Tag Archives: maize

Maize.

Researchers hack corn to grow fatter and absorb more carbon dioxide

An international team of researchers wants to level up corn by boosting its ability to capture CO2 from the atmosphere.

Maize.

Image credits Juraj Varga.

Corn (or maize) is a fruit and one of the most important staple foods on the planet, exceeding even rice or wheat in quantity grown per year. However, in Australia, while corn has the widest geographical spread of all field crops, it lags behind its counterparts (such as wheat or rice) in yield.

One of the main issues maize has to grapple with in the land down under are harsh environmental conditions. In a bid to help the crop bloom to its full potential, an international team of researchers has been toying with its genome, to boost the plant’s ability to photosynthesize.

Sunny maize

“We developed a transgenic maize designed to produce more Rubisco, the main enzyme involved in photosynthesis, and the result is a plant with improved photosynthesis and hence, growth. This could potentially increase tolerance to extreme growth conditions,” said lead researcher Dr. Robert Sharwood from the ARC Centre of Excellence for Translational Photosynthesis, led by The Australian National University (ANU).

While all plants rely on photosynthesis to capture carbon dioxide from the atmosphere, they go about it in different ways. Plants like wheat and rice use an older and less efficient photosynthetic path (the ‘C3’ path), while other plants such as maize and sorghum use the more efficient C4 path.

Some of the most important food crops today (as well as many that are used for animal feed and biofuel production) rely on the C4 pathway. C4 plants are specially adapted to thrive in hot and dry environments — ones that are expected to be more prevalent in future decades.

“There is an urgent need to deliver new higher-yielding and highly adapted crop species, before crops are affected by the expected climate change conditions. These conditions will increase the threats against global food security, and the only way to prepare for them is through international research collaborations.”

One of the molecules that underpins photosynthesis is an enzyme known as Rubisco — which converts CO2 into organic compounds. Rubisco’s activity is much improved in C4 plants, making the process faster and more water-efficient. As a result, these plants are more tolerant to heat and drought, and tend to be more productive than their C3 counterparts. Maize has one of the most efficient Rubisco enzymes and uses “less nitrogen” to grow than other crops.

“So, our main question was, if we increase Rubisco content in maize, what would it do for the plant?” says co-author David Stern, from the Boyce Thompson Institute.

“We found that by boosting Rubisco inside the maize cells, we get an increase in crop productivity,”

Overall CO2 assimilation and crop biomass increased by 15%, the team reports. While quite excited with their results so far, the researchers plan to further increase the “pool of active Rubisco” in the plant to increase this percentage even further. Until then, however, they hope to pit their maize against real-field conditions — the crop has, thus far, only been tested in glasshouse and cabinet conditions.

However, if the team’s maize proves itself hardy enough to survive farmland, it could pave the way for further C4 crop species to receive the same treatment.

The paper “Overexpression of Rubisco subunits with RAF1 increases Rubisco content in maize” has been published in the journal Nature Plants.

Crops employ “austerity measures” to conserve water in drought conditions

A new study of plant roots found that grasses employ a type of “economic austerity” when confronted with drought conditions: the plants limit their root systems’ growth to preserve water in the soil. The discovery could potentially be used to improve crop yields.

Image credits Chris Devaraj

The world’s population has been growing rapidly over the past few decades, and this trend is not going to stop any time soon (see this and this.) The last thing you would want in this scenario is a shortage of food — which is exactly what scientist expect will happen. Seeing this, researchers from Carnegie Mellon University published a paper aiming to understand how agriculturally valuable plants react to drought.

Plants draw most of their water from soil, through their roots. However, not all plants have the same kinds of roots — the study examined grasses, a family which include key species of plants including maize, sorghum and sugarcane. Grasses rely on crown roots to extract water, a type of root unique to this family, which grow down from the regions of the shoot at soil surface (an area known as the crown, hence the name.) The root system starts to form after sprouting and continues to develop throughout the plant’s life.

Maize seedling with crown roots beginning to grow from the base of the shoot (red arrow).
Image credits Jose Sebastian

“Crown roots are like the lanes of a highway connecting the suburbs to the city. As the plant grows, new lanes are added to this highway to increase the flux of water and nutrients from the soil to the shoot,” explains Jose Sebastian, post-doctoral fellow at the Carnegie Institution for Science, and lead author of the study.

The effect of drought on crown root development was poorly documented up to now, so researchers had no way of estimating how the plants would react to a hotter and drier climate. The team, led by José Dinneny, was able to prove that water shortages causes the grasses to suppress crown root growth.

Their results show that the crown is crucial for sensing water availability in the topsoil. If water is scarce, the development of crown roots is suppressed and the grass plant maintains a more limited root system, the team found.

“We normally think about roots as providing access to water, thus it was initially unclear why a plant would shut down root growth under drought,” Dinneny explained.

“We discovered, however, that this response allows the plant to slow the extraction of water from soil and bank these reserves for the future; sort of like the plant version of economic austerity.”

These “austerity measures” are only employed when water is scarce. If moisture is reintroduced into the soil, crown root growth is quickly resumed, so the plant can take advantage of all available water. The team also determined that this suppression is much less pronounced in domesticated grasses such as maize and millet than in wild varieties.

“This suggests to us that plant breeding has unintentionally affected these crop plants’ abilities to cope with drought,” Dinneny said.

Artificial selection or agricultural plants such as maize or other grassy crops aimed at tailoring crown roots’ response to drought could improve these plants’ productivity and preserve ground-water resources.

The full paper, titled “Grasses suppress shoot-borne roots to conserve water during drought” has been published online in the journal PNAS.

Genetic tweak makes plants produce enzyme-replacing drug

Culturing mammalian cells is currently the only way to make some complex proteins used in certain drugs; but growing such cultures is an extremely difficult and delicate job, because they can harbor human pathogens and must therefore be kept under strict temperature conditions.

It’s a difficult job, but it’s definitely worth it; take a look at the rare lysosomal storage disease mucopolysaccharidosis I, for example – it’s as dangerous as it sounds, and it’s only treated with enzyme-replacement therapy. The enzymes must be produced in cells and this brings up huge production costs, which means, of course, very high costs, going up to hundreds of thousands of dollars a year.

This is where Allison Kermode, a plant biologist at Simon Fraser University in Burnaby, Canada, stepped in. Her husband works with people who have lysosomal storage disorders, and she decided to find a way to manufacture the necessary enzymes in plants – maize (corn) to be more precise. The thing is, you can insert human enzymes in plants, but they will be ‘decorated’ with sugar molecules specific in plants – but Kermode and her colleagues found a way to avoid these decorations.

The team tweaked the genes responsible for the production of the protein, not to alter the production itself, but to prevent the proteins from moving into the Golgi complex, a structure where the problematic sugars are added. The Golgi apparatus, as it is already known packages proteins inside the cell before they are sent to their destination; it is particularly important in the processing of proteins for secretion. The approach has been described as ‘very elegant’ by biologists.

It has to be said, we are still pretty far away from putting these drugs on the shelves, but Kermode’s research has proven to be functional, even though the resulting enzymes haven’t been tested on humans. The team also needs to ensure that the seeds produce the protein in higher quantities, but if all goes well, and there’s no reason to believe it won’t, maize may one day become the go-to way to make complex protein drugs.

Source: Nature Commun