Modulation of rhizosphere - associated microbiota by insect pest: a holobiont relationship

• Autor(a) principal: Márcia Leite Mondin
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://doi.org/10.11606/T.11.2019.tde-26082019-152849

Currently, we observe a growing number of researches that seek to unravel the causes, effects and possible biotechnological uses of the rhizosphere microbiota communities modulation in the complex interactions between plants and soil. We also know that the attack of herbivorous insects is a factor of considerable damage to agriculture and that has well established evolutionary relationships in natural systems. The present work tried to test some hypotheses about the direct connection between the rhizosphere microbiota and the insect pest attack. Beginning from the point that plants have well- established defense mechanisms against insects, it was verified that the rhizosphere microbiota seems to contribute actively to this system and thus to establish holobionte relationships. We had broad access to communities of the fungi and bacterial domain, through the new generation sequencing for rRNA 16S gene, region V3, and intergenic region ITS amplicons on soil, semi-soil and, insect gut samples from pest insects with general behavior (Order: Lepidoptera). Our results from the data analysis to Illumina Miseq sequencing outputs and, additional experiments, resulted in three articles presented here in chapters. In the first chapter, we discuss the modulating effect from the pest insect attack (Spodoptera frugiperda), on the Arabidopsis thaliana microbiota rhizosphere, for different physiological plant\'s stages. As a result, it was possible to discuss the differences between the modulation in the structure of bacterial communities and the modulation in the structure of the fungal communities after the attack of herbivorous insects. In the second chapter, we highlight the difference in the modulation of the bacterial community structure for different plant families. We used seedlings of Arabidopsis thaliana, Zea mays Sh2, Faseolus vulgaris, Solano lycopersicum and, Beta vulgaris exposed to the attack of Trichoplusia ni for one week. The rhizosphere microbiota analysis for each host plant groups, suggests that the influence of the plant species should be considered on the bacteria rhizosphere communities modulation after the insect attack. Besides, specific plant species may be less susceptible to rhizosphere modulation by insect attack. Another highlight was the microbiota rhizosphere effect in the biomass loss for plants sown on transplanted semi-soil. Based on the phenotypic data, we suggest the rhizosphere microbiota modulation after the herbivore may be involved in the plant biomass inhibition on the next seedlings generation. Finally, in the third chapter, we explore the Trichoplusia ni gut microbiota modulation through the microbial load obtained in the restricted feeding. The T. ni larvae from the same original population were divided into three populations. Each population was fed individually and restrictively with leaves of A. thaliana, S. lycopersicum or artificial caloric diet. We accessed the gut microbiota in T. ni after three generations of restricted feeding, and we verified that the gut microbiota in caterpillars of general behavior, could be altered due the obtaining of microbial load through alimentary diet. This modulation may be related to the degradation of metabolites that may be harmful to insect homeostasis. The gut microbiota of each population can also directly influence the food preferences of successive generations. In summary, all our results presented in each one of the chapters are important points that can help to clarify the complex relationships between plants/insects/microorganisms and, contributing to a better understanding of this holobiont system.