Pooid Grasses Research Articles

Allelopathic effects of Epichloë fungal endophytes: experiment and meta-analysis

Host-specific Epichloë spp. are endophytic fungal symbionts of pooid grasses that produce herbivore-deterring alkaloids and alter the host’s metabolite and protein profiles. Early observations suggested that Epichloë may have negative allelopathic effects on neighbouring plant species, particularly Trifolium spp. clovers, but subsequent allelopathy experiments produced variable results. We examined two hypotheses: (1) Epichloë strains differ in allelopathic effect, and (2) Epichloë allelopathy negatively affects other plant species. We performed a greenhouse experiment using root exudates from Lolium perenne L. hosting different E. festucae var. lolii (Latch, M.J. Chr. & Samuels) C.W. Bacon & Schardl strains to compare their allelopathic effects on native legumes and forbs. We then used meta-analysis to examine the evidence to date for allelopathic effects of Epichloë endophytes. We found little difference in effect among E. festucae var. lolii strains and very little evidence for negative allelopathic effects of Epichloë in cool-season grasses across a range of methodologies, target plant species, and response measures. Negative allelopathic effects were detected only for root hair measures, which were from a single study. Positive effects on biomass were found for some experimental subgroups, including legumes. However, the majority of response variables showed no evidence for Epichloë allelopathy. Although there is currently little evidence for negative Epichloë allelopathic effects, our meta-analysis identified several research gaps. Experiments testing the functional belowground effects of Epichloë presence may help to determine its effects on non-host plant performance via plant-soil feedbacks.

Testing dental calculus as a means to determine paleodiet of extinct equid Merychippus sp.

During the Miocene Epoch, radiation of merychippine equids may have coincided with a transitional North American habitat of forests with patches of open grassland, and merychippine diet may reflect this diverse environment. Dental calculus on teeth of extinct herbivores like Merychippus can incorporate a long-term dietary record in the form of plant microfossils, such as phytoliths and fibers. In the present study, the purpose was to test dental calculus as a measure of paleodiet in equids by identifying and comparing Merychippus paleodiet constituents among preliminary sample groups. Calculus samples obtained from seven isolated Barstovian age Merychippus teeth from sites in Nebraska, Oregon, and Maryland, USA contained plant microfossils that were identified to categories based upon morphological characteristics. Grass silica short-cell phytoliths of BOP clade, C 3 -pathway subfamilies were most frequent, comprising 45–57% of all calculus samples. Microfossils from woody taxa were also present in all assemblages (18–29%). Softwood tracheary elements and sedge grass phytoliths (Family Cyperaceae) were significantly more frequent in Merychippus from the Maryland site. The combined presence of hardwood and grass microfossils from each Merychippus specimen indicates a mixed browse/grass diet that included C 3 grasses, supporting recent micro- and mesowear analyses. Some significant differences among these preliminary samples suggest that calculus is a valid means to compare diet among regions. Within a broader context, this type of study can generalize aspects of the Merychippus paleoenvironment and stands as an evaluation for using microfossils from dental calculus as a means for diet determination. • Microfossils from calculus on 7 Merychippus teeth are used to find evidence of diet. • Presence of pooid grass phytoliths indicates C 3 grasses in the environment. • Presence of hardwood microfossils suggests browse in diet. • Tracheid microfossils indicate possible dietary inclusion of softwood species. • Microfossils in Merychippus calculus are consistent with previous findings.

Invasive grasses of sub-Antarctic Marion Island respond to increasing temperatures at the expense of chilling tolerance.

Global warming has large effects on the performance and spatial distribution of plants, and increasingly facilitates the spread of invasive species. Particularly vulnerable is the vegetation of cold environments where indigenous plants selected for cold tolerance can have reduced phenotypic plasticity and associated lower capacity to respond to warming temperatures. In contrast, invasive species can be phenotypically plastic and respond positively to climate change, but at the expense of stress tolerance. We investigate this trade-off in traits, measuring the photosynthetic response to warming, chilling tolerance and specific leaf area (SLA) of Pooid grasses. We compare this between invasive and non-invasive grasses and correlate this to their range expansions on a cold sub-Antarctic island that has warmed significantly in the past five decades. We determined whether these responses remained consistent after temperature acclimation. Invasive species responded strongly to warming, increasing photosynthetic rates by up to 2-fold, while non-invasive species did not respond. The response was associated with increased stomatal conductance, but not with modified photosynthetic metabolism. Electrolyte leakage and SLA were higher in invasive than in non-invasive species. Acclimation altered the photosynthetic response and invasive species responded to warm temperatures irrespective of acclimation, while non-invasive species responded only after acclimation to warm temperature. Traits scaled linearly with rates of range expansion and demonstrate that under sub-Antarctic conditions, anthropogenic warming over the last 50 years may have favoured species with greater capacity to respond photosynthetically to warming to the detriment of species that cannot, and negated the advantage that chilling tolerance would have conferred on endemic species in the past. This suggests that species of cold ecosystems could be particularly vulnerable to warming as selection for stress tolerance has limited their responsiveness to environmental change, while introduced invasive species may have no such limitations. We show mechanistic evidence of the physiology that underpins an apparent trade-off between warming and chilling tolerance traits.

