Transcriptome profiling reveals differential gene expression of detoxification enzymes in a hemimetabolous tobacco pest after feeding on jasmonate-silenced Nicotiana attenuata plants

Background The evolutionary arms race between plants and insects has driven the co-evolution of sophisticated defense mechanisms used by plants to deter herbivores and equally sophisticated strategies that enable phytophagous insects to rapidly detoxify the plant’s defense metabolites. In this study, we identify the genetic determinants that enable the mirid, Tupiocoris notatus, to feed on its well-defended host plant, Nicotiana attenuata, an outstanding model for plant-insect interaction studies. Results We used an RNAseq approach to evaluate the global gene expression of T. notatus after feeding on a transgenic N. attenuata line which does not accumulate jasmonic acid (JA) after herbivory, and consequently accumulates very low levels of defense metabolites. Using Illumina sequencing, we generated a de novo assembled transcriptome which resulted in 63,062 contigs (putative transcript isoforms) contained in 42,610 isotigs (putative identified genes). Differential expression analysis based on RSEM-estimated transcript abundances identified 82 differentially expressed (DE) transcripts between T. notatus fed on wild-type and the defenseless plants. The same analysis conducted with Corset-estimated transcript abundances identified 59 DE clusters containing 85 transcripts. In both analyses, a larger number of DE transcripts were found down-regulated in mirids feeding on JA-silenced plants (around 70%). Among these down-regulated transcripts we identified seven transcripts possibly involved in the detoxification of N. attenuata defense metabolite, specifically, one glutathione-S-transferase (GST), one UDP-glucosyltransferase (UGT), five cytochrome P450 (P450s), and six serine proteases. Real-time quantitative PCR confirmed the down-regulation for six transcripts (encoding GST, UGT and four P450s) and revealed that their expression was only slightly decreased in mirids feeding on another N. attenuata transgenic line specifically silenced in the accumulation of diterpene glycosides, one of the many classes of JA-mediated defenses in N. attenuata. Conclusions The results provide a transcriptional overview of the changes in a specialist hemimetabolous insect associated with feeding on host plants depleted in chemical defenses. Overall, the analysis reveals that T. notatus responses to host plant defenses are narrow and engages P450 detoxification pathways. It further identifies candidate genes which can be tested in future experiments to understand their role in shaping the T. notatus-N. attenuata interactio

Active injections of cytokinins by a free-living sap-feeding insect: a possible mechanism to delay herbivory induced senescence

Manipulations of plants by insects via growth hormones, such as cytokinins (CKs), have been suggested for decades. The focus has been on most obvious cases like “green-islands”. Evidence for an active transfer of CKs by the insect as well as manipulations of the plants perception of CKs has been elusive. We present the results on the interaction between the sap feeding mirid Tupiocoris notatus and the wild tobacco Nicotiana attenuata. We detected an increase of CK-levels and changes in CK related transcripts upon T. notatus attack. Two active CKs (isopentenyladenine and its riboside) have been detected in fifty-fold higher concentrations in the insects compared to leaves. Experiments with 15N-labeled plants showed that T. notatus transfers these CKs to the leaves on which it feeds. Plants with impaired CK perception showed a reduced attractiveness for mirids. While nutrient content was only marginally influenced by mirid feeding in wildtype plants, it was altered in plants with altered CK metabolism. Our results suggest that an active transfer of CKs by a free living insect maintains a homeostasis of nutrients even in highly damaged leaves to optimally exploit the food source

Herbivore-induced volatile blends with both "fast" and "slow" components provide robust indirect defence in nature

Plants emit volatile blends specific to particular herbivore interactions, which predators and parasitoids learn to associate with prey, increasing herbivore mortality and thereby plant fitness in a phenomenon termed indirect defence. Herbivore-induced plant volatile blends commonly include both rapid, transient green leaf volatiles (GLVs) and delayed, enduring sesquiterpenes. A few laboratory studies indicate that insects can use plant volatiles to time behaviour, but it is not known whether and how the temporal dynamics of plant volatile blends influence their function in indirect defence. We characterized the activity of the native herbivores Manduca sexta and Tupiocoris notatus and their predators, Geocoris spp., on their host plant Nicotiana attenuata in their natural habitat. Diurnal predator activity only partially overlapped with variable herbivore activity, and herbivore attack at the beginning or end of the photophase elicited plant volatile blends with distinct GLV and sesquiterpene profiles. In field trials, day-active Geocoris spp. predators preferred morning- over evening-typical GLV blends. Using plants genetically transformed so as to be unable to produce specific volatiles, we found that GLVs increased predation after dawn elicitations, whereas sesquiterpenes increased predation after dusk elicitations in field trials. We conclude that predators respond to temporal differences in plant volatile blends, and that the different dynamics of specific volatiles permit effective indirect defence despite variable herbivore activity in nature. © 2017 The Authors. Functional Ecolog

Onomastica epica nelle letterature d'oc e d'oil. I nomi degli idoli pagani.

Esame - attraverso alcuni testi appartenenti alle "Chansons de Geste" francesi - dei nomi degli idoli che si ritenevano adorati nelle societ\ue0 professanti religioni diverse dal quella cristiana. I nomi vengono fatti derivare, in maniera spesso indebita, non solo da ambiti coevi di diversa fede, ma anche dalla cultura/letteratura classica greca e latina e dal mondo popolare europeo

Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands

We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material