Czechia

Regulating the Organelle Band Organization in Male Meiosis of Arabidopsis
Yingrui Ma
Meiosis is a unique cell division process for sexual reproduction in plants and animals. In the meiotic cell cycle, a single round of DNA replication is followed by two rounds of chromosome division, called meiosis I and meiosis II. After Meiosis I, the divided homologous chromosomes are separated by the newly synthesized cell wall or a cell wall like structure. In dicotyledons, instead of a real cell wall, a band structure consisting of vesicles derived from different organelles, called an organelle band, is formed after the first chromosome division. The disruption of this structure in meiosis II can result in nuclear restitution and production of unreduced gametes. The mutation that leads to the disorder of the organelle band is named jason (jas). In this study, a suppressor of jas, called pel, was obtained through forward genetic screening. PEL is a vesicle membrane located protein, and located in the cytoplasm during meiotic cell cycle. The recovered organelle band in jas pel is sensitive to exocytotic vesicle trafficking inhibitors, suggesting that exocytotic vesicle trafficking pathway is important for organelle band maintenance in jas pel. Furthermore, destabilized actin filaments are found to partially recover the jas phenotype. vesicles can be transferred through actin filament, PEL and PEL interaction proteins transfer of exocytotic vesicles through actin filaments within male meiocytes. Taken together, this research suggests a process which involved exocytotic vesicle trafficking and actin dynamic to maintain the organelle band, acting as a physical barrier to prevent nuclear restitution during male meiosis.

SEB Conference 2024

Regulating the Organelle Band Organization in Male Meiosis of Arabidopsis

organelle band

vesicle trafficking

meiosis

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technical paper

Mineralised CaCO3 exoskeletons exist in over half of marine invertebrate taxa and are vital for structural support and defence. Calcification of these structures involves seawater uptake of calcium and dissolved inorganic carbon (DIC) and net excretion of generated protons. In crustacea, such as the intensively farmed whiteleg shrimp (Penaeus vannamei), calcification is intermittent due to rhythmic moulting and rehardening of the mineralised exoskeleton. This results in periodically rapid ion and acid-base fluxes, suggesting that exoskeleton growth is tightly coupled to seawater salinity and carbonate chemistry. However, the relationship between seawater ion availability and calcification in crustacea remains poorly characterised. In this study we reveal that mass-specific calcium and DIC uptake in post-moult P. vannamei is among the highest ever recorded in an adult animal and can be maintained in remarkably dilute seawater. Experiments exposing P. vannamei to a range of seawater chemistries, reveal that maximum flux rates of calcium and acid-base equivalents over the 0-2-hr post-moult period are particularly susceptible to adverse seawater chemistry. Substrate-limiting uptake rates can be compensated for over the following 20 hours, although net uptake ceases by 22 hours post-moult, regardless of water chemistry. Importantly, we found that decreased seawater calcium/DIC uptake impacts exoskeletal macrostructure (ratios of mineral, protein, and chitin), as well as calcium carbonate mineralogy. These findings suggest that although P. vannamei exhibits a strong ability to obtain sufficient calcium and DIC for calcification even in extremely dilute seawater, this involves trade-offs to the speed of post-moult mineralisation and exoskeleton composition and structural integrity.

Effects of seawater salinity, [Ca2+] and [DIC] on post-moult calcium and acid-base fluxes in whiteleg shrimp (Penaeus vannamei)

