Harnessing nuclear-organellar genome interactions for seed size heterosis in Arabidopsis thaliana
Lai, Linyi
Lai, Linyi
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https://hdl.handle.net/10379/18439
https://doi.org/10.13025/29233
https://doi.org/10.13025/29233
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Publication Date
2025-01-13
Type
doctoral thesis
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Abstract
The nucleus contains most of the genome, which often leads to the contribution of the cytoplasm to phenotypes being overlooked. However, there was evidence that cybrids (nucleus/cytoplasm-swapped lines), generated through backcrossing or haploid induction, can produce a heterosis-like effect that influences agronomic traits, such as seed size. Heterosis refers to the phenomenon where offspring exhibit superior phenotypes compared to their parents. Despite several hypotheses, the underlying mechanisms remain unclear. Seed size, a critical agronomic trait, is determined by multiple mechanisms. During double fertilization, the embryo and endosperm inherit the nuclear genome from both parents, while all seed structures contain cytoplasm inherited exclusively from the mother. Thus, cytonuclear disequilibrium arises and acts as a regulator for seed development. In this thesis, we generated a series of cybrid lines using the natural variations (accessions) found in Arabidopsis thaliana. By comparing different cybrid line combinations, we provide evidence that cytonuclear interactions significantly influence seed size and that these effects can be transmitted to the F1 generation. Additionally, a GWAS identified a nuclear-encoded gene, RLP15 that may specifically respond to the Col-0 cytoplasm in seed size determining. Our findings also highlight the importance of cytoplasmic inheritance in parental effects. This study underscores that harnessing natural variation in the cytoplasm between accessions can produce a heterosis-like effect that, in certain genetic backgrounds, may be equivalent to or even greater than heterosis out from hybridization. Moreover, the impact of cytoplasm swapping to F1 seed size can be cumulative and interactive with heterosis, suggesting that cytoheterosis is partially independent of traditional heterosis mechanisms. In conclusion, our results indicate a new avenue for improving traits in plant breeding programs by leveraging naturally occurring genome variations.
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Publisher
University of Galway
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Attribution-NonCommercial-NoDerivatives 4.0 International