James and the Giant Corn Genetics: Studying the Source Code of Nature

November 24, 2009

Summary of the Coverage of the Maize Genome here at J+TGC

Filed under: Genetics,Link Posts,Site Business — Tags: , , — James @ 10:47 am

Summarizing a couple of Virginia Walbot’s ten reasons you should care about the maize genome

Hear one of the lead authors of the maize genome paper explain how and why it was done in under four minutes.

Reviewing the quality of the genome sequence itself.

We can already see research made possible by the maize genome.

How maize fits in the family tree of grasses/grains

Read about how the maize genome project is helping researchers find more genes selected for during the domestication of maize.

Plants have more genes than people, why is this still news

Other people on the web react to the maize genome (also why different colors of corn are not different species)

Corn vs Maize

Filed under: Genetics,research stories,Site Business — Tags: , , — James @ 10:46 am

I use the words basically interchangeably on this site. I know it’s confusing and I at least attempt to pick one and use it all the way through a post (often without success, which I’ll catch, and wince at, days later). The problem is that naturally I use one word or the other depending on context.

The plant in question is studied internationally and while in America “corn” means those cool looking plants that you see me standing in front of one third of the time when you visit this blog, in british english the same word means any grain. I’ve never heard it explicitly said, but I assume the reason the geneticists who study the plant originally called it maize was to avoid confusion from those mixed definitions. It’s also possible “corn” was still considered a slang term back then, and not the sort of name a well educated scientist should be using regardless.

As a result of growing up in the midwest surrounded by corn and getting interested in comparative genomics by way of maize genetics, terms like “corn geneticist” and “corn genome” don’t sound right to my ear and ones like “maize plant” or “maize is selling for $5 a bushel” sound even worse. On the other hand, the sentence “Sequencing the maize genome is going to provide even more powerful tools to corn breeders” sounds fine, but I realize it can be confusing to people whose life experiences are different from my own.*

*An even weirder one: Back when I was still doing science that required writing with pen and paper instead of doing everything on the computer, without thinking about it I’d either cross my sevens or not depending on whether I was writing a number in a scientific context.

A crossed 7. Theoretically this is easier to distinguish from a 1, especially on tassel bags and row stakes that are going to be outside, exposed to the elements for months.

A crossed 7.

Theoretically a crossed 7 is easier to distinguish from a 1, especially on tassel bags and row stakes that are going to be outside, exposed to the elements for months. (And where a mistake has the potential to ruin a year or years of work. It’s not like maize geneticists can run down to Walmart and buy more seeds carrying the genotypes they’ve spent years putting together.)

November 23, 2009

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. (more…)

November 20, 2009

Bloggers on the Maize Genome

Filed under: Genetics,Link Posts,Plants — Tags: , , , , — James @ 3:31 pm

Update: PolITiGenomics just posted a piece on the corn genome as well.

You know I could keep talking about the maize genome all day (and I may very well do just that), but what are other bloggers saying about the most complicated plant genome ever published, of second most important single species for feeding people around the world? (Clearly I’m not at all excited) (more…)

Maize: The Genome Sequence Itself

Filed under: biology,Genetics,Plants — Tags: , , , , — James @ 1:45 pm

The corn genome is ~2.4 gigabases (2.4 billion As, Ts, Cs, and Gs) divided among ten chromosomes. The genome of sorghum, the most closely related species with a sequences genome to maize, is also divided into ten chromosomes, but it’s only less than 800 megabases long, approximately a third the size of maize.

What accounts for the size different? Well since their divergence, maize went through a whole genome duplication, doubling it’s genome to twenty chromosomes (which have since been reduced to ten again, as pieces of chromosomes broke apart and stuck to each other*). Since then a bunch of deletions have also occurred, so only sometimes like 20-30% of the genes from the ancestor of maize and sorghum can still be found in both duplicated regions. Clearly the genome duplication of maize is not responsibly (or at least not solely responsible) for the the enormous size of the maize genome. (more…)

About the Maize Genome Paper

Filed under: biology,Genetics,research stories — Tags: , , , — James @ 11:23 am

Looking at the maize genome paper in isolation it’d be easy to wonder what all the fuss was about. The paper itself is only four pages long with (plus a page of citations), with two figures, and as awesome as figure 1 is (and it really is very, VERY awesome), it doesn’t seem like an lot for a project that represents the work of more than 150 authors over four years. But the real fruits of the maize genome project are the sequences that can be found on either maizesequence.org or maizegdb.org and additional exciting research it is already enabling. And as the result of a quirk the way genome sequence is released to the research community, we can already get a sense of some of that other research. (more…)

The Family Tree Of Corn

Branches not to scale. Tree designed in Mesquite.

