| Plant pathogen resistance is mediated by a large repertoire of “ Resistance” (R) genes, which are often clustered in the genome and exhibit a high degree of genetic variation. Here, we show that an Arabidopsis thaliana R gene cluster is also subject to epigenetic variation. We describe a heritable but metastable epigenetic variant, bal, which overexpresses the R-like gene At4g16890 from a gene cluster on chromosome 4. The bal variant and Arabidopsis transgenics overexpressing the At4g16890 gene are dwarfed and constitutively activate the salicylic acid (SA)-dependent defense response pathway. Overexpression of a related R-like gene also occurs in the ssi1 (suppressor of SA insensitivity 1) background, suggesting that ssi1 is mechanistically related to bal. Another variant, cpr1 (constitutive expressor of PR genes), maps to the BAL locus, and interacts genetically with the bal variant in a paramutation-like phenomenon, in which the cpr1 allele becomes destabilized predominantly. |
