Poster abstracts
Poster number 115 submitted by Lichun Zhou
Natural variation in the plant polyadenylation complex
Lichun Zhou (Department of Plant and Soil Sciences, University of Kentucky), Kai Li (Department of Plant and Soil Sciences, University of Kentucky), Arthur G. Hunt (Department of Plant and Soil Sciences, University of Kentucky)
Abstract:
Messenger mRNA polyadenylation, the process wherein the primary RNA polymerase II transcript is cleaved and a poly(A) tract added, is mediated by a complex (the polyadenylation complex, or PAC) that consists of between 15 and 20 subunits. In plants, as many as fifteen subunits have been identified by sequence comparisons with the mammalian and yeast polyadenylation complexes, and some additional plant-specific subunits identified using genetic approaches. While analogies with the mammalian and yeast complexes have provided a good working understanding of the plant PAC, several aspects of the plant PAC raise interesting questions. For example, one subunit of the PAC, CPSF30 (or CPSF4), is an essential subunit in mammals and yeast, but entirely dispensable for plant growth and development [1]. To gain further insight into novelty in the plant PAC, we have begun a study of variation in subunits of the complex. For this, we drew upon a database of naturally-occurring variation in numerous geographic isolates of Arabidopsis thaliana [2]. Most of the subunits of the Arabidopsis CPSF and CstF complexes show patterns of variability that are consistent with their roles as essential proteins. However, for some subunits, the distributions of non-synonymous mutations suggest possible ancillary or regulatory functions apart from those needed for cleavage and polyadenylation. For a small subset of PAC subunits, the patterns of variability are characterized by relatively high ratios of non-synonymous/synonymous substitutions and the occurrence of premature stop codons in some Arabidopsis accessions. These features are most prominent in subunits encoded by gene families, and strongly suggest that some members of these families have lost function and are instead pseudogenes. In addition, some PAC subunits – isoforms of Pcf11, CFIm68, PAP, and FIP1 – have patterns of variation consistent with selection for new or altered function. We propose that the patterns of natural variation seen in Arabidopsis PAC subunits reflect both core functionality and regulatory interactions important for differential usage of poly(A) sites during growth and development.
References:
1. Hunt AG. mRNA 3' end formation in plants: Novel connections to growth, development and environmental responses. Wiley Interdiscip Rev RNA. 2020;11(3):e1575.
2. Genomes Consortium. 1,135 Genomes Reveal the Global Pattern of Polymorphism in Arabidopsis thaliana. Cell. 2016;166(2):481-91.
Keywords: polyadenylation, Arabidopsis, evolution