Research Article

Dominance hierarchy arising from the evolution of a complex small RNA regulatory network

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Science  05 Dec 2014:
Vol. 346, Issue 6214, pp. 1200-1205
DOI: 10.1126/science.1259442

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The prevention of fertilization through self-pollination (or pollination by a close relative) in the Brassicaceae plant family is determined by the genotype of the plant at the self-incompatibility locus (S locus). The many alleles at this locus exhibit a dominance hierarchy that determines which of the two allelic specificities of a heterozygous genotype is expressed at the phenotypic level. Here, we uncover the evolution of how at least 17 small RNA (sRNA)–producing loci and their multiple target sites collectively control the dominance hierarchy among alleles within the gene controlling the pollen S-locus phenotype in a self-incompatible Arabidopsis species. Selection has created a dynamic repertoire of sRNA-target interactions by jointly acting on sRNA genes and their target sites, which has resulted in a complex system of regulation among alleles.

Dominance cascades in self-incompatibility

Plants often cannot use their own pollen to set seed. This is known as self-incompatibility. Although some of the underlying genetics and mechanisms of self-incompatibility are understood, the evolution and maintenance of the system have remained mysterious. Durand et al. identified a collection of small RNAs and their respective matching targets within a self-incompatibility locus in Arabidopsis halleri. A subset of these alleles functioned in a dominant manner, which helps to explain how self-incompatibility is maintained.

Science, this issue p. 1200

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