Environmental and genetic regulation of mouth-form plasticity in ​Pristionchus pacificus

Phänotypische Plastizität beschreibt die Fähigkeit von Organismen, von identischem Genotyp, unterschiedliche Phänotypen als Reaktion auf Einflüsse der Umwelt zu entwickeln. Obgleich dieses Phänomen weit verbreitet ist, verbleiben die evolutionären Konsequenzen phänotypischer Veränderungen, ohne zugrunde liegender genetischer Veränderungen, ungeklärt. Eine Vielzahl von Ideen wurde unterbreitet, um die potentielle Relevanz phänotypischer Plastizität für die Evolution aufzuzeigen, jedoch bedarf die Formulierung expliziter und falsifizierbarer Hypothesen eines besseren mechanistischen Verständnisses der plastischen Entwicklung. Ein ideales Modellsystem für Studien zur phänotypischen Plastizität muss experimentelle genetische Untersuchungen erlauben, sowie Zugang zu Taxa gewährleisten, in welchen einer der alternativen Phänotypen fixiert wurde. Der Mundform-Polyphänismus der Nematoden aus der Familie der Diplogastridae erfüllt beide zuvor angeführten Kriterien. Genetisch uniforme Laborpopulationen von Pristionchus pacificus sind in der Lage zwei alternative Phänotypen, basierend auf unterschiedlichen Haltungsbedingungen, zu entwickeln. Die eurystomate (Eu) Morphe ist ein fakultativer Prädator mit weiter Mundhöhle und zwei hakenförmigen Zähnen. Bei der stenostomaten (St) Morphe hingegen, handelt es sich um einen nicht-aggressiven Mikrobivoren mit röhrenförmigem Mund und nur einem Zahn. Bisherige Studien demonstrierten eine zentrale Rolle von Pheromonen und identifizierten die Sulfatase EUD-1, die Sulfotransferase SULT-1 und den nukleären Hormonrezeptor NHR-40 als Regulatoren in der Mundformentscheidung von P. pacificus. Ziel meiner Dissertation ist es, weitere Umweltfaktoren und genetische Komponenten aufzuzeigen, welche diese Phänotypen kontrollieren. Ich entdeckte den Einfluss der Nahrungszusammensetzung und trug dazu bei, den Effekt einer Reihe von festen und flüssigen Nährmedien auf das Zahlenverhältnis der Morphen in einer Population zu identifizieren. Auf der Seite der Genetik fand ich heraus, dass eud-1 Teil eines chromosomalen Clusters von funktionell verwandten Genen ist, welcher an Supergene erinnert. Außerdem isolierte ich einen weiteren Transkriptionsfaktor, NHR-1, und identifizierte eine Reihe von gemeinsamen transkriptionalen Zielgenen von NHR-40 und NHR-1, welche möglicherweise direkt an der Produktion der alternativen Phänotypen beteiligt sind. Weiterhin beschrieb ich die Rolle von Heat Shock Proteinen in der Kanalisierung der Entwicklung alternativer Strukturen. Außerdem beteiligte ich mich an Studien, die eine genomweite Beschreibung der Chromatinzustände in P. pacificus bereitstellen und Histon-Acetylierung während der Ausprägung der Eu Morphe implizieren.Phenotypic plasticity is the ability of organisms with the same genetic complements to develop different phenotypes in response to environmental influences. This phenomenon is extremely widespread, but evolutionary consequences of phenotypic change in the absence of genetic change are currently unclear. Numerous ideas have been developed to explain the potential significance of phenotypic plasticity for evolution, but the formulation of explicit falsifiable hypotheses requires better mechanistic insight into plastic development. An ideal study system to investigate phenotypic plasticity must combine amenability to experimental genetic research and accessibility of lineages in which one of the alternative phenotypes has been fixed. Plasticity in feeding structures of diplogastrid nematodes satisfies both of these criteria. Isogenic lab populations of the species Pristionchus pacificus can develop two discrete alternative phenotypes depending on the rearing conditions. The eurystomatous (Eu) morph has a wide mouth with two hooked teeth and is a facultative predator. The stenostomatous (St) morph has a tube-like mouth with only one tooth and is a non-aggressive microbial grazer. Previous research uncovered the role of pheromones and identified the sulftase EUD-1, the sulfotransferase SULT-1 and the nuclear hormone receptor NHR-40 as regulators of mouth form decision in P. pacificus. In my thesis work, I aimed to reveal further environmental factors and genetic players controlling the phenotype. I discovered the effect of food composition and helped identify the effect of a range of solid and liquid media on the ratio between morphs in the population. On the genetic side, I found that eud-1 is part of a chromosomal cluster of functionally related genes, reminiscent of supergenes. Further, I isolated another transcription factor regulating morph decision, NHR-1, and identified a set of common transcriptional targets between NHR-40 and NHR-1, which may be the genes directly involved in making the alternative phenotypes. In addition, I elucidated the role of heat shock proteins in canalizing the development of discrete alternative morphologies. Finally, I participated in studies that provide a genome-wide description of chromatin states in P. pacificus and implicate histone acetylation in specifying the Eu morph

XVI Agricultural Science Congress 2023: Transformation of Agri-Food Systems for Achieving Sustainable Development Goals

The XVI Agricultural Science Congress being jointly organized by the National Academy of Agricultural Sciences (NAAS) and the Indian Council of Agricultural Research (ICAR) during 10-13 October 2023, at hotel Le Meridien, Kochi, is a mega event echoing the theme “Transformation of Agri-Food Systems for achieving Sustainable Development Goals”. ICAR-Central Marine Fisheries Research Institute takes great pride in hosting the XVI ASC, which will be the perfect point of convergence of academicians, researchers, students, farmers, fishers, traders, entrepreneurs, and other stakeholders involved in agri-production systems that ensure food and nutritional security for a burgeoning population. With impeding challenges like growing urbanization, increasing unemployment, growing population, increasing food demands, degradation of natural resources through human interference, climate change impacts and natural calamities, the challenges ahead for India to achieve the Sustainable Development Goals (SDGs) set out by the United Nations are many. The XVI ASC will provide an interface for dissemination of useful information across all sectors of stakeholders invested in developing India’s agri-food systems, not only to meet the SDGs, but also to ensure a stable structure on par with agri-food systems around the world. It is an honour to present this Book of Abstracts which is a compilation of a total of 668 abstracts that convey the results of R&D programs being done in India. The abstracts have been categorized under 10 major Themes – 1. Ensuring Food & Nutritional Security: Production, Consumption and Value addition; 2. Climate Action for Sustainable Agri-Food Systems; 3. Frontier Science and emerging Genetic Technologies: Genome, Breeding, Gene Editing; 4. Livestock-based Transformation of Food Systems; 5. Horticulture-based Transformation of Food Systems; 6. Aquaculture & Fisheries-based Transformation of Food Systems; 7. Nature-based Solutions for Sustainable AgriFood Systems; 8. Next Generation Technologies: Digital Agriculture, Precision Farming and AI-based Systems; 9. Policies and Institutions for Transforming Agri-Food Systems; 10. International Partnership for Research, Education and Development. This Book of Abstracts sets the stage for the mega event itself, which will see a flow of knowledge emanating from a zeal to transform and push India’s Agri-Food Systems to perform par excellence and achieve not only the SDGs of the UN but also to rise as a world leader in the sector. I thank and congratulate all the participants who have submitted abstracts for this mega event, and I also applaud the team that has strived hard to publish this Book of Abstracts ahead of the event. I wish all the delegates and participants a very vibrant and memorable time at the XVI ASC

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