What is in this article?:
- Banana gives up its secrets
- Bananas vitally important
- Bananas are vitally important for the food and economic security of more than 400 million people in southern countries, but are under constant pressure from a range of parasites.
- Crucial to develop new, more resistant varieties, although this is a complex operation given the very low fertility of cultivated banana varieties.
Bananas vitally important
According to the sequencing consortium, bananas are vitally important for the food and economic security of more than 400 million people in southern countries, but they are under constant pressure from a range of parasites. That pressure is particularly high in plantations producing the “export” bananas we find in our supermarkets. This makes it crucial to develop new, more resistant varieties, although this is a complex operation given the very low fertility of cultivated banana varieties.
The newly available genome sequence provides access to each one of the plant’s genes and to their position on its 11 chromosomes. The consortium said in a statement that this knowledge will make it much easier to identify the genes responsible for characters such as disease resistance and fruit quality. Lastly, it will be a vital tool for improving banana varieties using the many genetic resources available worldwide.
The banana is the first non-grassy plant in its botanical class, the monocotyledons, whose entire genome has been sequenced. Monocots include grasses, palms, lilies and other plants of mostly fleshy stature. Dicots, on the other hand, comprise more evolutionary recent plants including the majority of flowering plants and all true trees.
“The banana is the first monocot genome we have sequenced that’s not from a cereal, “ Lyons said. “That gives us a good opportunity to compare this group to its distant relatives and better understand the evolution of the monocot lineage.”
Already, researchers have been able to establish that banana has seen three episodes of complete genome duplication, at least two of which are independent of those seen in grasses. Unlike in the animal kingdom, duplicating an entire genome is nothing unusual in the plant world.
Said Lyons, “We sometimes joke that you as soon as you give a plant a funny look, it doubles its entire genome.”
This phenomenon, called polyploidy, is one of the main reasons why plant genomes present a challenge for scientists like Lyons, who are interested in understanding how genomes have changed over evolutionary time and relate that to the function of the organism.
Many of our domestic cultivars are polyploids, for example the mustards, many cereals such as wheat, or fruit like strawberry and watermelon. While most of the genes resulting from such events are generally lost over evolutionary time, some persist and lead to the emergence of new biological traits and functions.
“Consider for example, one of the master genes that regulate the development of a plant,” Lyons said. “A whole genome duplication event creates two copies. Over evolutionary time, these copies may change such that one copy is only active in leaves and the other only in flowers. This provides the plant with opportunities to develop all sorts of interesting developmental architectures.”
Researchers have already identified certain regulatory genes called transcription factors, which are particularly numerous in banana and contribute to important processes such as fruit ripening.
The work was conducted with financial support from the French National Research Agency. The banana genome sequence is publicly available on the CIRAD website.