Abstract
Tetranychus urticae (two-spotted spider mite) is a striking example of polyphagy among herbivores with an extreme record of pesticide resistance and one of the most significant pests in agriculture. The T. urticae genome contains a large number of cysteine- and serine-proteases indicating their importance in the spider mite physiology. This work is focused on the potential role of the Kunitz trypsin inhibitor (KTI) family on plant defense responses against spider mites. The molecular characterization of two of these genes, AtKTI4 and AtKTI5, combined with feeding bioassays using T-DNA insertion lines for both genes was carried out. Spider mite performance assays showed that independent KTI silencing Arabidopsis lines conferred higher susceptibility to T. urticae than WT plants. Additionally, transient overexpression of these inhibitors in Nicotiana benthamiana demonstrated their ability to inhibit not only serine- but also cysteine-proteases, indicating the bifunctional inhibitory role against both types of enzymes. These inhibitory properties could be involved in the modulation of the proteases that participate in the hydrolysis of dietary proteins in the spider mite gut, as well as in other proteolytic processes.
Highlights
The fact that higher plants are sessile organisms has favored the acquisition of sophisticated resources to prevent or hamper pest feeding (Walling, 2000; Wu and Baldwin, 2010)
The amino acid pair Trp-Pro, located in the loop between strands β5 and β6, and putatively involved in cysteine-protease inhibitory capability of AtKTI2 was only partially conserved in AtKTI1
To elucidate the response of AtKTI4 and AtKTI5 genes after mite feeding, we studied their effect on the spider mite performance using T-DNA insertion lines for both genes
Summary
The fact that higher plants are sessile organisms has favored the acquisition of sophisticated resources to prevent or hamper pest feeding (Walling, 2000; Wu and Baldwin, 2010). Such defenses can be constitutive and/or induced upon attack by herbivore pests. The perception of herbivory is not well understood and few plant receptors have been identified (Bonaventure, 2012; Santamaria et al, 2018a)
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