During the last glacial–interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1–8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across the Arctic spanning the past 50,000 years. Furthermore, we present 1,541 contemporary plant genome assemblies that were generated as reference sequences. Our study provides several insights into the long-term dynamics of the Arctic biota at the circumpolar and regional scales. Our key findings include: (1) a relatively homogeneous steppe–tundra flora dominated the Arctic during the Last Glacial Maximum, followed by regional divergence of vegetation during the Holocene epoch; (2) certain grazing animals consistently co-occurred in space and time; (3) humans appear to have been a minor factor in driving animal distributions; (4) higher effective precipitation, as well as an increase in the proportion of wetland plants, show negative effects on animal diversity; (5) the persistence of the steppe–tundra vegetation in northern Siberia enabled the late survival of several now-extinct megafauna species, including the woolly mammoth until 3.9 ± 0.2 thousand years ago (ka) and the woolly rhinoceros until 9.8 ± 0.2 ka; and (6) phylogenetic analysis of mammoth environmental DNA reveals a previously unsampled mitochondrial lineage. Our findings highlight the power of ancient environmental metagenomics analyses to advance understanding of population histories and long-term ecological dynamics.

Late Pliocene and Early Pleistocene epochs 3.6 to 0.8 million years ago1 had climates resembling those forecasted under future warming2. Palaeoclimatic records show strong polar amplification with mean annual temperatures of 11–19 °C above contemporary values3,4. The biological communities inhabiting the Arctic during this time remain poorly known because fossils are rare5. Here we report an ancient environmental DNA6 (eDNA) record describing the rich plant and animal assemblages of the Kap København Formation in North Greenland, dated to around two million years ago. The record shows an open boreal forest ecosystem with mixed vegetation of poplar, birch and thuja trees, as well as a variety of Arctic and boreal shrubs and herbs, many of which had not previously been detected at the site from macrofossil and pollen records. The DNA record confirms the presence of hare and mitochondrial DNA from animals including mastodons, reindeer, rodents and geese, all ancestral to their present-day and late Pleistocene relatives. The presence of marine species including horseshoe crab and green algae support a warmer climate than today. The reconstructed ecosystem has no modern analogue. The survival of such ancient eDNA probably relates to its binding to mineral surfaces. Our findings open new areas of genetic research, demonstrating that it is possible to track the ecology and evolution of biological communities from two million years ago using ancient eDNA.

Developing testa layers of the barley proanthocyanidin-free mutants ant 13-152, anf17-148, ant 18-159, ant19-109, ant22-1508, ant25-264, ant26-485, ant27-489, ant28-484 and ant29-2110 and their mother varieties, were analysed for accumulation of proanthocyanidins and their flavonoid precursors. In vitro infection of developing barley caryopses of wild type and mutants with Fusarium poae, F. culmorum and F. graminearum revealed all mutants except ant18-159 to be more sensitive to Fusarium attack than wildtype. Mutant ant 18-159 showed extreme resistance. Histological investigations of the infection process revealed that the hyphae were unable to penetrate the testa of this mutant. The testa layer of ant 18-159 accumulates small amounts of dihydroquercetin as a result of nonsense mutations in the structural gene for dihydroflavonol reductase. Authentic dihydroquercetin and an autographic assay proves this flavonoid to be a strong inhibitor of Fusarium growth and macrospore formation. Mutant ant 17-148, which accumulates the flavone chrysoeriol as a consequence of a mutation in the step catalysed by flavanone 3-hydroxylase, demonstrates that this flavone is not an inhibitor of Fusariwn growth in vivo. Comparison of flavonoid standards and monomers and polymers from other plants reveal monomeric flavonoids generally to be potent inhibitors

Proanthocyanidin (PA) and anthocyanin accumulation and location in developing leaves, flowers, and seeds of the legumes Medicago sativa, Lotus japonicus, Lotus uliginosus, Hedysarum sulfurescens, and Robinia pseudacacia were investigated by quantitative measurements and by histological analysis after staining with 1% vanillin/HCl, butanol/HCl, or 50% HC1. M. sativa leaves and flowers, L. japonicus leaves, and R. pseudacacia flowers do not contain PAs, but seeds of all investigated species contain PAs. Anthocyanins are absent in the seed coats of all five species and in leaves of L. japonicus. PA content generally increases as a function of development in leaves, but declines in flowers. With the exception of H. sulfurescens, flower PAs are synthesized in the parenchyma cells of the standard petal, while anthocyanins are located in the neighboring epidermal cells. Leucocyanidin reductase (LCR) catalyzes the conversion of 2,3-trans-3,4-cis-leucocyanidin to (+)-catechin and is the first enzyme in the PA-specific pathway. LCR activity was only detected in PA-containing tissues and generally declined during tissue development.

Isolated barley (Hordeum vulgare L.) aleurone layers have been widely used as a model system for studying gene expression and hormonal regulation in germinating cereal grains. A serious technological limitation of this approach has been the inability to confidently extrapolate conclusions obtained from isolated tissues back to the whole grain, where the co-location of several living and non-living tissues results in complex tissue-tissue interactions and regulatory pathways coordinated across the multiple tissues. Here we have developed methods for isolating fragments of aleurone, starchy endosperm, embryo, scutellum, pericarp-testa, husk and crushed cell layers from germinated grain. An important step in the procedure involves the rapid fixation of the intact grain to freeze the transcriptional activity of individual tissues while dissection is effected for subsequent transcriptomic analyses. The developmental profiles of 19 611 gene transcripts were precisely defined in the purified tissues and in whole grain during the first 24 h of germination by RNA sequencing. Spatial and temporal patterns of transcription were validated against well-defined data on enzyme activities in both whole grain and isolated tissues. Transcript profiles of genes involved in mitochondrial assembly and function were used to validate the very early stages of germination, while the profiles of genes involved in starch and cell wall mobilisation matched existing data on activities of corresponding enzymes. The data will be broadly applicable for the interrogation of co-expression and differential expression patterns and for the identification of transcription factors that are important in the early stages of grain and seed germination.