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bioRxiv · 10.1101/2022.07.18.499170

Fine-mapping and comparative genomic analysis reveal the gene composition at the S and Z self-incompatibility loci in grasses

Rohner, M.·Manzanares, C.·Yates, S.·Thorogood, D.·Copetti, D.·Lübberstedt, T.·Asp, T.·Studer, B.
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Abstract

Self-incompatibility (SI) is a genetic mechanism of hermaphroditic plants to prevent inbreeding after self-pollination. Allogamous Poaceae species exhibit a unique gametophytic SI system controlled by two multi-allelic and independent loci, S and Z. Despite intense research efforts in the last decades, the genes that determine the initial recognition mechanism are yet to be identified. Here, we report the fine-mapping of the Z-locus in perennial ryegrass (Lolium perenne L.) and provide evidence that the pollen and stigma components are determined by two genes encoding DUF247 domain proteins (ZDUF247-I and ZDUF247-II) and the gene sZ, respectively. The pollen and stigma determinants are located side-by-side and were genetically linked in 10,245 individuals of two independent mapping populations segregating for Z. Moreover, they exhibited high allelic diversity as well as tissue-specific gene expression, matching expected characteristics of SI determinants known from other systems. Revisiting the S-locus using the latest high-quality whole-genome assemblies revealed a similar gene composition and structure as found for Z, supporting the hypothesis of a duplicated origin of the two-locus SI system of grasses. Ultimately, comparative genomic analyses across a wide range of self-compatible and self-incompatible Poaceae species revealed that the absence of a functional copy of at least one of the six putative SI determinants is accompanied by a self-compatible phenotype. Our study provides new insights into the origin and evolution of the unique gametophytic SI system in one of the largest and economically most important plant families.

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Rohner, M., Manzanares, C., Yates, S., Thorogood, D., Copetti, D., Lübberstedt, T., Asp, T., Studer, B.. 2022-07-18. Fine-mapping and comparative genomic analysis reveal the gene composition at the S and Z self-incompatibility loci in grasses. https://doi.org/10.1101/2022.07.18.499170

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