Bio‐energetics underpins the spatial response of North Sea plaice (Pleuronectes platessa L.) and sole (Solea solea L.) to climate change

Climate change is currently one of the main driving forces behind changes in species distributions, and understanding the mechanisms that underpin macroecological patterns is necessary for a more predictive science. Warming sea water temperatures are expected to drive changes in ectothermic marine species ranges due to their thermal tolerance levels. Here, we develop a mechanistic tool to predict size‐ and season‐specific distributions based on the physiology of the species and the temperature and food conditions in the sea. The effects of climate conditions on physiological‐based habitat utilization was then examined for different size‐classes of two commercially important fish species in the North Sea, plaice, Pleuronectes platessa, and sole, Solea solea. The two species provide an attractive comparison as they differ in their physiology (e.g. preferred temperature range). Combining dynamic energy budget (DEB) models with the temperature and food conditions estimated by an ecosystem model (ERSEM), allowed spatial differences in potential growth (as a proxy for habitat quality) to be estimated for 2 years with contrasting temperature and food conditions. The resulting habitat quality maps were in broad agreement with observed ontogenetic and seasonal changes in distribution as well as with the recent changes in distribution which could be attributed to an increase in coastal temperatures. Our physiological‐based model provides a powerful tool to explore the effect of climate change on the spatio‐temporal fish dynamics, predict effects of local or broad‐scale environmental changes and provide a physiological basis for observed changes in species distributions.     

Influence of DNA isolation from historical otoliths on nuclear-mitochondrial marker amplification and age determination in an overexploited fish, the common sole (Solea solea L.)

Historical otolith collections are crucial in assessing the evolutionary consequences of natural and anthropogenic changes on the demography and connectivity of commercially important fish species. Hence, it is important to define optimal protocols for purifying DNA from such valuable information sources while avoiding any damage to the physical structure of the otolith. Before being able to conclude on the harmlessness of a method, it is important to validate protocols on different kinds of otoliths by testing purification methodologies under standardized conditions. Here we compare the effect of two DNA extraction methods on the success in identifying the age in an overexploited marine fish, the common sole (Solea solea L.). To ensure optimal future population genetic and demographic analyses, we assessed DNA quantity and tested the DNA quality by investigating the amplification success of a mitochondrial and nuclear marker. Our results show that the choice of the DNA extraction method had a significant effect on the success of using these otoliths in age and growth analyses. Standard commercial and published protocols resulted in a severe damaging of the otolith structure, hampering accurate preparation and analyses of the morphological structures of the otoliths. Shortening the lysis time and lowering the EDTA (ethylene diamine tetraacetic acid) and SDS (sodium dodecylsulphate) concentration turned out to be beneficial for the stability of otolith structure, while maintaining an overall high DNA quality measured through polymerase chain reaction amplification success. We therefore recommend that care should be taken when choosing the extraction method for a molecular study on archived samples, in order to enable the maximal use of information embedded in historical material.     

Interaction between exopolysaccharide and oxygenation levels on habitat selection in the sole Solea solea (L.)

A habitat selection experiment was conducted to examine the behavioural response of sole Solea solea to a combination of sediment quality (exopolysaccharides, EPS-free, i.e. 0 mg l⁻¹ and EPS-rich, i.e. 4 mg l⁻¹) and water oxygenation level (100 and 35% air saturation). The distribution of sole was influenced differently by the type of substratum depending on the water oxygenation level. In normoxia, sole settled preferentially on sand whereas under hypoxic conditions, sole settled preferentially on the muddy substratum. In order to explain these apparently counter-intuitive observations, it is proposed that, via cutaneous respiration, young sole are able to take advantage of the large quantities of oxygen produced by microphytobenthic organisms present in the upper few millimetres of muddy substratum.     

The influence of sand on the estimation of resting metabolic rate of juvenile sole, Solea solea (L.)

The influence of a sandy substrate on the estimation of the resting metabolic rate of juvenile sole was determined using a static type of respirometer. Oxygen consumption of fish deprived of sand was almost double that of fish provided with sand.     

