Biology subjects

Brzezinski, K.

Publications and source records attributed to Brzezinski, K..

5 recordsLinked to original sources

bioRxiv2024

Morphological criteria for staging near-hatching embryos of the domesticated Mallard (Anas platyrhynchos) and Swan Goose (Anser cygnoides)

Studying waterfowl embryology necessitates reliable and precise staging tables. These are descriptions of embryonic features throughout development from fertilisation to hatching stage, which are used to approximate the extent of embryonic development. Waterfowl staging tables have previously been established based on morphological features from fertilisation to approximately ten days before hatching. Embryonic changes over the final ten days of pre-hatching development have also been documented and proposed as useful staging criteria. However, the reliability of these changes as useful staging criteria across different waterfowl breeds has not been fully examined. To examine the reliability of these criteria-- which focus on size changes of the bill and middle toes--for staging near-hatching embryos, we examined twenty-seven Mallard and Swan Geese embryos and measured their beak and toe-length sizes. We compared our results with previously published data, and found that size variation across breeds within the same developmental stage is equivalent to within-breed variation across different stages, suggesting limited reliability of beak and middle toe length sizes for staging waterfowl embryos. Consequently, we devised novel staging criteria for waterfowl based on four easily measurable morphological traits and show that these criteria allow correct stage identification with over 70% accuracy. Our results highlight the importance of quantifying accuracy for developing reliable embryonic staging tables.

developmental biology↗

bioRxiv2022

Mortality without springing a leak: Locust gut epithelia do not become more permeable to fluorescent dextran and bacteria in the cold

The insect gut, which plays a role in ion and water balance, has been shown to leak solutes in the cold. Cold stress can also activate insect immune systems, but it is unknown if the leak of the gut microbiome is a possible immune trigger in the cold. We developed a novel feeding protocol to load the gut of locusts (Locusta migratoria) with fluorescent bacteria before exposing them to -2{degrees}C for up to 48 h. No bacteria were recovered from the hemolymph of cold-exposed locusts, regardless of exposure duration. To examine this further, we used an ex vivo gut sac preparation to re-test cold-induced fluorescent FITC-dextran leak across the gut and found no increased rate of leak. These results question not only the validity of FITC-dextran as a marker of paracellular barrier permeability in the gut, but also to what extent the insect gut becomes leaky in the cold.

physiology↗

bioRxiv2022

Copy number variations shape the structural diversity of Arabidopsis metabolic gene clusters and are associated with the climatic gradient

Metabolic gene clusters (MGCs) encode at least three different enzymes for a common biosynthetic pathway. Comparative genome analyses highlighted the role of duplications, deletions and rearrangements in MGC formation. We hypothesized that these mechanisms also contribute to MGC intraspecies diversity and play a role in adaptation. We assessed copy number variations (CNVs) of four Arabidopsis thaliana MGCs in a population of 1,152 accessions, with experimental and bioinformatic approaches. The MGC diversity was lowest in marneral gene cluster (one private deletion CNV) and highest in the arabidiol/baruol gene cluster where 811 accessions had gene gains or losses, however, there were no presence/absence variations of the entire clusters. We found that the compact version of thalianol gene cluster was predominant in A. thaliana and more conserved than the noncontiguogus version. In arabidiol/baruol cluster we found a large insertion in 35% of analyzed accessions, that contained duplications of the reference genes CYP705A2 and BARS1. The BARS1 paralog, which we named BARS2, encoded a novel oxidosqualene synthase. Unexpectedly, in accessions with the insertion, the arabidiol/baruol gene cluster was expressed not only in roots but also in leaves. Additionally, they presented different root growth dynamics and were associated with warmer climates compared to the reference-like accessions. We also found that paired genes encoding terpene synthases and cytochrome P450 oxidases had higher copy number variability compared to non-paired ones. Our study highlights the importance of intraspecies variation and nonreference genomes for dissecting secondary metabolite biosynthesis pathways and understanding their role in adaptation and evolution.

genomics↗

bioRxiv2020

Hyperkalemia, not apoptosis, accurately predicts insect chilling injury

During prolonged or severe chilling, the majority of insects accrue chilling injuries that are typically quantified by scoring neuromuscular function after rewarming. In the cold, these chill susceptible insects, like the migratory locust (Locusta migratoria) suffer a loss of ion and water balance that is hypothesized to initiate cell death. Whether apoptotic or necrotic cell death pathways are responsible for this chilling injury is unclear. Here, we use a caspase-3 specific assay to indirectly quantify apoptosis in three locust tissues (muscle, nerves, and midgut) following prolonged chilling and recovery from an injury-inducing cold exposure. Furthermore, we obtain matching measurements of injury, hemolymph [K+], and muscle caspase-3 activity in individual locusts to gain further insight into mechanistic nature of chilling injury. We hypothesized that apoptotic cell death in both muscle and nerve tissue drives motor defects following cold exposure in insects, and that there would be a strong association between cold- induced injury, hyperkalemia, and muscle caspase-3 activity. We found a significant increase in muscle caspase-3 activity, but no such increase was observed in either nervous or gut tissue from the same animals, suggesting that chill injury primarily relates to apoptotic muscle cell death. However, the levels of chilling injury measured at the whole animal level prior to tissue sampling were strongly correlated with the degree of hemolymph hyperkalemia, but not apoptosis. These results support the notion that cold-induced ion balance disruption triggers cell death but also that apoptosis is not the main cell death pathway driving injury in the cold. Significance StatementTemperature has profound effects on animal fitness and sets limits to animal distribution. To understand and model insect responses to climate, we need to know how temperature sets limits to their survival. There is strong evidence that a collapse of ion and water balance occurs in insects in the cold, and it is generally held that the resulting cold injury is caused by activation of programmed cell death (apoptosis). Here, we directly test this idea and show for the first time that although the loss of ion balance is a strong predictor of individual survival outcomes, apoptosis is not the primary cause of cold-induced injury.

physiology↗

bioRxiv2019

Chilling induces unidirectional solute leak through the locust gut epithelia

Chill-susceptible insects, like the migratory locust, often die when exposed to low temperatures from an accumulation of tissue damage that is unrelated to freezing (chilling injuries). Chilling injury is consistently associated with ion imbalance across the gut epithelia. It has recently been suggested that this imbalance is at least partly caused by a cold-induced disruption of epithelial barrier function. Here, we aim to test this hypothesis in the migratory locust (L. migratoria). First, chill tolerance was quantified by exposing locusts to -2{degrees}C for various durations and monitored for chill coma recovery time and survival 24h post-cold exposure. Longer exposure times significantly increased recovery time and caused injury and death. Ion-selective microelectrodes were also used to determine the presence of cold-induced ion imbalance. We found a significant increase and decrease of hemolymph K+ and Na+ concentrations over time, respectively. Next, barrier failure along the gut was tested by monitoring the movement of an epithelial barrier marker (FITC-dextran) across the gut epithelia during exposure to -2{degrees}C. We found minimal marker movement across the epithelia in the serosal to mucosal direction, suggesting that locust gut barrier function remains generally conserved during chilling. However, when tested in the mucosal to serosal direction, we saw significant increases of FITC-dextran with chilling. This instead suggests that while cold-induced barrier disruption is present, it is likely unidirectional. It is important to note that these data reveal only the phenomenon itself. The location of this leak as well as the underlying mechanisms remain unclear and require further investigation.\n\nSummary statementIn this study, we provide the first evidence for the presence of cold-induced paracellular leak along the gut of the migratory locust, and that this leak is strongest in the mucosal to serosal direction.

physiology↗