Poster: Transcription Regulation

Abs # 1071: Expression of Arabidopsis MeCP2 and its Correlation with Leaf Senescence

Presenter:	Lomeli, Shirley H., slomeli@calstatela.edu
Authors	Lomeli, Shirley H. (A)   Yang, Dennis H. (A)   Vellanoweth, Robert L. (A)
Affiliations:	(A): California State University, Los Angeles

We are interested in the process of aging and senescence in Arabidopsis thaliana and the genes that regulate this process. One of these may be the Arabidopsis histone deacetylase gene (HD). Expression of an antisense Arabidopsis HD gene results in an accumulation of acetylated histones and induces early senescence and ectopic expression of silenced genes. This evidence suggests the importance of HD in gene silencing and suggests that gene mis-silencing may be associated with senescence. In mammals, HD activity is recruited to silenced genes by interacting with MeCP2, a mammalian epigenetic silencing protein that binds to methylated DNA via the methyl-CpG binding domain (MBD). By sequence homology, we discovered two novel MeCP2 genes in Arabidopsis thaliana (AtMeCP2). The function of these homologs is unknown but, given the conservation in the DNA binding domains, they likely also bind to methylated DNA. To see if they are developmentally regulated and might contribute to senescence, we compared their relative spatial and temporal levels of gene expression using quantitative RT-PCR. RNA from all tissues at different developmental stages including vegetative, reproductive and senescent stages was extracted. As expected, RT-PCR results showed a decrease in AtMeCP2 expression as the leaves entered senescence. We visualized AtMeCP2 using GFP fusions to determine cellular localization throughout the lifespan. To test if the Arabidopsis homologs bind to methylated DNA and interact with other proteins, we performed in vitro binding studies and protein-protein interactions in vivo using the yeast two-hybrid system.