Inactivation of allergens and toxins

Plants are replete with thousands of proteins and small molecules, many of which are species-specific, poisonous or dangerous. With time humans have learned to avoid dangerous plants or inactivate many toxic compounds in food plants, but there is still room for improvement. The capacity, offered by genetic engineering, of turning off (inactivate) single genes in crop plants has opened up the possibility of altering the plant content in a far more precise manner than previously available. There are several tools to inactivate genes (classical mutagenesis, antisense RNA, RNA interference, post-transcriptional gene silencing, insertion of transposons and other genetic elements) each one with a mixture of advantages and disadvantages (speed, costs, selectivity, stability, reversibility, regulatory regime). There are different level at which to intervene (genes coding for toxins, allergens, enzymes, transporters or regulators), each one suited for a specific problem, and there are different problems to address. We will describe interventions to ameliorate food crops in terms of their content in allergens and toxins, especially in their edible parts, providing some paradigmatic examples. It will be stressed that reducing the content of natural toxins is often a threshold issue (“the dose makes the poison”) and a trade-off process: the least the content of natural toxins, the higher the susceptibility of a plant to pests and therefore the stronger the need to protect plants in field conditions. This has interesting consequences on the domestication process and the development of new pesticides to counter plant pests.