Epichloe novae-zelandiae, a new endophyte from the endemic New Zealand grass Poa matthewsii

ABSTRACTEpichloe endophytes (Clavicipitaceae) infect pooid grass genera worldwide but predominantly in the Northern Hemisphere, but appear to be rare in native grasses of the Southern Hemisphere. Because of benefits that hosts may receive from the symbiosis, Epichloe endophytes have been extensively studied and are considered important components of sustainable agriculture. There are only a few studies available on the incidence of endophyte infection in grasses of the Southern Hemisphere and most grass species have never been examined. Here we report on a survey of native grasses of New Zealand including 25 endemic or indigenous species. We sampled up to 10 plants per species at different sites from both the North and South Island of New Zealand and examined tissues microscopically for endophyte infection. Overall, only two species were found to be infected, Poa matthewsii (Matthew's bluegrass) and Dichelachne micrantha (short-hair plume grass). Based on analyses of tefA and tubB genes, both endophytes were found to be interspecific hybrids. The endophyte of the new host D. micrantha was previously described as Epichloe australiensis, while the endophyte of P. matthewsii is a new species named here E. novae-zelandiae. The new species is a hybrid derived from E. amarillans, E. bromicola and E. typhina subsp. poae. Alkaloid analyses in planta suggested that E. novae-zelandiae can produce small amounts of peramine, early pathway indole-diterpenes and ergot alkaloids, but no lolines or lolitrems. Target specific primers suggested the presence of genes for ergot alkaloids and peramine, but genes of only early pathway steps for the other alkaloids. Furthermore, genes for both mating type idiomorphs (MTA and MTB) were present, a single copy of MTA and two copies of MTB. Endophytes of native grasses may provide a genetic resource that could be exploited for developing pasture grass cultivars with improved performance.

A florigen paralog is required for short-day vernalization in a pooid grass.

Perception of seasonal cues is critical for reproductive success in many plants. Exposure to winter cold is a cue that can confer competence to flower in the spring via a process known as vernalization. In certain grasses, exposure to short days is another winter cue that can lead to a vernalized state. In Brachypodium distachyon, we find that natural variation for the ability of short days to confer competence to flower is due to allelic variation of the FLOWERING LOCUS T (FT1) paralog FT-like9 (FTL9). An active FTL9 allele is required for the acquisition of floral competence, demonstrating a novel role for a member of the FT family of genes. Loss of the short-day vernalization response appears to have arisen once in B. distachyon and spread through diverse lineages indicating that this loss has adaptive value, perhaps by delaying spring flowering until the danger of cold damage to flowers has subsided.

Epichloë endophytes of Poa alsodes employ alternative mechanisms for host defense: insecticidal versus deterrence

Some cool-season pooid grasses partner with symbiotic fungal endophytes in the Epichloe genus for defense against insect herbivores via fungal alkaloids. Poa alsodes, North American woodland grass, independently hosts two species of Epichloe that vary by produced alkaloids. E. alsodes produces insecticidal N-acetylnorloline. E. schardlii var. pennsylvanica (E. schardlii hereafter) has the gene for peramine, an insect-deterring alkaloid, production, but peramine was not detected. We tested the effects of the two endophytes on survival, feeding preference, and plant damage by the generalist herbivore, Spodoptera frugiperda. No larvae survived when feeding on plants harboring E. alsodes. In contrast, survival was only slightly reduced by plants harboring E. schardlii. However, larvae that fed on E. schardlii infected plants experienced delayed development and reduced pupal mass. Uninfected plants and plants infected with E. schardlii were damaged severely when single larvae fed upon them, whereas larvae fed negligibly on plants infected with E. alsodes. Preference did not match performance. Larvae strongly avoided feeding on E. schardlii but not E. alsodes-infected leaves where survival was zero. When E. schardlii was experimentally removed, larval leaf choices suggested that this endophyte is responsible for deterrence. High levels of N-acetylnorloline were detected from E. alsodes infected plants. Peramine was not detected in the experimental plants harboring E. schardlii, so it remains unclear what mechanisms caused avoidance and developmental delays. The two endophytes may protect their common host in different ways: E. alsodes by larval mortality and E. schardlii by deterring feeding and negative effects on development.

