Genetic Maize - Navigating the maze of GMOs

As flood waters are receding or moving downriver, I have been wondering what is in the water. The health and environmental risks now faced by the flooded areas and beyond were ignored for a while, but seem to be coming out - notedly in a few AP and NPR stories. The CDC has an entire website devoted to health after a flood. The flooding all over Iowa is extensively covered by the Des Moines Register, but the one article on health issues is severely lacking, focusing on injuries instead of infection. Many ignore the environmental consequences.

Fecal bacteria from manure lagoons and sewers will reside in mud left behind by the floodwaters. People cleaning up debris are at risk of tetanus and other infections in scrapes and scratches. Residual water will be a breeding ground for mosquitoes that may carry West Nile and other viruses. And, of course, the mold will grow.

Topsoil has been washed away. Pre-emergent herbicides may have effects from from their intended fields. Nitrogen from fertilized fields and animal waste will flow downstream, likely not causing problems until reaching the Gulf (this has been covered by some news outlets but is typiclly and incorrectly blamed on ethanol, more on that in another post).

All this on top of the structural damage and destruction of public and private property…

I’m upset about my own field - but am thankful that this is the only way I’ve been affected by the floods.

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Monsanto’s press releases on Roundup Ready 2 Yield uses the term “advanced gene mapping and insertion process”. This sounds impressive, but what does it mean? A colleague asks: “can advanced gene mapping and insertion tech improve yield of the plant or would other factors like selection and crop physiology really be what’s improving yields?”

From the press release:

[David Nothmann, Monsanto’s Soybean Agronomic Trait Lead,] said Roundup Ready 2 Yield technology is based on an advanced gene-mapping and insertion process. “Through gene mapping, Monsanto has identified specific DNA regions in soybeans that have a positive impact on yield,” he explained. “Using these new insertion and selection technologies, the Roundup Ready 2 Yield gene is situated in one of these DNA regions.”

There has undoubtedly been decreased yield in Roundup Ready crops when compared to conventionally bred crops. This has two possible causes: lag “a temporary or transient problem associated with the introduction of a new technology” or drag “an inherent yield reduction associated with the technology itself”. There is a lot of evidence that the problem is in fact lag, but more research must be done. Some of the issues are discussed in Challenges in Comparing Transgenic and Nontransgenic Soybean Cultivars.

I covered the topic of yield lag/drag somewhat in my post Exposed, Indeed.

GM seeds are often “one hit wonders” that excel in one specific trait, but not particularly for increased yield. Non-GM lines, on the other hand, are improved every year, with the best yielding plants being used to produce the next year’s seed. I recently attended a seminar presented by a scientist from Pioneer where he said that they were working to develop better yielding lines that would work in conjunction with their primary transgenic traits. The companies are aware that this is a problem with their products, and are of course working to solve it, to avoid losing sales.

Back to the question at hand - as I understand it, advanced gene mapping is a selection tool.  The companies start with huge experimental fields (much larger than what an academic lab can afford) in multiple locations with different climates that include many varieties of the crop in question. They measure yield and determine genetic markers* for each variety/location combo, using known markers for yield as the starting point. The researchers are then able to see which varieties do and do not have certain markers. They cross varieties that have different markers, with the goal of a super high yielding plant that has all of the markers that are positively correlated with yield and none of the markers that are negatively correlated with yield. They have fields in multiple locations so they can choose the markers that confer an advantage in a variety of climates - ensuring that the plants will perform no matter what the location or conditions. There are a lot of benefits of this method over blind selection, the biggest of which (in my opinion) is that you don’t have to know what’s happening physiologically in the plant. Knowing what each gene does (and what each mutation to each gene does) is nice, but really not necessary for the purpose of breeding bigger better plants.

As for the “insertion process” part, I admit that I’m not 100% sure why positioning the insertion in an area of the genome that is correlated with high yield would matter (any readers who know, feel free to enlighten me!). I can think of a few reasons why the specific position of the transgene insertion does matter, but all of them are part of the normal process running up to a marketable genetically engineered crop. In fact, I’m in the process of some of those stages right now. Once the gene of interest is chosen, a compatible promoter must also be chosen. I imagine that a constitutive promoter (always on, in every cell) would be used for the glyphosate resistance trait. The gene construct is introduced into many plant cells that are then grown into individual adult plants. Each introduction is called an event. Each event is treated separately because the position of insertion is different each time. When the insertion lands in the middle of a gene, it can stop the gene’s normal expression - so many events are investigated to see which ones have the least effect on the plant’s normal gene expression while at the same time producing the desired trait. A video on Monsanto’s website says that they used Agrobacterium instead of biolistic transformation in RR2 because it is “gentler”, causing less damage to the surrounding DNA. They then screened many events using genetic markers to find the best ones - an expensive process that (to my knowledge) has not been done before. They say that having the insertion in one of the areas near a marker for high yield increases yield an additional 7 to 11 percent.

Edit: I don’t know why I was having a mental block on this! What I said in the last paragraph stands but I’ve figured out why having the insertion in a high yield correlated area would matter. If the insertion is near an allele for a gene that is correlated with poor yield, selecting for the trait of interest would bring along the area that you don’t want. Having the insertion in a  “good” area of the genome (assuming that it isn’t actually interrupting any genes) eliminates this problem.

