Wageningen, The Netherlands
August 26, 2013
Flowering plants came into being when duplications took place in the genome of their ancestors. Charles Darwin wondered how all those flowering plants were able to conquer the world relatively quickly. DNA research can now provide part of the answer.
DNA duplications gave rise to new functions
Genes that are found in all flowering plants, and in no other organisms, have been compared with each other by a group of German, Belgian and Dutch researchers, including Ruud de Maagd from Wageningen UR Plant Research International. The researchers found large numbers of DNA duplications in the very parts of the genome that are unique to flowering plants. In some cases, so-called tandem duplications of a gene have taken place, resulting in identical pieces of DNA lying alongside each other. In other cases, a piece of a genome has been duplicated in its entirety. The researchers published some of their findings on this in Nature Communications on 19 August 2013.
Flowering plant became dominant
It is not true to say that complete copies can still always be found in the DNA, as surplus DNA often disappears again over the course of evolution. However, remnants may still remain as the copies took on different functions and sometimes developed new functions. The researchers have now been able to make a good case showing that this type of duplication has contributed to the development of a new function in plants: they began producing flowers. This evolution, hundreds of millions of years ago, was so successful that flowering species now dominate the plant kingdom.
Cereals do have vernalisation genes
The position and order of so called MADS-box genes, which switch other genes on and off, appeared to be the same in the DNA of all flowering plants. With this knowledge, the researchers also unravelled another mystery. It is already known that winter cereals first need to go through a cold period before they are able to flower, but the vernalisation gene – the so-called FLC gene, seen in other plants requiring a cold period in order to be able to flower – has not previously been found in winter cereals. However, now that the researchers knew exactly where they had to look, they were able to find genes related to FLC genes. This gave new direction to the study of vernalisation in cereals.
A piece of the evolution puzzle resolved
Ruud De Maagd emphasises that this study resolves only part of the puzzle of flowering plants, as research has only been done into the MADS-box genes (main regulators) found in flowering plants, and many more genes are involved in the formation of floral organs. This study is unable to clarify what the genome of the common ancestor of all flowering plants looked like. In order to gain clues regarding this, the entire genome of many more flowering plants and gymnosperms (coniferous trees and cycads) would have to be compared. That would take a while, as few genomes of gymnosperms are fully known at present.
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