Antibiofilm Activity of Invasive Plants against Candida albicans: Focus on Baccharis halimifolia Essential Oil and Its Compounds

The extracts of five invasive plants were investigated for antifungal and antibiofilm activities against Candida albicans, C. glabrata, C. krusei, and C. parapsilosis. The antifungal activity was evaluated using the microdilution assay and the antibiofilm effect by measurement of the metabolic activity. Ethanol and ethanol-water extracts of Reynoutria japonica leaves inhibited 50 % of planktonic cells at 250 μg mL⁻¹ and 15.6 μg mL⁻¹, respectively. Ethanol and ethanol-water extracts of Baccharis halimifolia inhibited >75 % of the mature biofilm of C. albicans at 500 μg mL⁻¹. The essential oil (EO) of B. halimifolia leaves was the most active (50 % inhibition (IC₅₀) at 4 and 74 μg mL⁻¹against the maturation phase and 24 h old-biofilms of C. albicans, respectively). Oxygenated sesquiterpenes were the primary contents in this EO (62.02 %), with β-caryophyllene oxide as the major component (37 %). Aromadendrene oxide-(2), β-caryophyllene oxide, and (±)-β-pinene displayed significant activities against the maturation phase (IC₅₀=9–310 μ mol l⁻¹) and preformed 24 h-biofilm (IC₅₀=38–630 μ mol l⁻¹) of C. albicans with very low cytotoxicity for the first two compounds. C. albicans remained the most susceptible species to this EO and its components. This study highlighted for the first time the antibiofilm potential of B. halimifolia, its EO and some of its components.     

Novel Miscanthus hybrids: Modelling productivity on marginal land in Europe using dynamics of canopy development determined by light interception

New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year⁻¹ biomass, with potential for 1.2–1.3 EJ year⁻¹ energy and 36.3–40.3 Mt year⁻¹ carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over the current commercial miscanthus variety.     

Genomic analyses reveal natural selection on reproduction related genes between two closely related Populus (Salicaceae) species

Identifying the factors that cause reproductive isolation and their relative importance in species divergence is crucial to our understanding of speciation processes. In most species, natural selection is commonly considered to play a large role in driving speciation. Based on whole genome re-sequencing data from 27 Populus alba and 28 Populus adenopoda individuals, we explored the factors related to reproductive isolation of these two closely related species. The results showed that the two species diverged ~5–10 million years ago (Ma), when the Qinghai–Tibet Plateau reached a certain height and the inland climate of the Asian continent became arid. In highly differentiated genomic regions, the relative divergence (F_ST) and absolute divergence (d_xy) were significantly higher than the genomic background, θπ and shared polymorphisms decreased whereas fixed differences increased, which indicated that natural selection played a key role in the reproductive isolation of the two species. In addition, we found several genes that were related to reproduction that may be involved in explaining the reproductive isolation. Using phylogenetic trees resolved from haplotype data of Populus tomentosa and P. adenopoda, the maternal origin of P. tomentosa from P. adenopoda was likely to be located in Hubei and Chongqing Provinces.     

THE FUNCTIONAL BASIS OF NATURAL SELECTION FOR VERTEBRAL TRAITS OF LARVAE IN THE STICKLEBACK GASTEROSTEUS ACULEATUS

Previous studies have demonstrated selective predation for vertebral traits of larvae in the stickleback Gasterosteus aculeatus. I tested the hypothesis that this selection results from a direct functional advantage to particular vertebral phenotypes by direct measurement of the burst swimming performance of larvae. Within a narrow window of lengths, burst speed did depend on vertebral phenotype. As in the previous predation experiments, performance was related more directly to the ratio of abdominal to caudal vertebrae (VR) than to the total number of vertebrae (VN), and the optimal VR decreased as larval length increased. Changes with length in the vertebral phenotype frequencies of wild larvae provided evidence of selection for VR and for VN in the wild. Larvae with particular VR increased in frequency in the wild at just those lengths when their relative performance was superior in the laboratory. The observed pattern of length-dependent selection for vertebral number provides an explanation for the widespread trends in vertebral number that occur among populations of related fishes.     

