Cloning and characterization of a self-compatible Sf haplotype in almond [Prunus dulcis (Mill.) D.A. Webb. syn. P. amygdalus Batsch] to resolve previous confusion in its Sf-RNase sequence

Abstract

Additional index words. self-incompatibility, S haplotype, S-RNase, SFB . Most of the elf-compatible (SC) cultivars of almond [Prunus dulcis (Mill.) D.A. . syn. P. amygdalus Batsch] have the Sf haplotype. In this study, we cloned and the S locus region of the Sf haplotype of SC 'Lauranne'. The relative orientation of SFBf and Sf-RNase and the physical distance between them similar to those of other functional self-incompatible (SI) S haplotypes of Prunus, that the genomic structure of the SC Sf haplotype appears to be intact. there is no apparent mutation in the coding sequence of SFBf, the Sf-RNase in this study and previously reported Sf-RNase sequences show discrepancies. , as opposed to previous indications, the 'Lauranne' Sf-RNase sequence encodes a residue in place of a previously reported arginine residue in the conserved C2 of Prunus S-RNase. Direct sequencing of the polymerase chain reaction products. the Sf-RNase of 'Tuono' confirmed that 'Tuono' Sf-RNase also encodes the histidine . We found another difference in the 'Lauranne' Sf-RNase sequence and other Sf-RNase sequences. Namely, 'Lauranne' Sf-RNase encodes a phenylalanine in place of a previously reported leucine residue in the conserved C5 region of S-RNase. This is also the case for 'Tuono' Sf-RNase. Expression analysis of Sf- and SFBf by reverse transcriptase-polymerase chain reaction showed that Sf- transcripts were barely detectable in pistil, whereas SFBf transcripts were at a similar level to the level that was observed with SFB of other functional S haplotypes of almond.We discuss the possible molecular mechanisms of SC observed with the Sf haplotype with special references to the expression of Sf-RNase.