Subfamily Pooideae Research Articles

Some unique anatomical scaling relationships among genera in the grass subfamily Pooideae

Abstract Members of the grass family Poaceae have adapted to a wide range of habitats and disturbance regimes globally. The cellular structure and arrangements of leaves can help explain how plants survive in different climates, but these traits are rarely measured in grasses. Most studies are focused on individual species or distantly related species within Poaceae. While this focus can reveal broad adaptations, it is also likely to overlook subtle adaptations within more closely-related groups (subfamilies, tribes). This study therefore investigated the scaling relationships between leaf size, Vein Length Area (VLA), and vessel size in five genera within the subfamily Pooideae. The scaling exponent of the relationship between leaf area and VLA was -0.46 (+/- 0.21), which is consistent with previous studies. In Poa and Elymus, however, minor vein number and leaf length were uncorrelated, whereas in Festuca these traits were positively correlated (slope = 0.82 +/- 0.8). These findings suggest there are broad-scale and fine-scale variation in leaf hydraulic traits among grasses. Future studies should consider both narrow and broad phylogenetic gradients.

The Grasses of Burdwan District, West Bengal

The object of the present investigation is to provide an account of the grasses of Burdwan. 75 grasses, out of which 45 belong to sub-family Panicoideae and 30 to the sub-family Pooideae, are reported from Burdwan District (22°56'& 25°53' N and 86°48' & 88°25' E). The habit, habitat, ecological notes and economic uses have been given. Some grasses recorded from Burdwan District appear to be very recent additions to the grass flora of West Bengal.

Complete mitochondrial genome of Agrostis stolonifera: insights into structure, Codon usage, repeats, and RNA editing.

Plants possess mitochondrial genomes that are large and complex compared to animals. Despite their size, plant mitochondrial genomes do not contain significantly more genes than their animal counterparts. Studies into the sequence and structure of plant mitochondrial genomes heavily imply that the main mechanism driving replication of plant mtDNA, and offer valuable insights into plant evolution, energy production, and environmental adaptation. This study presents the first comprehensive analysis of Agrostis stolonifera's mitochondrial genome, characterized by a branched structure comprising three contiguous chromosomes, totaling 560,800bp with a GC content of 44.07%. Annotations reveal 33 unique protein-coding genes (PCGs), 19 tRNA genes, and 3 rRNA genes. The predominant codons for alanine and glutamine are GCU and CAA, respectively, while cysteine and phenylalanine exhibit weaker codon usage biases. The mitogenome contains 73, 34, and 23 simple sequence repeats (SSRs) on chromosomes 1, 2, and 3, respectively. Chromosome 1 exhibits the most frequent A-repeat monomeric SSR, whereas chromosome 2 displays the most common U-repeat monomeric SSR. DNA transformation analysis identifies 48 homologous fragments between the mitogenome and chloroplast genome, representing 3.41% of the mitogenome's total length. The PREP suite detects 460C-U RNA editing events across 33 mitochondrial PCGs, with the highest count in the ccmFn gene and the lowest in the rps7 gene. Phylogenetic analysis confirms A. stolonifera's placement within the Pooideae subfamily, showing a close relationship to Lolium perenne, consistent with the APG IV classification system. Numerous homologous co-linear blocks are observed in A. stolonifera's mitogenomes and those of related species, while certain regions lack homology. The unique features and complexities of the A. stolonifera mitochondrial genome, along with its similarities and differences to related species, provide valuable insights into plant evolution, energy production, and environmental adaptation. The findings from this study significantly contribute to the growing body of knowledge on plant mitochondrial genomes and their role in plant biology.

