Release of viral transgenic plants to the environment: prospects and problems

摘要

Recent advances in the understanding of the molecular mechanisms of how viruses function and how they interact with plants have led to the development of non-conventional approaches to protection of plants against viruses. Many of these approaches, giving what is sometimes termed pathogen-derived protection, involve the introduction of viral or virus-based sequences into the plant's genome. Expression of these sequences then interferes with one or more of the viral functions, thus giving some protection against the virus. This topic has attracted considerable attention and has been reviewed several times previously {Beachy, 1988; Baulcombe, 1989; van den Elzen et at., 1989;Gadani et al., 1990; Hull, 1990a, 1990b, 1994; Loesch-Frles, 1990; Mayo and Barker, 1990; Joshi and Joshi, 1991; Harms, 1992; Hull and Davies, 1992; Wilson, 1993; Fitchen and Beachy 1993; several papers in the volume edited by Beachy, 1993; Wilson and Davies, 1994). The viral genes most frequently used to provide protection are those for the coat protein, the viral repllcase and the cell-to-cell movement protein (see above reviews for details). Among those also being considered as targets are Insect transmission factors and replication and expression control sequences. In the case of coat protein, protection is often given by the unmodified gene product. However, most other gene products are used In a form modified to affect normal functioning. There is Increasing evidence that in some situations it is the expressed RNA and not the gene product which gives the protection.