Total Phenoloxidase Research Articles

A Test of Immune Priming in the Kissing Bug Rhodnius pallescens (Hemiptera: Reduviidae) against the Entomopathogenic Fungus Beauveria bassiana (Hypocreales: Cordycipitaceae) in Panama

Abstract The assumption that the invertebrate immune system lacks memory and specificity has changed over time: many studies now indicate that a primary exposure of the host to a pathogen increases its resistance to a subsequent lethal challenge, a phenomenon known as immune priming. One group of insects in which immune priming has been little investigated is the hematophagous triatomine bugs. Herein, we tested the capability of the kissing bug Rhodnius pallescens Barber (Hemiptera: Reduviidae; hereafter kissing bugs), the vector of Chagas disease, to resist entomopathogenic fungi. Laboratory kissing bugs free of Wolbachia and Trypanosoma spp. as well as kissing bugs collected from the wild were used for tests with the entomopathogen Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae). Against laboratory kissing bugs, the fungus remained virulent for 94 d, indicating long-term viability. Kissing bugs collected from the wild that were exposed to a nonlethal dose of the fungus did not show increased survival against a lethal dose compared with controls inoculated with the lethal dose. However, kissing bugs inoculated with a nonlethal dose had higher levels of total phenoloxidase than control kissing bugs. Although the fungus activates the immune system of the kissing bugs, other variables may influence survival in the face of infection. Moreover, the lethality of the same strain was lower against wild kissing bugs, suggesting that the presence of symbionts or parasites influence the fungus–triatome (host) interaction. This work is one of the few studies that have investigated the fungus–host interaction in terms of immune priming in a hematophagous insect of public health importance. Implications are discussed.

Conservation agriculture practices impact on biological and microbial diversity in earthworm cast under maize-wheat system

Soil degradation is a major global concern due to its negative impact on soil quality and the sustainability of agricultural resources. The conservation agriculture (CA) approach, which includes three key principles such as zero tillage, retention of crop residue and crop rotation has gained widespread adoption to help mitigate the climate change effects on agricultural soils and meet the growing demand for increased production. Earthworm communities, along with microbial activity and diversity, are highly sensitive to tillage practices. Additionally, microbial activity and diversity quickly respond to different cropping systems, making them effective indicators for detecting short-term changes in soil functioning. We therefore, assess the effects of CA innovative approached after 6-years on biological and microbial diversity within earthworm cast in maize-wheat system (MWS). The treatments consist of PBM-RN0/ZTW-RN0 (permanent beds No-N control-both residues removed and wheat with zero tillage); PBM+RN0/ZTW+RN0 (permanent beds No-N control-both residues retained)-50% of maize stover and 25% of wheat residue retained; PBM-RN120/ZTW- RN120 (permanent beds with 120 kg N ha-1 both residues removed wheat with zero tillage); PBM+RN120/ZTW+RN120 (permanent beds with 120 kg N ha-1 both residues retained and wheat with zero tillage) and FBM-RN120/CTW-RN120 (fresh beds in maize/CT in wheat with 120 kg N ha-1 both residues removed). The result of present study showed that activities of carbon (C) cycle-related enzymes in the cast soils viz., dehydrogenase (DHA), β-glucosidase (β-glu), cellulase, and xylanase were significantly higher under PBM+RN120/ ZTW+RN120 than under PBM-RN0/ZTW-RN0. Specifically, the activities of these enzymes were 21.5, 26.8, and 76.5% higher under the PBM+RN120/ZTW+RN120 treatment, respectively. Moreover, the Alk-P activity was found to be 1.3 times higher in the PBM+RN120/ZTW+RN120 treatment than in the PBM-RN0/ZTW-RN0 treatment. The bacterial, fungal, and actinomycete counts in the cast soil ranged from 6.87 to 7.47 CFU (colony forming units) x 106 g-1 soil, 3.87–3.30 CFU x 104 g-1 soil, and 5.09–5.67 CFU x 104 g-1 soil, respectively. Total organic carbon (TOC) showed significant increases of 34.6% under PBM+RN120/ZTW+RN120 as compared to PBM-RN0/ZTW-RN0. The less labile C (Frac. 3), total carbohydrate carbon (TCHO), phenol oxidase (PHE) and peroxidase (PER) were observed as the sensitive indicators under different tillage, rate of nitrogen and residue management practices. This study suggests that permanent beds with crop residue retention with balance fertilization practices can be recommended and popularized to the overall improvement of soil biological pools within earthworm casts in MWS.