New insights into shepherds’ activities: Multi-proxy approach applied to fumier deposits from the north of Iberian Peninsula

The use of caves and/or rock shelters as a refugee for herds was a common practice in the Mediterranean area since the early Neolithic. Shepherds move the herds to pastures in higher altitudes, away from the settlements where the animals graze nearby the shelters where livestock is regrouped. Dung and residues produced during the occupation of these shelters were generally heaped and burnt to clean the site and prepare it for new usage, forming a characteristic deposit known as fumier. Fumier deposits are a great source of information to understand past herding practices including the animal's stabled, the management of the residues, the landscape, and the use of plants. In addition, they can provide a better understanding of site formation and postdepositional processes of archaeological sediments in caves and shelters including the impact of fire. Specific microarchaeological analyses are usually utilized to study fumier deposits. Here we present a multi-proxy approach that includes phytoliths, spherulites, ash pseudomorphs, and FTIR analyses, applied to the Neolithic levels of San Cristóbal, Los Husos II (Álava, Spain) and El Mirador (Burgos, Spain), located in the upper Ebro and Duero basins. This area in the north of the Iberian Peninsula constitutes a strategic location for the spread of the productive economy to the north, west, and interior of the Iberian Peninsula. Except for the lower Level XIII of San Cristóbal, where domestic activities were documented, our results showed similar behavior for the three studied sites, with no significant differences neither in terms of plant presence nor in the formation processes of the deposits. Up to seven and two possible complete stabling episodes were identified: three and two possible ones in San Cristóbal, and four in Los Husos II. Among the plants identified grasses of the C3 Pooideae subfamily were dominant, probably representing local grasses. The combining presence of thermally altered phytoliths, spherulites, and ash pseudomorphs points that the stabling episodes burned for several hours with temperatures ranging between 500 °C and 700 °C.

Can Aphid Herbivory Induce Intergenerational Effects of Endophyte-conferred Resistance in Grasses?

Plants have evolved mechanisms to survive herbivory. One such mechanism is the induction of defences upon attack that can operate intergenerationally. Cool-season grasses (sub-family Pooideae) obtain defences via symbiosis with vertically transmitted fungal endophytes (genus Epichloë) and can also show inducible responses. However, it is unknown whether these herbivore-induced responses can have intergenerational effects. We hypothesized that herbivory by aphids on maternal plants induces the intergenerational accumulation of endophyte-derived defensive alkaloids and resistance intensification in the progeny. We subjected mother plants symbiotic or not with Epichloë occultans, a species known for its production of anti-insect alkaloids known as lolines, to the aphid Rhopalosiphum padi. Then, we evaluated the progeny of these plants in terms of loline alkaloid concentration, resistance level (through herbivore performance), and shoot biomass. Herbivory on mother plants did not increase the concentration of lolines in seeds but it tended to affect loline concentration in progeny plants. There was an overall herbivore-induced intergenerational effect increasing the endophyte-conferred defence and resistance. Symbiotic plants were more resistant to aphids and had higher shoot biomass than their non-symbiotic counterparts. Since maternal herbivory did not affect the loline concentrations in seeds, the greater resistance of the progeny could have resulted from an inherited mechanism of epigenetic regulation. It would be interesting to elucidate the origin of this regulation since it could come from the host or the fungal symbiont. Thus, endophyte-driven differential fitness between symbiotic and non-symbiotic plants might be higher as generations pass on in presence of herbivores.

Major niche transitions in Pooideae correlate with variation in photoperiodic flowering and evolution of CCT domain genes.

The external cues that trigger timely flowering vary greatly across tropical and temperate plant taxa, the latter relying on predictable seasonal fluctuations in temperature and photoperiod. In the grass family (Poaceae) for example, species of the subfamily Pooideae have become specialists of the northern temperate hemisphere, generating the hypothesis that their progenitor evolved a flowering response to long days from a short-day or day-neutral ancestor. Sampling across the Pooideae, we found support for this hypothesis, and identified several secondary shifts to day-neutral flowering and one to short-day flowering in a tropical highland clade. To explain the proximate mechanisms for the secondary transition back to short-day-regulated flowering, we investigated the expression of CCT domain genes, some of which are known to repress flowering in cereal grasses under specific photoperiods. We found a shift in CONSTANS 1 and CONSTANS 9 expression that coincides with the derived short-day photoperiodism of our exemplar species Nassella pubiflora. This sets up the testable hypothesis that trans- or cis-regulatory elements of these CCT domain genes were the targets of selection for major niche shifts in Pooideae grasses.

