PhD defence: Gene regulatory network induced by Western flower thrips in Arabidopsis

Thrips are tiny cell-content-feeding insects that form important pests in food and ornamental plant-production worldwide. Currently, control management of thrips relies mainly on using chemical pesticides. To develop more sustainable crop production systems, it is essential to improve our knowledge on the plants’ natural immune response to thrips.  

The major aim of this PhD research was to explore the molecular mechanisms underlying natural defenses of the model plant Arabidopsis thaliana (Arabidopsis) in response to the Western flower thrips (Frankliniella occidentalis). To achieve this, we first designed several non-destructive bioassays to assess thrips performance on single Arabidopsis leaves or whole plants.  

Using RNA-sequencing in a high-density time series, combined with bioinformatic analyses, we were able to capture the transcriptional dynamics and chronology of genes within the gene regulatory network that is induced in leaves upon feeding by thrips. We confirmed that jasmonic acid is the predominant phytohormone modulating the plant's induced defense response against thrips and we identified several novel regulators to play a key role in the thrips-induced gene regulatory network.  

Additionally, we discovered that different phytohormonal-associated defenses are induced dependent on the thrips developmental stage. Moreover, locally infested leaves respond different from systemic non-infested leaves, and local infestation by thrips has different consequences for subsequent thrips feeding performance than local infestation by another insect, the cabbage moth (Mamestra brassicae), which is a tissue chewer.  

Collectively, this study provides a better understanding of thrips-induced defense responses, which can facilitate the development of more sustainable thrips-resistance breeding.