EXPRESSION AND INHERITANCE OF S-PROTEINS IN SELF-COMPATIBLE AND SELF-INCOMPATIBLE JAPANESE PEARS

Expression and inheritance of style specific S-2- and S-4-allele assoc iated S-proteins reported earlier (Hiratsuka et al., 1995) were studie d using progenies of self-compatible 'Osa-Nijisseiki'. The S-protein b ands of 'Osa-Nijisseiki', which was generated from self-incompatible ' Nijisseiki' as a mutant, were compared with those of 'Nijisseiki' by i soelectricfocusing polyacrylamide gel electrophoresis (IEF-PAGE). The protein band associated with S-4(sm)-allele in 'Osa-Nijisseiki' was st ained less densely with Coomassie Brilliant Blue (CBB) than did the ba nd from 'Nijisseiki'; the RNase activity of the former band was also w eaker than that of the latter as reported by Sassa et al. (1999, 1993) . However, no difference was observed in the S-2-protein band between 'Osa-Nijisseiki' and 'Nijisseiki'. The S-genotypes of the 'Osa-Nijisse iki' xself and 'Osa-Nijisseiki' x 'Nijisseiki' progenies were determin ed and their styles subjected to S-protein analyses. Progenies with th e S-4(sm)-gene from 'Osa-Nijisseiki' possessed a lightly stained S-4-p rotein band, whereas those of 'Nijisseiki' had almost the same density as did 'Nijisseiki'. The S-2-protein band was detected consistently i n progenies carrying the S-2-allele. Style specific S-2- and S-4-prote in bands including a faint S-4-band of Osa-Nijisseiki' were, thus, inh erited with no exception to the progenies carrying respective S-allele s. These results may show that the proteins reported here are the S-ge ne products of Japanese pears and that of 'Osa-Nijisseiki' is a mutant which represses the S-4-gene expression.