Gametophytic Self-incompatibility Research Articles

A survey of the Sli gene in wild and cultivated potato.

Inbred-hybrid breeding of diploid potatoes necessitates breeding lines that are self-compatible. One way of incorporating self-compatibility into incompatible cultivated potato (Solanum tuberosum) germplasm is to introduce the S-locus inhibitor gene (Sli), which functions as a dominant inhibitor of gametophytic self-incompatibility. To learn more about Sli diversity and function in wild species relatives of cultivated potato, we obtained Sli gene sequences that extended from the 5'UTR to the 3'UTR from 133 individuals from 22 wild species relatives of potato and eight diverse cultivated potato clones. DNA sequence alignment and phylogenetic trees based on genomic and protein sequences show that there are two highly conserved groups of Sli sequences. DNA sequences in one group contain the 533 bp insertion upstream of the start codon identified previously in self-compatible potato. The second group lacks the insertion. Three diploid and four polyploid individuals of wild species collected from geographically disjointed localities contained Sli with the 533 bp insertion. For most of the wild species clones examined, however, Sli did not have the insertion. Phylogenetic analysis indicated that Sli sequences with the insertion, in wild species and in cultivated clones, trace back to a single origin. Some diploid wild potatoes that have Sli with the insertion were self-incompatible and some wild potatoes that lack the insertion were self-compatible. Although there is evidence of positive selection for some codon positions in Sli, there is no evidence of diversifying selection at the gene level. In silico analysis of Sli protein structure did not support the hypothesis that amino acid changes from wild-type (no insertion) to insertion-type account for changes in protein function. Our study demonstrated that genetic factors besides the Sli gene must be important for conditioning a switch in the mating system from self-incompatible to self-compatible in wild potatoes.

Self-(in)compatibility in Tunisian apple accessions [Malus domestica. Borkh]: S-genotypes identification and pollen tube growth analysis.

Self-incompatibility studies have revealed a potential use of Tunisian apple resources for crop improvement and modern breeding programs and a likely correlation between the pollen tube growth and flowering period. Apples [Malus domestica. Borkh] exhibit an S-RNase-based gametophytic self-incompatibility (GSI) system. Four primer combinations were used to S-genotype eighteen Tunisian local apple accessions and twelve introduced accessions that served as references. Within the Tunisian local accessions, S2, S3, S7, and S28 S-alleles were the most frequent and were assigned to 14 S-genotypes; among them, S7S28, S3S7, S2S5, and S2S3 were the most abundant. PCA plot showed that population structuring was affected by the S-alleles frequencies and revealed a modern origin of the Tunisian varieties rather than being ancient ones. Nonetheless, the results obtained with 17 SSR markers showed a separate grouping of local Tunisian accessions that calls into question the hypothesis discussed. Pollination experiments showed that the pollen started to germinate within 24h of pollination but 48h after pollination in the "El Fessi" accession. The first pollen tubes arrived in the styles within 36h of pollination in two early flowering accessions known as "Arbi" and "Bokri", and after 72h of pollination in late flowering "El Fessi" and 48h after pollination in remaining accessions. The first pollen tube arrests were observed in accessions "Arbi" and "Bokri" within 84h of pollination, within 108h of pollination in "El Fessi" and within 108h of pollination in remaining accessions. In the apple accession called "Boutabgaya," the pollen tubes reached the base of the style within 120h of pollination without being aborted. Nevertheless, the self-compatible nature of "Boutabgaya" needs more studies to be confirmed. However, our results revealed the malfunction of the female component of the GSI in this accession. To conclude, this work paved the path for further studies to enhance the insight (i) into the relation between the flowering period and the pollen tube growth, (ii) self-compatible nature of "Boutabgaya", and (iii) the origin of the Tunisian apple.

The influence of the pollination compatibility type on the pistil S-RNase expression in European pear (Pyrus communis).