Infection with a non-lethal fungal parasite is associated with increased immune investment in the ant Myrmica scabrinodis

Social insects, such as ants, are preferred host organisms of pathogens and parasites because colonies are densely populated, and the number of potential hosts is high in the same place and time. Within a colony, individuals are exposed differentially to risks according to their function and age. Thus, older individuals forage and are therefore the most exposed to infection, predation, or physical stress, while young workers mostly stay inside the sheltered nest being less exposed. Immune investment is considered to be dependent on an individual’s age and pathogen pressure. Long-term exposure to a parasite could affect the immune activity of individuals in an intriguing way that interferes with the age-dependent decline in immunocompetence. However, there are only few cases in which such interferences can be studied. The myrmecopathogenic fungus Rickia wasmannii, which infects entire colonies without killing the workers, is a suitable candidate for such studies. We investigated the general immunocompetence of Myrmica scabrinodis ant workers associated with non-lethal fungal infection by measuring the levels of active phenoloxidase (PO) and total PO (PPO) (reflecting the amount of both active and inactive forms of the enzyme) in two age classes. The level of PO proved to be higher in infected workers than in uninfected ones, while the level of PPO increased with age but was not affected by infection. Overall, these results indicate that a long-term infection could go hand in hand with increased immune activity of ant workers, conferring them higher level of protection.

Enhancing Vicia faba’s immunity against Rhizoctonia solani root rot diseases by arbuscular mycorrhizal fungi and nano chitosan

BackgroundThe spreading of root rot disease of faba bean plant (Vichia faba L, VF) in Egypt is still of great challenge faced researchers since VF is an important legume in Egypt, because their seeds are used for human feeding. Fungicides are used for treatment of either seeds or soil; unfortunately they cause environmental pollution. Therefore, there is a need to continue research to find out safe natural solutions. In this regard, Arbuscular mycorrhizal fungi (AMF) and chitosan (micro or nanoform) were used as an inhibitory product against Rhizoctonia solani OM918223 (R.solani) either singly or in combinations.ResultsThe results employed herein have exhibited that R.solani caused root rot disease of VF plants in more than 80% of the plants under investigation. Chitosan nanoparticles (Chitosan NPs) were prepared by ionic gelatin method and characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM) imaging and Fourier transform infra-red (FTIR). Chitosan NPs are spherical with a diameter of 78.5 nm and exhibited the presence of different functional groups. The inhibitory natural products against R.solani were arranged according to their ability to inhibit the pathogen used in the following descending manner; combination of AMF with Chitosan NPs, AMF with micro chitosan and single AMF, respectively. Where, Chitosan NPs showed a potent influence on R.solani pathogen and reduced the pre-and post-emergence of R. solani. In addition, Chitosan NPs reduced Disease Incidence (DI %) and Disease Severity (DS %) of root rot disease and are widely functional through mixing with AMF by about 88% and 89%. Further, Chitosan NPs and micro chitosan were proved to increase the growth parameters of VF plants such as nutritional status (mineral, soluble sugar, and pigment content), and defense mechanisms including total phenol, peroxidase, and polyphenol oxidase in mycorrhizal plants more than non-mycorrhizal one either in infected or healthy plants. Moreover, activity of AMF as an inhibitory against R.solani and improvement natural agent for VF growth parameters was enhanced through its fusing with Chitosan NPs.ConclusionsThe use of AMF and Chitosan NPs increased faba bean plant resistance against the infection of root rot R. solani, with both prevention and cure together. Therefore, this research opens the door to choose natural and environmental friendly treatments with different mechanisms of plant resistance to disease.