The interaction of widespread stressors such as nitrate pollution and increasing temperatures associated with climate change are likely to affect aquatic ectotherms such as amphibians. The metamorphic and physiological traits of amphibian larvae during the critical onset of metamorphosis are particularly susceptible to these stressors. We conducted a common-garden experiment using Rana temporaria larvae subjected to four constant acclimation temperatures (18, 22, 26, 28 °C) crossed with three environmentally relevant nitrate concentrations (0, 50, 100 mg × L-1) to investigate the interactive and individual effects of these stressors on metamorphic (i.e., growth and development) and physiological traits (i.e., metabolism and heat tolerance) at the onset of metamorphosis. Larvae exposed to elevated nitrate concentrations and thermal stress displayed increased metabolic rates but decreased developmental rate, highlighting interactive effects of these stressors. However, nitrate pollution alone had no effect on either metamorphic or physiological traits, suggesting that detoxification processes were sufficient to maintain homeostasis but not in combination with increased acclimation temperatures. Furthermore, larvae exposed to nitrate displayed diminished abilities to exhibit temperature-induced plasticity in metamorphosis timing and heat tolerance, as well as reduced acclimation capacity in metabolic rate and heat tolerance to higher temperatures. These results highlight the importance of considering the exposure to multiple stressors when investigating how natural populations respond to global change.

Navigating ontogenetic pathways: amphibian developmental plasticity in a changing world

The gut microbiome is an important mediator of life-history traits in animals and performs essential functions that may allow hosts to exploit novel niches. However, sources of variation in microbiome abundance and composition within vertebrate species are poorly understood, particularly in wild birds. Here, we used 16S rRNA gene sequencing to describe the faecal microbiome of a trans-Saharan migratory passerine species breeding in Central Spain, the pied flycatcher (Ficedula hypoleuca), focusing on small-scale differences in bacterial composition and relative abundance between the natural habitat of the species (oakwood) and a newly created habitat (pinewood) located 1 km apart. We detected a difference in the composition of microbiomes of birds between the habitats, with birds from the oakwood showing a higher abundance of several bacterial taxa, such as Actinobacteriota and Proteobacteria. We observed no microbiome differences according to individual characteristics such as sex or age, although nestlings and females showed a higher abundance of certain bacteria, especially those in the oakwood habitat. We investigated metabolic pathways associated with the microbiome and detected a higher abundance of bacteria with fatty acid biosynthesis and degradation pathways and metabolite precursor and energy generation pathways in oakwood birds compared to pinewood birds. In the pinewood birds, we found a significant increase in bacteria with the L-alanine biosynthesis and pentose phosphate pathways. Our study improves our understanding of the gut microbiome composition of insectivore passerines and shows that local-scale environmental factors such as habitat are among the most important modulators of avian gut microbiome composition.

Small-scale habitat determines gut microbiota of a migratory passerine on its breeding ground

Healthy microbiota is very important for its host although defining it can be challenging because the composition of the microbiota is very diverse and highly variable depending on, for example, environment, genetics, and host health status. Drastic changes in environment or lifestyle can lead to the imbalance of microbiota. This can be problematic as healthy microbiota have myriad positive functions, including protection of a host from invasion of pathogenic bacteria and modulation of the immune system. We studied the effects of environmental conditions (water temperature and oxygen concentration) on zebrafish skin microbiota. We found that genotype did not have an effect on skin microbiota composition and extreme changes in water temperature only had a relatively minor effect. We further demonstrated that zebrafish skin microbiota composition changed when water temperature and oxygen concentration were altered but these perturbations did not permanently shift skin microbiota composition. Finally, we compared gut microbiota composition of healthy horses and horses suffering from inflammatory bowel disease (IBD). We show that IBD did not cause a dysbiosis in the entire gut microbiota but only approximately 200 OTUs (less than 1% of all analyzed OTUs) showed a significant increase or decrease in response to IBD. However, a metabolomic analysis revealed that the functioning of microbiota differed between healthy and IBD-horses. Overall, our results show that while zebrafish skin and horse gut microbiota appear robust and resilient to perturbations. However, a closer look revealed that the abundance of certain pathogenic bacteria was increased and microbiota metabolic were functions altered.

