1. Medical Research Institute; Wuhan University; Room 1612, Hubei Province Wuhan 430071 P.R. China
2. Department of Genetics; Harvard Medical School; 77 Ave Louis Pasteur, NRB 339 Boston, MA 02115 USA
3. State Key Laboratory of Silkworm Genome Biology; Southwest University; Chongqing 400715 China
4. Howard Hughes Medical Institute; Boston MA 02115 USA