The S-RNase gene plays an essential role in the gametophytic self-incompatibility (GSI) system of Pyrus. It codes for the stylar-expressed S-RNase protein which inhibits the growth of incompatible pollen tubes through cytotoxicity and the induction of programmed cell death in the pollen tube. While research on the Pyrus GSI system has primarily focused on the S-RNase gene, there is still a lack of insight into its spatiotemporal expression profile and the factors that regulate it. Previous studies have suggested that S-RNase expression in the style is influenced by pollination and is dependent on the compatibility type. We here continue on this basic hypothesis by analyzing the spatiotemporal expression of the S-RNase alleles in Pyrus communis "Conference" styles in response to different types of pollination; namely, upon full- and semi-compatible pollination and upon incompatible selfing. The results revealed that temporal dynamics of S-RNase expression are influenced by the pollen's compatibility type, indicating the presence of a signaling mechanism between pollen and style to control S-RNase production during pollen tube growth. In our experiment, S-RNase expression continuously decreased after cross-pollination and in the unpollinated control. However, after a fully incompatible pollination, S-RNase expression remained constant. Finally, semi-compatible pollination showed a initially constant S-RNase expression for both alleles followed by a strong decrease in expression. Based on these results and previous findings, we propose a regulatory mechanism to explain the effect of pollination and the associated compatibility type on S-RNase expression in the style. This proposed mechanism could be used as a starting point for future research.

The origin and the genetic regulation of the self-compatibility mechanism in clementine (Citrus clementina Hort. ex Tan.).

Self-incompatibility (SI) is a genetic mechanism common in flowering plants to prevent self-fertilization. Among citrus species, several pummelo, mandarin, and mandarin-like accessions show SI behavior. In these species, SI is coupled with a variable degree of parthenocarpy ensuring the production of seedless fruits, a trait that is highly appreciated by consumers. In Citrus, recent evidences have shown the presence of a gametophytic SI system based on S-ribonucleases (S-RNases) ability to impair self-pollen tube growth in the upper/middle part of the style. In the present study, we combined PCR analysis and next-generation sequencing technologies, to define the presence of S7- and S11-Rnases in the S-genotype of the Citrus clementina (Hort. ex Tan.), the self-incompatible 'Comune' clementine and its self-compatible natural mutant 'Monreal'. The reference genome of 'Monreal' clementine is presented for the first time, providing more robust results on the genetic sequence of the newly discovered S7-RNase. SNP discovery analysis coupled with the annotation of the variants detected enabled the identification of 7,781 SNPs effecting 5,661 genes in 'Monreal' compared to the reference genome of C. clementina. Transcriptome analysis of unpollinated pistils at the mature stage from both clementine genotypes revealed the lack of expression of S7-RNase in 'Monreal' suggesting its involvement in the loss of the SI response. RNA-seq analysis followed by gene ontology studies enabled the identification of 2,680 differentially expressed genes (DEGs), a significant number of those is involved in oxidoreductase and transmembrane transport activity. Merging of DNA sequencing and RNA data led to the identification of 164 DEGs characterized by the presence of at least one SNP predicted to induce mutations with a high effect on their amino acid sequence. Among them, four candidate genes referring to two Agamous-like MADS-box proteins, to MYB111 and to MLO-like protein 12 were validated. Moreover, the transcription factor MYB111 appeared to contain a binding site for the 2.0-kb upstream sequences of the S7- and S11-RNase genes. These results provide useful information about the genetic bases of SI indicating that SNPs present in their sequence could be responsible for the differential expression and the regulation of S7-RNase and consequently of the SI mechanism.

Intra- and inter-specific reproductive barriers in the tomato clade.

Tomato (Solanum lycopersicum L.) domestication and later introduction into Europe resulted in a genetic bottleneck that reduced genetic variation. Crosses with other wild tomato species from the Lycopersicon clade can be used to increase genetic diversity and improve important agronomic traits such as stress tolerance. However, many species in the Lycopersicon clade have intraspecific and interspecific incompatibility, such as gametophytic self-incompatibility and unilateral incompatibility. In this review, we provide an overview of the known incompatibility barriers in Lycopersicon. We begin by addressing the general mechanisms self-incompatibility, as well as more specific mechanisms in the Rosaceae, Papaveraceae, and Solanaceae. Incompatibility in the Lycopersicon clade is discussed, including loss of self-incompatibility, species exhibiting only self-incompatibility and species presenting both self-compatibility and self-incompatibility. We summarize unilateral incompatibility in general and specifically in Lycopersicon, with details on the 'self-compatible x self-incompatible' rule, implications of self-incompatibility in unilateral incompatibility and self-incompatibility-independent pathways of unilateral incompatibility. Finally, we discuss advances in the understanding of compatibility barriers and their implications for tomato breeding.

