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Figure 1 | Genome Biology

Figure 1

From: Pollen recognition during the self-incompatibility response in plants

Figure 1

Genetic control of self-incompatibility (SI). When allelic forms (haplotypes) of the S locus are matched in pollen (male tissue) and pistil (female tissue) the pollen is rendered incompatible. The incompatibility response is mediated by a variety of molecular mechanisms in different species. (a) In GSI the SI phenotype of the pollen is determined by its own haploid genome, and the growing pollen tubes are usually inhibited in the style (the S alleles of the male and female parent plants and the haplotype of the pollen are indicated). GSI dictates that S alleles are expressed co-dominantly in the pistil. Note that 50% of pollen from an S1S2 individual is compatible with the S1S3 pistil because half the pollen grains express the S1 allele and half the S2 allele. (b) In SSI the SI phenotype of the pollen is determined by the diploid genome of its parent plant, so if S alleles are expressed co-dominantly 'in the pollen', 100% of the pollen from a S1S2 individual will be inhibited by an S1S3 pistil (in SSI, pollen is usually inhibited on the stigma). SSI is possible because pollen S alleles are expressed sporophytically in diploid cells of the anther tapetum that supplies the S proteins to the pollen coating.

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