title: Cell-Cell Communication in Yeast Using Auxin Biosynthesis and Auxin Responsive CRISPR Transcription Factors.
abstract: An engineering framework for synthetic multicellular systems requires a programmable means of cell-cell communication. Such a communication system would enable complex behaviors, such as pattern formation, division of labor in synthetic microbial communities, and improved modularity in synthetic circuits. However, it remains challenging to build synthetic cellular communication systems in eukaryotes due to a lack of molecular modules that are orthogonal to the host machinery, easy to reconfigure, and scalable. Here, we present a novel cell-to-cell communication system in Saccharomyces cerevisiae (yeast) based on CRISPR transcription factors and the plant hormone auxin that exhibits several of these features. Specifically, we engineered a sender strain of yeast that converts indole-3-acetamide (IAM) into auxin via the enzyme iaaH from Agrobacterium tumefaciens. To sense auxin and regulate transcription in a receiver strain, we engineered a reconfigurable library of auxin-degradable CRISPR transcription factors (ADCTFs). Auxin-induced degradation is achieved through fusion of an auxin-sensitive degron (from IAA corepressors) to the CRISPR TF and coexpression with an auxin F-box protein. Mirroring the tunability of auxin perception in plants, our family of ADCTFs exhibits a broad range of auxin sensitivities. We characterized the kinetics and steady-state behavior of the sender and receiver independently as well as in cocultures where both cell types were exposed to IAM. In the presence of IAM, auxin is produced by the sender cell and triggers deactivation of reporter expression in the receiver cell. The result is an orthogonal, rewireable, tunable, and, arguably, scalable cell-cell communication system for yeast and other eukaryotic cells.
authors.affiliation: Department of Bioengineering, ‡Department of Electrical Engineering, §Department of Biology, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Arjun
authors.initials: A
authors.lastname: Khakhar
authors.affiliation: Department of Bioengineering, ‡Department of Electrical Engineering, §Department of Biology, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Bolten
authors.affiliation: Department of Bioengineering, ‡Department of Electrical Engineering, §Department of Biology, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nemhauser
authors.affiliation: Department of Bioengineering, ‡Department of Electrical Engineering, §Department of Biology, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Klavins
mesh_terms: D016960:Agrobacterium tumefaciens / Q000201:enzymology; D000581:Amidohydrolases / Q000378:metabolism; D064113:CRISPR-Cas Systems / Q000235:genetics*; D002450:Cell Communication / Q000187:drug effects; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D000094704:RNA, Guide, CRISPR-Cas Systems / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C014059:CYC1 protein, S cerevisiae; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D000094704:RNA, Guide, CRISPR-Cas Systems; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C015950:indoleacetamide; D045304:Cytochromes c; D000581:Amidohydrolases; C058772:indole-3-acetamide hydrolase
keywords: auxin biosynthesis; auxin synthetic biology; auxin-induced degradation (AID); cell−cell communication; inducible CRISPR transcription factors; multicellular systems