Project name: Comparative transcriptomics of tomato plants simultaneously infested with different species of herbivorous mites reveals distinct signatures of host defense suppression

Description: Tomato plants are commonly attacked by herbivorous mites, including by generalist Tetranychus urticae and specialists Tetranychus evansi and Aculops lycopersici. Mite feeding induces plant defense responses that reduce mite performance. However, via poorly understood mechanisms, T. evansi and A. lycopersici suppress plant defenses and, consequently, maintain a high performance on tomato. Accordingly, on a shared host, non-adapted T. urticae can be facilitated by either of the specialist mites, likely via the suppression of plant defenses. To better understand defense suppression and indirect plant-mediated interactions between herbivorous mites, we used microarrays to analyze transcriptomic changes in tomato after attack by either a single mite species (T. urticae, T. evansi, A. lycopersici) or two species simultaneously (T. urticae plus T. evansi or T. urticae plus A. lycopersici). Additionally, we assessed mite-induced changes in defense-associated phytohormones using LC-MS/MS. Compared to non-infested controls, jasmonates (JAs) and salicylate (SA) accumulated to higher amounts upon all mite-infestation treatments, but lowest increases were detected after single infestations with defense-suppressors. Strikingly, whereas 8 to 10% of tomato genes was differentially expressed upon single infestations with T. urticae or A. lycopersici, only 0.1% was altered in T. evansi-infested plants. Transcriptome analysis of dual-infested leaves revealed that T. evansi dampened T. urticae-triggered host responses on a genome-wide scale, while A. lycopersici primarily suppressed T. urticae-induced JA defenses. Our results provide valuable new insights into the mechanisms underlying host defense suppression and the plant-mediated facilitation of competing herbivores.Overall design: Tomato plants underwent 5 infestation treatments and one non-infested control treatment, with 4 biological replicates each.Specifically, tomato plants were infested for 7 days with: 1) T. urticae, 2) T. evansi, 3) A. lycopersici, 4) T.urticae and T. evansi, 5) T. urticae and A. lycopersici.For spider mite (T. urticae or T. evansi) infestations, 15 adult female mites were individually transferred to each of three leaflets (belonging to three different compound leaves) per plant, so that in total each plant was infested with 45 spider mites. For russet mite (A. lycopersici) infestations, a small section (ca. 0,5 cm2) of a leaf containging approximately 250 mobile stages of mites (counted using a stereomicroscope) was transferred to each of three leaflets (belonging to three different compound leaves) per plant, so that in total each plant was infested with 750 russet mites. For dual infestations, each of three leaflets received either 15 T. urticae + 15 T. evansi (in total 90 spider mites per plant), or 15 T. urticae + ca. 250 A. lycopersici (in total 45 spider mites and 750 russet mites per plant). After 7 days, infested leaflets and corresponding leaflets from non-infested controls were harvested and stored at -80C until total RNA was isolated. The three leaflets obtained from the same plant were pooled to form one biological replicate. This experiment was replicated four times in consecutive weeks, each time using six plants per treatment, resulting in a total of 144 samples (6 treatments x 6 plants x 4 experimental replicates). However, for the microarray hybridizations, equal amounts of RNA, isolated from each of the six plants per treatment, were pooled, resulting in a total of 24 samples (6 treatments x 4 experimental replicates).

Data type: Transcriptome or Gene expression

Sample scope: Multiisolate

Relevance: Agricultural

Last updated: 2018-07-09