Ancestral Chromosomes for Family Peronosporaceae Inferred from a Telomere-to-Telomere Genome Assembly of Peronospora effusa.

Downy mildew disease of spinach, caused by the oomycete Peronospora effusa, causes major losses to spinach production. In this study, the 17 chromosomes of P. effusa were assembled telomere-to-telomere, using Pacific Biosciences high-fidelity reads. Of these, 16 chromosomes are complete and gapless; chromosome 15 contains one gap bridging the nucleolus organizer region. This is the first telomere-to-telomere genome assembly for an oomycete. Putative centromeric regions were identified on all chromosomes. This new assembly enables a reevaluation of the genomic composition of Peronospora spp.; the assembly was almost double the size and contained more repeat sequences than previously reported for any Peronospora species. Genome fragments consistently underrepresented in six previously reported assemblies of P. effusa typically encoded repeats. Some genes annotated as encoding effectors were organized into multigene clusters on several chromosomes. Putative effectors were annotated on 16 of the 17 chromosomes. The intergenic distances between annotated genes were consistent with compartmentalization of the genome into gene-dense and gene-sparse regions. Genes encoding putative effectors were enriched in gene-sparse regions. The near-gapless assembly revealed apparent horizontal gene transfer from Ascomycete fungi. Gene order was highly conserved between P. effusa and the genetically oriented assembly of the oomycete Bremia lactucae; high levels of synteny were also detected with Phytophthora sojae. Extensive synteny between phylogenetically distant species suggests that many other oomycete species may have similar chromosome organization. Therefore, this assembly provides the foundation for genomic analyses of diverse oomycetes.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Effects of different depth of grain colour on antioxidant capacity during water imbibition in wheat (Triticum aestivum L.).

BACKGROUND: The importance of the effect of phytochemical accumulation in wheat grain on grain physiology has been recognised. In this study, we tracked phytochemical concentration in the seed coat of purple wheat during the water-imbibition phase and also hypothesised that the speed of germination was only relevant to its initial phytochemical concentration. RESULTS: The results indicate that the speed of germination was significantly reduced in the darker grain groups within the purple wheat. Total phenol content was slightly increased in all groups compared to their initial state, but the levels of other phytochemicals varied among groups. It is revealed that anthocyanin was significantly degraded during the water imbibition stage. Also, the activities of peroxidase, ascorbate peroxidase, catalase, glutathione S-transferase, glutathione reductase, and glutathione peroxidase in each grain colour group did not correlated with germination speed. Overall antioxidant activity was reduced as imbibition progressed in each group. Generally, darker grain groups showed higher total antioxidant activities than did lighter grain groups. CONCLUSION: These findings suggested that the reduced activity of reactive oxygen species, as controlled by internal antioxidant enzymes and phytochemicals, related with germination speed during the water imbibition stage in grains with greater depth of purple colouring. © 2016 Society of Chemical Industry.