Comparative and Phylogenetic Analysis Based on the Chloroplast Genome of Coleanthus subtilis (Tratt.) Seidel, a Protected Rare Species of Monotypic Genus.

Coleanthus subtilis (Tratt.) Seidel (Poaceae) is an ephemeral grass from the monotypic genus Coleanthus Seidl, which grows on wet muddy areas such as fishponds or reservoirs. As a rare species with strict habitat requirements, it is protected at international and national levels. In this study, we sequenced its whole chloroplast genome for the first time using the next-generation sequencing (NGS) technology on the Illumina platform, and performed a comparative and phylogenetic analysis with the related species in Poaceae. The complete chloroplast genome of C. subtilis is 135,915 bp in length, with a quadripartite structure having two 21,529 bp inverted repeat regions (IRs) dividing the entire circular genome into a large single copy region (LSC) of 80,100 bp and a small single copy region (SSC) of 12,757 bp. The overall GC content is 38.3%, while the GC contents in LSC, SSC, and IR regions are 36.3%, 32.4%, and 43.9%, respectively. A total of 129 genes were annotated in the chloroplast genome, including 83 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. The accD gene and the introns of both clpP and rpoC1 genes were missing. In addition, the ycf1, ycf2, ycf15, and ycf68 were pseudogenes. Although the chloroplast genome structure of C. subtilis was found to be conserved and stable in general, 26 SSRs and 13 highly variable loci were detected, these regions have the potential to be developed as important molecular markers for the subfamily Pooideae. Phylogenetic analysis with species in Poaceae indicated that Coleanthus and Phippsia were sister groups, and provided new insights into the relationship between Coleanthus, Zingeria, and Colpodium. This study presents the initial chloroplast genome report of C. subtilis, which provides an essential data reference for further research on its origin.

The role of plants in the formation of species-specific features in grass flies (Diptera, Chloropidae, Meromyza).

In the current manuscript, we present the results of comparative analysis of seven species of Meromyza flies in the “variegata” cluster and of the evolutionary close species M.inornata, based the following criteria: 1) 14 external key features; 2) shape and area of the anterior processes of postgonites; 3) mtDNA CO1 region and 4) host plant diversity data. We could demonstrate the primary role of host plants in species formation inside genus Meromyza and calculated the timing of the divergence of M.inornata and the species of “variegata” cluster. Based on our estimates of evolution rate for mtDNA CO1 gene, we could conclude that that divergence of herbs happened before the speciation of grass flies Meromyza. Meromyza species, close to the ancestral species of the cluster, are adapted to the wide range of host plants. We revealed the most informative variables h1, S and Plant analysing data with the following statistical methods: linear discriminant analysis - LDA, regularised discriminant analysis - RDA, flexible discriminant analysis – FDA and probabilistic neural network - PNN. The highest classification accuracy was achieved using PNN (99%) and the lowest when using LDA (95.8%). When the Plant trait was excluded, the classification accuracy decreased by 14%. We revealed the significant trends in size change of the anterior process of the postgonite amongst studies species. This morphological structure is an element of male reproductive apparatus critical for the restriction of interspecies mating. We determined three branches of speciation in the “variegata” cluster and five trends in the evolution of this cluster, based on the external morphological features. We showed that M.variegata and especially M.mosquensis, the species closest to the ancestral haplotype, have the largest number of features typical of those of M.inornata. Based on the external features and the area of the anterior process of the postgonite, we reconstructed the phylogenetic position of M.elbergi in the cluster. In accordance with the obtained outcomes, we could conclude that the distribution, species diversity and the adaptation of the grass flies to narrow oligophagy were directly connected to host plant diversity. The adaptation to different host plants could be the main factor in divergence of grass flies and their evolution started later than the diversification in the Pooideae subfamily of grasses.

