title: Induced instability of two Arabidopsis constitutive pathogen-response alleles.
abstract: Paramutation is an example of a non-Mendelian-directed allelic interaction that results in the epigenetic alteration of one allele. We describe a paramutation-like interaction between two alleles, bal and cpr1-1 (constitutive expressor of PR genes 1), which map to a complex R-like gene cluster on Arabidopsis chromosome 4. Both alleles cause dwarfing and constitutive defense responses, similar to another dwarf variant, ssi1 (suppressor of SA-insensitivity 1). Previous work has demonstrated that the bal and ssi1 phenotypes are caused by overexpression of an R-like gene from the cluster, which activates an salicylic acid-dependent defense pathway. Here, we show that the cpr1-1 variant does not alter gene expression from the R-like gene cluster. The bal and cpr1-1 alleles did not complement each other in F(1) hybrids, but F(2) populations that segregated bal and cpr1-1 alleles contained plants with normal morphology at a frequency of 20%. By using molecularly marked bal and cpr1-1 lines, we found that the majority of the normal phenotypes were correlated with inheritance of an altered cpr1-1 allele. Our observation that cpr1-1 is a metastable allele suggests that cpr1-1 is an epigenetic allele. The cpr1-1 allele is the third candidate epigenetic allele originating from this R-like gene cluster, making the region a possible hotspot of epigenetic variation.
authors.affiliation: Department of Biology, Washington University, One Brookings Drive, St. Louis, MO 63130, USA.
authors.forename: Trevor L
authors.initials: TL
authors.lastname: Stokes
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Richards
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D018506:Gene Expression Regulation, Plant; D005819:Genetic Markers; D014644:Genetic Variation; D007113:Immunity, Innate / Q000235:genetics; D010935:Plant Diseases; D014158:Transcription, Genetic
chemical_list: D005819:Genetic Markers