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Messenger RNA polyadenylation, the process wherein the primary RNA polymerase II transcript is cleaved and a poly(A) tract added, is a key step in the expression of genes in plants. Moreover, it is a point at which gene expression may be regulated by determining the functionality of the mature mRNA. Polyadenylation is mediated by a complex (the polyadenylation complex, or PAC) that consists of between 15 and 20 subunits. While the general functioning of these subunits may be inferred by extending paradigms established in welldeveloped eukaryotic models, much remains to be learned about the roles of individual subunits in the regulation of polyadenylation in plants. To gain further insight into this, we conducted a survey of variability in the plant PAC. For this, we drew upon a database of naturally-occurring variation in numerous geographic isolates of Arabidopsis thaliana. For a subset of genes encoding PAC subunits, the patterns of variability included the occurrence of premature stop codons in some Arabidopsis accessions. These and other observations lead us to conclude that some genes purported to encode PAC subunits in Arabidopsis are actually pseudogenes, and that others may encode proteins with dispensable functions in the plant. Many subunits of the PAC showed patterns of variability that were consistent with their roles as essential proteins in the cell. Several other PAC subunits exhibit patterns of variability consistent with selection for new or altered function. We propose that these latter subunits participate in regulatory interactions important for differential usage of poly(A) sites. [ABSTRACT FROM AUTHOR]

The genome-linked protein-proteinase (NIa) genes of three potyviruses (tobacco rein mottling virus[TVMV], tobacco etch virus[TEV], and potato virus Y [PVY]) were introduced into tobacco (Nicotiana tabacum L.) cultivar Burley 21 and transgenic plant lines were evaluated for viral symptoms and virus accumulation. Plant lines that expressed the TVMV NIa gene were resistant to infection by TVMV; inoculated plants did not develop disease symptoms after inoculation, and virus did not accumulate. Most lines that carried the TEV NIa and PVY NIa genes did develop symptoms after inoculation with TEV and PVY, respectively, but these symptoms abated with time (a response termed as recovery). Three genes, each consisting of two NIa coding regions (TEV NIa-PVY NIa, TEV NIa-TVMV NIa, and TVMV NIa-PVY NIa) were also introduced into Burley 21. Transgenic lines that carried either TEV NIa-PVY NIa or TEV NIa-TVMV NIa constructs either did not develop disease symptoms or exhibited the process of recovery after inoculation with TEV. TEV NIa-TVMV NIa and TVMV NIa-PVY NIa lines recovered from an initial infection after inoculation with TVMV. Likewise, TEV NIa-PVY NIa and TVMV NIa-PVY NIa transformed lines recovered from initial infection after inoculation with PVY. These results demonstrate that different potyvirus NIa-proteinase genes can be used for protection against virus infection and that multiple NIa genes may be used to produce plants that are protected against more than one potyvirus., POTYVIRUSES are the largest group of plant viruses and infect a wide range of host plants. Potyviruses are transmitted by aphids and are non-persistent in the aphid vector. Classical breeding [...]

Abstract Background Polyadenylation, an essential step in eukaryotic gene expression, requires both cis-elements and a plethora of trans-acting polyadenylation factors. The polyadenylation factors are largely conserved across mammals and fungi. The conservation seems also extended to plants based on the analyses of Arabidopsis polyadenylation factors. To extend this observation, we systemically identified the orthologs of yeast and human polyadenylation factors from 10 plant species chosen based on both the availability of their genome sequences and their positions in the evolutionary tree, which render them representatives of different plant lineages. Results The evolutionary trajectories revealed several interesting features of plant polyadenylation factors. First, the number of genes encoding plant polyadenylation factors was clearly increased from “lower” to “higher” plants. Second, the gene expansion in higher plants was biased to some polyadenylation factors, particularly those involved in RNA binding. Finally, while there are clear commonalities, the differences in the polyadenylation apparatus were obvious across different species, suggesting an ongoing process of evolutionary change. These features lead to a model in which the plant polyadenylation complex consists of a conserved core, which is rather rigid in terms of evolutionary conservation, and a panoply of peripheral subunits, which are less conserved and associated with the core in various combinations, forming a collection of somewhat distinct complex assemblies. Conclusions The multiple forms of plant polyadenylation complex, together with the diversified polyA signals may explain the intensive alternative polyadenylation (APA) and its regulatory role in biological functions of higher plants.