[1] Microsoft Res, 110 Glendon Ave,Suite PH1, Los Angeles, CA 90024 USA
[2] European Bioinformat Inst, European Mol Biol Lab, Cambridge CB10 1SD, England
[3] Univ Toronto, Donnelly Ctr Cellular & Biomol Res, Toronto, ON M5S 3E1, Canada
[4] Univ Calif Berkeley, Dept Plant & Microbial Biol, Berkeley, CA 94720 USA