Integrative Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America.|Integrative Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America.|Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom.|Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom.|Howard Hughes Medical Institute and Plant Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America.|Integrative Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America.