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TheBrassica S gene family: Molecular characterization of theSLR2 gene

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TheS gene family of higher plants includes secreted glycoprotein-encoding genes and transmembrane protein kinase-encoding genes all of which share sequence similarity to theS-locus genes ofBrassica. In our continuing effort to understand the structural and functional diversification of this gene family inBrassica, we analyzed theS-locus-relatedSLR2 gene fromB. oleracea andB. campestris. SLR2 is a flower-specific gene that exhibits a high degree of sequence similarity to theS-locus genes derived from theS 2 self-incompatibility haplotype. We present data which suggest that theSLR2 gene encodes a secreted protein as predicted from its nucleotide sequence. However, unlike other secreted glycoprotein-encoding members of theS gene family, the gene contains a 591 base-pair intron at or near its 3′ terminus. Based on this structure, we propose that this gene arose prior to speciation by partial duplication of an ancestral gene similar in structure to theS-locus-linkedSRK (S ReceptorKinase) gene. The high degree of variability inSLR2 transcript levels noted in differentBrassica strains was found to be correlated with the segregation of anSLR2 polymorphism, whereby a mutatedSLR2 allele containing a duplication within the promoter region directs low expression. The implications of these findings forSLR2 gene function are discussed.

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Correspondence to June B. Nasrallah.

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Tantikanjana, T., Nasrallah, M.E. & Nasrallah, J.B. TheBrassica S gene family: Molecular characterization of theSLR2 gene. Sexual Plant Reprod 9, 107–116 (1996). https://doi.org/10.1007/BF02153058

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Key words

  • Brassica
  • S gene family
  • S-locus related