One approach to transgenic resistance to nematodes involves disrupting
their feeding. Cysteine proteinases are major digestive enzymes
of many nematodes and small protein inhibitors (cystatins) from
plants have mediated nematode resistance when expressed in several
crops including tomato, Arabidopsis, rice, potato in the field,
banana and plantain. A second form of transgenic resistance
reduces nematode invasion and its concomitant damage in addition
to reducing the population that develops in roots. Two non-lethal
synthetic peptides are known to have this effect. The transgenic
plants secrete peptides from their roots due to an N-terminal cleaved
extracellular export signal.