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Characterization of Sf-RNase and SFBf adjacent regions in the S-locus of almond

Gomez, E. M., Prudencio, A. S., Dicenta, F., Ortega, E.
Acta horticulturae 2019 no.1231 pp. 105-108
almonds, enzyme activity, gametophytes, gene expression, genes, genotyping, haplotypes, intergenic DNA, loci, nucleotides, open reading frames, phenotype, pistil, pollen, promoter regions, proteins, ribonucleases, transcription (genetics)
Most almond cultivars are self-incompatible, and some of them are cross-incompatible. The incompatibility system is of the gametophytic type and it is controlled by the multiallelic locus S, which includes the S-RNase and the SFB genes, expressed in pistil and pollen respectively. The S(f) haplotype has traditionally been associated with self-compatibility. However, recent studies have reported the existence of almond cultivars genotyped as S(f) that show a self-incompatible phenotype. This finding reveals the presence of other unidentified components (named modifier factors) involved in the incompatibility system of this species, which could modulate gene expression, increasing or inhibiting the activity of S-RNase and SFB proteins. In this work the sequences of the S(f)-RNase promoter, and the 6 Kb intergenic region between the S(f)-RNase and the SFB(f) genes from two self-compatible and two self-incompatible almond selections carrying the S(f) haplotype, have been obtained. Differences among these sequences may belong to a change in the way the modifier factors bind to them or in the way these factors are acting over the transcription of the coding regions. The results showed no differences among the S(f)-RNase promoter sequences; however the intergenic regions were not identical. Interestingly, a new open reading frame (ORF) of 2,433 nucleotides long, which is transcribed and may play a role in the incompatibility system, was located in the region between the Sf-RNase and the SFB(f) in both self-compatible and self-incompatible almonds.