As accumulation of callose is one of the defence mechan isms against aphid infestation, the pen2 4 mutation, present in coi1 16 line, may contribute to the increased susceptibility of coi1 16 plants to infestation with M. persicae. It is also conceivable that the expressional changes of JA regulated genes observed by us in the aphid infested aos mutant were sufficient to sustain the same level of aphid resistance susceptibility as is present in wt plants. It should be noted that many genes known to be regulated by SA, ABA or auxin signalling were up regulated in aos plants. Several of these can be involved in defence against B. brassicae infestation and influence Inhibitors,Modulators,Libraries aphid fitness. As revealed by the insect fitness tests, physiological changes resulting from the fou2 mutation render plants more resistant to infestation than wt, despite the reduced intensity of the aphid induced responses.

As the observed resistance was not based on feeding deterrence, it is most probably based on antibiosis. Various defence related responses that are constitutively activated in fou2 plants, e. g. high expression of plant defensin proteins, pathogenesis related proteins or protease inhibitors, can exhibit an antibiotic effect on insect pests. Inhibitors,Modulators,Libraries The latter, for example, can disturb digestion and absorption of food in the insect gut. Moreover, the high activity of LOX enzyme in fou2 plants can increase production of reactive lipid peroxides, cause oxidative damage to Dacomitinib the insect gut and significantly decrease the nutritive quality of dietary proteins.

It should be noted, however, that the mechanism responsible for the manifestation of the fou2 phenotype is not fully understood. Therefore, we cannot eliminate the possibility that other, unknown, features of fou2 Inhibitors,Modulators,Libraries could play a role in mediating aphid resistance. Conclusions A comparison of transcriptional profiles of non chal lenged aos, fou2 and wt plants allowed us to identify more than 200 genes whose expression profiles in non challenged plants were dependent on endogenous jas monate status. Most of these transcripts were up regu lated in fou2 and down regulated in aos mutants, which points to a positive regulatory Inhibitors,Modulators,Libraries function of JA derived compounds. Many of the jasmonate dependent genes were connected to regulation of transcription, defence responses, redox balance and cell wall modification.

Upon infestation with Brevicoryne brassicae, the respon siveness of many genes was changed in aos and fou2 plants. Genes attributed to GO categories connected to the regulation of transcription and responses to stress were generally less induced in both mutants. In contrast, transcripts classified as involved in cell division and devel opment, cell wall modification and transport were more induced or not as much down regulated in the mutants compared to wt.