Prevalence and diversity of TAL effector-like proteins in fungal endosymbiotic Mycetohabitans spp.
Bibliographic record
Abstract
Endofungal Mycetohabitans (formerly Burkholderia) spp. rely on a type III secretion system to deliver mostly unidentified effector proteins when colonizing their host fungus, Rhizopus microsporus. The one known secreted effector family from Mycetohabitans consists of homologs of transcription activator-like (TAL) effectors, which are used by plant pathogenic Xanthomonas and Ralstonia spp. to activate host genes that promote disease. These Burkholderia TAL-like (Btl) proteins bind corresponding specific DNA sequences in a predictable manner, but their genomic target(s) and impact on transcription in the fungus are unknown. Recent phenotyping of Btl mutants of two Mycetohabitans strains revealed that the single Btl in one M. endofungorum strain enhances fungal membrane stress tolerance, while others in a M. rhizoxinica strain promote bacterial colonization of the fungus. The phenotypic diversity underscores the need to assess the sequence diversity and, given that sequence diversity translates to DNA targeting specificity, the functional diversity of Btl proteins. Using a dual approach to maximize capture of Btl protein sequences for our analysis, we sequenced and assembled nine Mycetohabitans spp. genomes using long-read PacBio technology and also mined available short-read Illumina fungal-bacterial metagenomes. We show that btl genes are present across diverse Mycetohabitans strains from Mucoromycota fungal hosts yet vary in sequences and predicted DNA binding specificity. Phylogenetic analysis revealed distinct clades of Btl proteins and suggested that Mycetohabitans might contain more species than previously recognized. Within our data set, Btl proteins were more conserved across Mycetohabitans rhizoxinica strains than across Mycetohabitans endofungorum, but there was also evidence of greater overall strain diversity within the latter clade. Overall, the results suggest that Btl proteins contribute to bacterial-fungal symbioses in myriad ways.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".