Host-plant resistance to western flower thrips in Arabidopsis

Abstract

The fact that plants are sessile organisms does by no means imply that they are helpless victims. Although they are harassed in some shape or form by members of all kingdoms of life, it is exactly this harassment that has shaped and defined the unique defensive arsenal of plants. Plants have evolved morphological features that hinder herbivory, like trichomes and leaf waxes (Panda and Khush 1995, Schoonhoven, van Loon et al. 2005), but likely even more important are the diverse chemical defenses (Schoonhoven, van Loon et al. 2005(Mithöfer and Boland 2012) that have evolved under the selection pressure of herbivores. Frankliniella occidentalis is often studied in relation to economically relevant (ornamental) crops, and some of these studies have revealed chemical resistance in plants against thrips herbivory. In chrysanthemum (Dendranthema grandiflora) using TLC and HPLC, isobutylamide was proposed as a candidate compound involved in thrips resistance (Tsao, Marvin et al. 2005). A different study, using nuclear magnetic resonance (NMR)-based metabolomics showed that thrips-resistant chrysanthemum varieties contained higher amounts of chlorogenic acid and additional bioassays with artificial diets confirmed the negative effect of this phenylpropanoid on the survival rate of juveniles (Leiss, Maltese et al. 2009). Although chlorogenic acid occurs in high levels in carrot plants (Daucus carota L.), NMR did not show differences in cholorogenic levels between resistant and susceptible carrots. Instead, the flavonoid luteolin, the phenylpropanoid sinapic acid and the amino acid β-alanine were correlated with thrips resistance in this plant species (Leiss, Cristofori et al. 2013). Using several wild and cultivated tomato species, the presence of acylsugars was correlated with lowered thrips feeding damage (Mirnezhad, Romero-Gonzalez et al. 2010). Using LC-MS on nine different pepper (Capsicum) cultivars showed a correlation with several tocopherols, alkanes, a sterol and a terpene in relation to thrips resistance, although no bioassays were done to confirm the activity of these compounds (Awang 2013). Studies with the model plant Arabidopsis thaliana using transcriptomics and different knockout mutants, revealed a prominent role for the phytohormone jasmonic acid (JA) in thrips resistance. Mutant plants hampered in their JA signaling pathway, were not able to trigger induced defenses leading to higher susceptibility in two-choice assays (De Vos, Van Oosten et al. 2005). The function of JA in thrips resistance is not restricted to Arabidopsis but is likely a general mechanism underlying resistance of plants to thrips. In Chinese cabbage (Brassica rapa), JA also played a crucial role in the induced defenses triggered by F. occidentalis (Abe, Shimoda et al. 2009). Depending on the plant species and analytic tools used, different candidate compounds have been brought forward that play a potential role in thrips resistance. This is perhaps not surprising, given the polyphagous nature of F. occidentalis. Correlations between ...

Gene regulatory network induced by Western flower thrips in Arabidopsis

“…is an important player in the regulation of defenses against thrips (Thoen, 2019;Wu et al, 2019). The overrepresentation of bHLH binding sites in many of the thrips-upregulated clusters corroborates the key role of MYC2 and other bHLH TFs such as bHLH017 (Table 1) in the thrips GRN.…”