James and the Giant Corn Rotating Header Image


How many maize/corn genes have actually been studied? (Not a lot)

When the maize genome paper came out last November (see the summary of this blog’s maize day coverage) it included information on 32,690 genes within the maize genome.  These were the genes which the researchers involved in sequencing the genome were very confident really were genes. And by themselves those 30,000+ genes put the maize genome way ahead of our own. Of course EVERY plant genome ever sequenced has contained more genes than we do, so you’d think by now this wouldn’t be news any more. We’re not the most genetically complex creatures on the planet, and we’ll just have to learn to live with that fact.

But where was I? Oh yeah, gene counts. 32,690 high confidence genes*. Of those, how many have been studied individually? (more…)

Plant Links of the Day: Diverse Citrus, Extinct Cucurbits, and more

When I woke up (which yes, was only a couple hours ago, but remember I’m on pacific time) I found a whole bunch of interesting plant links waiting in my RSS reader, and I thought I’d pass along a few to you guys.

Keith Robinson writing over at Omics! Omics! posted Celebrating Citrus where he catelogs some of the diversity available to him from local grocery stores before pointing out a citrus review article that suggests all that diversity can be traced back to only three wild species and wraps it up by pointing out the project to sequence the sweet orange genome.

Imagine if you could have a whole series of clementine-like fruits, with the size & easy peeling characteristics but with the whole range of other citrus flavors and colors genetically grafted in — cara cara clementines and blood clementines and ruby red clementines and perhaps even sweet lemontines and key clemenlimes.

Highly recommended.

The Biogeography of Darwin’s Gourd is a post I discovered through research blogging (speaking of which I should really write another entry that meets their standards some day). The gourd of the title is Sicyos villosus, a cucurbit (the group of plants that includes squashes, melons, and pumpkins) collected by Darwin from one of the islands in the Galapagos the better part of two centuries ago … and never again recorded by science. At this point the dried sample collected by Darwin may be the only existence the species ever lived:

The analysis of the cucurbit’s DNA, extracted from the seed samples taken by Darwin, revealed that S. villosus is closest in relation to cucurbits in North America and Mexico. The species probably diverged roughly 4 mya, when the Galapagos were still geologically young. Dispersal was not human in origin, meaning long distance from the mainland, potentially from its spiny fruits stuck to birds, the authors suggest.

How cool is it that we can learn so much from a single sample of a species that has otherwise vanished from the earth?

Finally, by way of DailyKos, comes a pointer to this valentine’s day themed article, clearly written for the non-scientist, where a summary written by me seems superfluous given the title: Sex, Drugs, and Paleo-botany! And yes, the exclamation point is in the original title as well.

The Taste of Tomatoes + Tomato Mutagenesis

An anonymous indian tomato vendor in Chennai, Tamal Nadu. photo mckaysavage, flickr (click to see photo in it's original context)

First, since I didn’t explicitly state it in my previous post, the paper on the longer lasting tomatoes developed by India’s National Institute for Plant Genome Research didn’t report any data on how the RNAi knock-down tomatoes actually taste.* The tomatoes are nearly twice as firm as tomatoes in which these genes are NOT knocked down, so it’s possible they’d seem unpleasantly crunchy, I don’t know how doubling the firmness of a tomato translates into the feeling when a person bites into one.

On the other hand, if the tomatoes do turn out to be tasty and delicious, it’s quite possible the trait could be replicated without genetic engineering. And if that turns out to be true, it’s absolutely the approach anyone developing longer lasting farmers to Indian farmers, or farmers anywhere, should take (for why I’m saying this, check out the bit in bold further into this post). (more…)

Scientists at India’s NIPGR Create a Longer-Lasting Tomato (Studying The Regulation of Fruit Ripening)


Author’s note: This would seem to be the week for vegetables I hated as a kid. Yesterday was onion, today tomato, if there’s a story about brinjal/eggplant in the next few days we’ll have hit all the big ones. 😉

Ripening tomatoes. Photo: Photos_by_Lina, fickr (click to see photo in its original context)

I was recently pointed to an early publication paper that went up on the Proceedings of the National Academy of Sciences website on Monday, where a research group at India’s National Institute of Plant Genome Research describes two genes from tomato that, when knocked down by RNAi*, result in tomatoes that can remain ripe but not spoiled for up to three times as long as tomatoes where these two genes function normally.

Their approach targets specific genes involved in breaking down certain proteins found in the cell walls of tomatoes (in fact in the cell walls of all plants). Breaking down the cell wall is a key part of ripening in fruits (which the tomato is, botanically if not culinarily). Which makes sense if you’ll think about it for a moment. One of the traits we associate with ripening is getting softer, from bananas to peaches if it’s still crunchy when you bite into it, it wasn’t ripe. What makes plants stiff and crunchy? The strength of their cell walls. Since, unlike vegetables, fruits WANT to be eaten**, as they ripen they begin to break down their cell walls to make themselves more appealing to passing animals. Unfortunately, ripening and spoiling are, in a lot of ways, the same process. If fruits aren’t eaten when they become ripe, they continue to get softer, transitioning from delicious looking -> unappetizing -> inedible -> a puddle of mush on your kitchen counter.

