About this Research Topic
Terrestrial plants, inter alia Eucalyptus trees, have evolved direct and indirect associations with microbes and insects. Each of these interactors produce specialized metabolites such as Abyssomycine C, a derivate of the para-aminobenzoic and folic acid biosynthesis (actinomyces), the polyketide Pederin, isolated from the intestine of the beetle Paederus spp, or numerous secondary allelopathic plant compounds that act as chemical defense and provide unique bio-fertilizer and pharmaceutical products. Their agonistic, antagonistic interactivities with the periphery environment foster, or negatively interfere with, food web functioning, plant fitness and adaptability.
Independent plant, microbe and insect reserach provides only a limited view of the biotic interactions that dictate plant-microbe-insect community structure. The diversity inside insect intestines, in phyllo-, rhizo-spheres and soils of natural and agriculturally-used systems accommodate a wealth of secondary metabolite-producing microbes as well as invasive plants. This causes a (re)organization of phyllo-, rhizo-sphere interactivities with insects and microbes in a new environment, thus providing an excellent working model for comparing or contrasting how bio-fertilizer and bio-medicinal active compounds affect plant fitness, adaptation, fecundity, and plant protection. Such compounds are industrially exploitable, and biotechnological endeavors have produced actinomycetal secondary metabolites, which can replace vancomycin in blocking multi-resistant germs. The mechanism of action of these compounds is currently unknown. During plant-Arthropoda (insects, arachnids, myriapods, and crustaceans) interactions, a huge amount of metabolically regulating products, with chemically different structures and with attractant (pheromones), alarming (kairomones) or deterrent (alloinsect, killing) properties (allomones, toxins) are synthesized and released. Once isolated, a few of these biologically significant compounds are of biotechnological or bio-medicinal interest. Insects either directly produce for defense relevant compounds, or transform precursor compounds, taken up during plant puncturing, into the end product. Molecules with a simple chemical structure, such as oxalic acids suppressing the growth of fungi, predators and bacteria, as well as more complex chemical compounds, such as the polyketide “Pederine”, produced by an intestinal Pseudomonas strain of Paederus spp., can be found among the compounds derived from insects intestinal microbiome, insects or plants. Other examples of compounds with a different structure are: cetoniacytone, produced by a Centonia aurata intestinal Actinomyces strain; or the alkaloid α pinene 1,8 cineol, produced by a Stenus species. Both compounds support anti-predatory behavior and inhibit the growth of tumors. Also secondary metabolites released by plants, exhibiting allelopathical effects, are of biotechnological value.
The advanced DNA sequencing technologies developed during the last decade opened the door to microbial community analysis. Thereby, an increased awareness of the importance of an organism’s microbiome and of the disease states associated with microbiome shifts has arisen. Furthermore, analysis of symbiotic microbiomes, associated with plant communities affected by invasive members, provide a better understanding of the microbial impact on plant fitness and adaptability in natural systems. In this Research Topic on Plant-Microbe-Insect Interaction we aim at gathering the current knowledge that has become available through the recent analytical possibilities for deciphering the specificity of plant-microbe-insect interactions in natural plant populations, and through the complete sequencing of genomes from beneficial (e.g., bee Apis mellifera, or the silk moth Bombyx mori), vector (e.g., the mosquito Anopheles gambiae) or pest insects (e.g., the red flour beetle Tribolium castaneum or the pea aphid Acy
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