Selective protein self-deprivation by Mormon crickets following fungal attack

Immune responses to infection result in behavioral changes that affect resource acquisition, such as general starvation and compensatory feeding to offset changes in resource allocation. Mormon crickets aggregate and march in bands containing millions of insects. Some bands are comprised of insects seeking proteins. They are also low in circulating phenoloxidase (PO) and more susceptible to fungal attack, as we have demonstrated in the lab. Here, we ask: Do Mormon crickets elevate PO and consume protein in response to infection by the pathogenic fungus Beauveria bassiana? B. bassiana was applied topically (day 0), and mortality began on day 5. Total protein, PO, and prophenoloxidase (proPO) were assayed in hemolymph on day 1 and 4. On day 1, PO titers were not different between inoculated and control insects, whereas by day 4, PO was greater in the inoculated group. proPO activity was unchanged. Circulating protein declined in inoculated insects relative to controls. As predicted, PO titers were elevated as a result of fungal infection, and hemolymph protein was reduced, but the insects did not compensate behaviorally. Indeed, during the first three days post-infection, infected insects reduced protein consumption while maintaining carbohydrate consumption similar to the controls. Following day 3, a more general reduction in protein and carbohydrate intake was evident in infected insects. Survivorship to infection was associated with the amount of protein consumed and unrelated to carbohydrate consumption. Selective protein deprivation by the host seems counterintuitive, but it might limit growth and toxin production by the invading fungus. Alternatively, the fungus might control the host diet to compromise host immunity to infection. Abrupt changes in allocation resulting from an infection can lead to changes in acquisition that are not always intuitive. Because protein acquisition drives aggression between members of the migratory band, B. bassiana application may reduce cannibalism and slow band movement.

Increased Phenoloxidase Activity Constitutes the Main Defense Strategy of Trichoplusia ni Larvae against Fungal Entomopathogenic Infections.

The cabbage looper Trichoplusia ni is an important agricultural pest worldwide and is frequently used as a model organism for assessing entomopathogenic fungi virulence, though few studies have measured the host response repertoire to fungal biocontrol agents. Here, we quantified the immune response of T. ni larvae following exposure to two entomopathogenic fungal species: Beauveria bassiana and Cordyceps javanica. Results from our study demonstrate that T. ni larvae exposed to fungal entomopathogens had higher total phenoloxidase activity compared to controls, indicating that the melanization cascade is one of the main immune components driving defense against fungal infection and contrasting observations from other insect-fungi interaction studies. We also observed differences in host response depending on the species of entomopathogenic fungi, with significantly higher induction observed during infections with B. bassiana than with C. javanica. Larvae exposed to B. bassiana had an increased expression of genes involved in prophenoloxidase response and the Imd, JNK, and Jak/STAT immune signaling pathways. Our results indicate a notable absence of Toll pathway-related responses, further contrasting results to other insect-fungi pathosystems. Important differences were also observed in the induction of antimicrobial effectors, with B. bassiana infections eliciting three antimicrobial effectors (lysozyme, gloverin, and cecropin), while C. javanica only induced cecropin expression. These results provide insight into the host response strategies employed by T. ni for protection against entomopathogenic fungi and increase our understanding of insect-fungal entomopathogen interactions, aiding in the design of more effective microbial control strategies for this important agricultural pest.

Assessment of Antioxidant and Polyphenol Profile of Chrysobalanus icaco from Southern Nigeria

Due to the distinguished medicinal value of Chrysobalanus icaco, it was of great interest to conduct phytochemical and antioxidant investigations on it. In this study, the polyphenol profile and antioxidant activity of C. icaco methanol crude extract and fractions were investigated. The crude extract of C. icaco was subjected to fractionation using methanol, n-hexane, ethyl acetate, and n-butanol as solvents. 2, 2-diphenyl-1picryl-hydrazyl (DPPH), 2,2’-azino-bis-(3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric ion reducing power (FRAP), ascorbate oxidase, total phenolic content, total flavonoids and polyphenol profile was determined using standard methods. A significant increase was observed in the DPPH radical scavenging activity, total flavonoids, total phenol, FRAP, ABTS, TAC and ascorbate oxidase of the crude extract when compared to methanol, ethyl acetate, n-hexane, n-butanol, and aqueous fractions. Polyphenols such as kaempferol, chlorogenic acid, catechin, quercetin, galic acid, pomolic acid, rutin, epicatechin, stigmasterol, sitosterol and caffeic acid were found in the different fractions. The total polyphenols content of different fractions of C icaco extract were as follows; methanol fraction > n-hexane fraction > ethyl acetate fraction > n-butanol fraction > aqueous fraction. The findings revealed that C icaco kernel could be used as a potent source of molecules with positive health attributes.