Specific functions of single pistil S-RNases in S-gene homozygous Pyrus germplasm

Gametophytic self-incompatibility (SI) is regulated by S-allele recognition; that is, pollen in a style with the same S-genotype will undergo programmed cell death and stop growing so that it is unable to complete double fertilization, ultimately resulting in the SI response. S-RNase is the female determinant of SI in pear (Pyrus). In the Pyrus genome, there are two different S-RNase alleles at the S-locus, which generate two different S-RNase products in the pistil. The extracted S-glycoprotein is actually a protein complex. In this study, artificial self-pollination was conducted at the bud stage to overcome SI in ‘Huanghua’ (S1S2) pear. Seven plants homozygous for S1-RNase and four homozygous for S2-RNase were selected from the selfed progeny of ‘Huanghua’ by S-gene molecular identification biotechnology. We investigated the function of single S-RNases isolated from the pistils of S-gene homozygous Pyrus germplasm. The pollen of ‘Huanghua’ could smoothly pass through the style of the S-gene homozygous germplasm and complete fertilization. S-RNases were extracted from flower styles of different genotypes and used to treat different types of pollen. The S-RNase from ‘Huanghua’ completely inhibited the growth of S1S2, S1S1, and S2S2 pollen, while the S-RNase from homozygous germplasm allowed some S1S2 pollen and different single genotypes of pollen to continue growing. These results further validate the core events of SI including cytoskeleton depolymerization and programmed cell death. By iTRAQ-based proteomic analysis of style proteins, a total of 13 S-RNase-related proteins were identified. In summary, we have created reliable S-RNase gene homozygous germplasm, which will play a crucial role in further research on SI in pear and in the development of the pear industry.

Comparative Physiological, Transcriptomic, and Metabolomic Analyses of Acacia mangium Provide New Insights into Its Molecular Mechanism of Self-Incompatibility

Acacia mangium is well known as a valuable commercial tree species in the Acacia genus. A. mangium was recently found to be self-incompatible (SI), but its SI mechanism is not clear, which has hindered the progress of genetic improvement of A. mangium with strong resistance. To confirm the SI type of A. mangium, pollen germination was observed via fluorescence microscopy at 0 h, 3 h, 6 h, 9 h, 12 h, and 24 h after self-pollination. We found over ninety percent of the pollen grains produced no pollen tube growth on the stigma/style. To further explore the SI molecular mechanism of A. mangium, tests of the transcriptome and metabolome were carried out after self-pollination. Observations of pollen germination after self-pollination using fluorescence microscopy suggested that the SI type of A. mangium is gametophytic self-incompatibility (GSI). A combined transcriptomic and metabolomic analysis showed that DEGs (differentially expressed genes) related to SI (6 S-glycoproteins, 93 F-box proteins, 69 26S proteasomes, 38 calcium-dependent protein kinases/calmodulin and 41 thioredoxin genes) were significantly enriched in six KEGG (sulfur metabolism, tyrosine metabolism, phenylalanine metabolism, butanoate metabolism, and valine, leucine, and isoleucine degradation). Further analysis of these six pathways revealed the enrichment of SI-related DEGs corresponding to succinate, methylmalonate, and 3-hydroxypropane. These three metabolites were significantly downregulated. The analysis of transcripts and metabolites suggested that transcripts of SI-related gene families (thioredoxin and F-box protein) were significantly upregulated under the regulation of transcription factors (TFs) after self-pollination, leading to a decrease in metabolites (such as succinate, methylmalonate, and 3-hydroxypropionate). We also further speculated that TFs (MYB, HB-HD-ZIP, AP2/ERF-ERF, and bZIP) and gene families (thioredoxin and F-box protein) were important factors related to the SI of A. mangium.

Gametophytic self-incompatibility in Maxillariinae orchids.