The origin and evolution of a two-component system of paralogous genes encoding the centromeric histone CENH3 in cereals

BackgroundThe cereal family Poaceae is one of the largest and most diverse angiosperm families. The central component of centromere specification and function is the centromere-specific histone H3 (CENH3). Some cereal species (maize, rice) have one copy of the gene encoding this protein, while some (wheat, barley, rye) have two. We applied a homology-based approach to sequenced cereal genomes, in order to finally trace the mutual evolution of the structure of the CENH3 genes and the nearby regions in various tribes.ResultsWe have established that the syntenic group or the CENH3 locus with the CENH3 gene and the boundaries defined by the CDPK2 and bZIP genes first appeared around 50 Mya in a common ancestor of the subfamilies Bambusoideae, Oryzoideae and Pooideae. This locus came to Pooideae with one copy of CENH3 in the most ancient tribes Nardeae and Meliceae. The βCENH3 gene as a part of the locus appeared in the tribes Stipeae and Brachypodieae around 35–40 Mya. The duplication was accompanied by changes in the exon-intron structure. Purifying selection acts mostly on αCENH3s, while βCENH3s form more heterogeneous structures, in which clade-specific amino acid motifs are present. In barley species, the βCENH3 gene assumed an inverted orientation relative to αCENH3 and the CDPK2 gene was substituted with LHCB-l. As the evolution and domestication of plant species went on, the locus was growing in size due to an increasing distance between αCENH3 and βCENH3 because of a massive insertion of the main LTR-containing retrotransposon superfamilies, gypsy and copia, without any evolutionary preference on either of them. A comparison of the molecular structure of the locus in the A, B and D subgenomes of the hexaploid wheat T. aestivum showed that invasion by mobile elements and concomitant rearrangements took place in an independent way even in evolutionarily close species.ConclusionsThe CENH3 duplication in cereals was accompanied by changes in the exon-intron structure of the βCENH3 paralog. The observed general tendency towards the expansion of the CENH3 locus reveals an amazing diversity of ways in which different species implement the scenario described in this paper.

Evolution and Breeding of Members of Pooideae Subfamily: Focusing on Upland Cereal Crops

Evolution and Breeding of Members of Pooideae Subfamily: Focusing on Upland Cereal Crops

The complete chloroplast genome sequence of Bromus catharticus Vahl. (Poaceae)

Bromus catharticus Vahl. belongs to the Pooideae subfamily of Poaceae. In this study, we sequenced and assembled the complete chloroplast genome of B. catharticus. The complete chloroplast genome was 134,718 bp in size, including a large single-copy region of 80,540 bp, a small single-copy region of 11,806 bp and a pair of reverse repeats of 21,186 bp in size. The annotation of B. catharticus indicates that it contained 89 protein-coding genes, 47 tRNA genes and eight rRNA genes. Our phylogenetic analysis of all protein-coding genes of the 36 grass complete chroloplast genomes using Cyperus rotundus as outgroup showed that B. catharticus is closely related to the Koeleria and Avena species to form the Pooideae lineage of the grass family.

TaWRKY10 transcription factor is a novel jasmonic acid signalling regulator involved in immunity against Septoria tritici blotch disease in wheat

Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is currently the main threat to worldwide wheat production in temperate climates. Understanding the genetic mechanisms that underpin the Z. tritici–wheat interaction will be crucial for generating new control strategies against STB. Plant hormones are essential regulators of growth and immunity. In particular, jasmonic acid (JA) plays a central role in defence against necrotrophic plant pathogens, but its role in mediating immunity against Z. tritici is largely unknown. Here we identify the transcription factor TaWRKY10 that is taxonomically restricted to the grass subfamily Pooideae as a novel regulator of JA responses in wheat. We demonstrate by using virus‐induced gene silencing that silencing TaWRKY10 leads to increased resistance against Z. tritici with an earlier onset of necrotic symptoms, but with reduced pathogen sporulation. Wheat plants silenced for TaWRKY10 show an up‐regulated JA response. Transcriptional profiling of TaWRKY10 knock‐down plants indicates that it is a negative regulator of the JA receptor TaCOI1 gene expression. Our data indicate that TaWRKY10 down‐regulates JA responses, contributing to the susceptibility of wheat to Z. tritici. We postulate that manipulating TaWRKY10 may provide a strategy to boost STB resistance in wheat.

