Salicylic Acid, a Plant Hormone, Suppresses Phytophagous Insect Immune Response by Interrupting HMG-Like DSP1

Salicylic acid is a plant hormone that can mediate various plant physiological processes. Salicylic acid can bind to human high mobility group box 1 (HMGB1) and interrupt its role in mediating immune responses. Dorsal switch protein 1 (DSP1) is an insect homolog of HMGB1. In this study, a DSP1 (Se-DSP1) encoded in Spodoptera exigua, a phytophagous insect, was characterized, and its potential role in immune response was explored. Upon bacterial challenge, Se-DSP1 was localized in the nucleus and released into the hemolymph. The released Se-DSP1 could mediate both cellular and humoral immune responses by activating eicosanoid biosynthesis. Salicylic acid could bind to Se-DSP1 with a high affinity. The immune responses of S. exigua were significantly interrupted by SA feeding. Larvae reared on tomatoes with high endogenous SA levels became more susceptible to entomopathogens. Taken together, these results suggest a tritrophic defensive role of plant SA against phytophagous insects.

Bottom-up effects on arthropod communities in Platycyamus regnellii (Fabaceae) fertilized with dehydrated sewage sludge

Sewage sludge is a nitrogen-rich organic compound, which can be used to aid development in plants such as Platycyamus regnellii (Fabaceae), in the recovery of degraded areas. This study aimed to assess the bottom-up effects on leaf mass and percentage ofground cover (leaf litter, herbaceous plants, and grasses) in P. regnellii trees fertilized (or not) with dehydrated sewage sludge and arthropod communities over 24 months. Platycyamus regnellii trees fertilized with dehydrated sewage sludge presented significantly more leavesper branch, branches per tree, and a higher percentage of ground cover compared to unfertilized trees. Phenacoccus sp. (Pseudococcidae) was the most abundant phytophagous insect associated with P. regnellii trees. Fertilization did not affect the abundance, diversity, and species richness of Hemiptera phytophagous on P. regnellii trees. However, fertilizedtrees presented higher abundance and species richness of trophobiont-tending ants compared to unfertilized trees, with Camponotus sp. being the most abundant regardless of the treatment. Fertilized P. regnellii trees also presented higher species richness of natural enemies compared to unfertilized ones, with Aranae and Dolichopodidae being the most abundant. We concluded that fertilization with dehydrated sewage sludge improved P. regnellii trees leafmass and ground cover and increased the diversity of trophobiont-tending ants and natural enemies. To our knowledge, this is the first study on the arthropods community associated withthis tree species. This suggests that upon fertilization, P. renellii trees are useful for ecological restoration in severely disturbed areas.

Infectious and parasitic diseases of phytophagous insect pests in the context of extreme environmental conditions

The density of phytophagous insect pest populations is related (directly and indirectly) to several groups of factors that can be broadly divided into: abiotic, biotic and anthropogenic. Each extreme in the abiotic environment at a macro-level leads to a series of consecutive extremes in the biotic environment, which eventually results in micro-level responses in the individual organisms. The manifestation of factors acts in aggregate or in a sequence, creating a chain of processes around us. Insects very efficiently use the abundance of nutritional resources, resulting in a tremendous increase in their population density, and triggering control mechanisms through the emergence of parasitic and pathogenic infections (viruses, bacteria, fungi, microsporidia, protozoa and nematodes). The development of entomopathogenic infections in host populations is directly dependent on the characteristics of both the antagonist and the insect. It is associated with the lifestyle and life cycle of the insect, with features encoded in the mechanism of pathogen action, and limited by the pathogen’s virulence and pathogenicity.

Author Correction: Construction of TUATinsecta database that integrated plant and insect database for screening phytophagous insect metabolic products with medicinal potential

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Construction of TUATinsecta database that integrated plant and insect database for screening phytophagous insect metabolic products with medicinal potential

Phytophagous insect larvae feed on plants containing secondary metabolic products with biological activity against other predatory organisms. Phytophagous insects can use their specialised metabolic systems to covert these secondary metabolic products into compounds with therapeutic properties useful to mankind. Some Asians drink tea decoctions made from phytophagous insect frass which is believed to be effective against inflammatory diseases. However, insects that can convert plant-derived secondary metabolic products into useful human therapeutic agents remain poorly studied. Here, we constructed the TUATinsecta database by integrating publicly plant/insect datasets for the purpose of selecting insect species. Using TUAT-insecta we selected the Asian swallowtail butterfly, Papilio xuthus larvae fed on several species of Rutaceous plants and examined whether the plant-derived secondary metabolites, especially those present in frass, were chemically altered or not. We extracted metabolic products from frass using three organic solvents with different polarities, and evaluated solvent fractions for their cytotoxic effects against several human cell lines. We found that chloroform frass extracts from P. xuthus larvae fed on Poncirus trifoliata leaves contained significant cytotoxic activity. Our findings demonstrate that screening of insect species using the ‘TUATinsecta’ database provides an important pipeline for discovering novel therapeutic agents that might be useful for mankind.