Poster: Evolution

Abs # 793: The fate of progenitor’s genes in newly formed Arabidopsis polyploids

Presenter:	Chen, Z. Jeffrey , zjchen@tamu.edu
Authors	Chen, Z. Jeffrey  (A)   Wang, Jianlin  (A)   Lee, Hyeon-Se  (A)   Tian, Lu  (A)   Madlung, Andreas  (B)   Comai, Luca  (B)
Affiliations:	(A): Texas A&M University (B): University of Washington
Web Site:	http://microarrayabc.tamu.edu

Polyploidization is an important feature for the evolution of eukaryotes especially plants. The fate of redundant genes resulting from genome duplication is poorly understood. Recent studies indicate that both genetic and epigenetic mechanisms are involved in regulating the redundant genes of polyploids, which can be activated or silenced upon polyploidization. However, the timing of this differential regulation and the maintenance of gene expression states are unclear. To elucidate consequences of genome duplication and mechanisms of gene regulation in polyploids, we have generated synthetic Arabidopsis suecica lines through interspecific hybridization between A. thaliana and A. arenosa. We have shown that some progenitor’s genes are differentially expressed in early generations, whereas others are silenced only in natural A. suecica lines, suggesting both rapid and possibly stochastic effects of polyploid formation on the expression of progenitor's genes. To determine whether the silenced genes are maintained by DNA methylation, we have produced transgenic A. suecica lines using RNAi interference (RNAi) for the genes encoding DDM1 and methyltransferase (MET1). Reactivation of some silenced genes was observed in the RNAi-ddm1 or -met1 lines, consistent with demethylation of the centromeric and rDNA repeats and of the genomic regions containing the target genes. These data suggest that gene activation and silencing is established through rapid processes, and that DNA methylation is responsible for the maintenance of progenitor's gene expression during genome duplication and polyploid formation.