Wednesday, March 4, 2015

TWiV TWiM and TWiP

I’m sure that most of you are not avid podcast listeners, but anyone who wants an interesting hour or so about microbiology, parasitism, or virology should check out This Week in Microbiology, This Week in Parasitism and/or This Week in Virology. The podcasts are hosted by Vincent Racaniello (and some other people), with topics from HIV and Ebola virus to antibacterial gene transfer to mosquito midguts. Most of the podcasts involve reading/responding to letters submitted by the audience (if might be fun to write a letter to TWiV/TWiM/TWiP yourself!), discussing papers, and occasionally having a guest scientist that talks about her research.

Since we’ve been talking about how cool plants are (despite being stationary :P), I found a TWiP episode (TWiP 77: Mixed messages) that talked about a paper recently published in Science. The paper is about the exchange of mRNA between a parasitic plant and its host. Rather compelling stuff:
Cuscuta pentagona (common name: dodder) is a plant that makes symplastic (symplast = inner side of plasma membrane where water can freely diffuse) connections with its host. Cuscuta pentagona grows in a coil around its host plant, and will then attach itself to the host plant using thin fibers called haustoria. This connection is analogous to the connection between plant roots and fungi’s mycelium—the connection allows for a transfer of water and nutrients. Dodder parasitizes a number of plants. In this study, the researchers used the agriculturally significant tomato plant, and a well-studied plant, Arabidopsis, as the host species. (Remember the fast plants from MCDB1AL? Same family.)

The researchers cut off three pieces of plant: one with just Arabidopsis or tomato, one piece with just Cuscuta, and one piece with both Cuscuta and the host plant. The researchers then used the transcriptome (total RNA) and created cDNA libraries to perform deep sequencing on the samples. In the sample that contained both host and parasite, about half of the sequences belonged to the host and the other half belonged to the parasite, as expected. In the sample that was just dodder, however, the researchers found that about 0.6% of the host plant genome in the sequences. In the host plant sample, they found that about 1% of the sequences were actually from the Cuscuta genome! Arabidopsis transferred more genetic material than the tomato plant. The researchers clearly show that mRNA transfer is occurring--whether this transfer is significant or not is still in question (mRNA transfer within a plant is common, but cross-species interaction have not been studied much). The research also has some implications about horizontal gene transfer. Listen to the podcast for more discussion (or read the paper)!

**In the podcast, they only really start talking about the paper around 17 minutes

Link to the paper they discussed:

If you want a 2-minute commitment instead of reading the paper, here’s a video:

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