R. Gutierrez-campos et al., The use of cysteine proteinase inhibitors to engineer resistance against potyviruses in transgenic tobacco plants, NAT BIOTECH, 17(12), 1999, pp. 1223-1226
As the processing mechanism of all known potyviruses involves the activity
of cysteine proteinases, we asked whether constitutive expression of a rice
cysteine proteinase inhibitor gene could induce resistance against two imp
ortant potyviruses, tobacco etch virus (TEV) and potato virus Y (PVY), in t
ransgenic tobacco plants. Tobacco lines expressing the foreign gene at vary
ing levels were examined for resistance against TEV and PVY infection. Ther
e was a clear, direct correlation between the level of oryzacystatin messag
e, inhibition of papain (a cysteine proteinase), and resistance to TEV and
PVY in all lines tested. The inhibitor was ineffective against tobacco mosa
ic virus (TMV) infection because processing of this virus does not involve
cysteine proteinases. These results show that plant cystatins can be used a
gainst different potyviruses and potentially also against other viruses, wh
ose replication involves cysteine proteinase activity.