Gene conversion within regulatory sequences generates maize r alleles with altered gene expression.
The maize r locus encodes a transcription factor that regulates the developmental expression of the plant pigment anthocyanin. In an unusual example of gene regulatory diversity, the R-sc (Sc, strong seed color) and the R-p (P, plant color) alleles of r have nonoverlapping tissue specificity and nonhomologous 5' flanking sequences. Heterozygotes between wild-type P and Sc mutants with Ds6 transposable element inserts (r-sc:m::Ds6 or sc:m) produce colored seed derivatives (Sc+) during meiotic recombination. The sc:m alleles with Ds6 insertion in 3' regions of r produce crossover Sc+ derivatives. sc:m alleles with Ds6 elements inserted in 5' regions produce rare Sc+ derivatives borne on nonrecombinant chromosomes. Among 52 such noncrossover Sc+ derivatives, 18 are indistinguishable from the Sc progenitor in phenotype and DNA sequence [Scp(+) alleles]. The remaining 34 derivatives have strong Sc+ expression, including darkly pigmented aleurone, scutellum, coleoptile, and scutellar node [Scp(e) alleles]. The coleoptile and scutellar node phenotypes are unique from either progenitor but are similar to those of some naturally occurring r alleles. Both classes of Sc+ derivatives are explained by gene conversion between the promoter region of Sc:124 and a homologous region located proximal to P. The recombinational intermediate formed between sc:m alleles and P results in deletion of the Ds6 element alone or both Ds6 and a nearby unrelated transposable element-like sequence.
Li
Y
Y
Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, USA.
Bernot
J P
JP
Illingworth
C
C
Lison
W
W
Bernot
K M
KM
Eggleston
W B
WB
Fogle
K J
KJ
DiPaola
J E
JE
Kermicle
J
J
Alleman
M
M
D000483:Alleles; D001483:Base Sequence; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics; D003433:Crosses, Genetic; D004251:DNA Transposable Elements / Q000235:genetics; D005785:Gene Conversion; D018506:Gene Expression Regulation, Plant; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009692:Nucleic Acid Heteroduplexes; D010641:Phenotype; D011995:Recombination, Genetic; D014157:Transcription Factors / Q000235:genetics; D003313:Zea mays / Q000235:genetics*
D004251:DNA Transposable Elements; D009692:Nucleic Acid Heteroduplexes; D014157:Transcription Factors