Abstract
Regulation of gene expression is at the frontier of plant responses to various external stimuli including stress. RNA polymerase-based transcription and post-transcriptional degradation of RNA play vital roles in this regulation. Here, we show that HUA ENHANCER 2 (HEN2), a co-factor of the nuclear exosome complex, influences RNAPII transcription elongation in Arabidopsis (Arabidopsis thaliana) under cold conditions. Our results demonstrate that a hen2 mutant is cold sensitive and undergoes substantial transcriptional changes compared to wild type when exposed to cold conditions. We found an accumulation of 5' fragments from a subset of genes (including C-repeat binding factors 1-3 [CBF1-3]) that do not carry over to their 3' ends. In fact, hen2 mutants have lower levels of full-length mRNA for a subset of genes. This distinct 5'-end accumulation and 3'-end depletion was not observed in other NEXT complex members or core exosome mutants, highlighting HEN2's distinctive role. We further used RNAPII-associated nascent RNA to confirm that the transcriptional phenotype is a result of lower active transcription specifically at the 3' end of these genes in a hen2 mutant. Taken together, our data point to the unique role of HEN2 in maintaining RNAPII transcription dynamics especially highlighted under cold stress.