Epigenetic mechanisms for breakdown of self-incompatibility in interspecific hybrids.
As a major agent of rapid speciation, interspecific hybridization has played an important role in plant evolution. When hybridization involves species that exhibit self-incompatibility (SI), this prezygotic barrier to self-fertilization must be overcome or lost to allow selfing. How SI, a normally dominant trait, is lost in nascent hybrids is not known, however. Here we demonstrate that hybrid self-fertility can result from epigenetic changes in expression of the S-locus genes that determine specificity in the SI response. We analyzed loss of SI in synthetic hybrids produced by crossing self-fertile and self-incompatible species in each of two crucifer genera. We show that SI is lost in the stigmas of A. thaliana-lyrata hybrids and their neo-allotetraploid derivatives and in the pollen of C. rubella-grandiflora hybrids and their homoploid progenies. Aberrant processing of S-locus receptor kinase gene transcripts as detected in Arabidopsis hybrids and suppression of the S-locus cysteine-rich protein gene as observed in Capsella hybrids are two reversible mechanisms by which SI might break down upon interspecific hybridization to generate self-fertile hybrids in nature.
Nasrallah
June B
JB
Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA. jbn2@cornell.edu
Liu
Pei
P
Sherman-Broyles
Susan
S
Schmidt
Renate
R
Nasrallah
Mikhail E
ME
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D029687:Capsella / Q000235:genetics; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D044127:Epigenesis, Genetic; D017343:Genes, Plant; D006239:Haplotypes; D006824:Hybridization, Genetic; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics; D010944:Plants / Q000235:genetics*; D012098:Reproduction / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D018744:DNA, Plant; D010940:Plant Proteins