Antisense transcription from stress-responsive transcription factors fine-tunes the cold response in Arabidopsis

Transcription of antisense long noncoding RNAs (lncRNAs) occurs pervasively across eukaryotic genomes. Only a few antisense lncRNAs have been characterized and shown to control biological processes, albeit with idiosyncratic regulatory mechanisms. Thus, we largely lack knowledge about the general role of antisense transcription in eukaryotic organisms. Here, we characterized genes with antisense transcription initiating close to the poly(A) signal of genes (PAS genes) in Arabidopsis (Arabidopsis thaliana). We compared plant native elongation transcript sequencing (plaNET-seq) with RNA sequencing during short-term cold exposure and detected massive differences between the response in active transcription and steady-state levels of PAS gene-derived mRNAs. The cold-induced expression of transcription factors B-BOX DOMAIN PROTEIN28 (BBX28) and C2H2-TYPE ZINC FINGER FAMILY PROTEIN5 (ZAT5) was detected by plaNET-seq, while their steady-state level was only slightly altered due to high mRNA turnover. Knockdown of BBX28 and ZAT5 or of their respective antisense transcripts severely compromised plant freezing tolerance. Decreased antisense transcript expression levels resulted in a reduced cold response of BBX28 and ZAT5, revealing a positive regulatory role of both antisense transcripts. This study expands the known repertoire of noncoding transcripts. It highlights that native transcription approaches can complement steady-state RNA techniques to identify biologically relevant players in stress responses.