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taxis.jpgMoving Genes Around

A recent report that a species of aphid can make carotene thanks to a gene it apparently acquired from a fungus got me to thinking about whether genes can flow between different plant species.

When an organism incorporates genetic material from another organism without being the offspring of that organism, this is called horizontal gene transfer (HGT), a.k.a., “lateral gene transfer”. (Vertical gene transfer occurs between parent and offspring.)

HGT is common in bacteria – it’s often how bacteria acquire genes for drug resistances, for instance.

Although much less common, there are cases of HGT between microbes and plants. (An excellent review can be found here.) Interest the subject of HGT in plants has been stimulated by the proliferation of GMO’s, especially transgenic crop plants, see here, for example.

The natural transfer of genes between fungi, bacteria and plants has been established, but to what degree will likely have to await a more complete array of genetically-sequenced plants.

Parasites as a Bridge for Gene Flow Between Diverse Plant Species

Striga_hermonthica.jpgParasitic plants form vascular connections with their host plants via haustoria to allow transfer of nutrients, water, and even mRNAs ( see Ref 1 below). Thus, it has been suspected that HGT of nuclear genes may occur in parasitic plants.

In a recent report, scientists have found evidence for nuclear gene transfer in the parasitic plant Striga. “Striga hermonthica (Del.) Benth. is a devastating parasitic plant that infests members of the grass family (Poaceae), including major crops such as sorghum (Sorghum bicolor) and rice (Oryza sativa).” (from Ref 2 below)

Briefly, these investigators searched for grass-specific genes within the genome of Striga. They did indeed find at least one grass specific gene. Thus, “…our comparative genomics analysis of a eudicot parasite and its monocot hosts presents a clear case for nuclear HGT.” (from Ref 2)

Bottom line: Research over the past decade has provided evidence that gene movement between distantly related plant species occurs, and that plant parasites are likely a vehicle for such movement.

Recent news regarding gene movement in fungi.

References

1. Westwood, J. H, J. I. Yoder, M. P. Timko, and C. W. dePamphilis (2010) “The evolution of parasitism in plants.” Trends in Plant Science Vol. 15, pp. 227-235. (Abstract)

2. Yoshida, S., S. Maruyama, H. Nozaki, and K. Shirasu (2010) “Horizontal gene transfer by the parasitic plant Striga hermonthica.” Science Vol. 328, p. 1128. (Abstract)

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