Major changes in gene expression between strains of diapausing and non-diapause spruce budworm despite little evidence of genetic divergence
Bibliographic record
Abstract
Abstract To survive harsh winter conditions, many insects enter a state of dormancy called diapause which allows them to withstand extreme temperatures and lack of food. When diapause is induced, insects enter a state of arrested development and low metabolic rate. Because diapause and environmental conditions are closely linked, variation within and between species in diapause induction, depth, and duration is extremely common. Studies investigating the genetic underpinnings of diapause tend to focus on either different populations and/or environmental variation, which runs the risk of confounding the genetic signal either due to isolation-by-distance or variation in environmental conditions. We use the eastern spruce budworm ( Choristoneura fumiferana ) to circumvent these issues and investigate within-population variation in diapause. C. fumiferana usually diapauses as second instar larvae, but a small subset of individuals does not diapause and instead continues through development. This non-diapause phenotype can be selected to create a non-diapause strain. Here, we present a chromosome-level assembly of such a non-diapause strain, and compare it to an earlier published genome assembly of the diapause strain. We did not find evidence of major chromosome rearrangements, indicating that the genetic variation between strains is likely small and multi-genic. Gene expression comparisons between the strains indicate major gene expression changes, where genes associated with glycolysis and environmental signaling processing increase in expression in the diapause strain. Lastly, we found that gene expression diverges halfway through the first instar, and not before, indicating that the signal to induce diapause happens early in the first instar. Significance statement The ability to enter diapause is a crucial adaptation for many insects to survive cold winters. The genetic underpinnings of the diapause phenotype has been the target of many investigations. However, many of these studies focus on variation in diapause on between geographic regions or changes in environmental conditions, which can lead to confounding factors. Here, we focus on within-population variation in diapause in the eastern spruce budworm, with two strains established from the same source population that vary in their ability to induce diapause. We present a chromosome level assembly of the non-diapause strain, and report that genetic changes between the diapause and the non-diapause line are likely small and involve multiple loci. Gene expression differences were extensive, and mostly associated with mechanisms to avoid freezing. This work sets the stage to further investigate how minimal genetic changes can lead to large-scale phenotypic changes as impactful as diapause.
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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 | 0.000 |
| 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) | 0.001 | 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 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".