A genetically definedtrans‐acting locus regulatesS‐locus function inBrassica

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Abstract
Summary: A new locus,SCF1, which regulatesS‐locus function has been identified inBrassica campestris. The spontaneousscf1mutation described in this paper causes the stigma to be receptive to all pollen including selfpollen, but does not affect the pollination phenotype of the male gametophyte. In the stigmas ofscf1homozygotes, theS‐locus‐linkedSLGgene and two other unlinked members of theS‐multigene family, all of which encode secreted glycoproteins, are coordinately down‐regulated at the RNA level, while the expression of theS‐locus‐derivedSRKgene, which encodes a putative receptor protein kinase, is unaffected. It is proposed that theSCF1locus encodes a positivetrans‐acting factor required for the enhanced transcription of several genes in the stigmatic papillar cells during pistil maturation. The effects of thescf1mutation provide strong support for the involvement of the clonedS‐genes in the operation of the pollen‐stigma interaction of incompatibility inB. campestrisand related crucifer species.