Gametophytic self-incompatibility (GSI) has been mainly described in species-rich clades within Orchidaceae. We report GSI for a genuswithin Maxillariinae, one of the most conspicuous and diverse subtribes of neotropical orchids. Here, we describe the reproductive system of Brasiliorchis picta, B. phoenicanthera, and B. porphyrostele. Anatomical studies of fruit development showed that pollen tubes of aborted, self-pollinated flowers degenerate half-way in the stylar channel and never reach the ovules. Spontaneous self-pollination and emasculation set no fruits for none of the sampled species, thus supporting the hypothesis that thesethree species studied rely on the agency of pollinators and pollinator-mediated cross-pollination to set fruit. Fruit set from cross-pollinations ranged from 33.4 to 77.5%. One self-pollinated fruit of B. porphyrostele developed to completion. All other fruits aborted between 10 and 21 days after pollination. These data support previous evidence of variable strength GSI being exhibited in orchid species. Additional studies of self-incompatibility systems are needed to evaluate their role in species diversification and evolution of reproductive strategies in Maxillariinae and to allow for effective conservation strategies of threatened orchid species.

HT-B and S-RNase CRISPR-Cas9 double knockouts show enhanced self-fertility in diploid Solanum tuberosum.

The Gametophytic Self-Incompatibility (GSI) system in diploid potato (Solanum tuberosum L.) poses a substantial barrier in diploid potato breeding by hindering the generation of inbred lines. One solution is gene editing to generate self-compatible diploid potatoes which will allow for the generation of elite inbred lines with fixed favorable alleles and heterotic potential. The S-RNase and HT genes have been shown previously to contribute to GSI in the Solanaceae family and self-compatible S. tuberosum lines have been generated by knocking out S-RNase gene with CRISPR-Cas9 gene editing. This study employed CRISPR-Cas9 to knockout HT-B either individually or in concert with S-RNase in the diploid self-incompatible S. tuberosum clone DRH-195. Using mature seed formation from self-pollinated fruit as the defining characteristic of self-compatibility, HT-B-only knockouts produced little or no seed. In contrast, double knockout lines of HT-B and S-RNase displayed levels of seed production that were up to three times higher than observed in the S-RNase-only knockout, indicating a synergistic effect between HT-B and S-RNase in self-compatibility in diploid potato. This contrasts with compatible cross-pollinations, where S-RNase and HT-B did not have a significant effect on seed set. Contradictory to the traditional GSI model, self-incompatible lines displayed pollen tube growth reaching the ovary, yet ovules failed to develop into seeds indicating a potential late-acting self-incompatibility in DRH-195. Germplasm generated from this study will serve as a valuable resource for diploid potato breeding.

Transcriptome Analysis of the Late-Acting Self-Incompatibility Associated with RNase T2 Family in Camellia oleifera.

The Camellia oil tree (Camellia oleifera Abel.) is an important nonwood forest species in China, and the majority of its cultivars are late-acting self-incompatibility (LSI) types. Although several studies have examined the mechanism of LSI, the process is quite complicated and unclear. In this study, pollen tube growth and fruit setting of two Camellia oil tree cultivars Huashuo (HS) and Huajin (HJ) were investigated after non and self-pollination, and transcriptomic analysis of the ovaries was performed 48 h after self-pollination to identify the potential genes implicated in the LSI of Camellia oil trees. The results showed that the fruit set of HS was significantly higher than that of HJ after self-pollination. Transcriptomic analysis revealed that plant hormone signal transduction, the phosphatidylinositol signaling system, ATP-binding cassette (ABC) transporters, reactive oxygen species (ROS) metabolism, and Ca2+ signaling were mainly contributed in the LSI of reaction of Camellia oil tree. Moreover, nine RNase T2 genes were identified from the transcriptome analysis, which also showed that CoRNase7 participated in the self-incompatibility reaction in HS. Based on phylogenetic analysis, CoRNase6 was closely related to S-RNase from coffee, and CoRNase7 and CoRNase8 were closely related to S-RNase from Camellia sinensis. The 9 RNase T2 genes successfully produced proteins in prokaryotes. Subcellular localization indicated that CoRNase1 and CoRNase5 were cytoplasmic proteins, while CoRNase7 was a plasma membrane protein. These results screened the main metabolic pathways closely related to LSI in Camellia oil tree, and SI signal transduction might be regulated by a large molecular regulatory network. The discovery of T2 RNases provided evidence that Camellia oil tree might be under RNase-based gametophytic self-incompatibility.

