You may not give plants enough credit. What looks like an innocent sunflower turning to catch the sun may actually be a riddle wrapped in an enigma shrouded in mystery. . . at least genetically.
Plants have some interesting genetic quirks that keep geneticists guessing. As challenges in finding gene-sequencing shortcuts, called barcodes, have made clear, deciphering plant genetics can be very tricky. Here’s five reasons plant DNA is totally confusing and completely fascinating to those who study it:
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| One mutant among many stripped Spathoglottis (Ground Orchid). |
1- Enter the Cell: One unique feature of a plant cell is the chloroplast, the engine of photosynthesis. The DNA from chloroplasts is some of the most reliable in a plant cell. That’s because it’s inherited from only one parent, making it easier to understand than the DNA in the nucleus. However, there is a little catch: Occasionally chloroplasts can be transferred from one organism to another, even from one species to another. As a result, a plant’s chloroplast may carry information totally unrelated to the species a geneticist is trying to study.
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| A Southern Crab Apple (Malus angustifolia) with the setting sun. |
2- Tangled Family Trees: A lot of plants are so long lived that they can do things we don’t typically see in animals. For example, you can have a mother tree reproducing with her great-grandson right beneath her. Plants overlap generations, travel minimally, and can clone themselves. They also mutate slowly. If genetic variation moves very slowly through a population, trees at one end of a forest can look different at the molecular level from trees at the other end, even though physically they are clearly the same species.
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| A Hawthorne (Crataegus L. Genus) bloom |
3- Two Genomes Are Better Than One: Plants have to withstand stressful conditions without the option of relocating. Fortunately, they’ve developed a handy trick to expand their adaptive repertoire: Pick up an extra genome. Through hybridization, organisms can double their genome, picking up additional sets of chromosomes. Animals with sex chromosomes—such as humans—are diploidic; they have two sets of chromosomes, one from each parent. Organisms with more than two sets are polyploidic. Wheat has 6 sets, 42 chromosomes total; coffee can have 8 sets of 11 chromosomes, or 88 total. Many sets makes deciphering one or two markers in the tangled skein of chromosomes in a plant cell’s nucleus a nearly impossible task.
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| A Bougainvillea Comm. ex Juss. sharing a plot of land with a couple of ancient Sabal Palms (Sabal palmetto). |
4- Sometimes, One Genome is Better Than Two: Given the stresses plants endure, they have all—at some point in their history—been polyploids. But that doesn’t mean they stay that way. Over time, genes that confer no advantage are dropped. The process is sped up by the fact that an imbalance in genetic material creates new problems. In plants as in animals, an extra chromosome can have serious effects. Klinefelter’s and Down’s syndrome are human examples, and certain crop diseases are caused by the existence of an extra chromosome. As a result, plant species such as mace, which were polyploidic 10 million years ago, have cast off most of the extra genes they once had so that today they are nearly diploidic. This makes these plants very confusing to analyze. For example, a diploid plant today might possess a genetic sequence that still bears the fingerprints of polyploidy—traces of other genomes.
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| A Florida Pineapple bloom (Ananas Mill.) |
5- The Fungus Among Us: You don’t often think about this, but all of life as you know it is covered with fungi. Some plants are more prone to fungal contamination than others, and the result is that as many as a quarter of plants are actually fungal. Another common culprit of contamination is microbial DNA that slips into a sample. Fortunately, these kinds of contaminations can be corrected when savvy scientists spot irregularities. As more plants (and for that matter microbes and fungi) are examined, geneticists can catch and correct more contamination errors.
