{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/147425"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/147425","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Genetic Analysis of Bacterial Food Perception and its Influence on Foraging Behavior in C. elegans","abstract":"The ability to adapt to changes in food conditions is critical for organismal homeostasis and survival. In this thesis, I explore the genetic and neuroendocrine mechanisms by which C. elegans evaluates bacterial food conditions and accordingly alters development and behavior. In Chapter One, I discuss the relationship between C. elegans and its bacterial diet. The influence of food on behavior suggests the presence of a gut-“brain” axis that senses and communicates information about nutritional state to the nervous system to elicit a behavioral response. In Chapter Two, I characterize a gain-of-function allele of scd-2, the C. elegans Anaplastic Lymphoma Kinase (ALK) gene ortholog, scd-2(syb2455),which I designed based on an oncogenic mutation in ALK. While animals with loss-of-function mutations in scd-2 are dauer-formation defective, scd-2(syb2455) animals enter dauer regardless of food conditions. In Chapter Three, I report that SCD-2 also regulates the food-dependent feeding and foraging behaviors known as dwelling and roaming; scd-2(syb2455) animals roam more and scd-2 loss-of-function animals roam less than wild type. Additionally, in contrast to wild-type animals, which express the gene encoding the TGF- signaling ligand DAF-7 exclusively in the ASI chemosensory neurons, scd-2(syb2455) animals constitutively express daf-7 in both the ASI and ASJ neurons. The expression of daf-7 in the ASJ neurons drives roaming in these animals. I demonstrate that daf-7 expression in the ASJ neurons is also affected by food; ingested food in the pharynx inhibits daf-7 expression in the ASJ neurons through SCD-2 signaling. From these data we propose a positive-feedback loop that regulates roaming behavior: in the absence of ingested food, active SCD-2 induces daf-7 expression in the ASJ neurons to promote roaming, which further reduces food consumption. To further investigate how daf-7 neuroendocrine signaling responds to nutritional state, in Chapter Four I describe a screen for satiety signals using the nutritional state-dependent daf-7 expression in the ASJ neurons in males as a readout for communication along the gut-“brain” axis. This screen yielded a loss-of-function allele of che-3 and a gain-of-function allele of pdfr-1. In Chapter Five, I discuss future directions for investigating how C. elegans interacts with its food environment.","abstract_html":"The ability to adapt to changes in food conditions is critical for organismal homeostasis and survival. In this thesis, I explore the genetic and neuroendocrine mechanisms by which C. elegans evaluates bacterial food conditions and accordingly alters development and behavior. In Chapter One, I discuss the relationship between C. elegans and its bacterial diet. The influence of food on behavior suggests the presence of a gut-“brain” axis that senses and communicates information about nutritional state to the nervous system to elicit a behavioral response. In Chapter Two, I characterize a gain-of-function allele of scd-2, the C. elegans Anaplastic Lymphoma Kinase (ALK) gene ortholog, scd-2(syb2455),which I designed based on an oncogenic mutation in ALK. While animals with loss-of-function mutations in scd-2 are dauer-formation defective, scd-2(syb2455) animals enter dauer regardless of food conditions. In Chapter Three, I report that SCD-2 also regulates the food-dependent feeding and foraging behaviors known as dwelling and roaming; scd-2(syb2455) animals roam more and scd-2 loss-of-function animals roam less than wild type. Additionally, in contrast to wild-type animals, which express the gene encoding the TGF- signaling ligand DAF-7 exclusively in the ASI chemosensory neurons, scd-2(syb2455) animals constitutively express daf-7 in both the ASI and ASJ neurons. The expression of daf-7 in the ASJ neurons drives roaming in these animals. I demonstrate that daf-7 expression in the ASJ neurons is also affected by food; ingested food in the pharynx inhibits daf-7 expression in the ASJ neurons through SCD-2 signaling. From these data we propose a positive-feedback loop that regulates roaming behavior: in the absence of ingested food, active SCD-2 induces daf-7 expression in the ASJ neurons to promote roaming, which further reduces food consumption. To further investigate how daf-7 neuroendocrine signaling responds to nutritional state, in Chapter Four I describe a screen for satiety signals using the nutritional state-dependent daf-7 expression in the ASJ neurons in males as a readout for communication along the gut-“brain” axis. This screen yielded a loss-of-function allele of che-3 and a gain-of-function allele of pdfr-1. In Chapter Five, I discuss future directions for investigating how C. elegans interacts with its food environment.","abstract_has_math":false,"creators":["Boor, Sonia"],"institution":"Massachusetts Institute of Technology","degree_name":"Doctoral","degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Biology","school":null,"contributors":[],"advisors":["Kim, Dennis H."],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022-09","date_published":"2022-09","updated_at":"2026-07-22T22:21:45Z","subjects":[],"languages":[],"rights":["In Copyright - Educational Use Permitted","Copyright retained by author(s)"],"rights_urls":["https://rightsstatements.org/page/InC-EDU/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1721.1/147425","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Kim, Dennis H."