Variation in climatic tolerance, but not stomatal traits, partially explains Pooideae grass species distributions.

Grasses in subfamily Pooideae live in some of the world's harshest terrestrial environments, from frigid boreal zones to the arid windswept steppe. It is hypothesized that the climate distribution of species within this group is driven by differences in climatic tolerance, and that tolerance can be partially explained by variation in stomatal traits. We determined the aridity index (AI) and minimum temperature of the coldest month (MTCM) for 22 diverse Pooideae accessions and one outgroup, and used comparative methods to assess predicted relationships for climate traits versus fitness traits, stomatal diffusive conductance to water (gw) and speed of stomatal closure following drought and/or cold. Results demonstrate that AI and MTCM predict variation in survival/regreening following drought/cold, and gw under drought/cold is positively correlated with δ 13C-measured water use efficiency (WUE). However, the relationship between climate traits and fitness under drought/cold was not explained by gw or speed of stomatal closure. These findings suggest that Pooideae distributions are at least partly determined by tolerance to aridity and above-freezing cold, but that variation in tolerance is not uniformly explained by variation in stomatal traits.

A 313 plastome phylogenomic analysis of Pooideae: Exploring relationships among the largest subfamily of grasses

In this study, we analyzed 313 plastid genomes (plastomes) of Poaceae with a focus on expanding our current knowledge of relationships among the subfamily Pooideae, which represented over half the dataset (164 representatives). In total, 47 plastomes were sequenced and assembled for this study. This is the largest study of its kind to include plastome-level data, to not only increase sampling at both the taxonomic and molecular levels with the aim of resolving complex and reticulate relationships, but also to analyze the effects of alignment gaps in large-scale analyses, as well as explore divergences in the subfamily with an expanded set of 14 accepted grass fossils for more accurate calibrations and dating. Incorporating broad systematic assessments of Pooideae taxa conducted by authors within the last five years, we produced a robust phylogenomic reconstruction for the subfamily, which included all but two supergeneric taxa (Calothecinae and Duthieeae).We further explored how including alignment gaps in plastome analyses oftentimes can produce incorrect or misinterpretations of complex or reticulate relationships among taxa of Pooideae. This presented itself as consistently changing relationships at specific nodes for different stripping thresholds (percentage-based removal of gaps per alignment column). Our summary recommendation for large-scale genomic plastome datasets is to strip alignment columns of all gaps to increase pairwise identity and reduce errant signal from poly A/T bias. To do this we used the “mask alignment” tool in Geneious software. Finally, we determined an overall divergence age for Pooideae of roughly 84.8 Mya, which is in line with, but slightly older than most recent estimates.

The complete chloroplast genome sequence of Beckmannia syzigachne

The first complete chloroplast genome (cpDNA) sequence of Beckmannia syzigachne was determined from Illumina HiSeq pair-end sequencing data in this study. The cpDNA is 136,181 bp in length, contains a large single-copy region (LSC) of 80,345 bp and a small single-copy region (SSC) of 12,810 bp, which were separated by a pair of inverted repeats (IR) regions of 21,513 bp. The genome contains 132 genes, including 85 protein-coding genes, 8 ribosomal RNA genes, and 39 transfer RNA genes. Further phylogenomic analysis showed that B. syzigachne clustered in a unique clade in the Pooideae subfamily.

Molecular Phylogenetics and Micromorphology of Australasian Stipeae (Poaceae, Subfamily Pooideae), and the Interrelation of Whole-Genome Duplication and Evolutionary Radiations in This Grass Tribe.