*Here, markers basically correspond to alleles of a gene. Wikipedia has a decent explanation of genetic markers, but unfortunately requires the understanding of much more jargon. If you’d like a more detailed explanation of genetic markers, please let me know, and I will be happy to write a post on the subject.

Raymer, PL and TL Grey (2003). Challenges in Comparing Transgenic and Nontransgenic Soybean Cultivars. Crop Science, 43, 1584-1589.

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Monsanto has had a few press releases lately that show they are working hard to change both their image and their products. The biggest by far is their three-point commitment to growing yields sustainably.

Develop better seeds - Monsanto will double yield in its three core crops of corn, soybeans and cotton by 2030, compared to a base year of 2000. The company will also establish a $10 million grant designed to accelerate breakthrough public sector research in wheat and rice yield.

Conserve resources - Monsanto will develop seeds that will reduce by one-third the amount of key resources required to grow crops by the year 2030. The company will also join with others to address habitat loss and water quality in agriculturally important areas.

Help improve farmers’ lives - The company will help improve the lives of farmers, including an additional five million people in resource-poor farm families by 2020.

The first two are good, but we expect improved seed from a seed company. I’m particularly interested in the third point. The press release tells us that “Monsanto also is committed to sharing its expertise in a way that gives [resource poor farmers] access to modern agricultural technology.” For example, “drought-tolerant maize for Africa that will be made available to farmers royalty-free.” Players include AATF, CIMMYT, the Bill and Melinda Gates Foundation, the Howard G. Buffett Foundation, and government researchers from Kenya, Uganda, Tanzania and South Africa. “Monsanto will also work with public institutions to develop products for non-commercial crops that are important in some world areas, including cassava, cowpea and papaya.” Some comments on the press release can be found in the NY Times Monsanto Seeks Big Increase in Crop Yields.

Improving the world’s food supply and keeping things as sustainable as possible is going to be difficult, and will require everyone working together. The Financial Times has a two part article about the history of the last Green Revolution and explains why the next one will be so much more difficult (see image below). Monsanto is simply one of the few organizations with the tools and the funds to make things happen, and with the correct dialogues, the advances will be good for people and for the environment.

Of course, the company isn’t perfect, and setting high goals isn’t the same as meeting them - but it’s time that GM opponents let go of the whole “Monstersanto” schitk. We need to have adult conversations about the real issues surrounding genetic engineering, not just sling insults at one company.

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It’s official. I won’t be able to plant any maize this year. My field seemed to be be ok at first, but now the flooding has spread. We can’t even get to the field because the road is flooded as well. I can’t tell you how happy I am that we waited to plant - if we had rushed, all of the seeds would have drowned. This image of what used to be a cornfield and is now a lake was taken by me on Thursday at about 9:30am. For more, see my Facebook album (no login required).

The field might dry out next week, but it’s really too late to plant because we’re almost past the summer solstice. The maize seedlings need to experience lengthening of days before shortening of days or they don’t grow properly. So, plan B is the greenhouse, where I can control day length with lamps.

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One of my research projects is to look at maize storage proteins (aka zeins) in a variety of modern corn varieties, landraces (older varieties), and teosinte (a maize progenitor in the same genus). See my post Teosintes are a puzzlebox of genes for more info.

Now, I’m adding another angle - Tripsicum ! I was talking to Sue Duvick of the USDA about my project (since I am using her lab’s HPLC after all) and she told me about her work making crosses between maize and Tripsicum in a search for improved grain quality.

Members of the Tripsicum genus are closely related to members of Zea genus. They’re all part of the tribe Maydeae in the subfamily Panicoideae. It’s such an important source of germplasm that the USDA ARS has been collecting Tripsicum samples along with maize and teosinte for safekeeping.

Sue was kind enough to provide me with seed samples to analyze. From the left is Tripsicum seed and seed capsules, a Tripsium and maize F1 hybrid, and two set of seeds that are mostly maize but derived from the F1. For comparison, on the bottom are teosinte and B73 (a typical maize inbred). Adult Tripsicum is a bunched perrenial grass, as you can see from the photo.

For some very interesting info on cross-generic hybrids, see the discussion at GardenWeb. There is even some specific discussion of maize x Tripsicum crosses. For example: the cross is “very easy if you carefully remove the husks, shorten the silks to about 1.5 inches, pollinate with Tripsacum pollen, then wrap the ears with paper while the seeds develop. The problem in the cross is that Tripsacum pollen doesn’t have enough “stuff” to grow pollen tubes the full length of the Maize ear. Shortening the silks solves this problem. …other results indicate that the best way to breed Tripsacum traits (such as pest resistance) into Maize is by first crossing Tripsacum with Zea diploperennis, then crossing these hybrids onto Maize.”

Gamma grass image from Sticks and Stones Nursery. Original Caption: “EASTERN GAMMA GRASS (Tripsicum) - Warm-season, rhizomatous bunch perennial grass. Spreads slowly. Height 5′-9′. Site-open, moist, well drained. Choice grazing for livestock and wildlife. Used for hay, cover/nesting, and erosion control. Hardy in zones 5 -10. American native.”

Seeds image taken by me. Grid is 0.5 cm.

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