Evolution

Unraveling the Origin of Cotton

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Science  09 Mar 2012:
Vol. 335, Issue 6073, pp. 1148
DOI: 10.1126/science.335.6073.1148-a
CREDIT: ISTOCKPHOTO.COM

The origin and evolution of Gossypium hirsutum, the most widely planted cotton species, is an unsolved puzzle because of its hybrid origin from Old and New World species. To better understand the evolution of cotton, Palmer et al. shotgun sequenced 454 2000-year-old archaeological samples of cotton from Africa and South America. On the basis of their results and comparisons with genetic data from extant species, they assigned the African lineage to the species G. herbaceum and the South American lineages to the species G. barbadense. From these data, the authors show that G. barbadense shows overall genome stability with few changes in the placement and number of transposable elements over the past 2000 years. In contrast, G. herbaceum showed significant differences in transposable element composition over time. On the basis of these results, the authors postulate that the ancient G. herbaceum lineage is more like the ancestral form of one of the original species parents of G. hirsutum than that of the extant lineages. Furthermore, they suggest that cotton genome evolution is characterized by bursts of transposable element activity followed by genome stability.

Mol. Biol. Evol. 29, 10.1093/molbev/mss070 (2012).

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