1 School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710072, China.
2 Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China.
3 Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Copenhagen N 2200, Denmark. Electronic address: rheller@bio.ku.dk.
4 School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710072, China. Electronic address: qiuqiang@lzu.edu.cn.