Super veg
Find out more about the food you eat.
To help plant breeders improve the potatoes and tomatoes we eat we need to understand the background to the qualities (e.g. flavour) we are interested in. Below are some of the qualities investigated by EU-SOL and how genes can affect them.
Genes and texture
Here we will look at two genes that are involved in tomato ripening. LePG and LeExp1. These genes both produce enzymes involved in the breakdown of cell walls in ripening tomato fruit, which I’ve nicknamed Chopper and Changer.
- LePG (Chopper). LePG is an enzyme that digests pectin chains (chops them up).
- LeExp1 (Changer). The role of LeExp1 is less clear. It has been suggested that this protein is responsible for altering the connections between different molecules in the wall, loosening the structure of the wall and possibly making it easier for other enzymes to access and digest these molecules.
In plants where both of these genes were knocked out the fruit were significantly firmer (while still appearing to ripen normally otherwise) and less susceptible to deterioration during long term storage.
However, in tomatoes where just one of these genes has been ‘knocked out’ (that is stopped from producing the protein they code for) there is little or no effect on the softening of the fruit during ripening. This suggests that a range of enzymes and other factors work together to influence texture. It is clear from this example that the breakdown of plant cell walls that occurs during ripening is not a simple process and more research needs to be done to understand the relationship between different enzymes.
Summary
The two genes we have looked at code for proteins (Chopper and Changer), which, working together as part of the ripening process, assist the breakdown of cell walls in tomatoes. This in turn leads to a softer cell walls and affects the overall firmness of the tomato.
In this way we can follow a simple causative path from the presence of a couple of genes amongst the millions found in a tomato’s DNA to the firmness of the tomatoes that we put into our mouth. It is also clear that these genes and the proteins they produce will have effects on other aspects of texture (e.g. mealiness) and that they are part of a complex ripening process that we do not fully understand.
What this research will do for us?
An understanding of what enzymes and genes are key to the breakdown of cell walls and other aspects of ripening in tomatoes will allow plant breeders to breed tomatoes with improved texture.
