Reference "Isolation and characterization of rice R genes: evidence for distinct evolutionary paths in rice and maize"

Reference ID

5348

Title

Isolation and characterization of rice R genes: evidence for distinct evolutionary paths in rice and maize

Source

Genetics, 1996, vol. 142, pp. 1021-1031

Authors (3)

Hu-J-P	Anderson-B
Wessler-S-R

Abstract

R and B genes and their homologues encode basic helix-loop-helix (bHLH)
transcriptional activators that regulate the anthocyanin biosynthetic pathway in
flowering plants. In maize, R/B genes comprise a very small gene family whose
organization reflects the unique evolutionary history and genome architecture of
maize. To know whether the organization of the R gene family could provide
information about the origins of the distantly related grass rice, we
characterized members of the R gene family from rice Oryza saliva. Despite being
a true diploid, O. sativa has at least two R genes. An active homologue (Ra)
with extensive homology with other R genes is located at a position on
chromosome 4 previously shown to be in synteny with regions of maize chromosomes
2 and 10 that contain the B and R loci, respectively. A second rice R gene (Rb)
of undetermined function was identified on chromosome 1 and found to be present
only in rice species with AA genomes. All non-AA species have but one R gene
that is Ra-like. These data suggest that the common ancestor shared by maize and
rice had a single R gene and that the small R gene families of grasses have
arisen recently and independently.