Cytonuclear interactions remain stable during allopolyploid evolution despite repeated whole‐genome duplications in Brassica
2019
Several
plastidmacromolecular protein complexes are encoded by both nuclear and
plastidgenes. Therefore, cytonuclear interactions are held in place to prevent genomic conflicts that may lead to incompatibilities. Allopolyploidy resulting from hybridization and genome doubling of two divergent species, can disrupt these fine-tuned interactions, as newly formed allopolyploid species confront biparental nuclear chromosomes with
uniparentally inherited
plastidgenome. To avoid any deleterious effects of unequal genome inheritance, preferential transcription of the
plastiddonor over the other one has been hypothesized to occur in allopolyploids. We used Brassica as a model to study the effects of
paleopolyploidyin diploid parental species, as well as the effects of recent and ancient allopolyploidy in Brassica napus on genes implicated in
plastidprotein complexes. We first identified redundant nuclear copies involved in those complexes. Compared to cytosolic protein complexes and to genome-wide
retention rates, genes involved in
plastidprotein complexes show a higher retention of genes in duplicated and triplicated copies. Those redundant copies are functional and undergoing strong purifying selection. We then compared transcription patterns and sequences of those redundant gene copies between resynthesized allopolyploids and their diploid parents. The neo-
polyploidsshowed no biased subgenome expression or maternal homogenization via
gene conversiondespite presence of some non-
synonymous substitutionsbetween
plastidgenomes of parental progenitors. Instead, subgenome dominance was observed regardless of the maternal progenitor. Our results provide new insights on the evolution of
plastidprotein complexes which could be tested and generalized in other allopolyploid species. This article is protected by copyright. All rights reserved.
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