Search Results (7)

Background: Gametophytic self-incompatibility (GSI) controlled by a multi-allelic S-locus, is inferred to have evolved before the spilt of the Rosidae and Asteridae. In Rosaceae, molecular characterisation of the genera Prunus and Malus reveals that different numbers of genes determine GSI specificity. In Prunus, one pistil-expressed (female) gene and one pollen (male) gene encode a series of stylar RNase (S-RNase) alleles and series of S-haplotype-specific F-box (SFB) alleles, respectively, thereby determining the female and male specificity. In contrast, in Malus, GSI specificity is controlled by one pistil gene and multiple pollen genes, known as SFB-brothers (SFBBs), which encode a series of S-RNase and SFBB alleles, respectively, within the S-locus, to determine female and male specificity. Despite these advances, the molecular mechanisms of these two genera remain largely unknown, and it is still uncertain how GSI originated or which factors shape the orientation, evolution, and function of the S-locus. Methods: Therefore, in this study, we applied a holistic integrative approach combining analyses of gene distribution, phylogenetic inference, biogeographic history, selective pressures, co-evolution, and protein interaction networks across three Prunus genomes (P. dulcis, P. persica, and P. avium) to elucidate the evolutionary forces driving sexual diversity and molecular specificity of GSI within the Rosaceae. Results: Our results indicated that rapid diversification of the Prunus S-locus was due to the repeated duplication events in the SFB, SLF, and S-RNase genes producing both functional and non-functional duplicates. Conclusions: In Rosaceae, diversity of S-locus mechanisms is shaped by lineage-specific selection, functional divergence, co-evolution of pistil- and pollen-expressed components, dynamic protein-interaction networks, geological history and climatic change. Full article

Self-incompatibility (SI) is a complex mechanism that prevents plants from self-fertilizing to preserve and promote genetic variability. The angiosperm species have developed two different SI systems, the sporophytic (SSI) and the gametophytic (GSI) systems. SI is a significant impediment to steady fruit production in fruit tree species of the Rosaceae. In Rosaceae, GSI is genetically regulated via a single locus, named the ‘S-locus’, which includes a minimum of two polymorphic and relatively intercorrelated S genes: a pistil-expressed S-RNase gene and several pollen-expressed SFBB (S-locus F-Box Brothers) or SFB (S haplotype-specific F-box protein). This necessitates the interaction of S-RNases with the male determinants. Although genetic and molecular analyses of S genes have shown that mutations in both pistils and pollen-specific components induce self-compatibility in many species and cultivars, other genes or molecules outside the S-locus can co-participate in the male gamete rejection in GSI. However, we highlight and synthesize the most recent knowledge on different mechanisms of GSI in Rosaceae in this current review. Full article

Self-incompatibility is a widespread genetic mechanism found in flowering plants. It plays a crucial role in preventing inbreeding and promoting outcrossing. The genes that control self-incompatibility in plants are typically determined by the S-locus female determinant factor and the S-locus male determinant factor. In the Solanaceae family, the male determinant factor is often the SLF gene. In this research, we cloned and analyzed 13 S₂-LbSLF genes from the L. barbarum genome, which are located on chromosome 2 and close to the physical location of the S-locus female determinant factor S-RNase, covering a region of approximately 90.4 Mb. The amino acid sequence identity of the 13 S₂-LbSLFs is 58.46%, and they all possess relatively conserved motifs and typical F-box domains, without introns. A co-linearity analysis revealed that there are no tandemly repeated genes in the S₂-LbSLF genes, and that there are two pairs of co-linear genes between S₂-LbSLF and the tomato, which also belongs to the Solanaceae family. A phylogenetic analysis indicates that the S₂-LbSLF members can be divided into six groups, and it was found that the 13 S₂-LbSLFs are clustered with the SLF genes of tobacco and Petunia inflata to varying degrees, potentially serving as pollen determinant factors regulating self-incompatibility in L. barbarum. The results for the gene expression patterns suggest that S₂-LbSLF is only expressed in pollen tissue. The results of the yeast two-hybrid assay showed that the C-terminal region of S₂-LbSLFs lacking the F-box domain can interact with S-RNase. This study provides theoretical data for further investigation into the functions of S₂-LbSLF members, particularly for the identification of pollen determinant factors regulating self-incompatibility in L. barbarum. Full article