Feeding on an exotic host plant enhances plasma levels of phenoloxidase by modulating feeding efficiency in a specialist insect herbivore.

Background: Exotic plant species represent a novel resource for invertebrates and many herbivorous insects have incorporated exotic plants into their diet. Using a new host plant can have physiological repercussions for these herbivores that may be beneficial or detrimental. In this study, we compared how using an exotic versus native host plant affected the immune system response and feeding efficiency of a specialist lepidopteran, the common buckeye (Junonia coenia: Nymphalidae, Hübner 1822). Materials and Methods: In a lab experiment, larvae were reared on either the exotic host plant, Plantago lanceolata (Plantaginaceae), or the native host plant, Mimulus guttatus (Phrymaceae). Beginning at second instar feeding efficiency data were collected every 2days until fifth instar when immune assays were performed. Immune assays consisted of standing phenoloxidase activity, total phenoloxidase activity, and melanization. Results: Interestingly, we found that all three immune system parameters were higher on the exotic host plant compared to the native host plant. The exotic host plant also supported higher pupal weights, faster development time, greater consumption, and more efficient approximate digestibility. In contrast, the native host plant supported higher efficiency of conversion of ingested and digested food. The relationship between immunity and feeding efficiency was more complex but showed a large positive effect of greater host plant consumption on all immune parameters, particularly for the exotic host plant. While not as strong, the efficiency of conversion of digested food tended to show a negative effect on the three immune parameters. Conclusion: Overall, the exotic host plant proved to be beneficial for this specialist insect with regard to immunity and many of the feeding efficiency parameters and continued use of this host plant is predicted for populations already using it.

Potential Symbiotic Effects of β-1,3 Glucan, and Fructooligosaccharides on the Growth Performance, Immune Response, Redox Status, and Resistance of Pacific White Shrimp, Litopenaeus vannamei to Fusarium solani Infection

The potential effects of dietary supplementation with β-1,3 glucan and fructooligosaccharides (β-1,3 GF) on antioxidant activities, immunological response, and growth performance of Pacific white shrimp (Litopenaeus vannamei) was investigated. Four diets (iso-energetic and iso-nitrogenous) with different levels of β-1,3 GF (0, 0.5, 1.0, and 1.5 g kg−1) were fed to healthy shrimp juveniles weighing 3 ± 0.5 g for 75 days. Shrimps were randomly distributed into 12 net enclosures at a density of 30 shrimp/net, and the experiment was performed in triplicate. The results revealed that long-term supplementation with 1.5 g kg−1 β-1,3 GF significantly improved shrimp weight gain, feed conversion ratio, and digestive enzyme profiles compared to the control diet group. However, there were no substantial variations in the contents of moisture, crude protein, total lipids, and ash in the muscles of shrimp fed on different diets. Surprisingly, all antioxidants (superoxide dismutase, catalase, glutathione peroxidase) and immune biomarkers (lysozyme, total hemocyte count, phenol oxidase, and respiratory burst) activities were significantly elevated with increasing levels of β-1,3 GF in the shrimp diet, and the highest values were recorded in the 1.5 g kg−1 diet groups. Challenge test results revealed that F. solani could cause a high mortality rate (86.7%) in a group fed a normal basal diet within 14 days at a dose of 5 × 104 conidia mL−1. Surprisingly, all dietary treated groups with different doses of β-1,3 GF showed high resistance against F. solani, represented by lower cumulative mortality rates (20–43.3%) compared to the control group. Moreover, most of the infected shrimp showed a typical black to brown gill lesion similar to that observed in the natural infection, where an identical fungus was successfully re-isolated from infected gills and muscles. Overall, this study recommends an appropriate incorporation level of β-1,3 GF that could enhance growth performance and improve the antioxidant activities, non-specific immunity, and disease resistance of L. vannamei, with an optimal level of 1.5 g kg−1.

