Wong, J. M. Y. | Search bioRxiv

bioRxiv2025

Feeding activity of soil oligochaetes under different soil moisture regimes assessed by the bait-lamina test.

The bait-lamina test is an easy and efficient method to quantify the feeding activity of soil invertebrates, commonly performed under field conditions to measure the impact of chemicals on soils. However, under natural conditions, feeding activity is also influenced by environmental factors such as soil moisture content. The extent of this influence on the results of the bait-lamina test is still poorly described and this can complicate their interpretation. In this study, we optimized the bait-lamina test under laboratory conditions, to assess the influence of soil moisture content on feeding activity of the earthworm Eisenia andrei and the enchytraeid Enchytraeus albidus, using LUFA 2.2 soil as a substrate. Feeding activity increased linearly with increasing soil moisture until a peak was reached, at a moisture content of 52 % of the maximum water holding capacity (WHC) for earthworms, and 68 % WHC for enchytraeids. Above the optimal moisture content, feeding activity was reduced and was less dependent on soil moisture. The increase in feeding activity up to the optimal moisture content was described by different slopes for the two species. Earthworms consumed the bait faster (on a per unit weight basis) than enchytraeids. Among the two species, the relationship established for E. albidus was the more similar to the response obtained in field conditions. Within the range of soil moistures considered by the model, our results demonstrate that feeding activity is positively correlated with soil moisture for two important soil invertebrates, but this increase, as well as the optimal soil moisture content, and the speed of bait consumption are species dependent. The model produced represents a first step for normalizing results from bait lamina tests in the field laying the foundation for future studies to validate its applicability across different soil types and field conditions. HighlightsThe optimal soil moisture leading to peak feeding activity was of 52 % and 68 % WHC for E. andrei and E. albidus respectively. Earthworms consumed the baits more than three times faster than enchytraeids. The influence of soil moisture on feeding activity up to the peak can be described by a linear model the slope of which depends on the species tested. The model obtained for E. albidus best represented the field situation.

ecology↗

bioRxiv2017

Transient telomerase inhibition alters cell cycle kinetics

Telomerase is the ribonucleoprotein reverse transcriptase that catalyzes the synthesis of telomeres at the ends of linear human chromosomes and contributes to proper telomere-loop (T-loop) formation. Formation of the T-loop, an obligate step before cell division can proceed, requires the generation of a 3-overhang on the G-rich strand of telomeric DNA via telomerase or C-strand specific nucleases. Here, we discover telomerase activity is critical for efficient cell cycle progression using transient chemical inhibition by the telomerase inhibitor imetelstat. Telomerase inhibition caused changes in cell cycle kinetics and increased the proportion of cells in G2 phase, suggesting delayed clearance through this checkpoint. Investigating the possible contribution of unstructured telomere ends to these cell cycle distribution changes, we observed that imetelstat treatment induced {gamma}H2AX DNA damage foci in a subset of telomerase-positive cells but not telomerase-negative primary human fibroblasts. Chromatin-immunoprecipitation with {gamma}H2AX antibodies demonstrated imetelstat treatment-dependent enrichment of this DNA damage marker at telomeres. Notably, the effects of telomerase inhibition on cell cycle profile alterations were abrogated by pharmacological inhibition of the DNA-damage-repair transducer ATM.\n\nAdditionally, imetelstat potentiation of etoposide, a DNA-damaging drug that acts preferentially during S/G2 phases of the cell cycle, also depended on functional ATM signaling. Our results suggest that telomerase inhibition delays the removal of ATM-dependent DNA damage signals from telomeres in telomerase-positive cancer cells. This demonstrates for the first time that telomerase activity directly facilitates the progression of the cell cycle through modulation of transient telomere dysfunction signals.

cancer biology↗