Effects of pyraclostrobin on growth,oxidative stress,and gene expression in relation to stress and ATP-binding cassette transporters in Tetrahymena thermophila

Pyraclostrobin(PYR),a widely used fungicide,has negative effects on fish and algae,but its toxicity in protozoa remains unclear.In this study,the effects of PYR on the growth,oxidative stress,and gene expression related to stress and ATP-binding cassette(ABC)transporters in Tetrahymena thermophila were investigated.The result showed that the 96-h IC_(50)of PYR against T.thermophila was 17.2 mg/L.Moreover,PYR inhibited the growth of T.thermophila in concentration-or time-dependent manner.A morphological study revealed that the shape and size of T.thermophila changed,and damage of cell membrane surface was observed by scanning electron microscopy after 96 h of PYR exposure.The activities of superoxide dismutase(SOD)and catalase(CAT)increased throughout the experiment.In contrast,the glutathione(GSH)content was increased at 24 h and 48 h of exposure and decreased at 96 h.Moreover,a significant increase in malondialdehyde(MDA)level was observed in T.thermophila after96 h of exposure.Furthermore,PYR upregulated the HSP703,HSP705,GPx2,and ABAC15 gene expression in the 0.1–5-mg/L groups and downregulated the HSP704,HSP90,TGR,and ABCC52 mRNA levels at 96 h of exposure.These results suggest that PYR may exert adverse effects on T.thermophila by inducing oxidative stress and changing the gene expression related to ABC transporters and stress,which may enrich the understanding of the toxicity mechanism of PYR in aquatic organisms and provide reference data for aquatic ecological risk assessments.

Genetic relationships among sympatric varieties of Acer mono in the Chichibu Mountains and Central Hokkaido, Japan

Acer mono Maxim. is one of the major components of cool temperate forests in Japan. Some of its many varieties are distributed sympatrically. Because of its great variability, the intraspecific taxonomy and nomenclature of the species are controversial. To understand the genetic relationships among these varieties and whether hybridization or introgression occurred among the sympatric varieties, we studied the genetic relationships among sympatric varieties of A. mono in the Chichibu Mountains (A. mono var. ambiguum, A. mono var. connivens, A. mono var. marmoratum) and Central Hokkaido (A. mono var. mayrii and A. mono var. glabrum) in Japan. Our results showed that varieties in Chichibu are genetically close, suggesting that hybridization or introgression might occur between these varieties, which could explain the higher genetic diversity of varieties in Chichibu than in Hokkaido. In contrast to the close relationships between the varieties in Chichibu, varieties in Hokkaido seemed relatively separated from each other; indeed, there may be reproductive isolation between the two varieties. The results provide new insight for the taxonomy of the varieties of A. mono, especially the sympatric varieties, in Japan.

Grazing and heat stress protection of native grass by a sand-fixing shrub in the arid lands of northern China

Shrub species are used in restoration projects on dryland for their facilitation effects,which include environmental improvements and protection from herbivore feeding.Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands.However,the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear.Here,our main purpose was to measure facilitation performance in terms of the survival of a native forage grass,Agropyron cristatum(L.)Gaertn.(Gramineae).,in accordance with the growth conditions of a sand-fixing benefactor shrub,Caragana microphylla Lam.,in the Hulun Buir Grassland,northern China.Six study sites with patches of A.cristatum and C.microphylla were established at the foot of fixed sand dunes.At each site,five quadrats were set in places where C.microphylla coverage was 100%and A.cristatum grew among the shrubs(shrub quadrats),and another five were set where A.cristatum grew alone without C.microphylla(grass quadrats).We measured the morphological traits of C.microphylla and A.cristatum in all 60 quadrats,along with the soil water content and soil temperature.The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects.We also used such models to elucidate the relationship between the average height of C.microphylla and the morphological traits of A.cristatum in the shrub quadrats.The maximum height,average grazed height,and the number of seed heads of A.cristatum were greater in the shrub quadrats than in the grass quadrats.The soil surface temperature was lower in the shrub quadrats.The maximum height and seed head number of A.cristatum were positively associated with the average height of C.microphylla.These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats,and that the degree of this protective effect depended on the shrub height.The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous.Livestock likely avoided grazing grasses in the C.microphylla patches because of the shrub's spiny leaves;only the upper parts of the grass stems(including the seed heads)protruding from the shrub canopy were grazed.The sand-fixing shrub thus moderates the grazing impact and soil temperature,and contributes to vegetation restoration and grazing system sustainability.

GC/FT-IR Analysis of Novel 4,6,9-Triene and 2,4,6,9-Tetraene Occurring in a Female Pheromone Gland of <i>Arctia plantaginis</i>(Erebidae: Arctiinae)

Fifteen subspecies of the wood tiger moth, Arctia plantaginis (Lepidoptera: Erebidae: Arctiinae), have been recorded in the Northern Hemisphere. An analysis of crude pheromone extracts by GC equipped with an electroantennographic (EAG) detector showed four EAG-active components (Comps. I–IV) that were commonly involved in the pheromone glands of two subspecies inhabiting Japan and Finland. Comp. I is a major component (>75%) and the others are minor components (3% - 15%). Their mass spectra, measured by GC/MS, revealed the chemical structures of C21 unsaturated hydrocarbons as follows: 3,6,9-triene for Comp. I, 4,6,9-triene for Comp. II, 1,3,6,9-tetraene for Comp. III, and 2,4,6,9-tetraene for Comp. IV. Comps. I and III are known Type II pheromone compounds, and their retention times coincide with those of the authentic standards with all Z configurations. As a next step, the extract was analyzed by GC/FT-IR to determine the configuration of Comps. II and IV. Their IR spectra showed two characteristic C-H bending absorptions around 990 and 945 cm-1 due to the conjugated dienyl moieties;thus, Z and E configurations were assigned to the double bonds at the 2- and 4-positions, respectively. Their Z double bonds at the 6- and 9-positions are indicated by no absorptions around 970 cm-1, due to the isolated double bonds with E configurations. Finally, the structures of Comps. II and IV were confirmed by synthesis using a double Wittig reaction. The synthetic (4E,6Z,9Z)-4,6,9-triene and (2Z,4E,6Z,9Z)-2,4,6,9-tetraene showed strong EAG activity, and their chemical data coincided well with those of the natural Comps. II and IV, indicating the correctness of the structure determination by GC/FT-IR analysis and its usefulness for Type II pheromone compounds.