Inducing Systemic Acquired Resistance (SAR) Against Root-knot Nematode Meloidogyne Javanica and Evaluation of Biochemical Changes in Cucumber Root.

For inducing systemic acquired resistance (SAR), Salicylic acid (SA), Ascorbic acid (AA), and silicon (Si) were applied on shoots, roots, and both of them simultaneously. Results showed that all treatments reduced the number of galls, root gall index, number of egg mass/root system, number of nematodes/root system, number of eggs/root system, number of nematodes/pot soil, the final population density of nematodes, and rate of reproduction. Treatments also increased growth criteria, including chlorophyll, shoot fresh weight, root fresh weight, shoots dry weight, root dry weight, shoots length, and root length. SA foliar and root application decreased infection criteria and increased total phenol, peroxidase, and phenol oxidase activities. Ascorbic acid and silicon increased total phenol, peroxidase, and phenol oxidase activities.

Experimental removal of extracellular egg‐associated microbes has long‐lasting effects for larval performance

Abstract Maternally transmitted microbes are ubiquitous. In insects, maternal microbes can play a role in mediating the insect immune response. Less is known about how ecological factors, such as resource use, interact with maternal microbes to affect immunity. In the context of a recent colonization of a novel host plant by the Melissa blue butterfly Lycaeides melissa, we investigated the interaction between host plant use and vertically transmitted, extracellular egg‐associated microbes in determining the strength of the insect immune response. We reared larvae on two different host plant species: a native host Astragalus canadensis and a novel host Medicago sativa. Egg‐associated microbes were removed through a series of antimicrobial egg washes prior to hatching. Immune response was measured through three assays: standing phenoloxidase (PO), total PO and melanization. We detected strong effects of microbial removal. Egg washing resulted in larvae with an increased immune response as measured by total PO—contrary to reports from other taxa. The effect of washing was especially strong for larvae consuming the native host plant. This result may explain why consumption of the egg casing is not a universal behaviour in insects, due to negative effects on larval immunity. Read the free Plain Language Summary for this article on the Journal blog.

Immune Response to Natural and Experimental Infection of Panulirus argus Virus 1 (PaV1) in Juveniles of Caribbean Spiny Lobster.

Simple SummaryExperimental immunological challenges are widely used to corroborate the success of breeding programs for lines resistant to specific pathogens, to test the efficiency of new vaccines, and to improve immunity of cultured animals. The validation of experimental infection protocols is complex because it requires comparison with naturally infected organisms at different stages of the infection. The present study compares the immune response of lobsters under a natural process of viral infection (PaV1), versus the defense response of experimentally infected organisms. Innate immunity for infected lobsters was measured through cellular and plasmatic components. The results indicate that the immune response of organisms naturally or experimentally infected by PaV1 was similar, and provides the bases to corroborate that the immunological challenge was not exacerbated. Appropriate infection protocols can be useful for research aimed at increasing resistance to infectious diseases and reducing the use of antibiotics in aquaculture.Experimental infections have been used to better comprehend the immune system of organisms, and to probe for additives that generate greater resistance and help reduce antibiotic use in aquaculture. We compared the immune response of juveniles of the Caribbean spiny lobster, Panulirus argus, infected naturally with Panulirus argus virus 1 (PaV1) versus organisms infected experimentally, to determine the analogy between both infectious processes. The immunological response was measured by hemagglutination activity, hemocyte count, and total phenoloxidase activity in plasma and hemocytes in 211 individuals that were either naturally infected (110), or had been injected with viral inoculum and followed for six months (101). The samples were classified into the following four groups according to the severity of the infection: 0, uninfected; 1, lightly; 2, moderately; and 3, severely infected), which was determined on the basis of PCR and histological criteria. A permutational MANOVA showed that both the origin (natural and experimental), and the severity of the infection contributed significantly to explain the variation in the immune response of lobsters. The lack of significance of the interaction term indicated that the immunological response changed with the severity of the infection in a similar way, regardless of its origin. The results of the present study suggest that the experimental viral infection of PaV1 produces a defense response similar to the natural pathways of contagion, and provides the bases to validate an immunological challenge protocol for the first time in crustaceans. The discussion includes the perspective of the conceptual models of immune response within an ecological context.

