Allelic diversity of S-RNase at the self-incompatibility locus in natural flowering cherry populations (Prunus lannesiana var. speciosa).
In the Rosaceae family, which includes Prunus, gametophytic self-incompatibility (GSI) is controlled by a single multiallelic locus (S-locus), and the S-locus product expressed in the pistils is a glycoprotein with ribonuclease activity (S-RNase). Two populations of flowering cherry (Prunus lannesiana var. speciosa), located on Hachijo Island in Japan's Izu Islands, were sampled, and S-allele diversity was surveyed based on the sequence polymorphism of S-RNase. A total of seven S-alleles were cloned and sequenced. The S-RNases of flowering cherry showed high homology to those of Prunus cultivars (P. avium and P. dulcis). In the phylogenetic tree, the S-RNases of flowering cherry and other Prunus cultivars formed a distinct group, but they did not form species-specific subgroups. The nucleotide substitution pattern in S-RNases of flowering cherry showed no excess of nonsynonymous substitutions relative to synonymous substitutions. However, the S-RNases of flowering cherry had a higher Ka/Ks ratio than those of other Prunus cultivars, and a subtle heterogeneity in the nucleotide substitution rates was observed among the Prunus species. The S-genotype of each individual was determined by Southern blotting of restriction enzyme-digested genomic DNA, using cDNA for S-RNase as a probe. A total of 22 S-alleles were identified. All individuals examined were heterozygous, as expected under GSI. The allele frequencies were, contrary to the expectation under GSI, significantly unequal. The two populations studied showed a high degree of overlap, with 18 shared alleles. However, the allele frequencies differed considerably between the two populations.
Kato
S
S
Department of Forest Resources Science, Faculty of Agriculture, University of Shizuoka, Shizuoka 422-8529, Japan. shuri-77@wk9.so-net.ne.jp
Mukai
Y
Y
D000483:Alleles; D000595:Amino Acid Sequence; D017343:Genes, Plant; D014644:Genetic Variation; D005828:Genetics, Population; D007564:Japan; D008969:Molecular Sequence Data; D010802:Phylogeny; D027861:Prunus / Q000235:genetics*; D012260:Ribonucleases / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D012260:Ribonucleases