Fagopyrum longistylum (Polygonaceae), a new species from Sichuan, China

A new species of Fagopyrum (Polygonaceae), Fagopyrum longistylum, is described and illustrated from Huili County, Sichuan Province, China on the basis of morphological, caryological, and molecular data. F. longistylum is morphologically similar to F. gracilipes from which it differs in having green stem and short-styled flowers with long anther but it is self-compatible. In addition, F. longistylum is a diploid species with 2n=2x=16 while F. gracilipes is tetraploid with 4n=4x=32. Molecular data based on nucleotide sequence polymorphisms of internal transcribed spacers (ITSs) and the maturase K (matK) gene confirm the separation of the new species.

Genomic Profiling of Virulence in the Soybean Cyst Nematode Using Single-Nematode Sequencing

Soybean cyst nematode (SCN) is one of the most important diseases in soybean. Currently, the main management strategy relies on planting resistant cultivars. However, the overuse of a single resistance source has led to the selection of virulent SCN populations, although the mechanisms by which the nematode overcomes the resistance genes remain unknown. In this study, we used a nematode-adapted single-cell RNA-seq approach to identify SCN genes potentially involved in resistance breakdown in Peking and PI 88788 parental soybean lines. We established for the first time the full transcriptome of single SCN individuals allowing us to identify a list of putative virulence genes against both major SCN resistance sources. Our analysis identified 48 differentially expressed putative effectors (secreted proteins required for infection) alongside 40 effectors showing evidence of novel structural variants, and 11 effector genes containing phenotype-specific sequence polymorphisms. Additionally, a differential expression analysis revealed an interesting phenomenon of coexpressed gene regions with some containing putative effectors. The selection of virulent SCN individuals on Peking resulted in a profoundly altered transcriptome, especially for genes known to be involved in parasitism. Several sequence polymorphisms were also specific to these virulent nematodes and could potentially play a role in the acquisition of nematode virulence. On the other hand, the transcriptome of virulent individuals on PI 88788 was very similar to avirulent ones with the exception of a few genes, which suggest a distinct virulence strategy to Peking.

DNA sequence differences are determinants of meiotic recombination outcome

Meiotic recombination is essential for producing healthy gametes, and also generates genetic diversity. DNA double-strand break (DSB) formation is the initiating step of meiotic recombination, producing, among other outcomes, crossovers between homologous chromosomes (homologs), which provide physical links to guide accurate chromosome segregation. The parameters influencing DSB position and repair are thus crucial determinants of reproductive success and genetic diversity. Using Schizosaccharomyces pombe, we show that the distance between sequence polymorphisms across homologs has a strong impact on meiotic recombination rate. The closer the sequence polymorphisms are to each other across the homologs the fewer recombination events were observed. In the immediate vicinity of DSBs, sequence polymorphisms affect the frequency of intragenic recombination events (gene conversions). Additionally, and unexpectedly, the crossover rate of flanking markers tens of kilobases away from the sequence polymorphisms was affected by their relative position to each other amongst the progeny having undergone intragenic recombination. A major regulator of this distance-dependent effect is the MutSα-MutLα complex consisting of Msh2, Msh6, Mlh1, and Pms1. Additionally, the DNA helicases Rqh1 and Fml1 shape recombination frequency, although the effects seen here are largely independent of the relative position of the sequence polymorphisms.

GAMYB gene in rye – sequence, polymorphisms, map location, allele-specific markers and relationship with selected agronomic traits

Background. A master GA-induced regulatory protein, crucial for development and germination of cereal grain and involved in anther formation is MYB transcription factor GAMYB, activating a vast number of genes including high-molecular-weight glutenin and α-amylase gene families. This paper presents the first attempt to characterize rye gene encoding GAMYB in relation to its sequence, polymorphisms and phenotypic effects. Results. ScGAMYB gene was identified and mapped on rye chromosome 3R using high-density DArT/DArTseq-based maps developed in two mapping populations. Comparative analysis of the gene sequence revealed its high level of homology to wheat and barley orthologues. Single nucleotide polymorphisms detected among rye inbred lines allowed developing AS-PCR markers for ScGAMYB (ten pairs of primers) which might be used to detect this gene in wide genetic stocks of rye and triticale. Segregation of ScGAMYB alleles showed significant relationship with quantitative traits including plant height, thousand grain weight, α-amylase activity, earliness per se and leaf rolling. Conclusions. The research showed the strong similarity of rye GAMYB sequence to its orthologues in other Graminae and confirmed the position in the genome consistent with the collinearity rule of cereal genomes. The statistically significant, however moderate association of ScGAMYB with many agronomic features has been pointed out, which proved that this gene is a QTL of pleiotropic character. The effect of ScGAMYB on flowering time was statistically the most significant. Developed sequence-based, allele-specific PCR markers could be useful in research and application purposes.