Transcriptomics Reveals the ERF2-bHLH2-CML5 Module Responses to H2S and ROS in Postharvest Calcium Deficiency Apples.

Calcium deficiency usually causes accelerated quality deterioration in postharvest fruit, whereas the underlining mechanism is still unclear. Here, we report that calcium deficiency induced the development of bitter pit on the surface of apple peels compared with the healthy appearance in control apples during postharvest storage. Physiological analysis indicates that calcium-deficient peels contained higher levels of superoxide anion (O2•−), malondialdehyde (MDA), total phenol, flavonoid contents and polyphenol oxidase (PPO) activity, and reduced calcium, H2S production, anthocyanin, soluble protein content, and peroxidase (POD) activity compared with those in calcium-sufficient peels. The principal component analysis (PCA) results show that calcium content, ROS, and H2S production were the main factors between calcium-deficient and calcium-sufficient apple peels. Transcriptome data indicated that four calmodulin-like proteins (CMLs), seven AP2/ERFs, and three bHLHs transcripts were significantly differentially expressed in calcium-deficient apple peels. RT-qPCR and correlation analyses further revealed that CML5 expression was significantly positively correlated with the expression of ERF2/17, bHLH2, and H2S production related genes. In addition, transcriptional co-activation of CML5 by ERF2 and bHLH2 was demonstrated by apple transient expression assays and dual-luciferase reporter system experiments. Therefore, these findings provide a basis for studying the molecular mechanism of postharvest quality decline in calcium-deficient apples and the potential interaction between Ca2+ and endogenous H2S.

Antioxidative and immunological response of shrimp Litopenaeus vannamei to combined stress of acute cold exposure and waterless duration: Implications for live transport

High mortality is a common phenomenon for live transport of shrimp Litopenaeus vannamei, and the biochemical mechanism underlying mortality remains incompletely known. This investigation explored the effect of combined stress of acute cold exposure (AC) and waterless duration (WD) on survivability, oxidative stress, antioxidative and immunity defence responses, and histological impairments. The survival profiles showed no significant difference between normal control (NC) and AC groups. The shrimps exposed to AC + WD stress, however, exhibited significantly higher mortality (p < 0.05) since 6 h afterwards, and the median survival probability was observed at 10.46 h. Overall, both the homeostasis of antioxidative and immunological response were disturbed in a duration time-dependent manner, and the impairment on hepatopancreas was observed. Significantly, the indicators of total haemocyte count (THC), viable haemocyte count (VHC) and peroxidase (POD) decreased while the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), phenol oxidase (PO), alanine transaminase (ALT) and aspartate transaminase (AST) increased (p < 0.05). Together, correlation analyses indicated that high mortality of L. vannamei was resulted from the disorder of antioxidative and immunological response. This study deepens our understanding into mortality of L. vannamei during waterless live transport.

Impacts of pH on the Fitness and Immune System of Pacific White Shrimp

The atmospheric partial pressure of CO2 (pCO2) has been increasing dramatically since the beginning of the industrial revolution and about 30% of the CO2 produced by anthropogenic activities was absorbed by the ocean. This led to a perturbation of the seawater carbonate chemistry resulting in a decrease of the average surface ocean pH by 0.1 and termed ocean acidification (OA). Projections suggest that pCO2 may reach 900 μatm by the end of the twenty-first century lowering the average pH of the surface ocean by 0.4 units. The negative impacts of OA on many species of marine invertebrates such as mollusks, echinoderms, and crustaceans are well documented. However, less attention has been paid to the impacts of low pH on fitness and immune system in crustaceans. Here, we exposed Pacific white shrimps to 3 different pHs (nominal pH 8.0, 7.9, and 7.6) over a 100-days experiment. We found that, even though there were no significant effects on fitness parameters (survival, growth and allometries between length and weight), some immune markers were modified under low pH. A significant decrease in total hemocyte count and phenoloxidase activity was observed in shrimps exposed to pH 7.6 as compared to pH 8.0; and phagocytosis rate significantly decreased with decreasing pH. A significant increase in superoxide production was also observed at pH 7.6 as compared to pH 8.0. All these results suggest that a 100-days exposure to pH 7.6 did not have a direct effect on fitness but lead to a modulation of the immune response.

