Pollen morphology of some species of the genus Cephalaria Schrad. (Caprifoliaceae) and its significance for taxonomy.

Palynology gives the evidence for identification and elimination of taxonomically complex genera. Pollen morphology of nine species (three subg., three sect.) of the genus Cephalaria Schrad. was studied using light microscopy and scanning electron microscopy. Pollen grains of all investigated species are triporate, suboblate to subprolate (P/E = 0.75-1.28), and large-sized (P = 58.52 µm-114.38, E = 63.84-119.70 µm). The outline of pollen grains in equatorial view is circular or elliptic, in polar view circular, circular-triangular, or triangular. Pores are distinct, lolongate, elliptic, or circular, with an annulus, operculum, and distinct or indistinct, wide halo surrounding the aperture. Exine sculpture is echinate-microechinate or echinate-microechinate-nanoechinate. Additional diagnostic characters at the species level in Cephalaria Schrad. that can be used for the purposes of taxonomy are size of pollen grains and pores, the shape of pores, the width of the annulus, structure of the exine, dimension of echini and microechini, location of microechini, and presence/absence of nanoechini. Palynomorphological data are compared with the taxonomical classification system of investigated taxa. It is shown that pollen grains morphology of the genus Cephalaria Schrad. is similar to the pollen morphology of the genus Dipsacus L., which confirms their inclusion in the Dipsaceae tribe.

Interactions between genetics and environment shape Camelina seed oil composition.

BACKGROUND: Camelina sativa (gold-of-pleasure) is a traditional European oilseed crop and emerging biofuel source with high levels of desirable fatty acids. A twentieth century germplasm bottleneck depleted genetic diversity in the crop, leading to recent interest in using wild relatives for crop improvement. However, little is known about seed oil content and genetic diversity in wild Camelina species. RESULTS: We used gas chromatography, environmental niche assessment, and genotyping-by-sequencing to assess seed fatty acid composition, environmental distributions, and population structure in C. sativa and four congeners, with a primary focus on the crop's wild progenitor, C. microcarpa. Fatty acid composition differed significantly between Camelina species, which occur in largely non-overlapping environments. The crop progenitor comprises three genetic subpopulations with discrete fatty acid compositions. Environment, subpopulation, and population-by-environment interactions were all important predictors for seed oil in these wild populations. A complementary growth chamber experiment using C. sativa confirmed that growing conditions can dramatically affect both oil quantity and fatty acid composition in Camelina. CONCLUSIONS: Genetics, environmental conditions, and genotype-by-environment interactions all contribute to fatty acid variation in Camelina species. These insights suggest careful breeding may overcome the unfavorable FA compositions in oilseed crops that are predicted with warming climates.

Endosperm of Angiosperms and Genomic Imprinting.

Modern ideas about the role of epigenetic systems in the regulation of gene expression allow us to understand the mechanisms of vital activities in plants, such as genomic imprinting. It is important that genomic imprinting is known first and foremost for the endosperm, which not only provides an embryo with necessary nutrients, but also plays a special biological role in the formation of seeds and fruits. Available data on genomic imprinting in the endosperm have been obtained only for the triploid endosperm in model plants, which develops after double fertilization in a Polygonum-type embryo sac, the most common type among angiosperms. Here we provide a brief overview of a wide diversity of embryo sacs and endosperm types and ploidy levels, as well as their distribution in the angiosperm families, positioned according to the Angiosperm Phylogeny Group IV (APG IV) phylogenetic classification. Addition of the new, non-model taxa to study gene imprinting in seed development will extend our knowledge about the epigenetic mechanisms underlying angiosperm fertility.

A Chromosome-Scale Assembly of the Garden Orach (Atriplex hortensis L.) Genome Using Oxford Nanopore Sequencing.

