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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
first of all reading the PLoS article is like
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
where to start. oh my god Ok first of all this research was done in an Access & Benefits Sharing partnership with the local community and the gov't of Mexico under the Nagoya Protocol, because Latin America's gotten wise to biopiracy.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Second of all, this discovery was 40 years. FORTY. YEARS. in the making. like. 40 YEARS AGO a scientist is running around Mexico, sees tall-ass corn growing in poor-ass dirt where no corn should be growing, & it's got big-ass aerial roots. Scientist says "huh. that's weird"
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Normally maize aerial roots look like this: (corn is on the left.) Lil dry nubs. but the Sierra Mixe maize's aerial roots look like this: GOOOOOOOPP Also science pls forgive me. "Goop" has so many fewer characters than "mucilage," the scientific word for goop.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Also note the maize pic says the lil root nubs are for "support." Literally we'd have this conversation. "What are those things for?" "Idk maybe they hold the plant up" ¯\_(ツ)_/¯ But we knew that was bullshit bc look at those lil nubs. They do nothing to hold the plant up.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Anyway. Not only did this crew prove that yes the goop has N-fixing bacteria in it (prob. Burkholderia spp?)- There are also wild teosinte plants in the area that have small aerial roots with a lil bit of goop on them, and the teosinte goop has N-fixing bacteria in it too.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
So as best as we can figure, 1) Looks like maybe teosinte has always done this, at least in some places? 2) In most domesticated maize the goop roots were bred out. 3) But this Sierra Mixe maize was bred for EXTRA GOOP ROOT.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
So indigenous folks in this area managed to take a trait that had disappeared in most other domesticated maize* and dialed it up to 50, and who knows how long that took. *probably for reasons we'll talk about later
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
The other thing I wanna get back to is how it took 40 years to go from "this dirt sucks but that corn is huge, wtf are those goop roots, wait is this all related?" ...to an actual confirmation that these goop roots do in fact fix N as scientists have suspected for 40 years.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Proving that a plant/plant symbiote is fixing N is INCREDIBLY DIFFICULT. There's a million places N could be from (dirt, rainwater, bird poops, N-fixing bacteria in the soil, etc). You have to prove beyond a shadow of a doubt that the N is coming from the air & nothin else.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
I'm seeing 7+ ways they tested to be sure. Some highlights: • Checking goop for nitrogenase genes (enzyme that a lot of N-fixing bacteria use)- we couldn't even do this til the 2000's. • Testing goop to see if it has low O2 inside (nitrogenase needs low O2 to work). It does!
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
And my personal favorite, • ACETYLENE REDUCTION ASSAY Buckle up kids 'cause this test is the worst and we're gonna talk about the time I almost blew up a building doing it.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Ahhh the acetylene reduction assay. So one of the best ways to test "does this fix N?" would be give the thing some N2 and see if the thing turns that N2 into biomass.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Except that's a horrific pain in the ass, because almost the entire atmosphere is N2. Something something is this result really N fixation or are we just shit scientists who can't seal test tubes properly? It's too much drama.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
An easy* way around this: instead of N2, give the sample a hit of sweet, sweet acetylene. It's almost identical to N2. So most nitrogenase enzymes will go "eh fuck it" & break down acetylene too. It turns into ethylene, so if you get ethylene, YAY, you know there's nitrogenase.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
So the other thing about acetylene is it loves to explode. LOVES IT Flashback to an underground soil science project, in a basement lab, and I get there to feed the samples their acetylene at 11pm because fuck it, that's when science happens.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
I flip on the hood, turn on the gas, go to wait the requisite number of minutes. But before they're up I'm like "why does it smell like garlic in here" "OH GOOOODDDD THAT'S AN ACETYLENE LEAK" Switched off the gas, turned hood to max, fixed hoses, didn't. move. for like. 15 min.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
(if anyone asks "why were they having undergrads fool around w acetylene in the middle of the night in an underground lab?" all I can say is it was a soil science program that made milkshakes on the lab equipment 2-3x/year and was still teaching kids how to mouth pipette in 2005)
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
So anyway, just so you know, that's an acetylene reduction assay. That's the kind of bullshit these scientists had to do for FORTY YEARS to bless us with the knowledge of what this maize can do.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
More about the goop corn: • It's almost more like a mini-tree than the crop corn we're used to. It's 16' feet tall and takes 8-9 months to make ears (crop corn takes ~3-4 months).
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
• It miiiiight grow slow bc it's throwing so much sugar at its N-fixing bacteria? • That might be why goop roots got bred out of maize in most other areas. It was better to have a plant that grew & yielded quickly, & only at Sierra Mixe did they really need N-fixing. ...Maybe.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
• So yeah it's an awesome fit for poor soils in tropical southern Mexico, • But probably not gonna be a smash hit in most North American gardens anytime soon. • So curious to see what its kids & grandkids are gonna look like though.
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Dr Sarah Taber 8 Aug 18
Replying to @SarahTaber_bww
Finally, this tweet is evergreen
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