The relationships between fish size and otolith dimensions in the common sole (Solea solea (Linnaeus, 1758)) captured in the Northeastern Mediterranean

Fish specimens were captured by a commercial bottom trawler at a depth of 50–80 m from Iskenderun Bay (Hatay, Turkey) between December 2017 and May 2018. The bottom trawl gear used was equipped with a 44 mm stretched mesh size net at the cod-end. Blind side and eyed side otolith lengths (OL), otolith breadths (OB) and otolith weights (OW) were measured from each specimen to the nearest 0.001 mm and 0.0001g respectively. A total of 110 fish (43 females and 67 males) were collected. Total length ranged from 20.8 to 28.2 cm and 68.0 to 166.1 g (males) and 21.1 to −28.5 cm and 74.5 to 201.4 g (females). The coefficients of determination between fish weight and otolith weight, and total length and otolith weight (sexes combined) were found as R² = .7694 (0.77) and R² = .6274 (0.63), respectively. A moderate positive relationship between the total length-otolith dimensions, and fish weight-otolith dimensions, was also demonstrated.     

Coupling of heart rate and locomotor activity in sole, Solea solea (L.), and bass, Dicentrarchus labrax (L.), in their natural environment by using ultrasonic telemetry

Field measurements of distance moved and heart rate in sole, Solea solea (L.) and bass, Dicentrarchus labrax (L.) using ultrasonic telemetry revealed two different strategies. Heart rate in the sole increases during activity, accurately reflecting fluctuation in metabolic rate and so can be used as a measure of metabolic rate in the field. In contrast, the relatively stable value of the heart rate in bass during the whole tracking period whatever the activity level suggests that in this species heart rate in the field cannot be associated with metabolic rate determination.     

Malnutrition may affect common sole (Solea solea L.) growth, pigmentation and stress response: molecular, biochemical and histological implications

In the last decades there have been several evidences that traditionally used live preys like rotifers and Artemia salina have nutritional deficiencies that result in a general decrease of fish health, causing anomalies in the development, in growth and in pigmentation. In this study a partial of total replacement of traditional live preys with preserved copepods that represent the natural food of the larvae was evaluated during Solea solea culture. In this study a positive effect of co-feeding preserved copepods in sole larviculture was observed since larvae fed this diet growth and survived better, showed a better tolerance to captive conditions and had a better response to the final thermal/density stress-test with respect to larvae fed a traditional diet. Morphometric data were fully supported by molecular and biochemical ones. Moreover, liver histological investigations, revealed that the inclusion of preserved copepods in the larval diet was able to improve lipid assimilation. In conclusion, preserved copepods may be considered a suitable food for sole when used as a supplement to the traditional diet based on rotifers and Artemia nauplii.     

TaDA1, a conserved negative regulator of kernel size,has an additive effect with TaGW2 in common wheat (Triticum aestivum L.)

Kernel size is an important trait determining cereal yields. In this study, we cloned and characterized TaDA1, a conserved negative regulator of kernel size in wheat (Triticum aestivum). The overexpression of TaDA1 decreased the size and weight of wheat kernels, while its down‐regulation using RNA interference (RNAi) had the opposite effect. Three TaDA1‐A haplotypes were identified in Chinese wheat core collections, and a haplotype association analysis showed that TaDA1‐A‐HapI was significantly correlated with the production of larger kernels and higher kernel weights in modern Chinese cultivars. The haplotype effect resulted from a difference in TaDA1‐A expression levels between genotypes, with TaDA1‐A‐HapI resulting in lower TaDA1‐A expression levels. This favourable haplotype was found having been positively selected during wheat breeding over the last century. Furthermore, we demonstrated that TaDA1‐A physically interacts with TaGW2‐B. The additive effects of TaDA1‐A and TaGW2‐B on kernel weight were confirmed not only by the phenotypic enhancement arising from the simultaneous down‐regulation of TaDA1 and TaGW2 expression, but also by the combinational haplotype effects estimated from multi‐environment field data from 348 wheat cultivars. A comparative proteome analysis of developing transgenic and wild‐type grains indicated that TaDA1 and TaGW2 are involved in partially overlapping but relatively independent protein regulatory networks. Thus, we have identified an important gene controlling kernel size in wheat and determined its interaction with other genes regulating kernel weight, which could have beneficial applications in wheat breeding.     

The population genomic basis of geographic differentiation in North American common ragweed (Ambrosia artemisiifolia L.)

