Mutations in <i>Arabidopsis</i> condensin genes disrupt embryogenesis,meristem organization and segregation of homologous chromosomes during meiosis
Bibliographic record
Abstract
Proper chromatin condensation and sister chromatid resolution are essential for the maintenance of chromosomal integrity during cell division, and is in part mediated by a conserved multisubunit apparatus termed the condensin complex. The core subunits of the complex are members of the SMC2 (Structural Maintenance of Chromosomes) and SMC4 gene families. We have cloned an Arabidopsis gene, AtCAP-E1, which is a functional ortholog of the yeast SMC2 gene. A second, highly homologous SMC2 gene, AtCAPE-2, was identified by the Arabidopsis genome project. SMC2 gene expression in Arabidopsis was correlated with the mitotic activity of tissues, with high level expression observed in meristematic cells. The two genes are differentially expressed with AtCAP-E1 accounting for more than 85% of the total SMC2 transcript pool. The titan3 mutant is the result of a T-DNA insertion into AtCAP-E1, but other than subtle endosperm defects, titan3 is viable and fecund. We identified a T-DNA insertion mutant of AtCAP-E2, which showed no obvious mutant phenotype, indicating that the two genes are functionally redundant. Genetic crosses were employed to examine the consequences of reduced SMC2 levels. Both male and female gametogenesis were compromised in double mutant spores. Embryo lethality was observed for both double homozygous and AtCAP-E1(-/-), AtCAP-E2(+/-) plants; arrest occurred at or before the globular stage and was associated with altered planes of cell division in both the suspensor and the embryo. Down regulation of both genes by antisense technology, as well as in AtCAP-E1(+/-), AtCAP-E2(-/-) plants results in meristem disorganization and fasciation. Our data are consistent with the interpretation that threshold levels of SMC2 proteins are required for normal development and that AtCAP-E2 may have a higher affinity for its target than AtCAP-E1.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".