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
2009
Hanada, Toshio | Fukuta, Kyoko | Yamane, Hisayo | Esumi, Tomoya | Tao, Ryutaro | Gradziel, T (Thomas) | Dandekar, Abhaya M. | Fernández i Martí, Ángel | Alonso, Jose M. | Socias i Company, Rafel
Most of the self-compatible (SC) cultivars of almond [Prunus dulcis (Mill.) D.A. Webb. syn. P. amygdalus Batsch] have the Sf haplotype. In this study, we cloned and characterized the S locus region of the Sf haplotype of SC 'Lauranne'. The relative transcriptional orientation of SFBf and Sf-RNase and the physical distance between them are similar to those of other functional self-incompatible (SI) S haplotypes of Prunus, indicating that the genomic structure of the SC Sf haplotype appears to be intact. Although there is no apparent mutation in the coding sequence of SFBf, the Sf-RNase sequence in this study and previously reported Sf-RNase sequences show discrepancies. First, as opposed to previous indications, the 'Lauranne' Sf-RNase sequence encodes a histidine residue in place of a previously reported arginine residue in the conserved C2 region of Prunus S-RNase. Direct sequencing of the polymerase chain reaction products from the Sf-RNase of 'Tuono' confirmed that 'Tuono' Sf-RNase also encodes the histidine residue. We found another difference in the 'Lauranne' Sf-RNase sequence and other reported Sf-RNase sequences. Namely, 'Lauranne' Sf-RNase encodes a phenylalanine residue in place of a previously reported leucine residue in the conserved C5 region of Prunus S-RNase. This is also the case for 'Tuono' Sf-RNase. Expression analysis of Sf-RNase and SFBf by reverse transcriptase-polymerase chain reaction showed that Sf-RNase transcripts were barely detectable in pistil, whereas SFBf transcripts were accumulated at a similar level to the level that was observed with SFB of other functional SI 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.
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