bims-plasge 2025-10-19 papers

Issue of 2025–10–19
two papers selected by
Vera S. Bogdanova, ИЦиГ СО РАН

Proc Natl Acad Sci U S A. 2025 Oct 21. 122(42): e2504381122

Ubiquitin-mediated degradation restricts spatiotemporal accumulation of the cytoplasmic male sterility protein WA352 to anthers in rice.

Zixu Zhang, Zhi Ding, Xueye Feng, Jingjing Huang, Xu Peng, Yubin Xiao, Wubei Zong, Zhe Zhao, Yao-Guang Liu, Yongyao Xie, Letian Chen.

Cytoplasmic male sterility (CMS) is caused by mitochondrial genes that are constitutively expressed in plant tissues, although the encoded proteins preferentially accumulate in anthers. The mechanisms regulating CMS protein accumulation remain unclear. Here, we explored this process using wild-abortive CMS (CMS-WA) rice (Oryza sativa). We show that WA352, the causal protein of CMS-WA, is degraded by the ubiquitin-proteasome system (UPS). Structural analysis and protein truncation assays revealed that the N terminus of WA352 is critical for its anchoring to the inner mitochondrial membrane and its UPS-mediated degradation. Functional complementation confirmed that WA352151-352, lacking the N-terminal domain, accumulates constitutively in vegetative tissues, causing a reactive oxygen species burst and retarding rice growth. We further identified three mitochondrion-localized F-box proteins that participate in WA352 ubiquitination and degradation. Our findings demonstrate that UPS-mediated regulation restricts WA352 accumulation to anthers, allowing it to specifically disrupt anther development, thus helping to explain the male-specific effects of CMS genes in plants.

Keywords: cytoplasmic male sterility; mitochondria; protein degradation; rice; ubiquitin–proteasome system

DOI: https://doi.org/10.1073/pnas.2504381122

Ann Bot. 2025 Oct 15. pii: mcaf254. [Epub ahead of print]

Hybridization between different Brassica allohexaploid lineages produces viable, fertile progeny but does not improve genome stability or fertility in F1 hybrids.

Daniela Quezada-Martinez, Poonam Bangia, Jacqueline Batley, Annaliese S Mason.

BACKGROUND AND AIMS: Hybridization events are crucial in the evolution of plants. Experimental hybridization between extant lineages can help us understand the evolutionary consequences of merging different species. Brassica allohexaploids (2n = AABBCC) offer a unique opportunity to test the effects of hybridization between allopolyploids from different species origins, and specifically whether these new hybrids are fertile and perform better than the parents.
METHODS: We hand-pollinated between Brassica allohexaploid genotypes from different species origins to analyze the crossability between species: carirapa (2n = 54; B. carinata × B. rapa), junleracea (B. juncea × B. oleracea), naponigra (B. napus × B. nigra), and NCJ (B. napus × B. carinata × B. juncea). We also analyzed a subset of resulting F1 hybrids for fertility and genomic changes.
KEY RESULTS: We obtained 9,052 new allohexaploid hybrid seeds, with a range of 0.0-4.6 seeds per flower bud crossed. Specific female and male parent genotypes affected the crossing success rate (number of seeds/bud crossed). The F-1 hybrids showed mid-parent heterosis for seed fertility ranging from -64 to 275%, while best-parent heterosis ranged from -79 to 241%. Most of the F-1 hybrids had similar quantities of copy number variation (CNV) events compared to the parents, with the majority of these events (76%) directly inherited from one of the parents.
CONCLUSIONS: We conclude that combining different allohexaploid types via hand pollination is feasible without any extra measures to ensure embryo survival, despite the different species origins, with strong maternal genotype effects on success rate. Novel hybrids between allohexaploid lineages showed similar fertility and stability to their parents, suggesting that there is no selection against CNVs in the hybridization event, nor is there an immediate gain in seed fertility associated with an increase in heterozygosity in the allohexaploids.

Keywords: Brassica allohexaploid; Brassica carinata ; Brassica juncea ; Brassica napus ; Brassica oleracea ; cross-pollination; heterosis; hybrids; interspecific hybridization; self-pollination

DOI: https://doi.org/10.1093/aob/mcaf254