Czechia

Laminarin, one of the main storage polysaccharides of brown algae and diatoms, was recently found to be an important molecule in the world’s oceans by accounting for up to 26 ± 17 % of the particulate organic carbon. While digestive enzymes breaking down laminarin (laminarinases) have been intensely studied in a number of adult marine invertebrates, data on larval stages remain scarce. Abundantly inhabiting kelp forests as ecosystem engineers, especially sea urchins are found in laminarin-rich areas, suggesting that laminarin digestion plays a significant role throughout their life cycle. Considering the high laminarin abundance in microalgae, i.e. the food source of echinoderm larvae, digestive degradation might be beneficial, if not crucial, not only in adult sea urchins but also for larval performance within plankton. 
To disentangle the ecological and physiological role of laminarin for sea urchin larvae we conducted perturbation experiments with different laminarin concentrations and food sources (laminarin-rich and -poor microalgae) to evaluate the impact onto larval nutrition and performance. We analyzed (I) growth, survival and settlement success, as well as (II) laminarinase activity and expression patterns during larval development of the painted sea urchin Lytechinus pictus in response to the feeding regimes. 
The results contribute to a better understanding of laminarin dependent digestive dynamics in the early life stages of echinoderms, potentially affecting the recruitment of these important ecosystem engineers. 


SEB Conference Prague 2024

Sea urchin larval digestion - the role of laminarin for larval fitness

larval morphology

lytechinus pictus

carbohydrate digestion

technical paper

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Male crickets attract females by producing calls with their forewings. Louder calls travel further and are more effective at attracting mates. However, crickets are much smaller than the wavelength of their call, and this limits their power output. A small group called tree crickets make acoustic tools called baffles which reduce acoustic short-circuiting, a source of dipole inefficiency. Here, we ask why baffling is uncommon among crickets. We hypothesize that baffling may be rare, because like other tools they offer insufficient advantage for most species. To test this, we modelled the calling efficiencies of crickets within the full space of possible natural wing sizes and call frequencies, in multiple acoustic environments. We then generated efficiency landscapes, within which we plotted 112 cricket species across 7 phylogenetic clades. We found that all sampled crickets, in all conditions, could gain efficiency from tool use. Surprisingly, we also found that calling from the ground significantly increased efficiency, with or without a baffle, by as much as an order of magnitude. We found that the ground provides some reduction of acoustic short-circuiting but also halves the air volume within which sound is radiated. It simultaneously reflects sound upwards, allowing recapture of a significant amount of acoustic energy through constructive interference. Thus, using the ground as a reflective baffle is an effective strategy for increasing calling efficiency. Indeed, theory suggests that this increase in efficiency is accessible not just to crickets, but to all acoustically communicating animals whether they are dipole or monopole sound sources.

The Ground is Good: A Numerical Approach to Understanding Acoustic Tool Use in Crickets

Environmental variability is common in most aquatic environments, yet it has been largely stabilized in laboratory experimental physiology aimed at understanding physiological responses to environmental challenges. Climate change is expected to increase climate variability and exacerbate environmental extremes, yet we know less about the impacts of this variability on fish physiology. This information will be crucial in gauging species' vulnerability to climate change. Incorporating variability into experimental designs is challenging and leads to difficulties in interpreting data within experiments and across multiple experiments where the experimental designs can be different. In this presentation I will discuss how we have been incorporating variability into our experiments to closely match natural environments, the lessons we have learned with respect to sampling times/durations in thermally variable experiments, and the types of physiological data that we collect that can be applied to real-world scenarios. I will use examples from our published research on the physiology of wild Atlantic salmon from thermally distinct rivers in Atlantic Canada and discuss a new and on-going experimental design in our lab that focuses on incorporating both daily and seasonal environmental variability into physiological experiments in salmonids from eggs to adults.

The ups and downs of incorporating environmentally relevant variability in laboratory experiments

Human activities represent one of the most dramatic forms of environmental change, affecting global biodiversity. Anthropogenic noise has increased in the last century with detrimental effects for wildlife on both individual and population levels. Sound pollution can compromise animal heath by imposing chronic stress and damaging the auditory system, affect intra- and inter specific relationships by disrupting communication and masking the presence of predators.
Shrews produce high-pitched laryngeal calls (“twittering calls”), with unclear function. It has been suggested as rudimentary echo-orientation mechanism, communication, or response to stressful stimuli. In this study, we analysed greater white-toothed shrews (Crocidura russula), trapped along a gradient of anthropogenic noise with the goal to link twittering calls to exposure to environmental stressors, through the analysis of faecal glucocorticoid levels. We hypothesize that animals inhabiting noisier locations would experience higher levels of stress, produce more twittering calls, and reduce exploratory behaviour to balance stress demands.
We live trapped 25 shrews in 6 locations with different sound patterns and maintained them in captivity for 5 consecutive days, for repeated measurement of twittering calls, exploratory behaviour, and stress levels.
Results show that variation in noise levels influences the shrews’ stress response, independently of the average noise levels. Neither average noise levels nor its variation induced a change of vocalisations. While time in captivity resulted in a reduction of exploratory behaviour and twittering calls, we did not find evidence supporting a link between stress levels and twittering calls.


