Characterisation of an intron-split Solanales microRNA

Medina Calzada, Zahara (2017) Characterisation of an intron-split Solanales microRNA. Doctoral thesis, University of East Anglia.

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MicroRNAs (miRNAs) are a distinct class of short endogenous RNAs with central roles in post-transcriptional regulation of gene expression that make them essential for the development and normal physiology of several groups of eukaryotes, including plants. In the last 15 years, hundreds of miRNA species have been identified in plants and great advances have been achieved in the understanding of plant miRNA biogenesis and mode of action. However, many miRNAs, generally those with less conventional features, still remain to be discovered. Likewise, further layers that regulate the pathway from miRNA biogenesis to function and turnover are starting to be revealed.
In the present work we have studied the tomato miRNA “top14”, a miRNA with a non-canonical pri-miRNA structure in which an intron is in between miRNA and miRNA*. We have found that this miRNA is conserved within the economically important Solanaceae family and among other members of the Solanales order also agriculturally relevant, like in sweet potato, while its peculiar intron-split pri-miRNA structure is exclusively kept in the more closely related genera Solanum, Capsicum and Nicotiana. In these three genera, two different pri-miRNA variants were detected; one spliced and the other one retaining the intron. After testing the mature miRNA production from the wild type tomato MIRtop14, from a version without intron and from another version without splicing capability, it was found that the intron influenced the accumulation of mature miRNA. Finally, a mRNA cleaved by this miRNA was identified; the mRNA coding for LOW PHOSPHATE ROOT (LPR), a protein which in Arabidopsis is involved in the arrest of root growth under phosphate starvation conditions. Interestingly, although LPR is widely conserved in plants, included in all the ones harbouring miRNAtop14, LPR cleavage was found to occur only in the three genera where the intron-split pri-miRNA structure is conserved.
The current study indicates that MIRs encoded by less canonical loci should be included in future miRNA searches, since they may be producing mature miRNAs with a function, as seen in this investigation. Furthermore, our results suggest that this miRNA may be regulated through intron retention. In case of being confirmed, it would add to the few recently reported examples of post-transcriptional regulation of a miRNA and should encourage the research of less known layers of miRNA regulation. Finally, the study of this miRNA sheds light to the crosstalk between miRNA biogenesis and splicing and, in a broader context, to the complex interactions between the different RNA regulatory networks operating in plants.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Bruce Beckett
Date Deposited: 20 Jul 2018 08:41
Last Modified: 15 Sep 2020 00:38


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