by Rahul Jayaraman '19
Protests have been occurring throughout the world about the genetic makeup of our food. Many of these protests have created extreme backlash against companies (such as Monsanto) that sell genetically modified crops (1). Misconceptions about genetic modification have been widespread. However, what if there were an alternative that would leave people feeling satisfied that their food has not been tampered with? (2)
Epigenetics is a relatively modern branch of biology that follows the idea that an organism’s environment can impel a change in its genome – which was one of the first evolutionary theories proposed (3). This newfangled science suggests that DNA expression can be controlled by changing external conditions, which could have long-standing implications for the way we manipulate plants and other foodstuffs to meet our needs.
In the 1950s, this theory of evolution, derided by the the scientific community for so long, had begun to appear as a real possibility once researchers started to investigate how DNA was stored. In the nucleus, DNA is compacted into chromatin. The building block of life, DNA consists of nucleotides that control protein synthesis. However, there is another level of organization that controls which genes are expressed (4). For example, this other control system takes genes that have not been used since fetal development and packages them away so that transcription cannot occur for that sequence of bases during an organism’s lifetime.
The most important of these mechanisms is methylation. Bases attached to a methyl group are blocked from being transcribed into RNA, so the genes they encode cannot be expressed. Another mechanism is compaction. If the chromatin is compacted densely enough, then the transcription enzymes cannot reach the DNA, and thus the expression of that gene is restricted or even fully eliminated (5). A combination of these two strategies may be applied as an alternative to genetic modification. In fact, careful examination of the plant genes may even provide clues as to how to alter the environmental conditions in order to bring about a genomic change.
Tests on plants such as cabbages have demonstrated that plants can adapt to a wide variety of situations after epigenetic modification. More specifically, scientists demethylated the DNA at specific loci and allowed those genes to be expressed, increasing the plant’s resistance to a particular climate or an antibody secreted by a given plant virus. Nevertheless, this can only be done with the fertilized plant ovule; if more cells are present, like in a seed, then the DNA must be altered in every cell. These methods can also confer antiviral resistance in plants and therefore prevent plants from rotting in storehouses.
Amazingly, epigenetics has already begun to take off – for instance, epigenetic inheritance has been used to make drought-resistant rice. The default setting for the drought-resistance gene is “off”; in more scientific terms, it is heavily methylated and packaged using histones. Scientists, instead of trying to change the accessible genes to make the rice drought-resistant, merely reversed the methylation with a simple reaction.
The sheer simplicity of epigenetic methods compared to traditional genetic modification makes this new field of biology a viable alternative to the much-scorned GMOs.