Preventing ripening entirely is relatively easy, and there are plenty of known mutants in tomatoes and other species that never ripen (these naturally mutant tomatoes stay green and hard no matter how long you wait). But getting part of the way to ripeness but stopping before crossing the line into spoiled is a much less tractable problem. (more…)

We got to genetics in class today and the story of the shrunken 2 gene

Arabidopsis that carries broken copies of both the AP1 (apetala1) and CAL (cauliflower) genes. The flower bearing stems have been replaced by these cauliflower-head-like growths. Image from "Genome-Wide Analysis of Gene Expression during Early Arabidopsis Flower Development" by Frank Wellmer et al (in PLOS Genetics a creative commons licensed journal). Article here: http://dx.doi.org/doi:10.1371/journal.pgen.0020117

Just in time for me to put together my worksheet for Thursday! I’ve managed to work in the CAL gene, which I talked about last week in my discussion of Cruciferous vegetables:

Cauliflower plants (and broccoflower plants) have broken copies of the CAL gene, which (when it isn’t broken) is helps the plant decide to switch from producing stems that were bear flowers to the flowers themselves. Without a functional version of CAL, cauliflowers just keep making denser and denser stems, producing the distinctive heads of cauliflower. If you have journal access, you can read more about the CAL gene at this science paper: http://dx.doi.org/10.1126/science.7824951

I also threw in a question that uses the shrunken2 gene (one of the two most common genes that convert normal starchy corn into sweet corn). From the question in question:

Note the shriveling of the yellow kernels that carry two broken copies of the shrunken2 gene, the purple kernels carry either one broken and one working copy of shrunken2, or two working copies. The change in color is controlled by another gene nearby on the same chromosome, shrunken2 itself has no effect on the color of corn kernels. Photo credit goes to MG Neuffer and MaizeGDB.

Corn kernels without a working copy of the shrunken2 gene can’t convert very much of the sugar provided by photosynthesis in the leaves of the corn plant into starch. Instead, sugar itself accumulates in the kernel making the corn taste quite sweet.

When sugary corn kernels are dried, they shrivel up, while starchy ones remain relatively round and smooth. This has to do with the fact that sugars are water soluble while starch is not. So, as I understand it, corn kernels with more sugar are also a greater percentage water than corn kernels that are made mostly of starch.

The mutant form of shrunken2 was identified by John Laughnan, a maize geneticist at the University of Illinois Urbana-Champaign. The story of the discovery as told in Maize Genetics and Breeding in the 20th Century by Peter Peterson and Angelo Bianchi: (more…)

A new plant (in the apartment, not the world)

A christmas gift from my folks that only just arrived:

I don’t believe people can identify this plant from this picture, but just in case someone wants to take a shot at it, I won’t reveal the answer until below the fold. (more…)

“New” Cruciferous Vegetables

A stalk of brussels sprouts photo credit: cbmd, flickr (click for photo in original context)

Last week Greg over at Pie-ence was talking about the amazing variety of vegetable crops breed out of a handful of species within the genus Brassica, specifically Brassica rapa and Brassica oleracea.* I’m referring to these as cruciferous vegetables, which is actually a wider category including all the vegetables within the mustard family of plants (scientifically this is called the Brassicaceae). But one of the cool things about having so many kinds of vegetables within the same couple of species is that, because they’re the same species, they can still be interbreed with each other to create “new”** vegetables. (more…)

Genome Sequencing vs Genetic Mapping

There was a recent paper in Science about the mapping of the Artemisia annua genome. I’ve seen several people interpret this as another genome sequence. It’s hard to blame anyone for this confusion given headlines like “Scientists map the maize genome!” to describe the sequencing of the maize genome. So what’s the difference between a sequenced genome and a mapped genome? I’m glad you asked! (more…)

The Newly Published Soybean Genome and Fractionation

Here’s the key statistic: The maize genome paper estimated that roughly a quarter of maize genes are currently retained as duplicate pairs from maize’s whole genome duplication, while the soybean paper estimates just over half of soybean genes are similarly retained after soybean’s (apparently slightly older) duplication. <– had it buried at the end of this, but figured it’d be more fun to start out with something cool.

But first of all, let’s do this the right way this time. Here’s the paper in Nature describing the soybean genome. Here’s one of the places you can download the entire sequence from. Hopefully that establishes, beyond a reasonable doubt, that the soybean genome has, in fact, been published. (more…)

Strawberry Genome Sequenced (Correction included)

After already needing to correct this post, I must now invalidate the whole thing. Seems I’ve been taken in by a premature press release that was turned into reliable sounding articles on news sites and was then picked up by blogs like mine that took the those sites to be credible sources. It’s a big mess. ::sigh::

Among the many things I’m currently missing at the Plant and Animal Genome conference, in addition to an update on the banana genome I’ve just learned (thanks to Mary over at OpenHelix) that the sequencing of the woodland strawberry genome has been completed!

I don’t know yet if the sequence has been released to the public yet. Either way I can’t find the sequence so I can’t yet comment on the quality of the sequence, or any ancient duplications in the lineage (though we already know it must share the ancient hexaploidy of the rosids, possible all eudicots).

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

What we do know is that modern domesticated strawberries are octoploid, the result of two recent whole genome duplications, but the woodland strawberry doesn’t have any duplications modern enough to be obvious from cytogenetics, visually looking at chromosomes.

Sequencing a genome is a complicated process but it started out with the work of Janet Slovin, a USDA scientist who created the inbred line* used in sequencing and seems to be the front woman from the project (Janet was kind enough to comment and point out the original article was misleading on this point, check out the link she included as well!), she’s quoted in the linked article.
And if you know how I can get my hands on the sequence please PLEASE, drop me a line at jcs98 (at) jamesandthegiantcorn (dot) com.