Key message
Epigenetic dominance modifier.
Abstract
In polymorphic loci, complex genetic dominance relationships between alleles are often observed. In plants, control of self-incompatibility (SI) expression via allelic interactions in the Brassicaceae is the best-known example of such mechanisms. Here, with emphasis on two recently published papers, we review the progress toward understanding the dominance regulatory mechanism of SI in the Brassicaceae. Multiple small RNA genes linked to the Self-incompatibility (S) locus were found in both Brassica and Arabidopsis genera. Mono-allelic gene expression of the male determinant of SI, SP11/SCR, from a dominant S-allele is under epigenetic control by such small RNA genes. Possible evolutionary trajectories leading to the formation of multilayered dominance hierarchy in Brassicaceae are discussed. We also identify some remaining questions for future studies.

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Acknowledgements
This work was supported in part by Grants-in-Aid for Scientific Research on Innovative Areas (23113002, 16H06467, 16H06464 to S.T.; 16H01467 to S.F.), Grants-in-Aid for Scientific Research (21248014, 25252021, 16H06380 to S.T.), Grant-in-Aid for Challenging Exploratory Research (15K14626 to S.F.) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), and Japan Science and Technology Agency (JST) PRESTO program (JPMJPR16Q8) to S.F.
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Communicated by Mengxiang Sun.
A contribution to the special issue ‘Plant Reproduction Research in Asia’.
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Fujii, S., Takayama, S. Multilayered dominance hierarchy in plant self-incompatibility. Plant Reprod 31, 15–19 (2018). https://doi.org/10.1007/s00497-017-0319-9
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DOI: https://doi.org/10.1007/s00497-017-0319-9