (18{degrees}C), 2) heat (32{degrees}C), and 3) cold (6{degrees}C). This experiment was replicated with B. psygmophilum cultured from O. arbuscula to characterize ex hospite symbiont responses. Both thermal challenges elicited classic environmental stress responses (ESRs) in O. arbuscula regardless of symbiotic state, with hosts responding more strongly to cold challenge. Hosts also exhibited stronger responses than in hospite symbionts. In and ex hospite B. psygmophilum both downregulated genes associated with photosynthesis under thermal challenge; however, ex hospite symbionts exhibited greater gene expression plasticity and differential expression of genes associated with ESRs. Taken together, these findings suggest that O. arbuscula hosts may buffer environments of B. psygmophilum symbionts; however, we outline the future work needed to confirm this hypothesis.

molecular biology↗

bioRxiv2023

Photosymbiosis reduces the environmental stress response under a heat challenge in a facultatively symbiotic coral

The symbiosis between corals of the order Scleractinia and dinoflagellates of the family Symbiodiniaceae is sensitive to environmental stress. The oxidative bleaching hypothesis posits that extreme temperatures lead to accumulation of photobiont-derived reactive oxygen species ROS, which exacerbates the coral environmental stress response (ESR). To understand how photosymbiosis modulates coral ESRs, these responses must be explored in hosts in and out of symbiosis. We leveraged the facultatively symbiotic coral Astrangia poculata, which offers an opportunity to uncouple the ESR across its two symbiotic states (symbiotic, aposymbiotic). Colonies of both symbiotic states were exposed to three temperature treatments for 15 days: i) control (static 18{degrees}C), ii) heat challenge (increasing from 18 to 32{degrees}C), and iii) cold challenge (decreasing from 18 to 6{degrees}C) after which host gene expression was profiled. Cold challenged corals elicited widespread differential expression, however, there were no differences between symbiotic states. In contrast, symbiotic colonies exhibited greater gene expression plasticity under heat challenge, including enrichment of cell cycle pathways involved in controlling photobiont growth. Counter to the oxidative bleaching hypothesis, this plasticity did not include signatures of stress, and rather a dampened ESR under heat challenge was observed, suggesting that photobionts reduce the hosts ESR under elevated temperatures in A. poculata.

ecology↗

bioRxiv2023

Urbanization and fragmentation interact to drive mutualism breakdown and the rise of unstable pathogenic communities in forest soil

Temperate forests are particularly threatened by urbanization and fragmentation, with over 20% (120lJ000 km2) of recently urbanized land in the U.S. subsuming natural forests. We leveraged a unique, well-characterized urban-to-rural and forest edge-to-interior gradient to identify the combined impact of these two land use changes - urbanization and forest fragmentation - on soil microbial community in native, remnant forests. We found evidence of mutualism breakdown between trees and their fungal root mutualists (ectomycorrhizal (ECM) fungi) with urbanization, where ECM fungi colonized fewer tree roots and had less connectivity in soil microbiome networks in urban forests compared to rural forests. However, urbanization did not reduce the relative abundance of ECM fungi in forest soils; instead, forest fragmentation alone led to strong reductions in ECM fungal abundance. At forest edges, ECM fungi were replaced by plant and animal pathogens, as well as copiotrophic, xenobiotics-degrading, and nitrogen-cycling bacteria, including nitrifiers and denitrifiers. Urbanization and fragmentation interacted to generate "suites" of microbes, with urban interior forests harboring highly homogenized microbiomes, while edge forests microbiomes were more heterogeneous and less stable, showing increased vulnerability to low soil moisture. When scaled to the regional level, we found that forest soils are projected to harbor high abundances of fungal pathogens and denitrifying bacteria, even in rural areas, due to extreme, widespread forest fragmentation. Our results highlight the potential for soil microbiome dysfunction - including increased greenhouse gas production - in temperate forest regions that are subsumed by urban expansion, both now and in the future. Significance StatementUrbanization and forest fragmentation are increasingly altering Earths ecosystems, yet the effects on soil microbiomes, crucial for plant health and climate regulation, remain unclear. Our data indicate that, in forested land, these two combined, compounding stressors reshape the soil microbiome in ways that could lead to more pathogen infections of plants and animals, higher rates of N loss due to denitrification, and the possibility of tree symbiont extinctions. By identifying the specific environmental stressors that lead to these microbiome shifts, our analysis can be used to inform urban development and forest management plans to mitigate impacts on the soil microbiome to sustain environmental quality and the ecosystem services that remnant native forests provide to society in the coming decades. ClassificationBiological Sciences/Ecology

ecology↗