The mainly Australian grass genus Austrostipa (tribe Stipeae) comprising approximately 64 species represents a remarkable example of an evolutionary radiation. To investigate aspects of diversification, macro- and micromorphological variation in this genus, we conducted molecular phylogenetic and scanning electron microscopy (SEM) analyses including representatives from most of Austrostipa’s currently accepted subgenera. Because of its taxonomic significance in Stipeae, we studied the lemma epidermal pattern (LEP) in 34 representatives of Austrostipa. Plastid DNA variation within Austrostipa was low and only few lineages were resolved. Nuclear ITS and Acc1 yielded comparable groupings of taxa and resolved subgenera Arbuscula, Petaurista, and Bambusina in a common clade and as monophyletic. In most of the Austrostipa species studied, the LEP was relatively uniform (typical maize-like), but six species had a modified cellular structure. The species representing subgenera Lobatae, Petaurista, Bambusina as well as A. muelleri from subg. Tuberculatae were well-separated from all the other species included in the analysis. We suggest recognizing nine subgenera in Austrostipa (with number of species): Arbuscula (4), Aulax (2), Austrostipa (36), Bambusina (2), Falcatae (10), Lobatae (5), Longiaristatae (2), Petaurista (2) and the new subgenus Paucispiculatae (1) encompassing A. muelleri. Two paralogous sequence copies of Acc1, forming two distinct clades, were found in polyploid Austrostipa and Anemanthele. We found analogous patterns for our samples of Stipa s.str. with their Acc1 clades strongly separated from those of Austrostipa and Anemanthele. This underlines a previous hypothesis of Tzvelev (1977) that most extant Stipeae are of hybrid origin. We also prepared an up-to-date survey and reviewed the chromosome number variation for our molecularly studied taxa and the whole tribe Stipeae. The chromosome base number patterns as well as dysploidy and whole-genome duplication events were interpreted in a phylogenetic framework. The rather coherent picture of chromosome number variation underlines the enormous phylogenetic and evolutionary significance of this frequently ignored character.

Characterisation of Cellulose Synthase Like F6 (CslF6) Mutants Shows Altered Carbon Metabolism in β-D-(1,3;1,4)-Glucan Deficient Grain in Brachypodium distachyon.

Brachypodium distachyon is a small, fast growing grass species in the Pooideae subfamily that has become established as a model for other temperate cereals of agricultural significance, such as barley (Hordeum vulgare) and wheat (Triticum aestivum). The unusually high content in whole grains of β-D-(1,3;1,4)-glucan or mixed linkage glucan (MLG), considered a valuable dietary fibre due to its increased solubility in water compared with cellulose, makes B. distachyon an attractive model for these polysaccharides. The carbohydrate composition of grain in B. distachyon is interesting not only in understanding the synthesis of MLG, but more broadly in the mechanism(s) of carbon partitioning in cereal grains. Several mutants in the major MLG synthase, cellulose synthase like (CSL) F6, were identified in a screen of a TILLING population that show a loss of function in vitro. Surprisingly, loss of cslf6 synthase capacity appears to have a severe impact on survival, growth, and development in B. distachyon in contrast to equivalent mutants in barley and rice. One mutant, A656T, which showed milder growth impacts in heterozygotes shows a 21% (w/w) reduction in average grain MLG and more than doubling of starch compared with wildtype. The endosperm architecture of grains with the A656T mutation is altered, with a reduction in wall thickness and increased deposition of starch in larger granules than typical of wildtype B. distachyon. Together these changes demonstrate an alteration in the carbon storage of cslf6 mutant grains in response to reduced MLG synthase capacity and a possible cross-regulation with starch synthesis which should be a focus in future work in composition of these grains. The consequences of these findings for the use of B. distachyon as a model species for understanding MLG synthesis, and more broadly the implications for improving the nutritional value of cereal grains through alteration of soluble dietary fibre content are discussed.

Cross-reactivity in Skin Prick Test Results of Members Within Pooideae Subfamily.

