Characterization and cDNA Cloning for S_f-RNase, a Molecular Marker for Self-compatibility, in Japanese Apricot (Prunus mume)

Abstract

Self-compatible cultivars of Japanese apricot (Prunus mume Sieb. et Zucc.) have a common S-RNase (S_f-RNase) gene that can be used as a molecular marker for self-compatibility. In this study, we further characterized S_f-RNase by comparing S-RNase of self-compatible 'Kensaki' (S_fS_f) and self-incompatible 'Nankou' (S₁S₇). cDNA libraries from the styles with stigmas of these two cultivars were constructed and cDNAs encoding S_f-, S₁-, and S₇-RNases were cloned. Deduced amino acid sequences from these cDNAs all contained two active domains of the T2/S type RNase family and five conserved regions of the rosaceous S-RNase. RNA blot analysis showed that the S_f-, S₁-, and S₇-RNase genes were transcribed in the pistil but not in the leaf as with other S-RNase genes of Prunus. Furthermore, 2D-PAGE analysis revealed that S_f-RNase has molecular mass, isoelectric point, and immunological characteristics similar to other S-RNase. These results indicate that the pollen-S gene that is supposedly tightly linked to the S_f-RNase gene may be responsible for the self-compatibility observed in the S_f-haplotype.