Abstract
A large number of plant genes are aligned with partially overlapping genes in antisense orientation. Transcription of both genes would therefore favour the formation of double-stranded RNA, providing a substrate for the RNAi machinery, and enhanced antisense transcription should therefore reduce sense transcript levels. We have identified a gene pair that resembles a model for antisense-based gene regulation as a T-DNA insertion into the antisense gene causes a reduction in antisense transcript levels and an increase in sense transcript levels. The same effect was, however, also observed when the two genes were inserted as transgenes into different chromosomal locations, independent of the sense and antisense gene being expressed individually or jointly. Our results therefore indicate that antagonistic changes in sense/antisense transcript levels do not necessarily reflect antisense-mediated regulation. More likely, the partial overlap of the two genes may have favoured the evolution of antagonistic expression patterns preventing RNAi effects.
Highlights
The expression of genetic information involves a sequence of molecular processes, including transcript synthesis, processing, turnover, transport and translation
Expression of sense and antisense transcripts results in the production of nat-siRNAs that cleave the P5CDH transcript [6]. Another class of natsiRNAs, which is induced by the bacterial pathogen Pseudomonas syringae carrying effector avrRpt2, represses PPRL, a putative negative regulator of the RPS2 resistance pathway [7]
The biogenesis of both nat-siRNAs requires RNA-dependent RNA Polymerase 6 (RDR6), which probably synthesises secondary dsRNA substrates
Summary
The expression of genetic information involves a sequence of molecular processes, including transcript synthesis, processing, turnover, transport and translation. Work on yeast and animals has identified model genes that illustrate the regulatory influence of antisense transcription on sense transcript synthesis, processing, or stability. This has led to the proposal that NATs have evolved to comprise a second tier of gene expression in eukaryotes [2]. Expression of sense and antisense transcripts results in the production of nat-siRNAs that cleave the P5CDH transcript [6] Another class of natsiRNAs, which is induced by the bacterial pathogen Pseudomonas syringae carrying effector avrRpt, represses PPRL, a putative negative regulator of the RPS2 resistance pathway [7]. The biogenesis of both nat-siRNAs requires RNA-dependent RNA Polymerase 6 (RDR6), which probably synthesises secondary dsRNA substrates
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