About the Authors
Plant Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America
Howard Hughes Medical Institute, La Jolla, California, United States of America
The authors have declared that no conflicts of interest exist.
JLN and JC conceived and designed the experiments. JLN performed the experiments. JLN and TCM analyzed the data. TCM wrote scripts and performed bioinformatic analysis. JLN, TCM, and JC wrote the paper.