A molecular biologist explores ways to revolutionize agriculture.
The complete absence of sex in a few species has long fascinated biologists, but their research is driven by more than just curiosity. Hybrid plants are the mainstay of agriculture, but require ongoing breeding and selection to maintain their desirable traits. Apomixis, or asexual reproduction by seeds, is rare among commercially important crops, but engineering plants capable of this could produce stable crops with valuable traits.
Three Herculean tasks are involved: alteration of meiosis (the cell division that normally reduces the number of chromosomes in the sex cells, or gametes) to maintain the full maternal genome; fertilization-independent development of the embryo; and formation of the endosperm tissue that nourishes the embryo.
Raphaël Mercier of the French National Institute for Agricultural Research in Versailles and his team have taken a step towards achieving this goal. Using a combination of three mutants, they engineered a mustard weed that produces gametes carrying the complete maternal genome (I. d'Erfurth et al. PLoS Biol. 7, e1000124; 2009). Their breakthrough came while characterizing a mutation in the aptly named omission of second division (osd1) gene, which causes the reproductive cells to skip the second meiotic division. By combining an osd1 mutant with mutations that modify two other steps in meiosis, the team made meiosis similar to mitosis — cell division that occurs in non-reproductive cells.
Conservation of the genes involved across crop species fosters hopes that the strategy can be applied to many of them. The problem of endosperm formation will have to be overcome, and unfertilized seeds will need to be coaxed into development. The available tool kit of mutants affecting these processes makes me optimistic that these challenges will be overcome. However, convincing consumers that heavily engineered plants can secure future food supplies may require more than scientific ingenuity.
Discuss this paper at http://blogs.nature.com/nature/journalclub