Physical mapping of a pollen modifier locus controlling self-incompatibility in apricot and synteny analysis within the Rosaceae

Instituto Valenciano de Investigaciones Agrarias-IVIA, Apartado Oficial, 46113 Moncada, Valencia, Spain.
Plant Molecular Biology (Impact Factor: 4.26). 04/2012; 79(3):229-42. DOI: 10.1007/s11103-012-9908-z
Source: PubMed


S-locus products (S-RNase and F-box proteins) are essential for the gametophytic self-incompatibility (GSI) specific recognition in Prunus. However, accumulated genetic evidence suggests that other S-locus unlinked factors are also required for GSI. For instance, GSI breakdown was associated with a pollen-part mutation unlinked to the S-locus in the apricot (Prunus armeniaca L.) cv. 'Canino'. Fine-mapping of this mutated modifier gene (M-locus) and the synteny analysis of the M-locus within the Rosaceae are here reported. A segregation distortion loci mapping strategy, based on a selectively genotyped population, was used to map the M-locus. In addition, a bacterial artificial chromosome (BAC) contig was constructed for this region using overlapping oligonucleotides probes, and BAC-end sequences (BES) were blasted against Rosaceae genomes to perform micro-synteny analysis. The M-locus was mapped to the distal part of chr.3 flanked by two SSR markers within an interval of 1.8 cM corresponding to ~364 Kb in the peach (Prunus persica L. Batsch) genome. In the integrated genetic-physical map of this region, BES were mapped against the peach scaffold_3 and BACs were anchored to the apricot map. Micro-syntenic blocks were detected in apple (Malus × domestica Borkh.) LG17/9 and strawberry (Fragaria vesca L.) FG6 chromosomes. The M-locus fine-scale mapping provides a solid basis for self-compatibility marker-assisted selection and for positional cloning of the underlying gene, a necessary goal to elucidate the pollen rejection mechanism in Prunus. In a wider context, the syntenic regions identified in peach, apple and strawberry might be useful to interpret GSI evolution in Rosaceae.

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Available from: Elena Zuriaga, Feb 04, 2014
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    • "In this cultivar , self-compatibility is caused by breakdown of pollen function, and this trait is not linked to the S locus, but seems located in the lower region of linkage group 3 (Cachi & W ¨ unsch, 2011). Recently, modifiers leading to pollen self-compatibility in apricot have also been located in chromosome 3 (Zuriaga et al., 2012, 2013). The function or identity of this factor in 'Cristobalina' is still unknown, but genetic evidence shows that it may be heterozygous in 'Cristobalina' (W ¨ unsch & Hormaza, 2004a; Cachi & W ¨ unsch, 2011). "
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    ABSTRACT: Sweet cherry is a self-incompatible fruit tree species in the Rosaceae. As other species in the family, sweet cherry exhibits S-RNase-based gametophytic self-incompatibility. This mechanism is genetically determined by the S-locus that encodes the pollen and pistil determinants, SFB and S-RNase, respectively. Several self-compatible sweet cherry genotypes have been described and most of them have mutations at the S-locus leading to self-compatibility. However, ‘Cristobalina’ sweet cherry is self-compatible due to a mutation in a pollen function modifier that is not linked to the S-locus. To investigate the physiology of self-compatibility in this cultivar, S-locus segregation in crosses involving ‘Cristobalina’ pollen, and pollen tube growth in self- and cross-pollinations, were studied. In the crosses with genotypes sharing only one S-haplotype, the non-self S-haplotype was inherited more frequently than the self S-haplotype. Pollen tube growth studies revealed that the time to travel the whole length of the style was longer for self-pollen tubes than for cross-pollen tubes. Together, these results suggest that ‘Cristobalina’ pollen tube growth is slower after self-pollination than after cross-pollination. This reproductive strategy would allow self-fertilisation in the absence of compatible pollen but would promote cross-fertilisation if cross-compatible pollen is available, a possible case of cryptic self-incompatibility. This bet-hedging strategy might be advantageous for an ecotype that is native to the mountains of the Spanish Mediterranean coast, in the geographical limits of the distribution of this species. ‘Cristobalina’ blooming takes place very early in the season when mating possibilities are scarce and, consequently, self-compatibility may be the only possibility for this genotype to produce offspring.
    Annals of Applied Biology 01/2014; 164(1). DOI:10.1111/aab.12079 · 2.00 Impact Factor
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    ABSTRACT: Loss of pollen-S function in Prunus self-compatible cultivars has been mostly associated with deletions or insertions in the S-haplotype-specific F-box (SFB) genes. However, self-compatible pollen-part mutants defective for non-S-locus factors have also been found, for instance, in the apricot (Prunus armeniaca) cv. 'Canino'. In the present study, we report the genetic and molecular analysis of another self-compatible apricot cv. termed 'Katy'. S-genotype of 'Katy' was determined as S(1)S(2) and S-RNase PCR-typing of selfing and outcrossing populations from 'Katy' showed that pollen gametes bearing either the S(1)- or the S(2)-haplotype were able to overcome self-incompatibility (SI) barriers. Sequence analyses showed no SNP or indel affecting the SFB(1) and SFB(2) alleles from 'Katy' and, moreover, no evidence of pollen-S duplication was found. As a whole, the obtained results are compatible with the hypothesis that the loss-of-function of a S-locus unlinked factor gametophytically expressed in pollen (M'-locus) leads to SI breakdown in 'Katy'. A mapping strategy based on segregation distortion loci mapped the M'-locus within an interval of 9.4 cM at the distal end of chr.3 corresponding to ∼1.29 Mb in the peach (Prunus persica) genome. Interestingly, pollen-part mutations (PPMs) causing self-compatibility (SC) in the apricot cvs. 'Canino' and 'Katy' are located within an overlapping region of ∼273 Kb in chr.3. No evidence is yet available to discern if they affect the same gene or not, but molecular markers seem to indicate that both cultivars are genetically unrelated suggesting that every PPM may have arisen independently. Further research will be necessary to reveal the precise nature of 'Katy' PPM, but fine-mapping already enables SC marker-assisted selection and paves the way for future positional cloning of the underlying gene.
    PLoS ONE 01/2013; 8(1):e53947. DOI:10.1371/journal.pone.0053947 · 3.23 Impact Factor
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