show Abstracthide AbstractWe developed a stringent selection pipeline for lncRNA identification, combining high-throughput RNA sequencing and computational approaches. Using this pipeline, we annotated 1,353 lncRNAs in Arabidopsis thaliana. We further found that one fifth of the lncRNAs were associated with Polycomb repressive complex 2 (PRC2). Some PRC2-associated lncRNAs could repress the transcription of their neighboring genes through mediating histone H3 lysine 27 trimethylation. Overall design: Identification of Arabidopsis lncRNA through high throughput sequencing.