Sequence-space expansion is driven by the emergence of new signaling

1. University of California, Berkeley Department of Comparative Biochemistry 7 2. Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division 8 3. University of California, Berkeley Department of Bioengineering 9 4. University of California, Berkeley Department of Plant and Microbial Biology 10 5. University of California, Berkeley Department of Chemical and Biomolecular Engineering 11 6. Lawrence Berkeley National Laboratory, Environmental Genomics and Systems Biology 12 Division 13 7. Center for Biosustainability, Danish Technical University, Lyngby, Denmark 14 8. Center for Synthetic Biochemistry, Shenzhen Institutes for Advanced Technologies, 15 Shenzhen, China 16 * Correspondence: amukhopadhyay@lbl.gov 17