OUR ARCHAEAL COUSINS: EVOLUTION AND FUNCTION OF EUKARYOTIC HOMOLOGS IN SEDIMENTARY ARCHAEA JENNIFER F. BIDDLE AND ROSA LE N-ZAYAS SCIENTIFIC AND TECHNICAL SUMMARY EXPLORING THE ORIGIN AND EVOLUTION OF LIFE IS A THEME OF THE NASA EXOBIOLOGY PROGRAM AND RECENT CLUES TO THE ANCESTRY OF EUKARYOTES HAVE SURFACED FROM GENOMIC INVESTIGATIONS INTO SEDIMENTARY ARCHAEAL COMMUNITIES. GENOMES OF LOKIARCHAEOTA AND THORARCHAEOTA ALONG WITH ADDITIONAL DEEP BRANCHING ARCHAEAL RELATIVES SHARE GENOMIC SIGNATURES WITH EUKARYOTES AND ARE PHYLOGENETICALLY IMPLICATED AS THE NEAREST NEIGHBORS OF THE BRANCH OF LIFE WHICH EVOLVED INTO MULTICELLULAR ORGANISMS. A BETTER UNDERSTANDING AND GROUNDTRUTHING OF THIS VIEW OF THE TREE OF LIFE IS NEEDED INCLUDING PROOF BEYOND GENOMES. CURRENTLY THE LOKIARCHAEOTA AND THORARCHAEOTA ARE KNOWN ONLY FROM METAGENOMIC DATASETS. THESE DEEPLY BRANCHING ARCHAEAL GENOMES HOUSE EUKARYOTIC SIGNATURES SUCH AS GTG/RAG FAMILY GTPASES ACTIN HOMOLOGS AND SYNTHESIS OF ETHER-LINKED AND FATTY ACID ESTER LINKED MEMBRANES WITH BACTERIAL/EUKARYOTIC G3P STEREOCHEMISTRY. THESE FEATURES ARE SUGGESTED BY FUNCTIONAL AND PHYLOGENETIC INFERENCE TO LINK THE ARCHAEAL BRANCH OF LIFE TO THE EUKARYOTIC ONE. ADDITIONAL GENOMES OF THESE ARCHAEA WILL BETTER ELUCIDATE SHARED PATHWAYS WITH THE EUKARYOTES PROVIDING CLEARER PHYLOGENETIC INTERPRETATIONS TO THE RELATIONSHIP BETWEEN THE GROUPS. WE HYPOTHESIZE THAT ADDITIONAL GENOMIC ANALYSIS WILL HELP TO DETERMINE THE DIRECTIONALITY OF TRANSFER OF THESE GENES INCLUDING GENES SHARED WITH THE BACTERIAL DOMAIN AND ALSO FURTHER CONSTRAIN THE AMOUNT OF GENETIC OVERLAP BETWEEN DOMAINS. WE CURRENTLY HAVE DEEPLY BRANCHING ARCHAEAL GENOMES FROM THESE GROUPS RECOVERED FROM THE MARINE SEDIMENTARY DEEP BIOSPHERE AND WITH EXISTING DATA WILL HARVEST EUKARYOTIC AND BACTERIAL HOMOLOGS FOR IN-DEPTH PHYLOGENETIC STUDY. ADDITIONALLY WE WILL DEVELOP MICROCOSMS FROM ANAEROBIC MARINE SEDIMENTS AND DETECT THE EXPRESSION OF THESE EUKARYOTIC HOMOLOGS WITHIN THESE ARCHAEAL RELATIVES USING METAGENOMICS AND METATRANSCRIPTOMICS. OUR ULTIMATE GOAL WILL BE TO VISUALIZE EXPRESSED HOMOLOGS WITHIN ARCHAEAL CELLS USING FLUORESCENT IN-SITU HYBRIDIZATION TECHNIQUES FOR BOTH RIBOSOMAL SIGNATURES AND MRNA OF EUKARYOTIC HOMOLOGS. OUR RESEARCH WILL PROVIDE CONCLUSIVE EVIDENCE THAT THESE ARCHAEAL COUSINS DO EXPRESS EUKARYOTIC HOMOLOGS AND OUR METHODOLOGY WILL ALLOW FOR INTERPRETATION INTO THEIR INVOLVEMENT IN CELL CYCLES. USING MULTIPLE DATASETS WE WILL HAVE THE ABILITY TO ASSESS THE DIVERSITY OF EUKYAROTIC HOMOLOG SIGNATURES AND BETTER DEVELOP OUR UNDERSTANDING OF THE BIODIVERSITY AND PHYLOGENETIC EXTENT OF HOMOLOG EVOLUTION IN ARCHAEA AND EUKARYOTES. THIS PROJECT WILL LEAD TO A BETTER UNDERSTANDING OF THE EVOLUTION OF COMPLEX LIFE BY EXAMINING OUR SINGLE CELLED COUSINS THE DEEPLY BRANCHING ARCHAEA. MANAGEMENT SUMMARY SAMPLES WILL BE COLLECTED AND DATA WILL BE GENERATED WITH ALL INFORMATION STORED IN APPROPRIATE DATA REPOSITORIES SUCH AS DRYAD AND NCBI. PI BIDDLE WILL OVERSEE THE PROJECT AND PARTICIPATE IN DATA GENERATION ANALYSIS AND PUBLICATION. POSTDOCTORAL ASSOCIATE LE N- ZAYAS WILL GENERATE ANALYZE AND PUBLISH DATA.