Abstract
BackgroundPlants have developed a variety of mechanisms to counteract aphid attacks. They activate their defences by changing the expression of specific genes. Previously we identified an activation tag mutant of Arabidopsis thaliana on which Myzus persicae population development was reduced. Activation tag mutants are gain-of-function in which the expression of a gene is increased by the insertion of the Cauliflower mosaic virus 35S enhancer that acts on the natural promoter. By further characterizing this previously identified mutant we identified a gene that reduces performance of M. persicae and also provided clues about the mechanism involved.ResultsWe show that SKU5 SIMILAR 13 (SKS13), a gene whose expression in wild type plants is restricted to pollen and non-responsive to M. persicae attack, is overexpressed in the A. thaliana mutant showing reduced performance of M. persicae. Monitoring M. persicae feeding behaviour on SKS13 overexpressing plants indicated that M. persicae have difficulties feeding from the phloem. The constitutive expression of SKS13 results in accumulation of reactive oxygen species, which is possibly regulated through the jasmonic acid pathway. The enhanced resistance is not aphid species specific as also the population development of Brevicoryne brassicae was affected.ConclusionsWe demonstrate that constitutive expression in leaves of the pollen-specific gene SKS13 can enhance plant defence, resulting in a reduction of M. persicae population development and also decreases the transmission of persistent viruses. Overexpression of SKS13 in A. thaliana also affects B. brassicae and possibly other phloem feeding insects as well. Identifying genes that can enhance plant defence against insects will be important to open up new avenues for the development of insect resistant crop plants.
Highlights
Plants have developed a variety of mechanisms to counteract aphid attacks
Identification of SKU5 SIMILAR 13 (SKS13) as a gene conferring enhanced resistance to M. persicae Using inverse PCR we could determine that mutant 3790 contains a T-DNA including a 35S enhancer that is located on chromosome 3 at position 4,350,852 in the 3’-UTR region of the Brassinosteroid Receptor Like gene (BRL3, At3g13380; Figure 2a)
Two other genes, SKU5 Similar 11 (SKS11, At3g13390) and SKU5 Similar 13 (SKS13, At3g13400) are located within a distance of approximately 8 kb of the enhancer (Figure 2a), a distance over which the enhancer can effectively activate the expression of genes [25]
Summary
Plants have developed a variety of mechanisms to counteract aphid attacks. They activate their defences by changing the expression of specific genes. Activation tag mutants are gain-of-function in which the expression of a gene is increased by the insertion of the Cauliflower mosaic virus 35S enhancer that acts on the natural promoter By further characterizing this previously identified mutant we identified a gene that reduces performance of M. persicae and provided clues about the mechanism involved. Plants have evolved a series of defense traits to directly affect the aphid’s feeding behavior These defenses include physical and chemical traits that can be constitutively present or induced upon aphid attack [5]. Inducible defenses require recognition of the attacking aphid and subsequent transcriptional reprogramming This includes the activation of general wound responses. Constitutive activation of the JA pathway in an Arabidopsis thaliana mutant leads to enhanced aphid resistance, whereas blocking the JA pathway results in aphid susceptibility [14]
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