Anti‐insect defenses of Achnatherum robustum (sleepygrass) provided by two Epichloë endophyte species

AbstractMany pooid grasses (Poaceae) harbor Epichloë species (Hypocreales), endophytic fungi that often produce toxic alkaloids which may provide anti‐insect protection for their hosts. Two natural populations of Achnatherum robustum (Vasey) (sleepygrass), in the Lincoln National Forest, Cloudcroft, and Weed (NM, USA), are infected with the endophyte species Epichloë funkii (KD Craven & Schardl) JF White and Epichloë sp. nov. We tested whether: (1) these endophytes affect survival, growth, and development of the insect herbivore Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) (fall armyworm), (2) larval diets alter adult fecundity (assessed as number of larvae or eggs produced by females and number of spermatophores that males transfer to females when enclosed in pairs within each feeding group), and (3) infections affect leaf consumption in larval no‐choice and choice experiments. Individual larvae were reared on Epichloë infected vs. uninfected clipped leaves from the Cloudcroft and Weed population plants. Overall, armyworm survival was not affected when fed infected sleepygrass from either population. However, larvae that fed on Weed‐infected plants were smaller and had longer development than larvae that fed on uninfected and Cloudcroft‐infected plants. Males fed on Weed‐infected leaves had reduced mating success. Interestingly, pupal mass increased when larvae fed on either the infected leaf types. However, heavier females from both infected diets did not lay more eggs than lighter females from uninfected diets. In a no‐choice test, larvae on Weed‐infected plants diet consumed more leaf biomass than larvae from three other groups. In choice tests, larvae avoided feeding on leaves infected with either of the endophytes relative to uninfected leaves. Thus, the two Epichloë may provide direct protection to sleepygrass from insect herbivory by deterrence. The Weed population endophyte may provide stronger indirect protection than the Cloudcroft endophyte by reducing insect fitness or increasing risks of predation and parasitism through delayed development, even though larvae may consume more leaf biomass.

Vegetation response during the lead-up to the middle Miocene warming event in the Northern Rocky Mountains, USA

The mid-Miocene climatic optimum (MMCO; initial warming beginning ca. 18Ma and with peak warming ca. 17–14.75Ma) constitutes the Earth's most recent greenhouse episode, characterized by a transient shift to higher global atmospheric CO2 levels and warmer, possibly wetter, climatic conditions. Combined with the spread of grass-dominated habitats, it has been suggested that the MMCO lead to significant turnover and modernization of fauna and flora. However, records documenting local vegetation change during the MMCO are rare, hence this hypothesis remains largely untested. Herein, we combine phytolith assemblages and δ13C records from paleosol organic matter from the Railroad Canyon section (RCS), eastern Idaho, to provide the first direct, detailed, and continuous, long-term record of vegetation composition and structure in a single basin during the lead-up to the MMCO (22.9–15.2Ma; late Arikareean–early Barstovian). Phytolith assemblage analysis indicates that grasses, primarily C3 pooids, dominated early–middle Miocene vegetation. Potential C4 PACMAD grasses were present by ca. 21.6–20.7Ma (late Arikareean) and vary in abundance (0.4–17.2% of diagnostic phytoliths) through the section. Although relatively rare overall, PACMAD grasses decrease significantly through time, in parallel with declining diatom abundances and an increase in pooid grasses. In contrast, paleosol δ13Corg indicates 0–29.1% C4 vegetation but no consistent temporal change. Where both phytolith- and isotope-based estimates are made from the same paleosol, they are within error most (82%) of the time; thus, the apparent discrepancy in temporal trends could either be due to differences in the resolution of the two records, or could be explained if many PACMADs were not C4 grasses, but instead water-loving C3 species. Overall, these data suggest that open-habitat mosaic vegetation with grass-dominated grasslands and open woodlands occurred in the North Rocky Mountains, USA, by at least the early Miocene, more comparable to the timing for the spread of grass-dominated habitats in the Great Plains than previously thought. Additionally, phytolith data suggest that overall vegetation structure remained relatively stable throughout the RCS, inconsistent with published paleosol morphology data. This points to regionally unique floral patterns decoupled from global climate change leading into the MMCO.