The recognition of pollen and pistil in the self-incompatibility process is generally determined by the interaction between the pollen S gene and pistil S gene located at the S locus. However, the regulatory mechanism of self-incompatibility in goji remains unknown. In this study, we used the self-compatible strain ‘13–19’ and self-incompatible strain ‘xin9’ from Ningxia as parents to create an F1 hybrid population. Reciprocal cross-pollination was performed within the same plant to evaluate the self-compatibility of the parents and F1 progeny. The parents and progeny were subjected to whole-genome resequencing, and mixed pools of DNA were constructed using 30 self-compatible and 30 self-incompatible individuals. Association analysis using the SNP-index method and Euclidean distance was employed to identify the key candidate region of the S locus. The candidate region was further annotated using the Swiss-Prot database to identify genes within the region. Additionally, transcriptome sequencing data from different organs/tissues, as well as from pistils of self-compatible and self-incompatible strains at control (0 h), short (0.5 h), medium (8 h), and long (48 h) time points after self-pollination and cross-pollination, were analyzed to assess differential gene expression and screen for self-compatibility-related loci. Specific primers were designed for PCR amplification to determine the S-RNase genotypes of the extreme parents. The results revealed that the S locus in goji is located within a 32.2 Mb region on chromosome 2 that contains a total of 108 annotated genes. Differential expression analysis showed that ten genes, including Lba02g01064, were specifically expressed in stamens, with four of them annotated as F-box genes, potentially serving as determinants of self-compatibility in stamens. Lba02g01102 was exclusively expressed in pistils and annotated as an S-RNase gene, likely involved in self-compatibility. The expression of Lba02g01102 in pistils decreased after self-pollination and cross-pollination. Six candidate genes exhibited significant changes after self-pollination and cross-pollination. Both parents and progeny carried two S-RNase alleles, and the S-RNase genotypes showed a significant correlation with self-compatibility, with the self-compatible progeny containing the S8-RNase allele. The identification of the S locus in goji provides molecular markers for future marker-assisted breeding and offers genetic resources for studying the mechanism of self-incompatibility in goji, thus contributing to the improvement of goji varieties. Full article

Streptococcus pneumoniae is an important human pathogen causing both mild and severe diseases. In this work, we determined the complete genome sequence of the S. pneumoniae clinical isolate BM6001, which is the original host of the ICE Tn5253. The BM6001 genome is organized in one circular chromosome of 2,293,748 base pairs (bp) in length, with an average GC content of 39.54%; the genome harbors a type 19F capsule locus, two tandem copies of pspC, the comC1-comD1 alleles and the type I restriction modification system SpnIII. The BM6001 mobilome accounts for 15.54% (356,521 bp) of the whole genome and includes (i) the ICE Tn5253 composite; (ii) the novel IME Tn7089; (iii) the novel transposon Tn7090; (iv) 3 prophages and 2 satellite prophages; (v) 5 genomic islands (GIs); (vi) 72 insertion sequences (ISs); (vii) 69 RUPs; (viii) 153 BOX elements; and (ix) 31 SPRITEs. All MGEs, except for the GIs, produce excised circular forms and attB site restoration. Tn7089 is 9089 bp long and contains 11 ORFs, of which 6 were annotated and code for three functions: integration/excision, mobilization and adaptation. Tn7090 is 9053 bp in size, flanked by two copies of ISSpn7, and contains seven ORFs organized as a single transcriptional unit, with genes encoding for proteins likely involved in the uptake and binding of Mg²⁺ cations in the adhesion to host cells and intracellular survival. BM6001 GIs, except for GI-BM6001.4, are variants of the pneumococcal TIGR4 RD5 region of diversity, pathogenicity island PPI1, R6 Cluster 4 and PTS island. Overall, prophages and satellite prophages contain genes predicted to encode proteins involved in DNA replication and lysogeny, in addition to genes encoding phage structural proteins and lytic enzymes carried only by prophages. ΦBM6001.3 has a mosaic structure that shares sequences with prophages IPP69 and MM1 and disrupts the competent comGC/cglC gene after chromosomal integration. Treatment with mitomycin C results in a 10-fold increase in the frequency of ΦBM6001.3 excised forms and comGC/cglC coding sequence restoration but does not restore competence for genetic transformation. In addition, phylogenetic analysis showed that BM6001 clusters in a small lineage with five other historical strains, but it is distantly related to the lineage due to its unique mobilome, suggesting that BM6001 has progressively accumulated many MGEs while losing competence for genetic transformation. Full article