The robustness and resilience of skin and gut microbiota

Organisms require resources for growth, reproduction, and survival. However, due to limited resources, organisms must trade off limited resources among competing processes. They sense and monitor the availability of nutrients using nutrient-sensing pathways, which can initiate physiological changes or modify gene expression. Previous studies have proposed that the mechanistic target of rapamycin (mTOR), a signalling pathway, plays a fundamental role in facilitating adaptive plasticity when individuals face limitations in their energy resources. Despite the fundamental importance of this process in evolutionary biology, how nutritional limitation is regulated through the expression of genes governing this pathway and its consequential effects on fitness remain understudied, particularly in birds. We employed dietary restriction to mimic resource depletion and investigated its impact on body mass, reproduction, and gene expression in Japanese quails (Coturnix japonica). Quails were exposed to feeding at 20%, 30%, and 40%, restriction levels or ad libitum for 2 weeks. All restricted groups had reduced body mass, although decreases in the number and egg mass were only found in severe restrictions.Additionally, restriction reduced the expression of mTOR and insulin-like growth factor-1 (IGF1) genes, whereas the ribosomal protein S6 kinase-1 (RPS6K1) and autophagy-related genes (ATG9A and ATG5) were increased. Proportionally higher reproductive investment was associated with individual variation in mTOR expression. Furthermore, we observed sex-specific responses to body mass and gene expression, indicating that sexes can cope with nutritional deficits differently and emphasise the importance of considering sexual differences in studies of dietary restriction.

Nutrient-sensing genes expression mediate resource allocation in Japanese quails

Inter-individual variability is the range of phenotypes produced between conspecifics within a population, and such variability is ubiquitously observed among animals. Investigating inter-individual variability can help develop a more comprehensive understanding of how phenotypes respond to environmental change. The Baja California chorus frog (Pseudacris hypochondriaca) is a thermally robust species found in a variety of ecosystems that differ in temperature and elevation throughout its latitudinal range (∼1400 km) from Santa Barbara County, California to Baja California, Mexico. We aimed to investigate how inter-individual variability in developmental traits changes within and between temperatures. Chorus frog eggs were incubated as eggs and tadpoles at 15°C or 22°C. Once tadpoles reached Gosner Stage 33 (hind limb toe differentiation), oxygen consumption rate (V̇O2), swimming speed, and morphology were measured. Average time to stage, wet mass, dry gut-free mass and body length all decreased at 22°C, while mass-specific V̇O2 and swimming speed increased. We observed decreased variability at 22°C compared to 15°C in time to reach stage, wet mass, dry gut-free mass and body length. In contrast, variability in mass-specific V̇O2 increased at 22°C and variability in swimming speed was unchanged between temperatures. Overall, the effect of temperature on inter-individual variability is trait-specific and should be explored further to understand the implications of temperature-induced plasticity.

Inter-individual variability in developmental traits in tadpoles of the Baja California chorus frog (Pseudacris hypochondriaca) in response to temperature

Mentoring programmes can improve the attainment and retention of minoritized students in higher education, but schemes vary widely in their design and delivery. Universities have been urged to measure the effect of such programmes and to identify their most effective features at a local level. PEMENTOS (PEer MEntoring TO Succeed) was designed as such. Mentors and mentees were asked to arrange a number of in-person, one-hour “core meetings”. Mentors attended a mid-point review meeting, and both mentors and mentees were invited to attend an end-of-programme meeting. Pre- and post-intervention surveys showed that the sampled mentees were statistically significantly more confident and less worried about university life at the end of the programme than they were to start with. The biggest increases in confidence were seen in response to the statements “I feel confident about managing my time” and “I feel confident about planning my revision”, and the biggest reductions in worry were seen in response to the statement “I feel worried about adapting to university life” and “I feel worried about how to meet people and make friends”. Non-white mentees reported a greater increase in confidence about socializing with their peers and about managing their finances than white mentees did. We found that mentees logged in to our VLE at almost twice the rate of non-participants, and the fraction of assessment submissions was higher for mentees than for mentors and non-participants. Class attendance was also higher for mentees than non-participants, painting an encouraging picture of enhanced engagement among PEMENTOS participants.