Using haplotype and QTL analysis to fix favorable alleles in diploid potato breeding.

At present, the potato (Solanum tuberosum L.) of international commerce is autotetraploid, and the complexity of this genetic system creates limitations for breeding. Diploid potato breeding has long been used for population improvement, and because of an improved understanding of the genetics of gametophytic self-incompatibility, there is now sustained interest in the development of uniform F1 hybrid varieties based on inbred parents. We report here on the use of haplotype and quantitative trait locus (QTL) analysis in a modified backcrossing (BC) scheme, using primary dihaploids of S. tuberosum as the recurrent parental background. In Cycle 1, we selected XD3-36, a self-fertile F2 individual homozygous for the self-compatibility gene Sli (S-locus inhibitor). Signatures of gametic and zygotic selection were observed at multiple loci in the F2 generation, including Sli. In the BC1 cycle, an F1 population derived from XD3-36 showed a bimodal response for vine maturity, which led to the identification of late versus early alleles in XD3-36 for the gene CDF1 (Cycling DOF Factor 1). Greenhouse phenotypes and haplotype analysis were used to select a vigorous and self-fertile F2 individual with 43% homozygosity, including for Sli and the early-maturing allele CDF1.3. Partially inbred lines from the BC1 and BC2 cycles have been used to initiate new cycles of selection, with the goal of reaching higher homozygosity while maintaining plant vigor, fertility, and yield.

The genome sequence and demographic history of Przewalskia tangutica (Solanaceae), an endangered alpine plant on the Qinghai-Tibet Plateau.

To adapt to high-altitude habitats, many alpine plants develop self-compatible breeding systems from outcrossing. The genetic bases for this shift and the resulting demographic consequences remain largely unexplored. Here, we present a high-quality, chromosome-level genome assembly of the monotypic and endangered alpine perennial Przewalskia tangutica (Solanaceae) occurring on the Qinghai-Tibet Plateau (QTP). Our assembled genome is approximately 3 Gb, with a contig N50 size of 17 Mb, and we identified one lineage-specific whole-genome duplication. We found that the gametophytic self-incompatibility (GSI) syntenic locus to the other obligate outcrossing Solanaceae species was broken by the inserted the long terminal repeats, and changes in the flower-specific expression of the homologous genes, and the linked GSI genes in this species. Such changes may have led to its self-compatibility. We identified three deeply diverged lineages in the central distribution of this species, and the gene flow between them was weak but continuous. All three lineages diverged and decreased their population sizes since the largest glaciations occurred in the QTP approximately 720-500 thousand years ago. In addition, we identified one obvious hybrid population between two lineages, suggesting that genetic exchanges between and within lineages still occur. Our results provide insights into evolutionary adaptation through facultative self-pollination and demographic consequences of this alpine rare species in arid habitats.

Disentangling the components of pollen limitation in a widespread herb with gametophytic self-incompatibility.

Seed production is frequently limited by the receipt of insufficient or low-quality pollen, collectively termed "pollen limitation" (PL). In taxa with gametophytic self-incompatibility (GSI), incompatible pollen can germinate on stigmas but pollen tubes are arrested in styles. This allows for estimates of pollen performance before, during, and after self-recognition, as well as insight into the factors underlying pollen quality limitation in GSI taxa. We scored pollen performance following self and outcross pollinations in Argentina anserina to identify the location of self-recognition and establish the relationship between pollen tubes and seed production. We then estimated quantity and quality components of PL from >3300 field-collected styles. We combined our results with other studies to test the prediction that low pollen quality, but not quantity, drives higher PL in self-incompatible (SI) taxa than in self-compatible taxa (SC). Self and outcross pollen germinated readily on stigmas, but 96% of germinated self-pollen was arrested during early tube elongation. Reproduction in the field was more limited by pollen quality than by quantity, and pollen failure near the location of self-recognition was a stronger barrier to fertilization than pollen germination. Across 26 taxa, SI species experienced stronger pollen quality, but not quantity, limitation than SC species. Evaluating pollen performance at multiple points within pistils can elucidate potential causes of pollen quality limitation. The receipt of incompatible pollen inhibits fertilization success more than insufficient pollen receipt or poor pollen germination in A. anserina. Likewise, pollen quality limitation drives high overall PL in other SI taxa.

