Expression and Inheritance of S-Proteins in Self-Compatible and -Incompatible Japanese Pears.

Abstract

Expression and inheritance of style specific S2- and S4-allele associated S-proteins reported earlier (Hiratsuka et al., 1995) were studied using progenies of self-compatible 'Osa-Nijisseiki'.The S-protein bands of 'Osa-Nijisseiki', which was generated from self-incompatible 'Nijisseiki' as a mutant, were compared with those of 'Nijisseiki' by isoelectricfocusing polyacrylamide gel electrophoresis (IEF-PAGE). The protein band associated with S4sm-allele in 'Osa-Nijisseiki' was stained less densely with Coomassie Brilliant Blue (CBB) than did the band from 'Nijisseiki'; the RNase activity of the former band was also weaker than that of the latter as reported by Sassa et al. (1992, 1993). However, no difference was observed in the S2-protein band between 'Osa-Nijisseiki' and 'Nijisseiki'. The S-genotypes of the 'Osa-Nijisseiki' x self and 'Osa-Nijisseiki' x 'Nijisseiki' progenies were determined and their styles subjected to S-protein analyses. Progenies with the So4sm-gene from 'Osa-Nijisseiki' possessed a lightly stained S4-protein band, whereas those of 'Nijisseiki' had almost the same density as did 'Nijisseiki'. The S2-protein band was detected consistently in progenies carrying the S2-allele.Style specific S2- and S4-protein bands including a faint S4-band of 'Osa-Nijisseiki' were, thus, inherited with no exception to the progenies carrying respective S-alleles. These results may show that the proteins reported here are the S-gene products of Japanese pears and that of 'Osa-Nijisseiki' is a mutant which represses the S4-gene expression.