Common ragweed (Ambrosia artemisiifolia L.) is an invasive, wind‐pollinated plant nearly ubiquitous in disturbed sites in its eastern North American native range and present across growing portions of Europe, Africa, Asia, and Australia. Phenotypic divergence between European and native‐range populations has been described as rapid evolution. However, a recent study demonstrated major human‐mediated shifts in ragweed genetic structure before introduction to Europe and suggested that native‐range genetic structure and local adaptation might fully explain accelerated growth and other invasive characteristics of introduced populations. Genomic differentiation that potentially influenced this structure has not yet been investigated, and it remains unclear whether substantial admixture during historical disturbance of the native range contributed to the development of invasiveness in introduced European ragweed populations. To investigate fine‐scale population genetic structure across the species' native range, we characterized diallelic SNP loci via a reduced‐representation genotyping‐by‐sequencing (GBS) approach. We corroborate phylogeographic domains previously discovered using traditional sequencing methods, while demonstrating increased power to resolve weak genetic structure in this highly admixed plant species. By identifying exome polymorphisms underlying genetic differentiation, we suggest that geographic differentiation of this important invasive species has occurred more often within pathways that regulate growth and response to defense and stress, which may be associated with survival in North America's diverse climatic regions.     

Isolation and Identification of Pathogens Causing Marigold (Tagetes erecta L.) Black Spot in Beijing,China

Black spot leads to great marigold losses worldwide. The disease is characterized by black spots on leaves and stems in its early stages, and the whole plant has black rot at the advanced stage. In this report, 6 of 217 Alternaria strains isolated from lesions of marigold plants in Beijing were randomly selected. The morphological characteristics and a pathogenic tree based on two protein‐coding genes (gpd and alt a 1) indicated that Alternaria tagetica is the causal agent of marigold black spot in Beijing. All six Alternaria strains could successfully re‐infect marigold, but they could not infect carrot or zinnia by either spore spray in a greenhouse or planting experiments in the epidemic area. This is the first report of the A. tagetica pathogen being isolated from marigold in Beijing.     

Identification,release and olfactory detection of bile salts in the intestinal fluid of the Senegalese sole (<Emphasis Type="Italic">Solea senegalensis</Emphasis>)

Olfactory sensitivity to bile salts is wide-spread in teleosts; however, which bile salts are released in sufficient quantities to be detected is unclear. The current study identified bile salts in the intestinal and bile fluids of Solea senegalensis by mass spectrometry–liquid chromatography and assessed their olfactory potency by the electro-olfactogram. The main bile salts identified in the bile were taurocholic acid (342 mM) and taurolithocholic acid (271 mM) plus a third, unidentified, bile salt of 532.3 Da. These three were also present in the intestinal fluid (taurocholic acid, 4.13 mM; taurolithocholic acid, 0.4 mM). In sole-conditioned water, only taurocholic acid (0.31 μM) was released in sufficient quantities to be measured (release rate: 24 nmol kg⁻¹ min⁻¹). Sole had high olfactory sensitivity to taurocholic acid but not to taurolithocholic acid. Furthermore, olfactory sensitivity was higher in the upper (right) olfactory epithelium than the lower (left). These two bile acids contribute about 40% of the olfactory potency of intestinal fluid and account for the difference in potency at the two epithelia. Taurocholic acid (but not taurolithocholic acid), and possibly other types of bile acid not tested, could be used as chemical signals and the upper olfactory epithelium is specialised for their detection.     

Chemical Composition,Antibacterial, Schistosomicidal,and Cytotoxic Activities of the Essential Oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae)