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. 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In this thesis, I explore the genetic and neuroendocrine mechanisms by which C. elegans evaluates bacterial food conditions and accordingly alters development and behavior. In Chapter One, I discuss the relationship between C. elegans and its bacterial diet. The influence of food on behavior suggests the presence of a gut-“brain” axis that senses and communicates information about nutritional state to the nervous system to elicit a behavioral response. In Chapter Two, I characterize a gain-of-function allele of scd-2, the C. elegans Anaplastic Lymphoma Kinase (ALK) gene ortholog, scd-2(syb2455),which I designed based on an oncogenic mutation in ALK. While animals with loss-of-function mutations in scd-2 are dauer-formation defective, scd-2(syb2455) animals enter dauer regardless of food conditions. In Chapter Three, I report that SCD-2 also regulates the food-dependent feeding and foraging behaviors known as dwelling and roaming; scd-2(syb2455) animals roam more and scd-2 loss-of-function animals roam less than wild type. Additionally, in contrast to wild-type animals, which express the gene encoding the TGF- signaling ligand DAF-7 exclusively in the ASI chemosensory neurons, scd-2(syb2455) animals constitutively express daf-7 in both the ASI and ASJ neurons. The expression of daf-7 in the ASJ neurons drives roaming in these animals. I demonstrate that daf-7 expression in the ASJ neurons is also affected by food; ingested food in the pharynx inhibits daf-7 expression in the ASJ neurons through SCD-2 signaling. From these data we propose a positive-feedback loop that regulates roaming behavior: in the absence of ingested food, active SCD-2 induces daf-7 expression in the ASJ neurons to promote roaming, which further reduces food consumption. To further investigate how daf-7 neuroendocrine signaling responds to nutritional state, in Chapter Four I describe a screen for satiety signals using the nutritional state-dependent daf-7 expression in the ASJ neurons in males as a readout for communication along the gut-“brain” axis. This screen yielded a loss-of-function allele of che-3 and a gain-of-function allele of pdfr-1. In Chapter Five, I discuss future directions for investigating how C. elegans interacts with its food environment."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Genetic Analysis of Bacterial Food Perception and its Influence on Foraging Behavior in C. elegans"]}]}],"canonical_facts":{"dc:contributor.advisor":["Kim, Dennis H."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Biology"],"dc:creator":["Boor, Sonia"],"dc:date.accessioned":["2023-01-19T19:49:28Z"],"dc:date.available":["2023-01-19T19:49:28Z"],"dc:date.issued":["2022-09"],"dc:description.abstract":["The ability to adapt to changes in food conditions is critical for organismal homeostasis and survival. In this thesis, I explore the genetic and neuroendocrine mechanisms by which C. elegans evaluates bacterial food conditions and accordingly alters development and behavior. In Chapter One, I discuss the relationship between C. elegans and its bacterial diet. The influence of food on behavior suggests the presence of a gut-“brain” axis that senses and communicates information about nutritional state to the nervous system to elicit a behavioral response. In Chapter Two, I characterize a gain-of-function allele of scd-2, the C. elegans Anaplastic Lymphoma Kinase (ALK) gene ortholog, scd-2(syb2455),which I designed based on an oncogenic mutation in ALK. While animals with loss-of-function mutations in scd-2 are dauer-formation defective, scd-2(syb2455) animals enter dauer regardless of food conditions. In Chapter Three, I report that SCD-2 also regulates the food-dependent feeding and foraging behaviors known as dwelling and roaming; scd-2(syb2455) animals roam more and scd-2 loss-of-function animals roam less than wild type. Additionally, in contrast to wild-type animals, which express the gene encoding the TGF- signaling ligand DAF-7 exclusively in the ASI chemosensory neurons, scd-2(syb2455) animals constitutively express daf-7 in both the ASI and ASJ neurons. The expression of daf-7 in the ASJ neurons drives roaming in these animals. I demonstrate that daf-7 expression in the ASJ neurons is also affected by food; ingested food in the pharynx inhibits daf-7 expression in the ASJ neurons through SCD-2 signaling. From these data we propose a positive-feedback loop that regulates roaming behavior: in the absence of ingested food, active SCD-2 induces daf-7 expression in the ASJ neurons to promote roaming, which further reduces food consumption. To further investigate how daf-7 neuroendocrine signaling responds to nutritional state, in Chapter Four I describe a screen for satiety signals using the nutritional state-dependent daf-7 expression in the ASJ neurons in males as a readout for communication along the gut-“brain” axis. This screen yielded a loss-of-function allele of che-3 and a gain-of-function allele of pdfr-1. In Chapter Five, I discuss future directions for investigating how C. elegans interacts with its food environment."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["https://hdl.handle.net/1721.1/147425"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["In Copyright - Educational Use Permitted","Copyright retained by author(s)"],"dc:rights.uri":["https://rightsstatements.org/page/InC-EDU/1.0/"],"dc:title":["Genetic Analysis of Bacterial Food Perception and its Influence on Foraging Behavior in C. elegans"],"dc:type":["Thesis"],"thesis:degree_name":["Doctoral","Doctor of Philosophy"]},"updated_at":"2026-07-22T22:21:45Z"}