BioProject

Polyadenylation of pre-mRNAs is critical for efficient nuclear export, stability and translation of the mature mRNAs, and thus for gene expression. More...

Polyadenylation of pre-mRNAs is critical for efficient nuclear export, stability and translation of the mature mRNAs, and thus for gene expression. The bulk of pre-mRNAs are processed by canonical nuclear poly(A) polymerase (PAPS). Both vertebrate and higher-plant genomes encode more than one isoform of this enzyme, and these are co-expressed in different tissues. However, in neither case is it known whether the isoforms fulfil different functions or polyadenylate distinct subsets of pre-mRNAs. Here we show that the three canonical nuclear PAPS isoforms in Arabidopsis are functionally specialized due to their evolutionarily divergent C-terminal domains. A strong loss-of-function mutation in PAPS1 causes a male gametophytic defect, while a weak allele leads to reduced leaf growth that results in part from a constitutive pathogen response. By contrast, plants lacking both PAPS2 and PAPS4 function are viable with wild-type leaf growth. Polyadenylation of SMALL AUXIN UP RNA (SAUR) mRNAs depends specifically on PAPS1 function. The resulting reduction in SAUR activity in paps1 mutants contributes to their reduced leaf growth, providing a causal link between polyadenylation of specific pre-mRNAs by a particular PAPS isoform and plant growth. This suggests the existence of an additional layer of regulation in plant and possibly vertebrate gene expression, where the relative activities of canonical nuclear PAPS isoforms control de novo synthesized poly(A)-tail length and hence expression of specific subsets of mRNAs. Overall design: Comparing inflorescences and seedlings from paps1-1 mutants and WT. 4 biological replicates for each genotype and tissue. Less...