agriculture biology Genetics Plants

The Domestication of Maize

Twenty thousand years ago, not a single crop species existed in its current form. Almost* every bite of food you eat today is the result huge amounts of human artificial selection, both unconsciously and intentionally by farmers and plant breeders. Sometimes the obvious changes are minor, for example between wild and domesticated strawberries:

Wild strawberry (left) and domesticated strawberry (right)
Wild strawberry (left) and domesticated strawberry (right)

Clearly one of the major traits early strawberry growers selected for was bigger fruits. Which makes sense since it takes about the same amount of time an effort to pick a strawberry either way, but if you’re picking the ones on the right you’ll have more pounds of fruit picked at the end of the day.

But even in this case, the similarity in form hides major changes at the genome left. Strawberries went through two whole genome duplications during domestication (looks like it’s more complicated than I made it sound see comments), so each of the cells in the strawberries on the right contain eight copies of each chromosome, while the strawberry on the left contains the more standard two copies of each chromosome.

On the other end of the spectrum is maize.

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Transmitting DNA sequences to the stars

It’s a gloriously non-sensical project. To mark the 35th anniversary of the Drake-Sagan transmission, a guy named Joe Davis flew down to Puerto Rico and used the Arecibo radio telescope* to transmit the genetic sequence that encodes for the protein rubisco** to three nearby stars. While covering some awesomeness (using the most powerful radio transmitter on the planet to broadcast signals into space from an iPhone), and some criticisms (what is a DNA sequence going to mean to extra terrestrial life that almost certainly won’t contain DNA and absolutely wouldn’t use the same sequences to encode for the same amino acids), the author left one key question unanswered. Which plant’s rubisco sequence was shouted out to the cosmos?

Fortunately he posted the sequence here, and using BLAST it was easy to identify the gene as belonging to Nicotiana tabacum. The tobacco plant. Seriously? The gene that encodes for the rubisco protein is one of the more widely sequenced plant genes out there, as differences in the sequence are often used to study the relatedness of different plant species. He could pick from the sequences of organisms ranging from coconut to corn, from ferns to redwoods and the most worthy plant that came to mind was tobacco?

Oh well.

*Another awesome bit of science operated by Cornell

**Rubisco is the plant protein that plants use to grab CO2 molecules out of the air to turn into sugars. Providing us with both clean air and food to eat. It’s actually not very good at its job, which is why plants have to make so much of it. So much, in fact, that it truly is the single most abundant protein on the planet.

C4 plants like corn, sorghum, and sugar cane have actually redesigned their leaves and the way they do photosynthesis to get around the failings of rubisco.