We have investigated the chemical composition and the antibacterial activity of the essential oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae) (DA‐EO) against a representative panel of cariogenic bacteria. We have also assessed the in vitro schistosomicidal effects of DA‐EO on Schistosoma mansoni and its cytotoxicity to GM07492‐A cells in vitro. Gas chromatography (GC) and gas chromatography‐mass spectrometry (GC/MS) revealed that the monoterpenes cis‐piperitone oxide (35.2%), p‐cymene (14.5%), isoascaridole (14.1%), and α‐terpinene (11.6%) were identified by as the major constituents of DA‐EO. DA‐EO displayed weak activity against Streptococcus sobrinus and Enterococcus faecalis (minimum inhibitory concentration (MIC) = 1000 μg/ml). On the other hand, DA‐EO at 25 and 12.5 μg/ml presented remarkable schistosomicidal action in vitro and killed 100% of adult worm pairs within 24 and 72 h, respectively. The LC₅₀ values of DA‐EO were 6.50 ± 0.38, 3.66 ± 1.06, and 3.65 ± 0.76 μg/ml at 24, 48, and 72 h, respectively. However, DA‐EO at concentrations higher than 312.5 μg/ml significantly reduced the viability of GM07492‐A cells (IC₅₀ = 207.1 ± 4.4 μg/ml). The selectivity index showed that DA‐EO was 31.8 times more toxic to the adult S. mansoni worms than GM07492‐A cells. Taken together, these results demonstrate the promising schistosomicidal potential of the essential oil of Dysphania ambrosioides.     

Maternal control of seed weight in rapeseed (Brassica napus L.): the causal link between the size of pod (mother,source) and seed (offspring,sink)

Seed size/weight is one of the key traits related to plant domestication and crop improvement. In rapeseed (Brassica napus L.) germplasm, seed weight shows extensive variation, but its regulatory mechanism is poorly understood. To identify the key mechanism of seed weight regulation, a systematic comparative study was performed. Genetic, morphological and cytological evidence showed that seed weight was controlled by maternal genotype, through the regulation of seed size mainly via cell number. The physiological evidence indicated that differences in the pod length might result in differences in pod wall photosynthetic area, carbohydrates and the final seed weight. We also identified two pleiotropic major quantitative trait loci that acted indirectly on seed weight via their effects on pod length. RNA‐seq results showed that genes related to pod development and hormones were significantly differentially expressed in the pod wall; genes related to development, cell division, nutrient reservoir and ribosomal proteins were all up‐regulated in the seeds of the large‐seed pool. Finally, we proposed a potential seed weight regulatory mechanism that is specific to rapeseed and novel in plants. The results demonstrate a causal link between the size of the pod (mother, source) and the seed (offspring, sink) in rapeseed, which provides novel insight into the maternal control of seed weight and will open a new research field in plants.     

Characterization of culturable bacterial endophytes of switchgrass (Panicum virgatum L.) and their capacity to influence plant growth

Switchgrass (Panicum virgatum L.) is a perennial warm season grass that is native to the plains of North America and is widely grown as a forage, bioenergy or groundcover crop. Despite its importance, a bottleneck in switchgrass production is poor seedling vigor, which as a perennial crop represents an important time for management. Herein, data identify a suite of culturable bacterial microflora extracted from switchgrass, and show their capability to influence host plant growth and development. A total of 307 bacterial isolates were cultured and isolated from surface sterilized switchgrass biomass and sequence identified into 76 strains (subspecies classification), 36 species and 5 phyla. Approximately 58% of bacterial strains, when reintroduced into surface‐sterilized switchgrass seeds, were documented to increase lamina length (cm from base to tip after 60 days growth) relative to uninoculated controls. Ecologically, Phylum Firmicutes was the most abundant bacterial classification and encompassed 75% of all isolates. Although the culturable bacterial community studies herein represent an unknown and assumedly minor proportion of the total microbiome, by focusing on culturable bacteria, we delineate functional feedback between the presence of isolated bacteria and switchgrass seedling growth.     

Effect of adult females' predation risk on oviposition site selection in a water strider

In many egg‐laying species, females avoid ovipositing at sites where the predation risk is high. Previous studies have mainly focused on the risk for offspring. The effect of predation risk for the females has been considered in some taxa in which parents spend much time at an oviposition site for parental care or mating (e.g., birds, amphibians). In species in which females do not perform activities other than oviposition at sites, the effect of predation risk for females on oviposition site selection has been rarely investigated. We examined whether the predation risk for ovipositing females affects the decision on oviposition in the water strider Aquarius paludum insularis (Motschulsky) (Heteroptera: Gerridae). Adult A. paludum are preyed upon by a backswimmer, Notonecta triguttata (Motschulsky) (Heteroptera: Notonectidae), but N. triguttata does not prey upon eggs or early instars of A. paludum. We allowed female A. paludum to oviposit under one of three conditions: in presence of N. triguttata, in presence of its chemicals, and in absence of the predator or its cues (control). Female A. paludum less frequently oviposited in presence of N. triguttata than in its absence. Oviposition frequency did not differ between females in presence of chemicals of N. triguttata vs. those in the control. Female A. paludum recognized the predation risk upon themselves from the presence of N. triguttata and avoided ovipositing. This study is the first to directly show that the predation risk upon ovipositing females changes oviposition site selection in species in which the time spent at an oviposition site is short.     

