Thursday, February 23, 2012

In Russia, Plants Genetically Modify YOU!

OK, so I made a little outdated joke, bear with me. In fact it's not just in Russia, and it's not just people. Apparently, eating plants will influence an animal's genes.

First, a little background lesson in micro RNAs. miRNAs are very short sequences of RNA that do not translate into proteins. Instead, they have different regulatory roles within the cell, aiding or silencing the transcription of certain genes, and more and more of them are being discovered every year with ever more important roles. This year, a paper was published in Cell Research that found evidence that when animals eat plants, miRNAs from those plants can have a role in regulating the genes of the animals that ate them.

Plant miRNAs and animal miRNAs have some distinct differences that allow us to tell them apart. Plant miRNAs have a modification that makes them resistant to periodate, while mammalian miRNAs are not. Researchers thus extracted miRNAs from humans and tested them for sensitivity to periodate, and concluded that approximately 5% of the miRNAs in humans are originally from plants.

More evidence for this hypothesis comes from the fact that mice fed on rice have elevated levels of periodate-resistant miRNAs than mice fed on chow, which fits with the hypothesis that these periodate-resistant miRNAs originate from plants in the diet. Strangely, cooking the plants did not have an effect on the levels of plant miRNAs assimilated from the diet, indicating that these miRNAs are also heat-resistant.

OK so plant miRNAs can survive in animals without being digested and degraded. So what? What evidence is there that these miRNAs actually do something in animal tissues, rather than just float around passively?

Low Density Lipoprotein Receptor Adapter Protein 1 (LDLRAP1) is a protein that facilitates the removal of Low Density Lipoproteins from the circulatory system. Plant miRNA miR168 seems to be particularly good at binding the mRNA of LDLRAP1, which by doing so would lead to the organism making less LDLRAP1 protein. In fact, it was shown that those rice-fed mice had lower levels of LDLRAP1 than the chow-fed mice.

This indicates a far more direct role for a diverse diet for human health that goes beyond just getting the right level of nutrients. Eating too much of one thing can actually lead to things like the downregulation of certain genes that are needed for good physical health. There is still very much research to be done on this subject of course, but I personally found this fascinating.

The idea that genetic manipulation is so commonplace that it can happen even from the food that we eat is astounding. There is nothing "unnatural" about genetic manipulation or gene transfer from one organism to another, we're just starting to scratch the surface of how often it really happens.

Reference: Vaucheret and Chupeau (2012). Ingested plant miRNAs regulate gene expression in animals. Cell Research 22: 3-5

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