Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA.|College of Sciences, Northeastern University, Shenyang, China.|Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA.|Department of Biological Sciences and Wrigley Institute for Environmental Studies, University of Southern California, Los Angeles, California, USA.|Department of Biological Sciences and Wrigley Institute for Environmental Studies, University of Southern California, Los Angeles, California, USA.|Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA. fsun@usc.edu.