Primary structural features of rosaceous S-RNases associated with gametophytic self-incompatibility.
We isolated cDNA clones encoding five S-RNases (S1-, S3-, S5-, S6-, S7-RNases) from pistils of Pyrus pyrifolia (Japanese pear), a member of the Rosaceae. Their amino acid sequences were aligned with those of other rosaceous S-RNases sequenced so far. A total of 76 conserved amino acid residues were stretched throughout the sequence, but were absent from the 51-66 region which was designated the hypervariable (HV) region. The phylogenetic tree of rosaceous S-RNases showed that S-RNase polymorphism predated the divergence of Pyrus and Malus. Pairwise comparison of these S-RNases detected two highly homologous pairs, P. pyrifolia S1- and S4-RNases (90.0%) and P. pyrifolia S3- and S5-RNases (95.5%). The positions of amino acid substitutions between S1- and S4-RNases were spread over the entire region, but in the pair of S3- and S5-RNases, amino acid substitutions were found in the 21-90 region including the HV region. The substitutions in this restricted region appear to be sufficient to discriminate between S3 and S5 pollen and to trigger the self-incompatible reaction.
Ishimizu
T
T
Division of Protein Chemistry, Institute for Protein Research, Osaka University, Suita, Japan.
Shinkawa
T
T
Sakiyama
F
F
Norioka
S
S
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D005298:Fertility / Q000235:genetics; D005638:Fruit / Q000201:enzymology / Q000235:genetics*; D006238:Haploidy; D008969:Molecular Sequence Data; D012260:Ribonucleases / Q000235:genetics*; D019685:Rosales / Q000201:enzymology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D018076:DNA, Complementary; D012260:Ribonucleases; C022542:ribonuclease S