Genetic Architecture of Flowering-Time Variation in Brachypodium distachyon

The transition to reproductive development is a crucial step in the plant life cycle, and the timing of this transition is an important factor in crop yields. Here, we report new insights into the genetic control of natural variation in flowering time in Brachypodium distachyon, a nondomesticated pooid grass closely related to cereals such as wheat (Triticum spp.) and barley (Hordeum vulgare L.). A recombinant inbred line population derived from a cross between the rapid-flowering accession Bd21 and the delayed-flowering accession Bd1-1 were grown in a variety of environmental conditions to enable exploration of the genetic architecture of flowering time. A genotyping-by-sequencing approach was used to develop SNP markers for genetic map construction, and quantitative trait loci (QTLs) that control differences in flowering time were identified. Many of the flowering-time QTLs are detected across a range of photoperiod and vernalization conditions, suggesting that the genetic control of flowering within this population is robust. The two major QTLs identified in undomesticated B. distachyon colocalize with VERNALIZATION1/PHYTOCHROME C and VERNALIZATION2, loci identified as flowering regulators in the domesticated crops wheat and barley. This suggests that variation in flowering time is controlled in part by a set of genes broadly conserved within pooid grasses.

Bronze Age crop processing evidence in the phytolith assemblages from the ditch and fen around Fondo Paviani, northern Italy

The Terramare civilization (ca. 1650–1150 cal bce) on the Po plain in northern Italy is considered to have been an agrarian society typical of the European Bronze Age, with a subsistence economy based on arable and livestock farming, and which showed some innovations such as the introduction of millets as cultivars. Some questions are still open concerning the agricultural system, the food and non-food uses of plant resources and the organization of labour at these sites. In this paper, for the first time, phytolith analysis has been integrated with more standard archaeobotanical methods applied to material from the long-lasting settlement of Fondo Paviani, Verona. The aim of the study was to use phytoliths as a tool to investigate the cereal economy in order to detect different grass subfamilies and possibly provide hints about local crop processing activities. For this purpose, two contexts, a shallow ditch at the edge of the site that had been filled with domestic waste and a near-site fen with natural infilling, have been the objects of a multi-proxy inter-disciplinary investigation. This includes the analyses of phytoliths, pollen, NPP, sediment texture and micromorphology. The phytolith record shows remains of panicoid as well as pooid grasses, including chaff material with frequent traces of threshing that indicate the processing of cereals at the site and the possible use of chopped straw as fodder. The comparison of different kinds of evidence strengthens the interpretation and offers a new perspective on the application of phytolith analysis to Bronze Age northern Italy.

Desert agricultural systems at EBA Jawa (Jordan): Integrating archaeological and paleoenvironmental records

Located in the arid basalt desert of northeastern Jordan, the settlement of Jawa is by far the largest and best-preserved archaeological site in the region. The Early Bronze Age (EBA) settlement phase of Jawa (3500–3000 BCE) is characterized by a highly sophisticated water storage system made of a series of pools, dams, and canals. In addition, recent archaeological and geoarchaeological surveys have uncovered agricultural terrace systems in the nearby vicinity. In this study, four of these runoff terrace systems were investigated by detailed mapping. Additionally, thirteen sediment profiles from inside and outside the terrace systems were recorded and sampled. The examined samples were analyzed for bulk chemistry, texture, phytoliths, diatoms, and dung spherulites to supply information on the environmental and depositional conditions. The terrace systems were dated using optically stimulated luminescence (OSL). Ancient terrace agriculture was practiced on slopes, small plateaus, and valleys close to Jawa through the use of surface canals, which collected and diverted floodwater from nearby wadis or runoff from adjacent slopes. The terraced fields were usually arranged in cascades and comprised a system of risers, canals, and spillways. The terrace fills investigated yield OSL ages of around 3300 BCE, indicating that the terraces were constructed in the Early Bronze Age. The terrace fill sequences are composed of mixed unstratified fine sediments of local origin, reflecting low-energy fluvial deposition regimes. The phytolith record is dominated by Pooid grasses that include the most common Near Eastern cereals, such as wheat and barley. Increased phytolith concentrations in terrace fill sediments, as compared to samples from non-terrace deposits nearby, suggest increased plant growth and water availability within the terraces. Whether the terrace systems were used for growing food crops only or whether they were additionally used for grazing cannot be ascertained. Overall, quantitative phytolith analyses in arid environments are well suited to investigate temporal and spatial distributions of plant microfossil concentrations and their relation to human activity or paleoenvironmental conditions.

