H3-4 and infection: Considering the low abundance of OPDA-aa and the tissue-specific and developmentally controlled expression of GH3 and ILR1/ILL genes (Rampey et al. 2004; http://bar.utoronto.ca/), the regulation of cis-OPDA levels mediated by amido synthetases and amidohydrolases could be restricted to specific tissue types (e.g. in the damaged site of plants) upon wounding or pathogen infection.