Self-incompatibility in Prunus species is governed by a single locus consisting of two highly multi-allelic and tightly linked genes, one coding for an F-box protein—i.e., SFB in Prunus- controlling the pollen specificity and one coding for an S-RNase gene controlling the pistil specificity. Genotyping the allelic combination in a fruit tree species is an essential procedure both for cross-based breeding and for establishing pollination requirements. Gel-based PCR techniques using primer pairs designed from conserved regions and spanning polymorphic intronic regions are traditionally used for this task. However, with the great advance of massive sequencing techniques and the lowering of sequencing costs, new genotyping-by-sequencing procedures are emerging. The alignment of resequenced individuals to reference genomes, commonly used for polymorphism detection, yields little or no coverage in the S-locus region due to high polymorphism between different alleles within the same species, and cannot be used for this purpose. Using the available sequences of Japanese plum S-loci concatenated in a rosary-like structure as synthetic reference sequence, we describe a procedure to accurately genotype resequenced individuals that allowed the analysis of the S-genotype in 88 Japanese plum cultivars, 74 of them are reported for the first time. In addition to unraveling two new S-alleles from published reference genomes, we identified at least two S-alleles in 74 cultivars. According to their S-allele composition, they were assigned to 22 incompatibility groups, including nine new incompatibility groups reported here for the first time (XXVII-XXXV). Full article

There has been an increased interest in true potato seeds (TPS) as planting material because of their advantages over seed tubers. TPS produced from a tetraploid heterozygous bi-parental population produces non-uniform segregating progenies, which have had limited uniformity in yield and quality in commercial cultivation, and, thus, limited success. Inbreeding depression and self-incompatibility hamper the development of inbred lines in both tetraploid and diploid potatoes, impeding hybrid development efforts. Diploid potatoes have gametophytic self-incompatibility (SI) controlled by S-locus, harboring the male-dependent S-locus F-box (SLF/SFB) and female-dependent Stylar-RNase (S-RNase). Manipulation of these genes using biotechnological tools may lead to loss of self-incompatibility. Self-compatibility can also be achieved by the introgression of S-locus inhibitor (Sli) found in the self-compatible (SC) natural mutants of Solanum chacoense. The introgression of Sli through conventional breeding methods has gained much success. Recently, the Sli gene has been cloned from diverse SC diploid potato lines. It is expressed gametophytically and can overcome the SI in different diploid potato genotypes through conventional breeding or transgenic approaches. Interestingly, it has a 533 bp insertion in its promoter elements, a MITE transposon, making it a SC allele. Sli gene encodes an F-box protein PP2-B10, which consists of an F-box domain linked to a lectin domain. Interaction studies have revealed that the C-terminal region of Sli interacts with most of the StS-RNases, except StS-RNase 3, 9, 10, and 13, while full-length Sli cannot interact with StS-RNase 3, 9, 11, 13, and 14. Thus, Sli may play an essential role in mediating the interactions between pollen and stigma and function like SLFs to interact with and detoxify the S-RNases during pollen tube elongation to confer SC to SI lines. These advancements have opened new avenues in the diploid potato hybrid. Full article