MOLECULAR CHARACTERIZATION OF THE S-LOCUS IN 2 SELF-INCOMPATIBLE BRASSICA-NAPUS LINES

In Brassica species, self-incompatibility has been mapped genetically to a single chromosomal location, In this region, there are two closel y linked genes coding for the S locus glycoprotein (SLG) and S locus r eceptor kinase (SRK), They appear to comprise the pistil component of the self-incompatibility reaction. SLG and SRK are thought to recogniz e an unknown pollen component on the incompatible pollen, and the gene encoding this pollen component must also be linked to the SLG and SRK genes. To further our understanding of self-incompatibility, the chro mosomal region carrying the SLG and SRK genes has been studied, The ph ysical region between the SLG-910 and the SRK-910 genes in the Blas si ca napus W1 line was cloned, and a search for genes expressed in the a nther revealed two additional S locus genes located downstream of the SLG-910 gene, Because these two genes are novel and are conserved at o ther S alleles, we designated them as SLL(1) and SLL(2) (for S locus-l inked genes 1 and 2, respectively), The SLL(1) gene is S locus specifi c, whereas the SLL(2) gene is not only present at the S locus but is a lso present in other parts of the genomes in both self-incompatible an d self-compatible Brassica ssp lines, Expression of the SLL(1) gene is only detectable in anthers of self-incompatible plants and is develop mentally regulated during anther development, whereas the SLL(2) gene is expressed in anthem and stigmas in both self-incompatible and self- compatible plants, with the highest levels of expression occurring in the stigmas, Although SLL(1) and SLL(2) are linked to the S locus regi on, it is not clear whether these genes function in self-incompatibili ty or serve some other cellular roles in pollen-pistil functions.