Noisy places, noisy animals? - Shrew responses to sound pollution

Many fastidious (or unculturable) pathogens, such as the Candidatus Liberibacter spp. associated with citrus greening (HLB) disease pose an immense threat to crop production and cause billions of dollars in losses worldwide. Unlike studies of model plant-pathogen systems, studies of fastidious crop pathogens are greatly hindered due to the unculturable, obligate lifestyle of the pathogens and the relative recalcitrance of the host crops to conventional genetic and laboratory evaluation approaches. To overcome these bottlenecks, we developed an innovative plant hairy root-based efficacy testing system suitable for faster pre-screening of diverse resistance and susceptibility genes and small molecule-based antimicrobials. Using this approach, we identified multiple novel genes, antimicrobial peptides, and chemicals that showed efficacy against Candidatus Liberibacter spp. Ongoing field trials with selected candidates are promising, with improved crop yield and health. One or more of these solutions could be further deployed as products for crop disease management.

Novel strategies to screen and evaluate genetic- and chemical-based solutions for crop improvement

Plant Class I formins represent a unique family of cytoskeletal organizers that are at the same time integral membrane proteins. We have previously reported that the GFP fusion of the Arabidopsis formin AtFH1, which is considered to be the main housekeeping Class I formin expressed in majority of tissues according to the available gene expression data, also transiently localised to the tonoplast in the root transition zone at or around the time of major membrane rearrangements that generate the large central vacuole typical for differentiated plant cells (Oulehlová et al., 2019 – https://doi.org/10.1093/pcp/pcz102). It is currently unknown whether AtFH1 has an active role in tonoplast rearrangements or whether it transiently passes through the tonoplast while being sorted for vacuolar degradation. A newly prepared fusion of AtFH1 with a different, pH-insensitive fluorescent protein, as well as pharmacological treatment with concanamycin A, showed, in addition to known AtFH1-GFP localisation, also presence of AtFH1 within vacuolar lumen in the root elongation zone and mature tissues, supporting the degradation hypothesis. However, we also found quantitative, sometimes significant changes in vacuolar organization in mutants lacking AtFH1, using both established vacuolar morphology metrics and a newly developed method for quantitative evaluation of tonoplast topology, supporting a tonoplast-associated function of AtFH1. Therefore, depending on the exact developmental stage and conditions, both of the hypotheses may be correct.

The role of Arabidopsis Class I formin AtFH1 during vacuolar development – to use or to degrade?

Transposable Elements (TEs) are the major force in genome plasticity and gene evolution, with LTR retrotransposons (LTR-TEs) constituting the most abundant class. LTR-TEs are considered autonomous when they contain the coding sequence for the translation of all factors required for their replication and transposition, and nonautonomous if they require that such factors are provided in trans. While several autonomous LTR-TEs has been found mobile in Arabidopsis thaliana epigenetic mutants or epigenetic recombinant inbreed lines (epiRILs), non-autonomous LTR-TEs ha never observed mobile in real time experiments. In this study, we observe that the LTR_gypsy transposon ATGP2N mobilises in epiRILs and transpose with high specificity into ribosomal repeats. Notably, an identical homologous region is present in the LTRs of ATGP2N and the autonomous LTR-TE, suggesting that ATGP2N hijacks ATGP2 factors for its transposition. Our studies shed light on the transpositional dynamics of nonautonomous LTR elements and contribute to expanding our knowledge of LTR transposition mechanisms.

Mobilisation of a nonautonomous LTR-retrotransposon in Arabidopsis thaliana.

Transcription factors (TF) play a pivotal role in gene regulation; however, their biophysical properties remain poorly understood. Conventional techniques have provided relatively static perspectives of their action, limiting our understanding of their rapid (millisecond scale) dynamical behavior in cellula. Fortunately, over the past decade, novel microscopy techniques have emerged, enabling us to transcend the limitations of resolution and gain a comprehensive, nanoscale view of their in vivo biodynamics directly within the nucleus. To unravel and enhance the intranuclear diffusion of transcription factors, we have integrated molecular and microscopic approaches, facilitating a dynamic representation of their activity.

