Have you heard of Tomatosphere™? This is a really cool program operated in Canada through Let’s Talk Science. It is a free program offered to students from Kindergarten to Grade 12, where these students can study the effects of “space” on the germination of tomato seeds. Participating classes receive two packages of tomato seeds: one is a package of seeds from tomatoes that were sent into space or treated to space-simulation conditions, i.e., the experimental group; the second package contains seeds that spent time on plain old Earth, i.e., the control group. Students the study the germination of these two groups of seeds, expanding on the basic experiment depending on curriculum and grade level.
As a scientist and a gardener, I am in LOVE with this program. But I have a question for Tomatosphere™: I want to know if anyone is looking at the possibility of EPIGENETIC changes to the tomatoes. This begs the next question: what is epigenetics? That’s the question I am hoping to answer for you today.
To begin our understanding of epigenetics, let’s do a quick review of the central dogma of genetics and inheritance. The traits that make us a human (or a gorilla, or a tomato plant) are coded in our DNA. To express the trait, the DNA is transcribed into messenger RNA (mRNA), which is in turn translated into amino acids that are then put together to build the necessary proteins for each trait. We inherit these genes from our biological parents: one gene from the egg and one gene from the sperm. The trait that is expressed is the dominant gene. Differences in expression generally mean differences in the genes, or the specific DNA code.
For example, let’s look at blood types. Let’s say you inherit the “A gene” from your dad and the “O gene” from your mum. Your genotype will be AO. But since the A gene is dominant, you will only express this gene and you will have blood type A. This is called your phenotype. To change your blood type, you would need to change your genotype. That is the basics of inheritance.
Epigenetics throws a wrench into this understanding of genetics and inheritance. Epigenetics means “outside genetics”, and refers to changes in gene expression that are not a result of physical changes to the DNA sequence. In other words, changing our phenotype without changing our genotype. Epigenetic marks control the expression of genes, which ones are turned on, when, and how much. One of the most interesting things about epigenetics is that we can start to see how the environment plays a role in gene expression. Our lifestyles, our preferences, our exposures to certain environmental factors can all contribute to variations in how the same gene can be expressed across individuals. What’s more, is that it has been discovered that these changes in epigenetics can be inherited. What this means is that if you exposed to something in your environment that causes a change in how a gene in your DNA is expressed, this change could be passed on to your child, and even to your grandchild. This is referred to as transgenerational epigenetics. It is an emerging area of research and the exact mechanisms of how this works is being widely studied.
This brings us back to Tomatosphere™ and my question. In the experiment we have tomato seeds that were exposed to space conditions. These conditions may not have changed the gene sequence, the genotype, of the tomato, but they may have caused epigenetic changes. It has been shown that changes in the gene that controls ripening in tomatoes is impacted by epigenetics, so do we see changes in other factors with these space tomatoes? AND, what about the progeny? Do the tomato plants grown from the seeds of the space tomatoes also show epigenetic changes?