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Asked by Ryan to Alex on 25 Apr 2016.
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Alexander Taylor answered on 25 Apr 2016:
Great question! I study a partnership that some plants make with bacteria, called nodulation. Specifically, I’m interested in the way nodulation evolved, since most plants do everything they can to keep bacteria away.
Several different families of plants all evolved nodulation independently, kind of like how birds, bats, and insects all evolved wings independently. I want to know just how similar nodulation is in all the different families that do it, because that will give us clues about how it evolved. So I infect plants with their partner bacteria, and then I collect the plant roots and see which genes are being turned on and off as the plant welcomes in the bacteria. I can then compare those genes to the genes that other plants (that evolved nodulation independently) turn on when they’re nodulating. That way I can see if nodulation is the same or different in the different plant lineages, at a genetic level!
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Comments
Mark commented on :
Alexander has a great example. I think it’s worth adding that plants make lots of “business deals” with bacteria and other microorganisms, like fungi. In this way they act as “mutualists” where they each benefit the other. Plants provide things the bacteria can’t easily get, like sugars for energy, and the bacteria provide things that the plants can’t easily get, like chemical forms of nitrogen or phosphorus. Grasses actually leak sugars into the surrounding soil to “wake up” bacteria and get them to break down more organic matter, thereby releasing nitrogen into the water in the soil where roots can soak it up. My team recently discovered that some grasses create layers of tissue along their roots in which bacteria that fix nitrogen live, and these bacteria share some of the nitrogen they acquire from the atmosphere. Some fungi “move in” to plant roots and then send out long thin tendrils called hyphae that invade the tiniest pores in the soil, hunting for rare minerals like phosphorus. The fungi then “sell” the phosphorus to plants for sugars. Ecologists study these interactions the same way economists study how countries trade with each other.
Alex commented on :
Mark is adding an important point! Nodulation is far from the only partnership or “business deal” that plants make with microbes. In fact, one of these partnerships, with a specific fungus called “Arbuscular Mycorrhizal” (AM) fungus, appears on the earliest fossil plants. Many scientists think that this AM partnership allowed the first algae to get onto land and evolve into all the plants we see today. Early roots weren’t very well adapted for land, early soil was harsh and rocky, and these AM fungi were able to absorb nutrients and water in a way that the plants couldn’t. To this day, more than 80% of plants make this AM partnership. In fact, nodulation (the plant-bacteria partnership I study) seems to have evolved by recruiting the genetic machinery that originally evolved for the AM partnership!