The seeds of change
31 Mar 2010 by Evoluted New Media
Each year, farmers fork out for hardy and pest-resistant seeds which they can’t produce themselves because sexual reproduction can erase the very traits they wish to keep. Most plants used for food reproduce sexually, but Jean-Philippe Vielle-Calzada and his colleagues have been learning how to make them reproduce asexually.
Each year, farmers fork out for hardy and pest-resistant seeds which they can’t produce themselves because sexual reproduction can erase the very traits they wish to keep. Most plants used for food reproduce sexually, but Jean-Philippe Vielle-Calzada and his colleagues have been learning how to make them reproduce asexually.
They studied apomixis – a method of asexual reproduction resulting in seeds that are clones of the main plant – in Arabidopsis thaliana. They discovered the gene Argonaute 9 suppresses this type of reproduction in the plant.
“Agricultural companies and farmers around the world have a tremendous interest in this method,” said Vielle-Calzada, “It would allow them to simplify the labour-intensive cross-hybridisation methods they now use to produce hearty seeds with desirable traits.”
Researchers concentrated on the ovule – the reproductive structure which produces a single female gamete: when fertilised this becomes a seed. They identified active genes, reasoning this would enable them to study genes essential for guiding asexual reproduction.
Argonaute 9 and its proteins control whether a cell produces RNA or proteins by slicing up messenger RNA before it can be translated into protein. Vielle-Calzada said that identification of Argonaute activity in the ovule was interesting as it has never been found in Arabidopsis reproductive cells before.
Researchers mutated Argonaute 9 and found that instead of producing a single gamete, most of the ovules with the disrupted gene produced several gametes and carried the full complement of genetic material, suggesting that they had not undergone meisos.
“By cutting off the function of Argonaute, we caused a ‘schizophrenic’ reaction of the cells in the ovule, which were not supposed to become gametes,” Vielle-Calzada said, “It looks like Argonaute normally prevents those cells from being transformed into gamete precursors.” He suggests that the gene prevents initiation of apomixes in Arabidopsis.
“It’s possible that plants have a very old memory that allows them to reproduce asexually,” Vielle-Calzada said. The research raises the possibility that many – possibly even all – plants have the ability to reproduce through apomixis, but that the potential is suppressed by Argonaute 9.