Atriplex hortensis (2n = 2x = 18, 1C genome size ∼1.1 gigabases), also known as garden orach and mountain-spinach, is a highly nutritious, broadleaf annual of the Amaranthaceae-Chenopodiaceae alliance (Chenopodiaceae sensu stricto, subfam. Chenopodioideae) that has spread in cultivation from its native primary domestication area in Eurasia to other temperate and subtropical regions worldwide. Atriplex L. is a highly complex but, as understood now, a monophyletic group of mainly halophytic and/or xerophytic plants, of which A. hortensis has been a vegetable of minor importance in some areas of Eurasia (from Central Asia to the Mediterranean) at least since antiquity. Nonetheless, it is a crop with tremendous nutritional potential due primarily to its exceptional leaf and seed protein quantities (approaching 30%) and quality (high levels of lysine). Although there is some literature describing the taxonomy and production of A. hortensis, there is a general lack of genetic and genomic data that would otherwise help elucidate the genetic variation, phylogenetic positioning, and future potential of the species. Here, we report the assembly of the first high-quality, chromosome-scale reference genome for A. hortensis cv. "Golden." Long-read data from Oxford Nanopore's MinION DNA sequencer was assembled with the program Canu and polished with Illumina short reads. Contigs were scaffolded to chromosome scale using chromatin-proximity maps (Hi-C) yielding a final assembly containing 1,325 scaffolds with a N50 of 98.9 Mb - with 94.7% of the assembly represented in the nine largest, chromosome-scale scaffolds. Sixty-six percent of the genome was classified as highly repetitive DNA, with the most common repetitive elements being Gypsy-(32%) and Copia-like (11%) long-terminal repeats. The annotation was completed using MAKER which identified 37,083 gene models and 2,555 tRNA genes. Completeness of the genome, assessed using the Benchmarking Universal Single Copy Orthologs (BUSCO) metric, identified 97.5% of the conserved orthologs as complete, with only 2.2% being duplicated, reflecting the diploid nature of A. hortensis. A resequencing panel of 21 wild, unimproved and cultivated A. hortensis accessions revealed three distinct populations with little variation within subpopulations. These resources provide vital information to better understand A. hortensis and facilitate future study.

Comparative Phylogeography of Veronica spicata and V. longifolia (Plantaginaceae) Across Europe: Integrating Hybridization and Polyploidy in Phylogeography.

Climatic fluctuations in the Pleistocene caused glacial expansion-contraction cycles in Eurasia and other parts of the world. Consequences of these cycles, such as population expansion and subsequent subdivision, have been studied in many taxa at intraspecific population level across much of the Northern Hemisphere. However, the consequences for the potential of hybridization and polyploidization are poorly understood. Here, we investigated the phylogeographic structure of two widespread, closely related species, Veronica spicata and Veronica longifolia, across their European distribution ranges. We assessed the extent and the geographic pattern of polyploidization in both species and hybridization between them. We used genome-scale SNP data to clarify phylogenetic relationships and detect possible hybridization/introgression events. In addition, crossing experiments were performed in different combination between V. spicata and V. longifolia individuals of two ploidy levels and of different geographic origins. Finally, we employed ecological niche modeling to infer macroclimatic differences between both species and both ploidy levels. We found a clear genetic structure reflecting the geographical distribution patterns in both species, with V. spicata showing higher genetic differentiation than V. longifolia. We retrieved significant signals of hybridization and introgression in natural populations from the genetic data and corroborated this with crossing experiments. However, there were no clear phylogeographic patterns and unequivocal macroclimatic niche differences between diploid and tetraploid lineages. This favors the hypothesis, that autopolyploidization has happened frequently and in different regions. The crossing experiments produced viable hybrids when the crosses were made between plants of the same ploidy levels but not in the interploidy crosses. The results suggest that hybridization occurs across the overlapping areas of natural distribution ranges of both species, with apparently directional introgression from V. spicata to V. longifolia. Nevertheless, the two species maintain their species-level separation due to their adaptation to different habitats and spatial isolation rather than reproductive isolation.

Anemonastrum tenuicaule and A. antucense (Ranunculaceae), new combinations for a New Zealand endemic species and its South American relative.

A rational taxonomic circumscription of genera in tribe Anemoneae (Ranunculaceae) is briefly discussed. It is concluded that, in view of the morphological diversity of the group and recent molecular phylogenetic findings, a moderately narrow approach to the re-circumscription of genera earlier included in Anemone sensu lato is preferable, in particular, with the recognition of the lineage with the base chromosome number x = 7 (Anemone subgen. Anemonidium) as two genera, Hepatica sensu stricto and Anemonastrum in an expanded circumscription (including Anemonidium, Arsenjevia, Jurtsevia, and Tamuria). Following these conclusions, new nomenclatural combinations are proposed for two related species endemic to New Zealand and South America, respectively: Anemonastrum tenuicaule (= Anemone tenuicaulis, Ranunculus tenuicaulis) and Anemonastrum antucense (= Anemone antucensis). Information on typification is updated: the lectotype of Anemone antucensis is the specimen from P and not a specimen from G, and the lectotype of Ranunculus tenuicaulis is a specimen from AK. Biogeographic scenarios already proposed to explain the relationship of these two species and some other South America - New Zealand distribution patterns are discussed. It is concluded that the long-distance dispersal scenario fits best the available data for Anemonastrum. Two host-specific and geographically restricted species of Urosystis parasitizing A. tenuicaule and A. antucense are briefly discussed.