Microarray data of Flg22-inducible expression profiles identified a phytochelatin synthase gene; PCS1 whose corresponding mutants (pcs1-1; pcs1-2 and cad1-3) were all impaired in the callose response to Flg22. The transcriptional and indolic GSL profiles of the pcs1 mutant resemble those of the pen2 mutant; suggesting that it too is involved in the breakdown of 4-methoxy-indol-3-ylmethylGSL (Clay et al. 2009)