Positive Selection


This landscape covers use of a gene for selection that converts a neutral or toxic compound to a growth-promoting molecule. See also technical information for one mechanism that can be improved cooperatively.

About this technology landscape

Authored by Wei Yang and Marie Connett Porceddu. Assistance with some of the text and figures was provided by Shoko Okada and Leon Smith. An attorney opinion on one of the critical path patents was provided to CAMBIA by Foley and Lardner. We are grateful for technical assistance from Dr Nick dos Remedios and Neil Bacon for the web version and the development of software for biological sequence linking. We also thank Heidi Loder for proofreading the whole document. The preparation of this technology landscape was partially supported by a grant from Horticulture Australia Limited (Grant No.: HG03034). We welcome updates and inputs by others through the comments interface available on every page of this version of the technology landscape.

The positive selection approach has been of interest to address some issues associated with currently used negative selection methods and selectable marker genes:

In some areas, public acceptance questions use of certain selectable marker genes, notably genes encoding resistance to antibiotics, and some regulatory agencies discourage use of such systems in plants to be released into the field.
Selection systems based on genes conferring resistance to antibiotics or herbicides (“negative selection”) also stress living transgenic cells, in part by causing the release of phenolic substances from non-transformed, dying plant cells that may affect growth of transformed cells. This effect, which can hurt regeneration, limits their value in challenging tissue culture systems.

However, the use of both positive selection and certain negative selectable markers is constrained in certain jurisdictions by broad patents owned by companies that do not license them widely. Patents and patent applications with claims covering positive selection are described in this landscape.