Analysis of the S-locus structure in Prunus armeniaca L. Identification ofS-haplotype specific S-RNase and F-box genes

Abstract

The gametophytic self-incompatibility (GSI) system in Rosaceae has been proposed to be controlled by two genes located in the S -locusan S-RNase and a recently described pollen expressed S -haplotype specific F-box gene (SFB). However, in apricot (Prunus armeniaca L.) these genes had not been identified yet. We have sequenced 21 kb in total of the S -locus region in 3 different apricot S -haplotypes. These fragments contain genes homologous to the S-RNase and F-box genes found in other Prunus species, preserving their basic gene structure features and defined amino acid domains. The physical distance between the F-box and the S-RNase genes was determined exactly in the S2-haplotype (2.9 kb) and inferred approximately in the S 1-haplotype (< 49 kb) confirming that these genes are linked. Sequence analysis of the 5' flanking regions indicates the presence of a conserved region upstream of the putative TATA box in the S-RNase gene. The three identified S-RNase alleles (S1, S2 and S4) had a high allelic sequence diversity (75.3 amino acid identity), and the apricot F-box allelic variants (SFB1, SFB2 and SFB4) were also highly haplotype-specific (79.4 amino acid identity). Organ specific-expression was also studied, revealing that S1- and S2-RNases are expressed in style tissues, but not in pollen or leaves. In contrast, SFB1 and SFB2 are only expressed in pollen, but not in styles or leaves. Taken together, these results support these genes as candidates for the pistil and pollen S-determinants of GSI in apricot.

Identification and characterization of S-RNase genes and S-genotypes in Prunus and Malus species

“…To assess whether or not there is a correlation between S-pistil and Spollen genes that contributes to genetic variability, all published SFB genes found in Prunoideae have been analyzed in this study. A total of 10, 32, 17, 12, and 24 different alleles have been identified in plum, apricot, Japanese apricot, sweet cherry, and almond, respectively (Yamane et al 2003b;Romero et al 2004;Ushijima et al 2004;Vaughan et al 2006;Zhang et al 2007;Wu et al 2009Wu et al , 2013. In contrast, only four S-RNase alleles and four SFB alleles are identified for peach cultivars and their wild relatives in this study.…”

“…More recently, two additional S-haplotypes have been reported (Hanada et al 2014). Whereas, over 20 S-haplotypes are reported in other Prunus species such as almond, sweet cherry, plum, apricot, and Japanese apricot (Ushijima et al 2003(Ushijima et al , 2004Yamane et al 2003a, b;Romero et al 2004;Vaughan et al 2006;Zhang et al 2007;Wu et al 2009Wu et al , 2013. In apple, S-haplotype profiling has been widely used in characterizing apple cultivars (Janssens et al 1995;Bokszczanin et al 2009;Kim et al 2009;Long et al 2010;Minamikawa et al 2010).…”

Inheritance of S-genotypes in Paviot × Kabaasi apricot F1 progenies

“…Primer sequence Reference SRc-R 5'-GGC CAT TGT TGC ACA AAT TG-3' Vilanova et al [25] SRc-F 5'-CTC GCT TTC CTT GTT CTT GC-3' Romero et al [24] Kabaasi and Paviot cultivars were bidirectionally sequenced, BLAST searched in NCBI GenBank and in them, the S-alleles were determined as S 1 S 9 . Apricots belonging to the IranÀCaucasian eco-geographical group have been reported to be mostly selfincompatible, those in the European eco-geographical group, mostly self-compatible and 60% of the varieties in Turkey have been found to be self-incompatible.…”

Genetic Diversity in Apricot

“…The S-haplotype contains a female determinant, (S-RNase) encoding for a ribonuclease enzyme (McClure et al 1989), and the recently identified male determinant, S-haplotype-specific F-box gene (Entani et al 2003;Romero et al 2004;Halasz et al 2010). …”