PEMENTOS: An EDI-Focused Peer-Mentoring Scheme

Nitrogen is one of the most limiting nutrients for plant growth and is required in large amounts due to its role as a building block for essential molecules such as nucleic acids, chlorophyll, and proteins. As such, nitrogen application in the form of synthetic fertilizers is required to significantly increase crop yield and sustain a growing world population. We recently described the buzz root hairless mutant in Brachypodium distachyon. RNAseq analysis found an upregulation of nitrate transporters, NRT1.1A, NRT1.1B, and CIPK23 in the buzz mutant. In addition, RNAscope revealed partial colocalization of BUZZ mRNA and NRT1.1A in root hair tips. BUZZ also appears to mediate both primary and lateral root growth in a nitrate-dependent manner. Since evidence showing a direct link between root hairs and nitrogen acquisition is lacking in grasses, identifying additional components involved in nitrate acquisition as well as root hair growth can assist in efforts to improve NUE in cereal crops. We evaluated primary nitrate-responsive genes in the buzz mutant and found upregulation of NRT1.1, NRT2.1, TGA4, and NR1 in low nitrate conditions. We further determined nitrate uptake and nitrate use efficiency in buzz versus wild-type plants with normal root hairs. We also report the identification of five proteins that interact with BUZZ and functionally characterize them. Taken together, these data provide the foundational evidence of a heretofore unidentified genetic network that underlies nitrate responses in grasses and that also challenges the importance of root hairs in the uptake of this essential nutrient.

BUZZed on Nitrate: The effect of a root hairless mutant on nitrate acquisition in the model grass Brachypodium distachyon

For most organisms, the correct functioning of the immune system is essential to deal with pathogens and parasites. However, immune activation does not come without a cost. Indeed, immune activation is expected to trade off different reproductive components, potentially leading to accelerated reproductive senescence and even affecting the life history trajectories of offspring. We have recently investigated these questions in male field crickets (G. bimaculatus) using a combination of experimental approaches. Results from these long-term studies indicate that immune system activation reduces male investment in some but not all reproductive components. Immune-challenged males reduced their investment in mate attraction (i.e. calling effort) and courtship behaviour over time but did not alter their sperm production. Curiously, although sperm production was unaffected, immune-challenged males prioritised their resources for sperm protection, resulting in reduced accumulation of sperm damage, including DNA, and increased fertility. In addition, we found strong evidence that such immune-induced changes in the male germ line integrity have both short- and long-term intergenerational effects. The young offspring of immune-challenged males developed higher levels of activity and exploratory behaviour (i.e. bolder personalities), behavioural changes that even persisted into adulthood and led to different ageing trajectories. Overall, our findings highlight how immune activation can accelerate the decline of some reproductive traits, but suggest that males may respond to such reproductive costs by prioritising germline protection, with long-term consequences for offspring life-history trajectories. Furthermore, our results highlight the complex interplay between immune function, reproductive senescence and offspring phenotypes, providing valuable insights into evolutionary dynamics.

Trade-offs in reproductive senescence in males: intra and intergenerational effects

Phenotypic plasticity, both within and between generations, allows organisms to respond to a changing world. Here, we aim to investigate how paternal phenotypes interact to shape offspring life-histories, focussing on two ubiquitous animal experiences: ageing and feeding. We present preliminary results from an ongoing experiment using Drosophila melanogaster: a full-factorial design, where fathers were fed one of two diets (control and higher-sucrose) and male and female offspring collected when fathers were young (one week) and old (five weeks). These offspring were then assigned to diets either matching or mismatching those of their fathers, and their survival and weekly reproductive output measured. We find complex interactions between paternal age, paternal diet, and offspring diet shape different aspects of offspring life-history, in a sex-specific manner. This investigation illuminates how organisms cope with environmental variation over their own lifespans and between generations, exploring the myriad forms of information parents transfer to their offspring, and the conditions under which this occurs.

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Effects of seawater salinity, [Ca2+] and [DIC] on post-moult calcium and acid-base fluxes in whiteleg shrimp (Penaeus vannamei)

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Next from SEB Conference 2024

Effects of seawater salinity, [Ca2+] and [DIC] on post-moult calcium and acid-base fluxes in whiteleg shrimp (Penaeus vannamei)

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Regulating the Organelle Band through Actin Dynamics in Male Meiosis of Arabidopsis

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