Poster abstracts
Poster number 19 submitted by Tami Coursey
Plant Histone Readers EML1 and EML3 Differentially Impact Geminivirus Infection
Tami Coursey (Molecular, Cellular, and Developmental Biology), Milica Milutinovic (Institute for Biological Research Sinia Stankovi, University of Belgrade), Jelena Brkljacic (Arabidopsis Biological Resource Center, Ohio State University), David Bisaro (Molecular Genetics, Ohio State University)
Abstract:
Similar to their host counterparts, DNA viruses are often subject to chromatin formation. In plants, geminiviruses are circular, single-stranded DNA genomes that, within a host nucleus, are converted into replicative, double-stranded DNA forms. Bound by histone octamers to form non-integrating viral minichromosomes, DNA accessibility is regulated by post-translational modification (PTM) of exposed histone tails. While previous work has shown plants utilize repressive chromatin modifications as an antiviral defense, little is known about the proteins that recognize/read histone PTMs on viral chromatin. Upon binding specific histone PTMs, histone reader proteins can alter gene expression by recruiting nucleosome remodeling complexes and transcription factors. Using the geminivirus Cabbage leaf curl virus (CaLCuV) as a model viral pathogen, we are characterizing the activity and interaction of two plant putative histone readers, EMSY-LIKE proteins 1 and 3 (EML1 and EML3) with viral chromatin. EML1 and EML3 contain Agenet domains that share homology with other Royal Family domains (e.g. Tudor) in histone readers. Surprisingly, mutant Arabidopsis plants inoculated with CaLCuV exhibited hypersusceptibility (eml1) or increased tolerance (eml3) compared to wild-type plants. Transcriptional analysis indicated both EML1 and EML3 expression is up-regulated in response to geminivirus infection. Transiently expressed EML1 and EML3 also bind nucleosomes and CaLCuV, supporting their role as histone readers and confirming their interaction with viral chromatin. Binding the virus, EML proteins appear to impact expression of early and late viral genes during infection. We also noted changes in viral chromatin compaction in eml mutants, supporting a role for these histone readers in chromatin regulation. Surprisingly, despite the dramatically different phenotypes observed in infected mutant plants, biochemical studies indicate that EML1 and EML3 bind the same histone PTM. These results suggest that Agenet domain-containing EML proteins are histone readers that recruit different downstream effectors to alternatively promote virus infection or bolster plant antiviral defense pathways.
Keywords: geminivirus, chromatin, epigenetics