<i>Cenchrus purpureus</i> and <i>Cenchrus americanus</i> repeatome provide chromosomal markers to distinguish subgenomes
Bibliographic record
Abstract
Abstract Cenchrus L. is an important genus within the Poaceae family, comprising several species of high agronomic significance, such as Cenchrus purpureus and Cenchrus americanus , for production of forage and grains, respectively. Cenchrus americanus is a diploid species (2n = 2x = 14, AA genome), while Cenchrus purpureus is an allotetraploid (2n = 4x = 28, A’A’BB genome). The A’ subgenome is believed to be homeologous to and possibly derived from the A subgenome, while the origin of the B subgenome remains undefined. Despite their distinct subgenomic compositions, both species exhibit a high level of genome homology. The objective of the present work was the in silico characterization and comparative analysis of the repetitive fraction of the genomes of Cenchrus purpureus and Cenchrus americanus using genome skimming and a graph-based clustering approach, as well as the in situ hybridization of specific satellite DNA clusters into the chromosomes of both species. The repetitive fraction of the genome of C. purpureus and C. americanus corresponds to 52.23% and 76.82%, respectively. The most abundant repetitive elements in both species are the LTR retrotransposons. Satellite DNA sequences correspond to 2.55% and 4.17% of the genome of each species, respectively. Four new satellite sequences were identified as subgenome-specific sequences for both species, along with new centromeric variants. The ancestral relationship and the polyploidization-diploidization cycles played a fundamental role in the composition of their repetitive fraction. These cycles led Cenchrus americanus , a possible paleopolyploid, to a greater abundance of transposable elements compared to Cenchrus purpureus , a recent allopolyploid.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".