Evolution of the beta-amylase gene in the temperate grasses: Non-purifying selection, recombination, semiparalogy, homeology and phylogenetic signal

Low-copy nuclear genes (LCNGs) have complex genetic architectures and evolutionary dynamics. However, unlike multicopy nuclear genes, LCNGs are rarely subject to gene conversion or concerted evolution, and they have higher mutation rates than organellar or nuclear ribosomal DNA markers, so they have great potential for improving the robustness of phylogenetic reconstructions at all taxonomic levels. In this study, our first objective is to evaluate the evolutionary dynamics of the LCNG β-amylase by testing for potential pseudogenization, paralogy, homeology, recombination, and phylogenetic incongruence within a broad representation of the main Pooideae lineages. Our second objective is to determine whether β-amylase shows sufficient phylogenetic signal to reconstruct the evolutionary history of the Pooid grasses. A multigenic (ITS, matK, ndhF, trnTL, and trnLF) tree of the study group provided a framework for assessing the β-amylase phylogeny. Eight accessions showed complete absence of selection, suggesting putative pseudogenic copies or other relaxed selection pressures; resolution of Vulpia alopecuros 2x clones indicated its potential (semi) paralogy; and homeologous copies of allopolyploid species Festuca simensis, F. fenas, and F. arundinacea tracked their Mediterranean origin. Two recombination events were found within early-diverged Pooideae lineages, and five within the PACCMAD clade. The unexpected phylogenetic relationships of 37 grass species (26% of the sampled species) highlight the frequent occurrence of non-treelike evolutionary events, so this LCNG should be used with caution as a phylogenetic marker. However, once the pitfalls are identified and removed, the phylogenetic reconstruction of the grasses based on the β-amylase exon+intron positions is optimal at all taxonomic levels.

Brachypodium distachyon and Setaria viridis: Model Genetic Systems for the Grasses.

The family of grasses encompasses the world's most important food, feed, and bioenergy crops, yet we are only now beginning to develop the genetic resources to explore the diversity of form and function that underlies economically important traits. Two emerging model systems, Brachypodium distachyon and Setaria viridis, promise to greatly accelerate the process of gene discovery in the grasses and to serve as bridges in the exploration of panicoid and pooid grasses, arguably two of the most important clades of plants from a food security perspective. We provide both a historical view of the development of plant model systems and highlight several recent reports that are providing these developing communities with the tools for gene discovery and pathway engineering.

PHYTOCHROME C is an essential light receptor for photoperiodic flowering in the temperate grass, Brachypodium distachyon.

We show that in the temperate grass, Brachypodium distachyon, PHYTOCHROME C (PHYC), is necessary for photoperiodic flowering. In loss-of-function phyC mutants, flowering is extremely delayed in inductive photoperiods. PHYC was identified as the causative locus by utilizing a mapping by sequencing pipeline (Cloudmap) optimized for identification of induced mutations in Brachypodium. In phyC mutants the expression of Brachypodium homologs of key flowering time genes in the photoperiod pathway such as GIGANTEA (GI), PHOTOPERIOD 1 (PPD1/PRR37), CONSTANS (CO), and florigen/FT are greatly attenuated. PHYC also controls the day-length dependence of leaf size as the effect of day length on leaf size is abolished in phyC mutants. The control of genes upstream of florigen production by PHYC was likely to have been a key feature of the evolution of a long-day flowering response in temperate pooid grasses.

Epichloë endophytes alter inducible indirect defences in host grasses.

