See also: http://www-ciwdpb.stanford.edu/research/research_barton.php and http://www-ciwdpb.stanford.edu/news/archived_news_barton.php (source of images used in this review).

Plants go topless šŸ˜‰

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TOPLESS mutant embryo showing root
development at both poles of the embryo
(Photograph by J. Long).

Scientists in California have created a double-tailed plant: a mutant with a second root where its stalk would typically reside. The mutant was grown in order to study how the fate of a plant is determined in its embryonic stages – perhaps leading to agricultural plants with ‘more desirable traits’.

A variant of the gene known as TOPLESS can cause the development of a root instead of a shoot during the development of the plant Arabidopsis thaliana.

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Wild-type (left) and TOPLESS mutant (right) Arabidopsis embryos

Normally, the TOPLESS gene codes for a repressor protein, which inactivates the genes that cause root development in the shoot area of the plant. But when the TOPLESS gene is deactivated through mutation, root-producing genes are activated, and the fate of the top half of the plant cell goes from shoot to root.