Arabidopsis ubiquitin-conjugating enzyme UBC22 is required for female gametophyte development and likely involved in Lys11-linked ubiquitination
Bibliographic record
Abstract
Protein ubiquitination is critical for numerous processes in eukaryotes. The ubiquitin-conjugating enzyme (E2) is required for ubiquitination. The Arabidopsis genome has approximately 37 E2 genes, but in vivo functions for most of them remain unknown. In this study we observed that knockout mutants of Arabidopsis UBC22 had much-reduced silique length and seed number, with nearly 90% of ovules aborted. Analyses revealed that the majority of mutant embryo sacs displayed severe defects and often contained no gamete nuclei. There was no difference between mutant and wild-type Arabidopsis at the megaspore mother cell stage; however, the functional megaspore was either not present or appeared abnormal in a large portion of mutant ovules, suggesting that the defect started with functional megaspore degeneration in the mutants. Degeneration continued during megagametogenesis, such that the percentage of mature embryo sacs without any gamete nuclei was much greater than the percentage of developing ovules without a functional megaspore and, in addition, various abnormalities in megagametogenesis were observed. Additionally, heterozygous plants had only 13.1% of ovules aborted, indicating that the heterozygous sporophytic tissues could affect the development of the mutant female gametophyte. UBC22 is the sole member of an Arabidopsis E2 subfamily, and is more closely related to one type of E2s in animals that catalyzes Lys11-specific ubiquitination. Indeed, our results showed that Arabidopsis UBC22 could catalyze ubiquitin dimer formation in vitro in a Lys11-dependent manner, suggesting that it likely catalyzes Lys11-linked ubiquitination in plants. This study has thus identified one biochemical property of UBC22 and revealed a novel function in female gametophyte development.
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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) | 0.000 | 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 | 0.000 |
| 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".