TAR30, a homolog of the canonical plant TTTAGGG telomeric repeat, is enriched in the proximal chromosome regions of peanut (Arachis hypogaea L.)

Authors: Gao, Dongying; NASCIMENTO, ELIZA - University Of Brasilia; LEAL-BERTIOLI, SORAYA - University Of Georgia; ABERNATHY, BRIAN - University Of Georgia; JACKSON, SCOTT - University Of Georgia; ARAUJO, ANA - Embrapa Genetic Resources; BERTIOLI, DAVID - University Of Georgia

Submitted to: Chromosome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2022
Publication Date: 1/19/2022
Citation: Gao, D., Nascimento, E., Leal-Bertioli, S., Abernathy, B., Jackson, S., Araujo, A., Bertioli, D. 2022. TAR30, a homolog of the canonical plant TTTAGGG telomeric repeat, is enriched in the proximal chromosome regions of peanut (Arachis hypogaea L.). Chromosome Research. 30(1):77–90. https://doi.org/10.1007/s10577-022-09684-7.
DOI: https://doi.org/10.1007/s10577-022-09684-7

Interpretive Summary: Repetitive elements including transposons and tandem repeats are ubiquitous in the genomes of many sequenced plants. Once considered as ‘junk DNA’, they are recognized to have essential biological functions. For example, telomeric tandem repeats are extremely important for protecting the ends of chromosomes and maintaining normal cell division. However, tandem repeats in peanut, an important oil and food crop worldwide, are still poorly understood. We identified a new tandem repeat in the peanut genomes and revealed distinct distributions of this repeat within different wild accessions and between wild and cultivated peanuts. We also found potential amplification of TAR30 in cultivated genome. Our results provide some clues about evolution of repetitive sequences in peanut and help to understand the genomic changes during polyploidization and crop domestication.

Technical Abstract: Telomeres are the physical ends of eukaryotic linear chromosomes that play critical roles in cell division, chromosome maintenance and genome stability. In many plants, telomeres are comprised of TTTAGGG tandem repeat that is widely found in plants. We refer to this repeat as canonical plant telomeric repeat (CPTR). Peanut (Arachis hypogaea L.) is a spontaneously formed allotetraploid and an important food and oil crop worldwide. In this study, we analyzed the peanut genome sequences and identified a new type of tandem repeat with 10-bp basic motif TTTT(C/T)TAGGG named TAndem Repeat(TAR)30. TAR30 showed significant sequence identity to TTTAGGG repeat in 112 plant genomes suggesting that TAR30 is a homolog of CPTR. It also is nearly identical to the telomeric tandem repeat in Cestrum elegans. Fluorescence in situ hybridization (FISH) analysis revealed interstitial locations of TAR30 in peanut chromosomes but we did not detect visible signals in the terminal ends of chromosomes as expected for telomeric repeats. Interestingly, different TAR30 hybridization patterns were found between the newly induced allotetraploid ValSten and its diploid wild progenitors. The canonical telomeric repeat TTTAGGG is also present in the peanut genomes and some of these repeats are closely adjacent to TAR30 from both cultivated peanut and its wild relatives. Overall, our work identifies a new homolog of CPTR and reveals the unique distributions of TAR30 in cultivated peanuts and wild species. Our results provide new insights into the evolution of tandem repeats during peanut polyploidization and domestication.