GENETIC DIFFERENTIATION OF POLISH POPULATIONS OF SOREX ARANEUS L. III. INTERCHROMOSOMAL RECOMBINATION IN A HYBRID ZONE

Two parapatric chromosomal races of the common shrew (Sorex araneus) in Poland differ in their complement of metacentric arm combinations: hk, io, gr, nm (race IV), and hi, ko, gm, np (race II). In hybrids, these eight race-diagnostic metacentrics form two randomly segregating complexes. The first complex (C₁) occurs in the form of a ring configuration ok/kh/hi/io, or a chain o/ok/kh/hi/i (when there is Robertsonian polymorphism of the element io). The second complex (C₂) always takes the form of a six-element chain configuration r/rg/gm/mn/np/p. The C₂ complex may be shortened to five or even four elements, when acrocentrics g, m and n are present. In the contact zone we found shrews of pure races (race II or IV), as well as hybrids with C₁ or C₂ complexes, and recombinants hi, ko, gr, nm. Complex heterozygotes are likely to suffer reduced fertility due to malsegregation at meiosis. However, the C₁ hybrids with ring configurations occur with a high frequency throughout the contact zone. This suggest that their fitness is only slightly lowered relative to pure race individuals, in contrast to the hybrids with C₁ or C₂ chain configurations, which presumably have a more heavily reduced fertility. On the other hand, at the center of the zone there is a high proportion of recombinants, which, being chromosomal homozygotes, should display normal meiotic segregation. Furthermore, the high frequencies of recombinants within the contact zone should facilitate gene flow between the races. The occurrence of recombinants plays a similar role as the appearance of the maximum frequencies of acrocentric homozygotes described in several contact zones of S. araneus.     

MULTIVARIATE ANALYSIS OF SELECTION IN EXPERIMENTAL POPULATIONS DERIVED FROM HYBRIDIZATION OF TWO ECOTYPES OF THE ANNUAL PLANT DIODIA TERES W. (RUBIACEAE)

Morphologically variable F₂ genotypes derived from hybridization of coastal and inland ecotypes of the annual plant Diodia teres were used to identify selection on morphological traits in the natural habitat of each ecotype. These ecotypes occur in very different habitats, and have evolved pronounced morphological differentiation. Selection analysis can suggest whether present patterns of selection can explain morphological differences between ecotypes. F₂ genotypes were characterized morphologically, clonally replicated, and transplanted into the habitat of each ecotype. Selection was measured on six morphological traits. Directional and stabilizing selection occurred on many traits; direction and strength of selection varied sharply at different stages of growth, as revealed by a path-analysis approach that divided selection into a set of independent components. Directional selection favored traits of the native population at the coastal habitat, but less so at the inland habitat. Selection was of sufficient strength to create the observed morphological differences between ecotypes in 25–100 generations, given constant selection and sufficient genetic variation. In effects on fitness, most traits were neither independent nor consistently interactive with other traits. Rather, many traits entered into strong but evanescent interactions affecting particular components of fitness. Observed interactions did not support the hypothesis that the morphology of each ecotype was functionally integrated to a high degree.     

REGENERATION AND SEXUAL DIFFERENTIATION OF GRIFFITHSIA JAPONICA (CERAMIACEAE,RHODOPHYTA) THROUGH SOMATIC CELL FUSION1

Hybrid cells were obtained from somatic cell fusion among male, female, and tetrasporangial plants in Griffithsia japonica Okamura by a wound-healing process. Isolated fusion cells regenerated new mature plants with mixed reproductive structures. The plants regenerated from hybrid cells between male and female plants developed into 1) spermatangiate, 2) carpogonial, 3) bisexual with spermatangia and carpogonial branches, 4) mixed-phase with spermatangia and tetrasporangia, or 5) bisexual/mixed-phase plants with spermatangia, carpogonial branches, and tetrasporangia. About 70% of the plants regenerated from hybrid cells between male and female plants produced tetrasporangia that were always formed with spermatangia on a single cell. Some of those tetrasporangia released tetraspores, six of which gave rise to mature plants. The plants regenerated from hybrid cells between male and tetrasporangial plants developed into spermatangiate, tetrasporangiate, or mixed-phase plants with spermatangia and tetrasporangia. The plants regenerated from hybrid cells between female and tetrasporangial plants developed into carpogonial, tetrasporangiate, or mixed-phase plants with carpogonial branches and tetrasporangia. All types of reproductive structures we re functional.     

