Figure 7.

Two distinct myrosinase-glucosinolate systems occurring in Brassicales. (A) In leaves, myrosinases and glucosinolates accumulate in vacuoles of distinct cells. Tissue collapse accompanied by destruction of multiple cells results in the mixing of enzymes and substrates, and the production of toxic products against herbivores. (B) In roots, myrosinases and glucosinolates accumulate in ER bodies and vacuoles, respectively, in the same cells. Enzymatic reactions may be activated by (i) cosecretion of enzymes and substrates, (ii) translocation of enzymes into vacuoles, or (iii) destruction of a single cell.