Alterations of transcription levels of centromeric loci in Arabidopsis infected plants

CAMBIAGNO D; ALVAREZ ME

Potrero de Funes

Congreso; XLVII Reunión SAIB; 2011

SAIB

Higher eukaryotes chromatin is organized in domains of highly condensed and relaxed regions (heterochromatin and euchromatin respectively). Heterochromatin is characterized by transcriptional repressive marks (methylated DNA and methylated Histone H3 lysine 9) and contains few genes intercalated among thousands of short repetitive sequences. Recent studies revealed that chromatin marks are susceptible to be modified by stress. We found that in Arabidopsis, the infection with Pseudomonas syringae pv tomato (Pst) triggers heterochromatin decondensation and DNA demethylation, with centromeric repeats being target of these responses. To evaluate if these phenomena affect the transcription level of centromeric repeats, we quantified the abundance of transcripts of the centromeric locus TSI (Transcriptional Silenced Information) in naïve and infected plants. We included wild and mutant plants having alteration in heterochromatic epigenetic marks (ddm1, mom1 and vim1). We found a reduction of TSI transcripts in infected wild type plants. Mutants accumulate these TSI transcripts in basal conditions, but were unable to reduce them upon infection. In addition showed increased activation of defense genes and enhanced resistance to Pst. These results suggest that alteration of heterochromatin structure induced by bacterial infection may affect activation of plant defenses.