Comparative physical mapping links conservation of microsynteny to chromosome structure and recombination in grasses.
Nearly finished sequences for model organisms provide a foundation from which to explore genomic diversity among other taxonomic groups. We explore genome-wide microsynteny patterns between the rice sequence and two sorghum physical maps that integrate genetic markers, bacterial artificial chromosome (BAC) fingerprints, and BAC hybridization data. The sorghum maps largely tile a genomic component containing 41% of BACs but 80% of single-copy genes that shows conserved microsynteny with rice and partially tile a nonsyntenic component containing 46% of BACs but only 13% of single-copy genes. The remaining BACs are centromeric (4%) or unassigned (8%). The two genomic components correspond to cytologically discernible "euchromatin" and "heterochromatin." Gene and repetitive DNA distributions support this classification. Greater microcolinearity in recombinogenic (euchromatic) than nonrecombinogenic (heterochromatic) regions is consistent with the hypothesis that genomic rearrangements are usually deleterious, thus more likely to persist in nonrecombinogenic regions by virtue of Muller's ratchet. Interchromosomal centromeric rearrangements may have fostered diploidization of a polyploid cereal progenitor. Model plant sequences better guide studies of related genomes in recombinogenic than nonrecombinogenic regions. Bridging of 35 physical gaps in the rice sequence by sorghum BAC contigs illustrates reciprocal benefits of comparative approaches that extend at least across the cereals and perhaps beyond.
Bowers
John E
JE
Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30602, USA.
Arias
Miguel A
MA
Asher
Rochelle
R
Avise
Jennifer A
JA
Ball
Robert T
RT
Brewer
Gene A
GA
Buss
Ryan W
RW
Chen
Amy H
AH
Edwards
Thomas M
TM
Estill
James C
JC
Exum
Heather E
HE
Goff
Valorie H
VH
Herrick
Kristen L
KL
Steele
Cassie L James
CL
Karunakaran
Santhosh
S
Lafayette
Gmerice K
GK
Lemke
Cornelia
C
Marler
Barry S
BS
Masters
Shelley L
SL
McMillan
Joana M
JM
Nelson
Lisa K
LK
Newsome
Graham A
GA
Nwakanma
Chike C
CC
Odeh
Rosana N
RN
Phelps
Cynthia A
CA
Rarick
Elizabeth A
EA
Rogers
Carl J
CJ
Ryan
Sean P
SP
Slaughter
Keimun A
KA
Soderlund
Carol A
CA
Tang
Haibao
H
Wing
Rod A
RA
Paterson
Andrew H
AH
D001483:Base Sequence; D022004:Chromosome Structures; D022041:Euchromatin; D018745:Genome, Plant; D006570:Heterochromatin; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics; D020161:Physical Chromosome Mapping / Q000379:methods*; D006109:Poaceae / Q000235:genetics*; D011995:Recombination, Genetic; D045868:Sorghum / Q000235:genetics; D026801:Synteny
D022041:Euchromatin; D006570:Heterochromatin