ObjectiveMolecular similarities of grass pollen antigens have led to the view that cross-reactivity exists within members of the Pooideae subfamily of grasses. This has resulted in testing for only the most antigenically representative member of Pooideae, Timothy grass (Phleum pratense), despite little literature to support the claim that Phleum is the most representative member or that in vitro cross-reactivity correlates with in vivo cross-reactivity. The aim of the study was to determine if patients with allergic rhinitis symptoms and positive skin prick test results to meadow fescue (Festuca pratensis) also have positive results to Timothy grass.Study DesignRetrospective cross-sectional study.SettingTertiary care center in middle Missouri.MethodsA retrospective chart review identified patients ≥12 years old with a diagnosis of allergic rhinitis who underwent skin prick testing between March 2016 and July 2018, by using a search with CPT code 95004 (Current Procedural Terminology). Positive skin prick test results were based on wheal produced ≥3 mm than the negative control.ResultsAfter review of 2182 charts, 1587 patients met criteria to test for Phleum and Festuca. In total, 1239 patients had a positive result for Phleum or Festuca. Of these, 479 (38.6%) tested positive for Festuca alone, while 342 (27.6%) and 418 (33.7%) tested positive for Phleum alone and Phleum+Festuca, respectively.ConclusionClinical cross-reactivity among Pooideae members may not be as complete as traditionally thought. P pratense may not be the most antigenically representative subfamily member, and other grasses may need to be included in skin prick testing.

Phytolith records of flourishing early Holocene Pooideae linked to an 8.2 ka cold event in subtropical China

The grass subfamily Pooideae originated in a temperate niche during the late Cretaceous; it is the largest Poaceae subfamily, consisting of almost 4,000 species, which are distributed worldwide. Pooideae responses to climate changes at different time scales, and different ecological zones are thus important in understanding Poaceae evolutionary processes and their relationship with climate change. In the study described in this article, we reconstructed Pooideae variability during the early Holocene, as inferred by a phytolith sequence from the Lower Yangtze in subtropical China. The phytolith assemblage was marked by three increases in Pooideae phytoliths, dated to ca 8.4–8.0, 7.8–7.6, and 7.4–7.2 ka BP (before present, 1950 AD), with each representing pronounced increases in Pooideae extent and distribution. All these increases were within age ranges that agreed well with the timing of weak Asian Monsoon events, at 8.2, 7.7, and 7.3 ka BP. The first Pooideae flourishing period in subtropical China was the most significant, lasting for approximately four centuries and being characterized by a double peak, which equated with an event at 8.2 ka. This suggested that cold and/or dry conditions—which occurred over a period of several hundred years and were linked to weakening of the Asian monsoon—probably caused Pooideae to flourish in the Lower Yangtze region. Comparison of two diagnostic trapezoid phytolith types—namely wavy and wavy narrow—which showed different changes between ca 8.4 and 8.0 ka BP, suggested that they responded differently to the climate change represented by the 8.2 ka event. Our phytolith records have provided not only new data clarifying the detailed Pooideae response to the 8.2 ka event but also a reliable index for past cold climates in subtropical China.

Complete Chloroplast Genome of Psammochloa villosa (Poaceae), a Pioneer Grass Endemic to Sand Dunes in Northwest China

Psammochloa villosa is a sandy perennial grass (Poaceae) endemic to the northwest China, which has extremely important ecological and genetic values. To explore characterization and phylogenetic analysis of the complete chloroplast (cp) genome of Psammochloa villosa, we firstly sequenced and compared it with other cp genomes within Poaceae in this study. The result showed that the cp genome of P. villosa was 135 541 bp in size with a high A + T content of 61.2%, and had a typical quadripartite structure with the large (LSC, 80 272 bp) and small (SSC, 12 453 bp) single copy regions separated by two copies of inverted repeats (IRs, 21 408 bp each). We successfully annotated 134 genes, including 79 protein-coding genes, 42 tRNAs genes and ten rRNAs genes. Among these genes, 42 genes locate in IR regions. Additionally, we constructed a phylogenetic tree based on 40 cp genome sequences, which indicated that P. villosa has a closer relationship with the other species in subfamily Pooideae.