S^F-RNASE AND ITS RELATION TO SELF-COMPATIBILITY IN JAPANESE APRICOT

Self-compatible cultivars of Japanese apricot (Prunus mume Shieb. 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, inheritance of the S^f-RNase gene and self- compatibility was investigated using the progenies from controlled crosses. In all the crosses examined, the S^f-RNase gene was inherited to the progenies as one of the pistil S-alleles in a non-functional S-haplotype. In addition to the inheritance study, we characterized S^f-RNase by comparing S-RNases of self-compatible ‘Kensak’ (S^fS^f) and self-incompatible ‘Nanko’ (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 had Mr, pI, and immunological characteristics similar to other S-RNase. These results could indicate that the pollen-S gene supposed to be tightly linked to the S^f-RNase gene may be responsible for the self-compatibility observed in the S^f-haplotype.

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