Intergeneric transfer of ribosomal genes between two fungi
Bibliographic record
Abstract
BACKGROUND: Horizontal gene transfer, also called lateral gene transfer, frequently occurs among prokaryotic organisms, and is considered an important force in their evolution. However, there are relatively few reports of transfer to or from fungi, with some notable exceptions in the acquisition of prokaryotic genes. Some fungal species have been found to contain sequences resembling those of bacterial genes, and with such sequences absent in other fungal species, this has been interpreted as horizontal gene transfer. Similarly, a few fungi have been found to contain genes absent in close relatives but present in more distantly related taxa, and horizontal gene transfer has been invoked as a parsimonious explanation. There is a paucity of direct experimental evidence demonstrating the occurrence of horizontal gene transfer in fungi. RESULTS: We found a fungal field isolate from rice (Oryzae sativa) that contains ribosomal DNA sequences from two species of fungal rice pathogens (Thanatephorus cucumeris and Ceratobasidium oryzae-sativae). This field isolate has four types of ribosomal DNA internal transcribed spacers (ITS), namely pure ITS of C. oryzae-sativae, which was dominant in this field isolate, pure ITS of T. cucumeris, and two chimeric ITS, with ITS1 derived from C. oryzae-sativae and ITS2 from T. cucumeris, or ITS1 from T. cucumeris and ITS2 from C. oryzae-sativae. The presence of chimeric forms indicates that the intergeneric hybrid was not merely composed of nuclei from the parental species, but that nuclear fusion and crossing over had taken place. CONCLUSION: Hyphae of T. cucumeris and C. oryzae-sativae are vegetatively incompatible, and do not successfully anastomose. However, they parasitize the same host, and perhaps under the influence of host enzymes targeted to weaken pathogen cells or in dying host plant tissue, the fungal hyphae lost their integrity, and normal vegetative incompatibility mechanisms were overcome, allowing the hyphae to fuse. Based on the presence of other similarly anomalous isolates from the field, we speculate that these types of intergeneric hybridization events and occurrences of horizontal gene transfer may not be so rare in the field.
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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 | 0.001 |
| 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".