Epichloë endophytes are common symbionts living asymptomatically in pooid grasses and may provide chemical defences against herbivorous insects. While the mechanisms underlying these fungal defences have been well studied, it remains unknown whether endophyte presence affects the host's own defences. We addressed this issue by examining variation in the impact of Epichloë on constitutive and herbivore-induced emissions of volatile organic compounds (VOC), a well-known indirect plant defence, between two grass species, Schedonorus phoenix (ex. Festuca arundinacea; tall fescue) and Festuca pratensis (meadow fescue). We found that feeding by a generalist aphid species, Rhopalosiphum padi, induced VOC emissions by uninfected plants of both grass species but to varying extents, while mechanical wounding failed to do so in both species after one day of damage. Interestingly, regardless of damage treatment, Epichloë uncinata-infected F. pratensis emitted significantly lower quantities of VOCs than their uninfected counterparts. In contrast, Epichloë coenophiala-infected S. phoenix did not differ from their uninfected counterparts in constitutive VOC emissions but tended to increase VOC emissions under intense aphid feeding. A multivariate analysis showed that endophyte status imposed stronger differences in VOC profiles of F. pratensis than damage treatment, while the reverse was true for S. phoenix. Additionally, both endophytes inhibited R. padi population growth as measured by aphid dry biomass, with the inhibition appearing greater in E. uncinata-infected F. pratensis. Our results suggest, not only that Epichloë endophytes may play important roles in mediating host VOC responses to herbivory, but also that the magnitude and direction of such responses may vary with the identity of the Epichloë–grass symbiosis. Whether Epichloë-mediated host VOC responses will eventually translate into effects on higher trophic levels merits future investigation.

C4 photosynthesis promoted species diversification during the Miocene grassland expansion.

Identifying how organismal attributes and environmental change affect lineage diversification is essential to our understanding of biodiversity. With the largest phylogeny yet compiled for grasses, we present an example of a key physiological innovation that promoted high diversification rates. C4 photosynthesis, a complex suite of traits that improves photosynthetic efficiency under conditions of drought, high temperatures, and low atmospheric CO2, has evolved repeatedly in one lineage of grasses and was consistently associated with elevated diversification rates. In most cases there was a significant lag time between the origin of the pathway and subsequent radiations, suggesting that the ‘C4 effect’ is complex and derives from the interplay of the C4 syndrome with other factors. We also identified comparable radiations occurring during the same time period in C3 Pooid grasses, a diverse, cold-adapted grassland lineage that has never evolved C4 photosynthesis. The mid to late Miocene was an especially important period of both C3 and C4 grass diversification, coincident with the global development of extensive, open biomes in both warm and cool climates. As is likely true for most “key innovations”, the C4 effect is context dependent and only relevant within a particular organismal background and when particular ecological opportunities became available.

Thermal stress effects on grain yield in Brachypodium distachyon occur via H2A.Z-nucleosomes

BackgroundCrop plants are highly sensitive to ambient temperature, with a 1 ºC difference in temperature sufficient to affect development and yield. Monocot crop plants are particularly vulnerable to higher temperatures during the reproductive and grain-filling phases. The molecular mechanisms by which temperature influences grain development are, however, unknown. In Arabidopsis thaliana, H2A.Z-nucleosomes coordinate transcriptional responses to higher temperature. We therefore investigated whether the effects of high temperature on grain development are mediated by H2A.Z-nucleosomes.ResultsWe have analyzed the thermal responses of the Pooid grass, Brachypodium distachyon, a model system for crops. We find that H2A.Z-nucleosome occupancy is more responsive to increases in ambient temperature in the reproductive tissue of developing grains compared withvegetative seedlings. This difference correlates with strong phenotypic responses of developing grain to increased temperature, including early maturity and reduced yield. Conversely, temperature has limited impact on the timing of transition from the vegetative to generative stage, with increased temperature unable to substitute for long photoperiod induction of flowering. RNAi silencing of components necessary for H2A.Z-nucleosome deposition is sufficient to phenocopythe effects of warmer temperature on grain development.ConclusionsH2A.Z-nucleosomes are important in coordinating the sensitivity of temperate grasses to increased temperature during grain development. Perturbing H2A.Z occupancy, through higher temperature or genetically, strongly reduces yield. Thus, we provide a molecular understanding of the pathways through which high temperature impacts on yield. These findings may be useful for breeding crops resilient to thermal stress.