Investigation of transcription factor dynamics by super-resolution microscopy

In most plants, the proportion of transcribed DNA is a small portion of the genome, and this is particularly evident for species with large genomes, e.g. hexaploid wheat (Triticum aestivum), where the 85% of the genome is composed of non-expressed repetitive DNA elements, and only about 60% of the annotated genes are expressed. Indeed, it is known that the expression of large portions of plant genomes are blocked by transcriptional gene silencing (TGS) mechanisms, controlled by epigenetic marks such as DNA methylation. In the model plant Arabidopsis thaliana, the genome wide suppression of TGS activates the expression of silenced genes and mobilises repetitive elements, generating epigenetic and genetic variation and producing new phenotypes. However, attempts to exploit this variation in crop species has been so far largely unsuccessful, mostly due to the different and more complex epigenetic regulation of larger, and often polyploid, crop genomes. Therefore, we are developing a tool to directly screen in planta for conditions able to increase epigenetic variability via the suppression of TGS. For this purpose, wheat cv. ‘Fielder’ was transformed with a reporter GUS cassette containing DNA repeats, to attract DNA methylation and establish TGS on the transgenic locus. To prove that TGS was effectively silencing the reporter gene, we exposed transgenic seedlings to Zebularine, a cytidine analog that inhibits DNA methyltransferases and suppresses TGS, resulting in an increase in GUS expression. Ongoing and future work includes the use of this reporter line to test conditions, or breeding combinations, able to affect TGS in wheat, which can generate epigenetic and genetic variation. The exploitation of such diversity in breeding programs will potentially contribute to the improvement of wheat productivity and food sustainability.

Exploitation of silenced genes for wheat breeding

Out of the tens of thousands of edible species, only 2500 species of plants underwent any human selection, and only 250 species are currently considered domesticated. Before agriculture began in the Neolithic, humans in the Fertile Crescent exploited a large diversity of plants, collecting and cultivating them, but many were abandoned. 

While the occurrence of domestication and the development of agriculture are considered a pivotal point in human history, one significant question remains. What made certain wild plants more likely to be successfully domesticated? A potential answer to this question lies in mutation rate. Domestication relies on novel phenotypes, therefore if novel phenotypes arise more quickly in some species than others, humans may favour these species, continuing to grow them, and abandoning others.

Using transcriptomic data, the rate of mutation has been estimated for crop progenitors (those that were domesticated) and never-domesticated close relatives, which could, in theory, have been domesticated. In addition, a dN/dS analysis has been carried out to investigate selection across these species. We focused on two main groups of edible plants – legumes and cereals from the Fertile Crescent – including some which were likely managed during the Neolithic and then abandoned as a crop. 

Taking this alongside other factors that could have influenced the ‘domesticability’ of some species over others, our work opens a discussion about whether certain species are predisposed to succeed under certain conditions. It therefore has implications for using neo-domestication to ensure food security and for biodiversity response in a changing climate. 


Domesticate this, not that: the implications of mutation rate and selection on present-day agriculture

P7.16 
PlantAct: plant-soil solutions for climate challenges

Catherine A. Walsh1 , Heribert Hirt2

1Lancaster University, UK, 2King Abdullah University of Sciences and Technology, Saudi Arabia

Anthropogenic greenhouse gas (GHG) emissions have meant devastating impacts for our planet with associated climate change effects reaching crisis point. The recent surpassing of a 1.5C rise in global average temperature above pre-industrial levels as set by the 2015 Paris agreement, means an urgent need for action to prevent further temperature rises causing irreversible outcomes. Currently, agriculture contributes 25% of total GHG emissions, which suggests a conversion to more sustainable practices would significantly reduce GHG outputs. Despite driving climate change, global agriculture also suffers, with increasing frequencies of drought and flooding alongside soil degradation challenging food security. PlantAct is an international, interdisciplinary think tank tackling the problem, through applying plant and soil science solutions to address the intense difficulties facing agricultural production. Furthermore, PlantAct aims to connect with a range of disciplines to deliver resilient solutions to address nitrogen use efficiency, carbon sequestration and promote plant health whilst maintaining food security. A novel, holistic approach to our food system will not only relay environmental benefits but also foster a change in attitude towards more plant based diets to improve health and well-being. In doing so, PlantAct seeks to engage students, young scientists, and the next generation to help bring around the urgent overhaul required to reduce GHG emissions within the food system while providing carbon storage solutions to support the health of our planet into the future. 


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