Engineering zucchini yellow mosaic potyvirus as a non-pathogenic vector for expression of heterologous proteins in cucurbits

Plant virus vectors provide an attractive biotechnological tool for the tra nsient expression of foreign genes in whole plants. As yet there has been n o use of recombinant viruses for the improvement of commercial crops. This is mainly because the viruses used to create vectors usually cause signific ant yield loss and can be transmitted in the field. A novel attenuated zucc hini yellow mosaic potyvirus (AG) was used For the: development of an envir onmentally safe non-pathogenic virus vector. The suitability of AG as an ex pression vector in plants was tested by analysis of two infectious viral co nstructs, each containing a distinct gene insertion site. Introduction of a foreign viral coat protein gene into AG genome between the P1 and HC-Pro g enes, resulted in no expression in planta. In contrast. the same gene was s tably expressed when inserted between NIb and CP genes, suggesting that thi s site is more suitable for a gene vector. Virus-mediated expression of rep orter genes was observed in squash and cucumber leaves, stems, roots and ed ible fruit. Furthermore, AG stably expressed human interferon-alpha 2, an i mportant human anti-viral drug, without affecting plant development and yie ld. Interferon biological activity was measured in cucumber and squash frui t. Together, these data corroborate a biotechnological utility of AG as a n on-pathogenic vector for the expression of a foreign gene, as a benefit tra it, in cucurbits and their edible fruit. (C) 2001 Elsevier Science B.V. All rights reserved.