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How common is transgenic gene transfer between organisms in the wild?
Depending on your amount of exposure to the topic, you may think it is either fairly common or extremely rare. But is there a way to actually scientifically quantify its occurrence? The answer is yes.
Oh, and the answer to the prior topic of whether such a transfer is common or not is also yes. Go figure.
Researchers at the Leibniz-Gemeinschaft (Leibniz Institute) of Plant Genetics (as a collaboration with the Czech Academy of Sciences) recently looked into this question within vascular plants. These more or less make up all the plants you’d care to know about, all of which have an internal vascular system for moving water and nutrients. An example of a non-vascular plant would be mosses.
Now, it’s long been known that non-nuclear DNA transfers between plants is fairly common, just as it is in microorganisms that use methods like plasmids. In the case of plants, this means transfers between chloroplast DNA and mitochondria DNA, as both are not, let’s say, native DNA sources to the cells.
But it’s also been thought that transfer of nuclear DNA, such as the genome within the nucleus itself or as presented within ribosomal DNA (rDNA), is not transferred very often.
What they found is that such nuclear DNA transfer seems to be a very common biological mechanism used by plants. In a screening of barley genomes, the scientists discovered non-native rDNA in more than 16 different barley lines.
This rDNA itself was traced to five distinct spcies within the Panicoideae subfamily (which makes up thousands of species). And this rDNA is known to be non-native because these other species split off their own evolutionary lines more than 60 million years ago and are not sexually compatible anymore with barley.
Meanwhile, these rDNA transfers appear to have occurred recently, during genome duplication events. And these are not just short segments of transgenically transferred genes, some make up several hundred kilo-basepairs. That’s a decent amount, for those unaware.
What Does It Mean?
What’s interesting about these transfers is that they appear to be quite random, most of them made up of noncoding DNA. This in turn means that this rDNA has no effect on the barley genome at all. So their effect on the natural selection capabilities of the plant is fairly neutral. The gene transfer event is not positive or negative overall.
What’s the benefit of even having such a biological mechanism then? Perhaps it produces more positive genes in the end and there’s just a lot of junk that is waded through first.
Either way, this study shows that plants are not adverse at all to trading up genes with each other fairly often and fairly randomly.
Photo CCs: Escourgeon-Hordeum vulgare subsp. vulgare from Wikimedia Commons