[1] Univ N Carolina, Dept Biol, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Howard Hughes Med Inst, Chapel Hill, NC 27599 USA
[3] Univ N Carolina, Curriculum Genet & Mol Biol, Chapel Hill, NC 27599 USA
[4] Univ N Carolina, Dept Microbiol & Immunol, Chapel Hill, NC 27599 USA
[5] Univ N Carolina, Carolina Ctr Genome Sci, Chapel Hill, NC 27599 USA
[6] Two Blades Fdn, Evanston, IL 60201 USA
[7] Univ Calif Berkeley, Dept Plant & Microbial Biol, Berkeley, CA 94720 USA