Increasing temperature reduces cuticular melanism and immunity to fungal infection in a migratory insect

1. Few studies have considered how global warming affects disease resistance. Many ectotherms depress the melanisation of exposed surfaces to reflect more sunlight in warmer habitats. Because phenoloxidase (PO) enhances both cuticular melanisation and the innate immune response to invasion, we asked: is decreased melanism in response to higher temperatures associated with less PO activity and greater vulnerability to entomopathogenic fungal attack?2. We measured spontaneous PO activity from wounding and circulating total PO activity before topical application ofBeauveria bassianafungus and 2 days following inoculation.3.Melanoplus sanguinipesgrasshoppers reared in higher temperatures were paler, and had lower spontaneous PO activity and total PO both before and after the fungal attack. They were also more susceptible toBeauveria bassianafungal attack than those reared in cooler temperatures. Hence, thermoregulatory benefits of decreased melanism for growth, reproduction, and survival can be compromised by reduced PO activity and the immune response to fungal infection.4. As the Earth warms, these two functions of PO, thermoregulation and immunity, are likely to remain associated with one another, which may cause thermal melanism to be detrimental to an insect population's resilience to climate change.

PAP1 activates the prophenoloxidase system against bacterial infection in Musca domestica

We previously identified three putative prophenoloxidase-activating proteinase (mdPAP1, mdPAP2, and mdPAP3) genes from housefly Musca domestica by transcriptomic analysis. In this study, mdPAP1 cDNA was cloned, and the function of its encoded protein was analyzed. The cDNA of mdPAP1 was 1358 bp, and it contained a single open reading frame of 1122 bp encoding a predicted MdPAP1 protein of 373 amino acids. The estimated molecular weight of MdPAP1 was 41267.08 Da with an isoelectric point of 6.25. The deduced amino acid sequence of MdPAP1 exhibited high similarity to known PAPs of insects. mdPAP1 was detected in larvae, pupae, and adult housefly, and the expression level of mdPAP1 was upregulated in bacterial challenged larvae. The recombinant protein of MdPAP1 expressed in Escherichia coli could cleave the prophenoloxidase into phenoloxidase in M. domestica hemolymph infected by bacteria and result in a significant increase of the total phenoloxidase activity. In addition, RNA interference-mediated gene silencing of mdPAP1 significantly increased the mortality of M. domestica larvae. Results indicated that mdPAP1 was involved in the activation of the prophenoloxidase against bacterial infection in M. domestica.

Orally administered nano-polystyrene caused vitellogenin alteration and oxidative stress in the red swamp crayfish (Procambarus clarkii)

Nanoplastics (≤100 nm) represent the smallest fraction of plastic litter and may result in the aquatic environment as degradation products of larger plastic material. To date, few studies focused on the interactions of micro- and nanoplastics with freshwater Decapoda. The red swamp crayfish (Procambarus clarkii, Girard, 1852) is an invasive species able to tolerate highly perturbed environments. As a benthic opportunistic feeder, this species may be susceptible to plastic ingestion. In this study, adult P. clarkii, at intermolt stage, were exposed to 100 μg of 100 nm carboxylated polystyrene nanoparticles (PS NPs) through diet in a 72 h acute toxicity test. An integrated approach was conceived to assess the biological effects of PS NPs, by analyzing both transcriptomic and physiological responses. Total hemocyte counts, basal and total phenoloxidase activities, glycemia and total protein concentration were investigated in crayfish hemolymph at 0 h, 24 h, 48 h and 72 h from PS NPs administration to evaluate general stress response over time. Differentially expressed genes (DEGs) in the hemocytes and hepatopancreas were analyzed to ascertain the response of crayfish to PS NP challenge after 72 h. At a physiological level, crayfish were able to compensate for the induced stress, not exceeding generic stress thresholds. The RNA-Sequencing analysis revealed the altered expression of few genes involved in immune response, oxidative stress, gene transcription and translation, protein degradation, lipid metabolism, oxygen demand, and reproduction after PS NPs exposure. This study suggests that a low concentration of PS NPs may induce mild stress in crayfish, and sheds light on molecular pathways possibly involved in nanoplastic toxicity.

