There is a host of innovative and highly regarded research coming out of the School of Biological and Chemical Sciences and 82% of our School’s biology research outputs are rated as either world-leading (4-star) or internationally excellent (3-star) by the Research Excellence Framework 2014.
One example of such research comes from Professor Andrew Leitch, our Postgraduate Programme Director. He and colleagues at Queen Mary University London, the Royal Botanic Gardens Kew and Biology Centre CAS, Czech Republic have discovered how ‘giant’ plant genomes evolve.
Nuclear genome size, which is the total length of DNA molecules within the cell’s nucleus, can vary greatly between different plant species. Whilst it might be thought that larger or more complex plants would have more genes and therefore bigger genomes, this is not the case. For example, the oak tree genome is surprisingly over 100 times smaller than the genome of the famous festive plant, mistletoe.
It has been suggested that the size of a plant’s genome is dependent on the balance between the accumulation and removal of repetitive DNA, repeated sequences that have the ability to move around and multiply within the genome.
In the recent study, published in Nature Plants, the researchers confirmed this hypothesis, showing that plant species with larger genomes are less efficient at removing this repetitive DNA from their genomes. Instead these repeats become ‘fossilised’ in the genome, where they acquire mutations and begin to degrade. The degraded DNA sequences, known as ‘dark matter’, are then no longer recognized by the removal systems within the plant, and persist in the genome, which then continues to grow in size.
Larger genome sizes can also affect plant growth and species with giant genomes are frequently found among critically endangered plants. The findings provide a potential explanation as to why this may be. Professor Leitch said: "Previous studies have shown that plants with larger genomes are at greater risk of extinction, potentially because they are less able to adapt to changing environments. Indeed the accumulation of repeats and ‘dark matter’ in the genome has ecological consequences, shaping the distribution and persistence of biodiversity.”