Computational model proposes ploidy buffers developmental gene expression noise to explain hybrid vigour

Hybrid vigour, or heterosis, is the well-documented tendency of hybrid offspring to outperform their parents in traits such as growth, fertility, and stress tolerance. Its mechanistic basis has long been debated. A preprint posted on bioRxiv presents a computational model of multicellular development to argue that ploidy itself — independent of allelic complementation — buffers the deleterious consequences of stochastic gene expression noise.

The model demonstrates that as organisms increase in ploidy, from haploid to diploid and from diploid to tetraploid, the probability that noise-driven errors in gene expression propagate to incorrect cell fate determination decreases substantially. The author reasons that large multicellular organisms require millions of cell divisions and numerous cell fate specification events, making total control of expression noise biologically implausible. Increased ploidy, by averaging across more gene copies, reduces the effective noise at each decision point.

The framework is proposed to apply both to allopolyploid and autopolyploid plants — a domain with major relevance to crop science — and to diploid F1 hybrids relative to their inbred parents. The preprint has not yet been peer-reviewed and presents a theoretical rather than experimental result. Researchers in evolutionary genetics, developmental biology, and plant genomics are the primary audience for this work.