The use of cysteine proteinase inhibitors to engineer resistance against potyviruses in transgenic tobacco plants.

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 important potyviruses, tobacco etch virus (TEV) and potato virus Y (PVY), in transgenic tobacco plants. Tobacco lines expressing the foreign gene at varying levels were examined for resistance against TEV and PVY infection. There was a clear, direct correlation between the level of oryzacystatin message, inhibition of papain (a cysteine proteinase), and resistance to TEV and PVY in all lines tested. The inhibitor was ineffective against tobacco mosaic virus (TMV) infection because processing of this virus does not involve cysteine proteinases. These results show that plant cystatins can be used against different potyviruses and potentially also against other viruses, whose replication involves cysteine proteinase activity.

Isolation and characterization of a gene involved in ethylene biosynthesis from Arabidopsis thaliana.

The ethylene forming enzyme (EFE) is a key factor in ethylene biosynthesis. To understand better the regulation of ethylene biosynthesis in vegetative tissues, we set out to isolate and characterize a complementary DNA (cDNA) encoding the EFE from Arabidopsis thaliana. An A. thaliana cDNA library was screened with pTOM 13, a tomato cDNA coding for the EFE. A cDNA clone (pEAT1) was isolated. The cDNA is 1200 nucleotides (nt) in length and predicts a protein of M(r) 36,663. The insert includes the complete open reading frame of 972 bp and shows strong homology with several reported sequences, both at the nt and amino acid level. In whole seedlings, expression of pEAT1 was enhanced by wounding, ethrel, Fe2+, and 1-amino-cyclopropane-carboxylic acid (ACC) treatments. In contrast, heat shock had no effect on the expression.