About the Authors
Department of Integrative Biology, University of California Berkeley, Berkeley, California, United States of America
The authors have declared that no competing interests exist.
The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: DB BV. Performed the experiments: BV YZ. Analyzed the data: BV JJE SM DB. Contributed reagents/materials/analysis tools: DB. Wrote the paper: BV DB.