Abstract Detail

Comparative Genomics/Transcriptomics

Garcia, Sonia [1], Vitales, Daniel [1], Pascual-Díaz, Joan Pere [1], Heitkam, Tony [2], Baader, Luisa [2], Maiwald, Sophie [2], Mann, Ludwig [2], Weber, Beatrice [2], Rodriguez, Roi [1], Kovarik, Ales [3].

An unquiet sequence: mobility, evolution, and epigenetics of 5S rRNA genes in plants.

The RNA world hypothesis describes an ancient world more than 2 billion years ago where 'proto'-life was based on RNA. In that world, 'proto'-life would have exploited the RNA's dual ability to store genetic information and to act as an enzyme. From this would have evolved life based on DNA, which took over the role of information storage, while proteins took over most enzymatic functions. But critical RNA functions remained, notably those involving ribosomal RNA (rRNA) -among other important RNAs such as tRNAs, mRNAs and miRNAs. Ribosomal RNAs comprise 80% of the RNA found in a typical cell, and the abundance of rRNA genes is key in processes of DNA repair and genome stability. In eukaryotes, there are four ribosomal RNA genes. The 18S, 5.8S, and 26S rRNA genes are coded in a single operon (called 45S rDNA in animals and 35S rDNA in plants) and the 5S rRNA gene is usually coded outside this operon, by 5S rDNA. In plants, most species present the 18S-5.8S-26S separated from the 5S rRNA genes (termed S-type), although there are few exceptions in which all genes are linked (termed L-type).   5S rDNA is perhaps the most enigmatic of all the rRNA genes. It consists of a small transcriptional unit of about 120 base pairs, containing all major regulatory elements. Here, we explore the evolutionary dynamism of 5S rDNA in plants. Despite its critical importance, many aspects of 5S rDNA biology remain unexplored, such as its mode of molecular evolution, genomic arrangements, and epigenetic regulation. 5S rDNA is an "unquiet" genomic actor that can be found either (1) scattered in the genome, (2) tandemly arranged, (3) associated with other tandem repeat families, (4) truncated, pseudogenised, and linked to transposable elements, or (5) in extrachromosomal circular units. The impact of 5S rDNA epigenetic regulation is not well understood either, but there is evidence that epigenetics affects its evolutionary rate and copy number. We delve into the mechanisms involved in the genomic arrangements, mobility, and epigenetic regulation of 5S rDNA in a group of plant species from the sunflower family in which, exceptionally, contrasting rDNA organisations are found, taking as model species from genera Artemisia (L-type) and Tragopogon (S-type).

Related Links:
First description of linked rRNA genes in angiosperms

1 - Spanish Research Council (CSIC), Institut Botanic De Barcelona, Passeig del Migdia s/n, Barcelona, 08038, Spain
2 - Technische Universität Dresden, Institute of Botany, Zellescher Weg 20b, Dresden, D-01062 , Germany
3 - Academy of Sciences of the Czech Republic, Institute of Biophysics, Kralovopolska 135, Brno, CZ-61265, Czech Republic

Keywords:
ribosomal DNA
repetitive DNA
molecular evolution
eccDNA
transposable elements
Asteraceae
cytogenetics
concerted evolution.

Presentation Type: Oral Paper
Session: CGT1, Comparative Genomics/Transcriptomics I
Location: /
Date: Tuesday, July 20th, 2021
Time: 11:30 AM(EDT)
Number: CGT1007
Abstract ID:174
Candidate for Awards:Margaret Menzel Award