This active multiefflux pump of inhibitory substance is a very important part of the antimicrobial compound defence in bacteria [ 27].
The combined transcriptome from all tissues and individuals was annotated to assign putative gene products to both major gene ontology categories as well as specific roles in responses to cold and heat, metabolism of xenobiotic compounds, defence, hypoxia, osmoregulation and ecdysis.
The role of phenylpropanoid compounds in defence appears to be restricted to a minor class of compounds that are often referred to as phytoalexins.
However, both high levels of piceasides and flavonoids in the less susceptible genotypes demonstrated the importance of the phenolic compounds in defence.
Initially when all predators are naïve, prey has to be more or less constantly defended, but as predators associate defence with prey traits (for instance visual signals), it no longer pays prey individuals to invest maximally in defence compound secretion.
For example, pisatin demethylase gene (PDA) from Nectria species detoxifies one specific class of the plant defence compound [ 4].
It was however shown that CYP71A12 expression responded in a similar way to aphid infestation than CYP71B15, which is involved in synthesis of the defence compound camalexin [ 92].
We recently showed that the constitutive antibacterial activity present in the haemolymph of H. axyridis beetles can be attributed to the chemical defence compound harmonine.
No effect on growth was observed suggesting that the reduction in pathogenicity was not directly due to the increased homocysteine levels (Additional file 7), but more likely to enhanced downstream responses such as ethylene signalling and/or defence compound synthesis.
The increase in the vitamin nicotinate, a stress protective molecule [ 22] and malonate, a defence compound [ 23], further supports the hypothesis that the partial lack of GS activity mimics stress conditions.
