Project Summary/Abstract Nutrition in fetal and juvenile stages can have long-lasting consequences throughout the life of an organism. In humans, poor nutrition in utero has been linked to type-II diabetes and cardiovascular disease despite otherwise healthy diets later in life. In nature, animals can use the information from early diet to make environment-appropriate developmental decisions that increase fitness of the adult. The mechanisms that connect early-life diet and nutrition to developmental decisions and disease is poorly understood. Identifying these mechanisms could 1) inform risk prevention strategies, 2) enable targeted therapy to increase or decrease the positive or negative effects of diet, and 3) address a fundamental gap in our understanding of development: how does the environment influence phenotype? To identify the mechanisms of dietary influence – a form of developmental plasticity – the Werner lab uses the experimentally tractable model nematode Pristionchus pacificus. When juvenile P. pacificus are reared in dietary restrictive conditions they develop a narrow mouth with a single denticle or “tooth”, and are obligate bacterivores. However, if juveniles are reared in well-fed conditions that often lead to crowding, they develop a wide mouth with two teeth, and can prey on other nematodes for food or competitive advantage. The discrete developmental decision (bacterivore vs. predator) in a genetic model organism provides a powerful system to investigate the molecular mechanisms of developmental plasticity. Since receiving funding from the ESI-MIRA in the summer of 2023, the Werner Lab has used both targeted mutagenesis and unbiased forward-genetic screens to identify genes which sense the nutritional and/or metabolic state and affect morph choice. From previous work PI-Werner also identified epigenetic modifications that affect both the developmental decision and the timing of the decision. This Administrative Supplement request is for a Zeiss Axioscope 7 microscope capable of fluorescence and differential interference contrast (DIC) (price quote = $52,316). This microscope can be used to reveal the tissue-specific expression patterns of diet-sensing genes by fusing them to fluorescent reporters (e.g., GFP/RFP). Additionally, a series of DIC images at multiple focal planes (a ‘z-stack’) can be used for Geometric Morphometrics, which has become an important tool for statistically assessing differences in morphological shape. These features are not compatible with the microscope currently in the Werner Lab. However, if funded, fluorescence and DIC on the Axioscope 7 can reveal when, where and how diet- sensing genes influence “switch” gene transcription – and ultimately development.