tly con tribute to the regulation of defence connected genes under stress conditions. The GO terms denoted tran scription selleck chemicals llc regulation activity and response to stress with the sub nodes defence responses and response to wounding were statistically significantly overrepresented ack both in aos and fou2 mutants. These categories taken together contributed almost half of the genes whose responsiveness was negatively affected in aos and fou2 plants. Although the majority of the genes that responded to B. brassicae infestation in wt plants were induced in the challenged aos as well, their regulation was weaker in the mutant than in wt. Twenty two genes, whose products are involved in regulation of transcription and 34 transcripts connected to defence showed no induction or weaker up regulation upon infestation in the aos mutant.

Inhibitors,Modulators,Libraries Several transcription factors and defence related proteins were, in contrast to wt, either not induced or down regulated in the aphid challenged aos plants, i. e. BTB and TAZ domain protein 5, dehydration responsive element binding protein 2A, ethylene responsive tran scription factors ERF11 and ERF13, myb family transcrip tion factor, C2H2 type family protein, DARK INDUCIBLE 11, sulfotransferase family protein, strictosidine synthase, plant defensine 1, cysteine rich antifungal protein 1 precursor, heat shock protein 81 1 and arginase. These observations clearly show that JA signalling is important in the activation of defensive responses trig gered by B. brassicae attack.

However, the fact that some genes were up regulated during infestation despite of the lack of AOS enzyme activity indicates that JA signalling is, as expected, not the only system controlling gene regulation. Interestingly, Inhibitors,Modulators,Libraries some of the defence related transcripts accumulated in the Inhibitors,Modulators,Libraries non challenged aos plants as compared to wt, probably as a result of stress connected to the lack of JA or an imbalance between JA and SA signalling pathways. In the fou2 mutant, several transcription factors and defence related genes were already up regulated in non challenged plants compared to wt, indicating constant activation of defence caused by the increased endogenous JA levels. Often the induction of these genes was stronger in non challenged fou2 mutants in comparison to wt than in the infested wt compared to aphid free wt.

In such cases no additional induction was noted in the aphid attacked fou2 mutant compared to the aphid free fou2 control. For other genes a slight Inhibitors,Modulators,Libraries additional induction of already up regulated Brefeldin_A transcripts was observed in fou2 plants attacked by B. brassicae. Out of 41 transcription factors and 74 defence related genes up regulated upon B. brassicae infestation in wt, but having changed aphid triggered regulation in one or both mutants, 37 and 69 genes, respectively, were less up regulated or not induced in the fou2 mutant so in response to infestation. These results indicate that the activation of defence responses may have an overall induc tion threshold