Branches lengths not remotely to scale. Tree designed in Mesquite.

This family tree shows the relationship of a few of the species in the grass family tree that I think people might be most familiar with. Genomes that were published before today are marked in green (there were only two, sorghum and rice), the maize genome which was just published today is marked in yellow, and brachypodium (which you shouldn’t feel at ALL bad if you haven’t heard of) is marked in grey as its genome project is in the final stages (a draft assembly was released to the public last winter) so it’ll probably be the next grass genome to be published. After that I’m less sure, I know there’s a foxtail millet genome project, but I don’t have any idea how far along the process of genome sequencing, assembly and annotation the genome project is.
What’s important to know about the relationship of the sequenced grasses? (more…)

Patrick Schnable on the Maize Genome

Filed under: Genetics,Plants — Tags: , , , , — James @ 1:25 am

Let me know if you have any trouble with the embedded video. The embedding code from ISU doesn’t seem to play well with wordpress.

I’ve got several posts on the maize genome coming out scheduled to go up later today. Living on the west coast (not to mention having a circadian clock that seems convinced I should actually be living on Honolulu time) it’s the only way to get information up in time for morning readers in most of the US.

Anyway, hopefully some of what I’ve written makes sense (I’ll be running a lot of long computational jobs at work so I’ll have plenty of time to answer questions in the comment sections about all the stuff I’ve written that doubtless makes no sense at all). But to start us off this morning, how about a short (<4 minutes) video from Patrick Schnable one of the two lead authors on the maize genome paper. After four years of talking about the corn genome project as well as it’s challenges and benefits, one gets very good at it.*

[flowplayer src=http://www.ag.iastate.edu/video/media/52/Sequencing_the_Maize_Genome.mp4]

See the video in it’s original context here. I’m assuming since ISU provides embedding code they’re ok with me showing it here.

*Fair disclosure, there are important reasons I may be biased in my evaluation.

November 19, 2009

Why should you be excited about the corn genome?

Filed under: food,Plants,research stories — Tags: , , — James @ 5:36 pm

Virginia Walbot has ten reasons in the latest issue of PLOS genetics. PLOS journals are all open access so anyone can read it without a subscription.

The two reasons I think will be the most interesting to non-biologists are #1 and #10:

Corn was domesticated a short 10,000 years ago and domestication is normally a huge genetic bottleneck that results in the loss of much of the gene diversity found in the wild ancestor. (Modern tomatoes are more diverse than heirlooms because breeders are intentionally working to bring some of that diversity back over.) Yet two lines of corn, which certainly shared many common ancestors in the last 10,000 years, contain more genetic differences than humans and chimpanzees which have been evolving separately for 3.5 MILLION years. That’s 10,000 years vs 3,500,000 years!

Number ten drives home how essential corn is to the world today with statistics like American farmers growing so much corn last year than it works out to a metric ton for every man, woman, and child in this country. Or that corn and cornfeed animals feed a billion people around the globe (those aren’t rice numbers, but hopefully it drives home why corn has definitely earned it’s place as one of the big three grains that support civilization around the world).

h/t to the beekeeper (who I haven’t see around the blog in months) for pointing me at this PLOS genetics coverage of the maize genome papers coming out both there and in Science.

Corn Genome

Filed under: biology,Genetics — Tags: , , — James @ 3:25 pm

So I was mixed up and didn’t think this could be publically mentioned until tomorrow, but the finalized corn genome has come out. Edited this link to point to the ISU coverage which seems to be more detailed than the release from Wash U. If Wash U can mention it, so can I. Expect tomorrow to be a day of corn here at Jamesandthegiantcorn (though it would have been more fun if I could had started the day of corn before this news was publically announced.)

Lots of corn … and maybe some genomics. Consider yourselves forwarned!

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