Polyphyly of the grass tribe Hainardieae (Poaceae: Pooideae): identification of its different lineages based on molecular phylogenetics, including morphological and cytogenetic characteristics

The small pooid grass tribe Hainardieae comprises six genera with approximately ten species; however, this tribe was not accepted by all previous taxonomic treatments. To study the relationships among these genera and to infer the phylogeny and evolutionary patterns, we used sequence variation of the internal transcribed spacers (ITS) of nuclear ribosomal and chloroplast (cp) matK DNA and morphology. Many genera of the Aveneae/Poeae tribe complex additionally were included. Both molecular datasets showed Hainardieae to be highly polyphyletic, and its genera to branch with different groups of the Aveneae/Poeae. Parapholis and Hainardia are corroborated as being closely related, and belonging to a firmly supported Eurasian clade together with Catapodium incl. Scleropoa, Cutandia, Desmazeria, Sphenopus, Vulpiella (subtribe Parapholiinae) and with Cynosurus as sister to this assemblage. The other genera of traditionally recognised Hainardieae are positioned phylogenetically distant: Mediterranean Narduroides is verified as more or less related to Festuca and relatives (subtribe Loliinae), whereas the west Eurasian Pholiurus is close to the lineage of Poa and relatives (subtribe Poinae). North American Scribneria is sister to Deschampsia and both genera should be unified under a common subtribe (Aristaveninae or Holcinae). The phylogenetic position of the Algerian genus Agropyropsis (close to Narduroides and within the Loliinae) is suggested on morphology only, because no molecular data was obtained for it. Considering classification, we support the abandonment of tribe Hainardieae and argue to abandon Poeae subtribe Scribneriinae. Poeae subtribe Parapholiinae is redefined with a novel genus content, due to the exclusion of Agropyropsis and Pholiurus and the inclusion of Vulpiella.

Identification of extracellular siderophores and a related peptide from the endophytic fungus Epichloë festucae in culture and endophyte-infected Lolium perenne

A number of genes encoding non-ribosomal peptide synthetases (NRPSs) have been identified in fungi of Epichloë/Neotyphodium species, endophytes of Pooid grasses, including sidN, putatively encoding a ferrichrome siderophore-synthesizing NRPS. Targeted gene replacement and complementation of sidN in Epichloë festucae has established that extracellular siderophore epichloënin A is the major product of the SidN enzyme complex (Johnson et al., 2007a). We report here high resolution mass spectrometric fragmentation experiments and NMR analysis of an isolated fraction establishing that epichloënin A is a siderophore of the ferrichrome family, comprising a cyclic sequence of four glycines, a glutamine and three Nδ-trans-anhydromevalonyl–Nδ-hydroxyornithine (AMHO) moieties. Epichloënin A is unusual among ferrichrome siderophores in comprising an octapeptide rather than hexapeptide sequence, and in incorporating a glutamine residue. During this investigation we have established that desferrichrome siderophores with pendant trans-AMHO groups can be distinguished from those with pendant cis-AMHO groups by the characteristic neutral loss of an hydroxyornithine moiety in the MS/MS spectrum. A minor component, epichloënin B, has been characterized as the triglycine variant by mass spectrometry. A peptide characterized by mass spectrometry as the putative deoxygenation product, epichloëamide has been detected together with ferriepichloënin A in guttation fluid from ryegrass (Lolium perenne) plants infected with wild-type E. festucae, but not in plants infected with the ΔsidN mutant strain, and also detected at trace levels in wild-type E. festucae fungal culture.

Synonymous Codon Usage, GC3, and Evolutionary Patterns Across Plastomes of Three Pooid Model Species: Emerging Grass Genome Models for Monocots

We have analyzed factors affecting the codon usage pattern of the chloroplasts genomes of representative species of pooid grass family. Correspondence analysis of relative synonymous codon usages (RSCU) showed that genes on secondary axis were correlated with their GC(3S) values (all r>0.3, p<0.05), indicating mutational bias as an important selective force that shaped the variation in the codon usage among chloroplast genes. The Nc-plot showed that although a majority of the points with low-Nc values were lying below the expected curve, a few genes lied on the expected curve. Nc plot clearly showed that mutational bias plays a major role in codon biology across the monocot plastomes. The hydrophobicity and aromaticity of encoded proteins of each species were found to be other factors of codon usage variation. In the view of above light, besides natural selection, several other factors also likely to be involved in determining the selective constraints on codon bias in plastomes of pooid grass genomes. In addition, five codons (B. distachyon), seven codons (H. vulgare), and four codons (T. aestivum) were identified as optimal codons of the three grass chloroplasts. To identify genes evolving under positive selection, rates of nonsynonymous substitutions (Ka) and synonymous substitutions (Ks) were computed for all groups of orthologous gene pairs.