Researchers shed light on how flowers make male and female parts
Botanists at the University of Leeds in the UK have shown evolution in progress, tracing how a gene mutation more than 100 million years ago led flowers to make male and female parts in different ways. As well as demonstrating how diversity stems from such genetic 'mistakes', the research should provoke further investigation into how plants make flowers, the origins of the fruits we eat. The research, funded in part by a Marie Curie Research Training grant of the EU's Seventh Framework Programme (FP7), was recently presented in the Proceedings of the National Academy of Sciences (PNAS) journal. In a number of plants, the gene involved in making male and female organs has duplicated to create two, very similar, copies. In rockcress (Arabidopsis), for example, one copy still makes male and female parts, but the other copy has taken on a completely new role, making seed pods shatter open. Likewise, in snapdragons (Antirrhinum), both genes are still linked to sex organs, but one copy makes mainly female parts, while still retaining a small role in male organs, but the other copy can only make male parts. 'Snapdragons are on the cusp of splitting the job of making male and female organs between these two genes, a key moment in the evolutionary process,' said lead researcher Brendan Davies, a professor of Plant Development at Leeds' Faculty of Biological Sciences. 'More genes with different roles give an organism added complexity and open the door to diversification and the creation of new species.' By tracing back through the evolutionary 'tree' for flowering plants, the researchers determined that the gene duplication took place around 120 million years ago. However, the mutation which separates how snapdragons and rock cress use this extra gene emerged some 20 million years later. The researchers discovered that the different behaviour of the gene in each plant was linked to one amino acid. Although the genes look very similar, some of the proteins they encode lack this amino acid. When it is present, the activity of the protein is limited to making only male parts, but when the amino acid isn't there, the protein is able to interact with a range of other proteins involved in flower production, enabling it to make both male and female parts, the scientists said. 'A small mutation in the gene fools the plant's machinery to insert an extra amino acid and this tiny change has created a dramatic difference in how these plants control making their reproductive organs,' explained Professor Davies. He said that this process was 'evolution in action', but cautioned that 'we don't know yet whether this mutation will turn out to be a dead end and go no further or whether it might lead to further complexities'. Nonetheless, Professor Davies said the research was 'an excellent example of how a chance imperfection sparks evolutionary change', highlighting that 'if we lived in a perfect world, it would be a much less interesting one, with no diversity and no chance for new species to develop'. The researchers are planning to study the protein interactions which enable the production of both male and female parts as part of further investigation into the genetic basis by which plants produce flowers.
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