Characterization of a pollen-part self-compatible apple (Malus × domestica Borkh.) mutant induced by γ-ray mutagenesis

Self-compatibility (SC) in a naturally self-incompatible fruit tree species is a highly interesting trait for breeding objectives and a valuable tool for investigating the mechanism of the gametophytic self-incompatibility (GSI) system. This study focused on apple (Malus × domestica Borkh.), carried out γ-ray mutagenesis, and succeeded in producing a self-compatible mutant. The reciprocal pollination test showed that a pollen factor is involved in its SC. Results on S-RNase genotyping by allele-specific PCR amplification of the progenies of the mutant revealed that SC in the mutant was not caused by a nonfunctional pollen S factor in either one of the S-haplotypes but presumably by an S-chromosomal alteration (i.e., reciprocal translocation of an S-haplotype or a partial S-chromosomal duplication). Amplicon sequencing of S-haplotypes of progeny individuals suggested that the most probable S-chromosomal alteration in the mutant could be a translocation of an S-haplotype to a nonhomologous chromosome; such S-chromosomal alteration made it possible for the mutant to produce S-heteroallelic pollen grains that overcome self-incompatibility by competitive interaction between the two different S-factors in a pollen grain. These results supported the idea of a “collaborative non-self-recognition system by multiple factors” based on the GSI system in apple, similar to those in Pyrus of Rosaceae and Solanaceae. Implications for breeding self-compatible apple using the mutant induced in this study are briefly discussed.

Phenology, floral and reproductive biology of Dichorisandra rhizantha Aona (Commelinaceae), an endemic endangered species in an Atlantic Forest fragment.

Commelinaceae is an important component of the Atlantic Forest and its analysis can provide information on the conservation of that species. This study had the objective of analyzing the phenology and floral and reproductive biology of Dichorisandra rhizantha, growing in an Atlantic Forest fragment, to obtain data related to the form of reproduction and pollination mechanism of this species. We monitored the phenophases and reproductive biology of the D. rhizantha in the area studied using different methodologies and microscopy techniques (LM, SEM and FM). The flowering period occurs during the dry season. The species is andromonoecious and has daytime anthesis (4:30 a.m.-1:30 p.m.). It has purple zygomorphic flowers and rimose but functionally poricidal anthers. The pollen viability was 97.6% and the two floral morphs investigated contained a large quantity of pollen grains. The time of greatest stigma receptivity (anthesis) coincided with the pollen viability. Cross-pollination was the only efficient reproductive system of the species, with observation of gametophytic self-incompatibility and pollen tubes growth only as far as the middle or lower third of the pistil. We observed bee species of the genera Xylocopa and Euglossa visiting the flowers and acting as effective pollinators. The immature fruits were formed after about 3.25 ± 1 days, and the presence was noted of ants of the genus Cephalotes acting as dispersers of the seeds, with aril serving as the reward. Although the natural reproductive system is efficient, D. rhizantha is endangered, mainly due to fragmentation of habitat caused by deforestation and urban encroachment.

Self S-RNase restricts ABF-LRX signaling cascade to arrest pollen tube during pear self-incompatibility reaction.

