IMMUNODETECTION OF THE PLUM POX VIRUS HELPER COMPONENT IN INFECTED PLANTS AND EXPRESSION OF ITS GENE IN TRANSGENIC PLANTS

Tobacco plants (Nicotiana tabacum cv. Xanthi) have been transformed vi a Agrobacterium tumefaciens vectors, with cDNAs corresponding to the p lum pox virus (PPV) cistron 2 encoding helper component (HC-Pro) and w ith the first two and half cistrons of the PPV genome. Presence of the HC-Pro in PPV-infected plants and transgenic plants transformed with the gene coding for this protein was investigated using specific polyc lonal antibodies produced against the PPV HC-Pro. The results suggest that two proteases are involved in the processing of the PPV N-termina l polyprotein to yield a protein of 48 k (HC-Pro). HC-Pro autolyticall y cleaves at its carboxyl-terminus and a proteolytic activity, probabl y associated with the protein (P 1) encoded by the cistron 1, is requi red for the cleavage in planta between the proteins derived from cistr ons 1 and 2.