Expression of ZmGA20ox cDNA alters plant morphology and increases biomass production of switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.) is considered a model herbaceous energy crop for the USA, for its adaptation to marginal land, low rainfall and nutrient‐deficient soils; however, its low biomass yield is one of several constraints, and this might be rectified by modulating plant growth regulator levels. In this study, we have determined whether the expression of the Zea mays gibberellin 20‐oxidase (ZmGA20ox) cDNA in switchgrass will improve biomass production. The ZmGA20ox gene was placed under the control of constitutive CaMV35S promoter with a strong TMV omega enhancer, and introduced into switchgrass via Agrobacterium‐mediated transformation. The transgene integration and expression levels of ZmGA20ox in T0 plants were analysed using Southern blot and qRT‐PCR. Under glasshouse conditions, selected transgenic plants exhibited longer leaves, internodes and tillers, which resulted in twofold increased biomass. These phenotypic alterations correlated with the levels of transgene expression and the particular gibberellin content. Expression of ZmGA20ox also affected the expression of genes coding for key enzymes in lignin biosynthesis. Our results suggest that the employment of ectopic ZmGA20ox and selection for natural variants with high level expression of endogenous GA20ox are appropriate approaches to increase biomass production of switchgrass and other monocot biofuel crops.     

Effects of cyanobacteria,fish kairomones,and the presence of ostracods on the demography of Simocephalus vetulus (Cladocera)

Simocephalus vetulus is a large (2.0–4.0 mm at maturity) cladoceran often found in the littoral region of lakes and ponds, and capable of moderate growth rates even on poor‐quality cyanobacterial diets. It frequently co‐occurs with fishes and similar sized ostracods such as Heterocypris incongruens, but little is known of its response to fish kairomones or its interactions with potential competitors. We studied the demographic responses of S. vetulus fed the green alga Scenedesmus acutus, Microcystis cf. aeruginosa strain A, Microcystis cf. aeruginosa strain B, or Limnothrix sp. Experiments were conducted separately and together in the presence of Heterocypris incongruens and cichlid fish (Oreochromis) kairomones. A diet of Limnothrix sp. resulted in the lowest population growth rate (0.21±0.023 d^?1), while on diets of S. acutus or Microcystis, population growth was higher (0.30±0.009 d^?1). The presence of ostracods resulted in significantly higher growth rates of S. vetulus fed Limnothrix (0.33±0.01 d^?1), but not Microcystis or S. acutus. Regardless of the diet, the presence of fish kairomones resulted in significantly higher growth rates as compared with controls, particularly when ostracods were also present. Coexistence with ostracods may be beneficial to S. vetulus, particularly when food quality is poor.     

First report of Alternaria leaf spot caused by Alternaria alternata (Fries.) Kiessler on Sonchus oleraceus L. and Convolvulus arvensis L. in Algeria

Alternaria leaf spot caused by Alternaria alternata (Fries.) Kiessler was found on sow thistle (Sonchus oleraceus L.) and field bindweed (Convolvulus arvensis L.) in the experimental station of ENSA (Ecole Nationale Supérieure d'Agronomie) in Algiers, Algeria, during the winter of 2016. Necrotic spots in the form of concentric circles were observed on the leaves of both weeds with disease incidence of approximately 70% and disease severity ranging from 50% to 70%. Fungi were isolated from the infected leaves and identified as A. alternata, based on morphological and molecular analyses (using genetic marker internal transcribed spacer, ITS of rDNA). Pathogenicity tests confirmed that A. alternata is the causing agent of leaf spot disease of sow thistle and field bindweed in accordance with the original symptoms. To the best of our knowledge, this is the first report of sow thistle and field bindweed naturally infected by A. alternata in Algeria.