Gametophytic self-incompatibility (GSI) has been widely studied in flowering plants, but the study on mechanism of arresting pollen tube growth by self S-RNase in the GSI species is limited. In this study, two leucine-rich repeat extensin genes, PbLRXA2.1 and PbLRXA2.2, were identified based on transcriptome and quantitative real-time PCR analyses. The expression levels of these two LRX genes were significantly higher in the pollen grains and pollen tubes of self-compatible cultivar 'Jinzhui' (a spontaneous bud mutation of the self-incompatible cultivar 'Yali') than in 'Yali'. Both PbLRXA2.1 and PbLRXA2.2 positively mediated pollen tube growth and attenuated self S-RNase toxicity on pollen tube growth by stabilizing actin cytoskeleton and cell wall integrity. This result indicates that the abnormal expression of PbLRXA2.1 and PbLRXA2.2 involve in the breakdown of self-incompatibility in 'Jinzhui'. The PbLRXA2.1 and PbLRXA2.2 promoters were directly bound by an ABRE-binding factor PbABF.D.2. Knockdown of PbABF.D.2 expression decreased PbLRXA2.1 and PbLRXA2.2 expression and inhibited pollen tube growth. Notably, the expressions of PbLRXA2.1, PbLRXA2.2, and PbABF.D.2 were repressed by self S-RNase, suggesting that self S-RNase can arrest pollen tube growth by restricting the PbABF.D.2-PbLRXA2.1/PbLRXA2.2 signal cascade. These results provide a novel insight of the pollen tube growth arrested by self S-RNase.

Solanum carolinense L.

<i>Solanum carolinense</i> L.

DETERMINATION OF SELF-(IN) COMPATIBILITY USING MOLECULAR MARKERS OF SOME APRICOT CULTIVARS WHICH CULTIVATED IN TURKEY

In fruit trees, gametophytic self-incompatibility is one of the major problem because of preventing self-fertilization controlled by a single locus with some allelic variants. Among the fruits, apricots also show self-incompatibility especially originated from Middle-Asian and Iranian-Caucasian. In present study, it was determined self-compatible/incompatible of some apricot cultivars which cultivated in Turkey. 17 Turkish and 42 foreign apricot cultivars were used in this study. Analyses were carried out using three primer pairs (SRc-R-SRc-F, EM-PC2consFD / EM-PC3consRD and AprFBC8). A total 5 S-RNase alleles (S2, S3, S6, S9 and S11) were determined in the 11 new Turkish cultivated apricots and a total 8 (S3, S7, S8, S9, S11, S12, S13 and SC) were determined in old Turkish apricot cultivars. A total 11 S-RNase alleles (S2, S3, S4, S6, S7, S8, S9, S11, S12, S19 and SC) were determined in foreign 42 apricot cultivars. It was determined self (in)compatibility alleles of 11 new Turkish and 38 foreign apricot cultivars first time with this study. These results can be used for plantation new orchards and breeding programs. Also, pollinator cultivars should be considered for plantation new orchards for these self-incompatible cultivars because of some Turkish and foreign apricot are mostly self-incompatible.

Disentangling the components of pollen limitation in a widespread herb with gametophytic self-incompatibility

Disentangling the components of pollen limitation in a widespread herb with gametophytic self-incompatibility

Fine-Mapping and Comparative Genomic Analysis Reveal the Gene Composition at the S and Z Self-incompatibility Loci in Grasses.

Self-incompatibility (SI) is a genetic mechanism of hermaphroditic plants to prevent inbreeding after self-pollination. Allogamous Poaceae species exhibit a unique gametophytic SI system controlled by two multi-allelic and independent loci, S and Z. Despite intense research efforts in the last decades, the genes that determine the initial recognition mechanism are yet to be identified. Here, we report the fine-mapping of the Z-locus in perennial ryegrass (Lolium perenne L.) and provide evidence that the pollen and stigma components are determined by two genes encoding DUF247 domain proteins (ZDUF247-I and ZDUF247-II) and the gene sZ, respectively. The pollen and stigma determinants are located side-by-side and were genetically linked in 10,245 individuals of two independent mapping populations segregating for Z. Moreover, they exhibited high allelic diversity as well as tissue-specific gene expression, matching the expected characteristics of SI determinants known from other systems. Revisiting the S-locus using the latest high-quality whole-genome assemblies revealed a similar gene composition and structure as found for Z, supporting the hypothesis of a duplicated origin of the two-locus SI system of grasses. Ultimately, comparative genomic analyses across a wide range of self-compatible and self-incompatible Poaceae species revealed that the absence of a functional copy of at least one of the six putative SI determinants is accompanied by a self-compatible phenotype. Our study provides new insights into the origin and evolution of the unique gametophytic SI system in one of the largest and economically most important plant families.