Litter inputs drive increases in topsoil organic carbon after scrub encroachment in an alpine grassland

Shrub encroachment into grasslands can greatly alter soil organic carbon (SOC), nitrogen (N) cycling processes, and carbon (C) pools. However, the effects of shrub encroachment on the soil microbial community and its feedback on the chemical composition of SOC are not well understood in the alpine ecosystems. This study aims to evaluate the impact of the encroachment of the shrubs Salix cupularis and Hippophae rhamnoides on SOC, soil microbial biomass C (MBC) and N (MBN), microbial community structure, and enzyme activities of the topsoil (0–30 cm) and explore the underlying mechanisms in the eastern Tibetan Plateau grasslands of China. We found that while SOC increased under both S. cupularis (16.0 % increase) and H. rhamnoides (23.3 % increase), only the increase in H. rhamnoides was significant in comparison with the adjacent grass soils. The recalcitrant C pool increases were not significant in S. cupularis or H.rhamnoides soils. Additionally, shrub encroachment significantly increased the soil organic N and the activities of N-acetyl-β-glucosaminidase (NAG) and leucine aminopeptidase (LAP). Shrub encroachment significantly increased MBC and MBN, as well as enhanced the total bacteria PLFAs, gram-negtive bacteria PLFAs, arbuscular mycorrhizal fungi, actinomycetes, and hydrolytic enzyme activities, but suppressed the ratio of total fungi to total bacteria PLFAs and phenol oxidase activity in comparison with grassland communities. Redundancy analysis (RDA) showed that litterfall mass, litter N, and root N were the main factors affecting the soil microbial community. Our findings highlight that the encroachment of shrub H. rhamnoides tends to increase soil C sequestration as a result of the high quantities of plant litter input and the changes in the composition of soil microbial communities as well as increased complex C compounds in soil organic matter.

Effect of two contrasting biochars on soil microbiota in the humid tropics of Peninsular Malaysia

Report on soil microbial community in tropical soil of humid tropics remained limited despite the current research interest in biochar-microbe study in various climatic regions. A field-trial spanning three consecutive crop cycles of Zea mays var. Masmadu was conducted in tropical Acrisols of Peninsular Malaysia. Palm kernel shell and rice husk biochars of different feedstock and pyrolysis conditions were used for amendment. Soil samples were collected during maize harvesting and were analyzed for physicochemical properties (pH, CEC, organic C, labile active C), microbial biomass (C, N), and seven C-cycle enzymes activity (total cellulase, endoglucanase, β-glucosidase, xylanase, invertase, phenol oxidase, peroxidase). Total soil genomic DNA was extracted and subjected to the analysis of bacterial 16S rRNA and fungal ITS gene abundance quantification. Microbial genetic profiling was fingerprinted by using DGGE. Significant increases of all measured soil physicochemical properties, microbial biomass C, microbial biomass N, and gene abundances were observed in all biochar amended soils. Significant changes of total cellulase, endoglucanase, phenol oxidase, and peroxidase were not detected. A significant shift in microbial genotypic and enzymatic functional diversity based on microbial C-cycle enzymes was not detected. Correlation data revealed significant linkages of soil microbial biomasses and gene abundances with all measured soil physicochemical properties. The biochar influences the microbial community by elevating microbial habitat potential to a more favorable state and increasing labile active carbon sources in the field trial.