Abstract
The stylar proteins of 22 varieties of Japanese pear (Pyrus serotina Rehd., 21 selfincompatible and one self-compatible) were analyzed by isoelectric focusing-polyacrylamidegel electrophoresis (IEF-PAGE) to identify the S-allele proteins (S-proteins) associated withself-incompatibility (SI). The corresponding relationships between the protein bands and thefour alleles S2, S3, S4 and S5, were examined for each variety for which the allele composition was already known.
Experiment 1 comprised the IEFs on the four major varieties. Analysis of the band patterns, isolated at intervals pH 310, 58 and 46.5 revealed that three bands (hereafter, tentatively referred to as) (a) at isoelectric point (pI) 6.6, (c) at pI 5.3 and (d) at pI 5.0 werethe putative proteins corresponding to the S4 allele. Band (b) at pI 5.6 and (e) at pI 6.0 werealso the putative proteins corresponding to the S2 allele and the S5 allele, respectively. Allthe bands described above exhibited a positive periodic acid Schiff's (PAS) reaction. Thereforethe presence of glycoproteins was suspected. Experiment 2 comprised IEFs on the other 18varieties. The results compiled from both experiments showed that among 21 varieties (otherthan one self-compatible variety), the correspondence between the bands and S-alleles wasrelatively high on band (c) in 19 varieties. This band was thought to be associated with theS4 allele. Other bands demonstrated rather low correspondences; band (a) exhibited the relationship in 15 varieties, band (b) in 13 varieties and band (d) in 13 varieties. No differencein protein band patterns was exhibited between the self-incompatible variety 'Nijisseiki' andits self-compatible strain 'Osa-Nijisseiki', which was assumed to be a stylar part mutant ofthe S-gene. Our discussion compares the results of this study with research on S-proteinsin other species, and includes suggestions for future research methods.