Diurnal changes in phosphoenolpyruvate carboxylase and pyruvate, orthophosphate dikinase properties in the natural environment: interplay of light and temperature in a C4 thermophile

Activities of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) were measured in leaf extracts of field grown Amaranthus paniculatus L. (C₄) during a natural diurnal irradiance and temperature pattern. Enzyme assays were run at both fixed (30°C) and the corresponding leaf temperature at the time of harvest. Light activation of PEP carboxylase (PEPCase) at fixed assay temperatures was expressed as a decrease in S_0–5 (PEP) after a threshold (> 330 μmol m^–2 s^–1) photon fluence rate was surpassed at noon. Earlier in the morning, increase in apparent enzyme affinity for PEP was observed when the assay was run at leaf temperature, indicating a physiologically meaningfull effect of temperature on S^0.5 (PEP). The 3.3-fold increase in PEPCase activity at low PEP and fixed assay temperature between the minimal and maximal irradiance and temperature hours of the day, became 12.8-, 11.5- and 7.4-fold when assays were run at the corresponding leaf temperature during three diurnal cycles with respective temperature differences (max minus min) of 9.0, 8.3 and 7.4°C. The extent of malate inhibition was the same for both day and night forms of PEPCase assayed at 35°C, but increased considerably with night enzyme at 25°C. The results indicate that light increases the apparent affinity of PEPCase for PEP and that at lower temperatures malate becomes more inhibitory. Pyruvate orthophosphate dikinase activity started to increase immediately after sunrise and the 10-fold increase at fixed temperature became 14.8-, 14.2- and 13.1-fold when assays were run at the above leaf temperatures. This indicates that the light effect predominates with pyruvate, orthophosphate dikinase, while with phosphoenolpyravate carboxylase, light and temperature co-operate to increase the day enzyme activities.     

Testing the ecological relevance of Daphnia species designations

1. Molecular approaches have increasingly revealed hidden genetic structure within ecologically important species, leading to the creation of sibling species whose ecological relevance is often unclear. A prime example is Daphnia galeata mendotae, which was split into D. dentifera and D. mendotae based on differences at two allozyme loci. 2. In a set of lake populations in Michigan USA, we test the geographical and temporal consistency of the genetic structure underlying this species split. We also test the morphological relevance of this molecular variation and its ecological significance in lakes. In essence, we ask: does recognition of these new species provide valuable information for plankton ecologists? 3. We found that D. dentifera and D. mendotae represent morphologically and ecologically distinct forms that are distributed among lakes in non‐random fashion, which were remarkably stable over 6 years. Key differences between the species concern their body and head shape, vertical habitat use within lakes and distribution among lakes of different size. We hypothesise that these differences represent specialisation to habitats that differ in risk of invertebrate predation. 4. Reproductive barriers alone are insufficient to explain the pattern of genetic structure; in some lakes complete introgression is apparent. However, parent species and hybrids exhibit a stable co‐existence in many lakes, which suggests that ecological specialisation reinforces divergence within this taxon.     

Life history patterns of parental and hybrid Daphnia differ between lakes

1. We investigated whether Daphnia galeata × hyalina hybrids of Lake Constance and Lake Greifensee show the same pattern of life history parameters as previously reported for D. galeata × cucullata hybrids and whether such a pattern is consistent between Daphnia populations from those two lakes. 2. Hybrids in Lake Constance were intermediate in size compared with the parental species. Hybrids in Lake Greifensee were smaller than D. galeata. The intrinsic growth rate (r) of hybrids from Lake Constance was not significantly different from the faster growing parental taxon D. galeata. However, r of hybrids from Lake Greifensee was significantly lower than that of D. galeata. 3. The observed juvenile body length differences between the taxa varied with the clutch number. The first clutch juvenile lengths of the three taxa did not differ for Lake Constance. First clutch juveniles of Lake Greifensee D. galeata were smaller than hybrid first clutch juveniles. The third clutch juvenile length did not differ between taxa from Lake Greifensee, but D. galeata juveniles from Lake Constance were bigger than those of D. hyalina. 4. The life history pattern found in Lake Constance corresponds to previous findings from other studies. The hybrids in this lake combine the faster population growth of one parental species with a relatively small size. In the case of Lake Greifensee hybrids, the relatively large size of first clutch juveniles and the small size of the adults could be interpreted as dual adaptations to invertebrate and fish predation. We speculate that the lower population growth rate of the hybrids is a trade‐off for this twofold protection.