Abstract Detail

Comparative Genomics/Transcriptomics

Sancho, Rubén [1], Scarlett, Virginia [2], Vogel, John [2], Des Marais, David [3], Catalan, Pilar [1].

Transposable elements (TE) dynamics in the model grass genus Brachypodium: abundance, distribution and evolution of TE families.

Transposable elements (TEs) are mobile DNA sequences that represent a large genomic fraction and a source of genetic variability in the eukaryotic genomes. We investigate the abundance, distribution and evolution of TE families in five species of the model grass genus Brachypodium: the three annual species of the B. distachyon polyploid complex (B. hybridum-4x and its progenitors B. distachyon-2x and B. stacei-2x), and the ancestral B. mexicanum-4x and recently evolved B. sylvaticum-2x perennials. Our preliminary results show that the B. distachyon genome is more enriched in TEs (36.4% of masked genome) than that of B. stacei (31.1%), for a similar genome size, although their descendant allopolyploid B. hybridum shows more TE enrichment (37.3%) than any of its progenitors for a duplicated genome size. The two B. hybridum homeologous subgenomes D (distachyon-type) and S (stacei-type) show TE enrichments with respect to the chromosomes of their respective progenitor genomes (1.5-2% more than B. distachyon and 4-5% more than and B. stacei   masked genomes per chromosome), which would support the hypothesis of increased enrichment of the repeteome after the polyploid shock. B. hybridum has an intermediate proportion of Gypsy TEs (10.9% of total masked genome: 13% B. hybridum-D and 8.5% B. hybridum-S) between those of its progenitor genomes (B. distachyon: 12.7%; B. stacei: 6.5%) but a larger proportion of TIRs and non-TIR/helitrons (9.8%: 9.6% B. hybridum-D and 10% B. hybridum-S, and 12.4%: 11.8% B. hybridum-D and 13% B. hybridum-S, respectively) than them (B. distachyon, TIR: 8.8% and non-TIR: 9.6%; B. stacei, TIR: 8.5% and non-TIR: 10.7%). B. mexicanum accumulates the highest repetitive genomic proportion within the genus (71.2% of its genome corresponds to TEs), being 40.4% of it Gypsy LTRs. This value duplicates the TE proportion of any other species studied in Brachypodium, and largely explains the paramount differences found among its large genome size (1.5 Gbp) and the small genomes of the other polyploid species of the genus (e.g., B. hybridum: 509 Mbp). The abundance, distribution and dynamics of the TE families in the studied Brachypodium species are interpreted in the light of their phylogeny.

1 - University of Zaragoza: Universidad de Zaragoza, Agricultural and Environmental Sciences, High Polytechnic School of Huesca, Ctra. Cuarte km 1, Huesca, Aragón, 22071, Spain
2 - DOE Joint Genome Institute, Plant Functional Genomics, Berkeley, CA, USA
3 - Massachusetts Institute of Technology (MIT), Department of Civil and Environmental Engineering, MIT, 15 Vassar Street, Cambridge, MA, 02139, USA

Keywords:
transposable elements
Brachypodium.

Presentation Type: Poster
Session: P1, Comparative Genomics/Transcriptomics Posters
Location: Virtual/Virtual
Date: Monday, July 19th, 2021
Time: 5:00 PM(EDT)
Number: P1GT005
Abstract ID:342
Candidate for Awards:None