Journal: Plant and Cell Physiology

Over the years, the domestication of grasses like wheat, rice, barley, and sorghum for consumption has resulted in certain modifications to their morphology. One such modification is the partial or complete elimination of the ‘awns’, which are the bristle- or needle-like appendages extending from the tip of the lemma in grass spikelets. The awn protects the grains from animals, promotes seed dispersal, and helps in photosynthesis in grasses like barley and wheat. However, its presence also hinders manual harvesting and reduces its value as livestock feed, explaining its elimination during domestication.

 

In the past, genetic studies have revealed the mechanism underlying awn development in crops such as rice and wheat. These indicate the possibility of the existence of complex and distinct genetic networks controlling awn formation in a species-specific manner. In fact, the existence of an awn-inhibiting gene in sorghum was identified in 1921, but remained uncharacterized thereafter. Now, a group of researchers—led by Prof. Wataru Sakamoto of Okayama University and including Prof. Hideki Takanashi of the Graduate School of Agriculture and Life Science, Tokyo University—has finally shed light on this subject. Their research was published in Plant & Cell Physiology on 30 May 2022.

 

Justifying the rationale behind studying awn inhibition in sorghum, Prof. Sakamoto says, “Sorghum is an important C4 crop for high biomass and bioenergy. It has a high tolerance to drought, besides being the fifth largest cultivated cereal crop. Also, it is a morphologically diverse crop with a relatively small genome size, making it suitable for genetic studies in various agronomical traits.”

 

For the purpose of this study, a recombinant inbred population derived from a cross between “awnless” (BTx623) and “awned” (Takakibi NOG) sorghum varieties was created. “The prospect of gene hunting in sorghum using the population we generated for the last ten years was motivating”, comments Prof. Sakamoto. Using next-generation sequencing, the researchers established a high-density genetic map of this recombinant cultivar. Next, they performed quantitative trait loci analysis of the sorghum germplasm to identify the gene controlling awn development. They also conducted genome-wide association studies to identify the origins of the awn-inhibiting gene. Lastly, they introduced the awn-inhibiting gene in an awned rice cultivar to check its functionality in other grass species.

 

The researchers observed that approximately half of the recombinant cultivar population studied did not develop awns, just like their awnless parent. Moreover, they found a single locus on the cultivar chromosome to be responsible for regulating the absence as well as shortening of awns in the cultivars studied. They identified the gene corresponding to this locus as DOMINANT AWN INHIBITOR, or DAI.

 

The researchers found that DAI encodes a protein in the ALOG family, which negatively regulates awn formation as a transcription factor. Interestingly, when DAI was introduced into the awned rice cultivar, it suppressed awn formation. In the words of Prof. Sakamoto, “It was surprising that DAI also inhibits awn elongation in rice grains, because no such genes have been reported in rice. Thus, eliminating awns in cereal grains have occurred differently among cereal crops, but the mechanism can be shared between them.” 

 

In short, this study has established the importance of DAI for the development of modern awnless cultivars. Also, it points to the existence of a common mechanism of awn inhibition, despite the existence of species-specific inhibitors. Going ahead, further analysis is needed to understand the transcriptional regulation of DAI besides clarifying the association of DAI with sorghum domestication. As Prof. Sakamoto points out, “In the long term, the understanding of genetic traits affecting cereals can help us in making new varieties.”

University of Wisconsin release

 

Every day, plants around the world perform an invisible miracle. They take carbon dioxide from the air and, with the help of sunlight, turn it into countless chemicals essential to both plants and humans.

 

Some of these chemicals, known as aromatic compounds, are the starting material for a wealth of useful medications, such as aspirin and morphine. Yet, many of these chemicals come from fossil fuels because it’s hard to get plants to make enough of them to harvest economically. Others are essential human nutrients and can only be obtained through our food since our bodies are unable to make them.

 

In new work, scientists at the University of Wisconsin–Madison identified a way to release the brakes on plants’ production of aromatic amino acids by changing, or mutating, one set of genes. The genetic change also caused the plants to absorb 30% more carbon dioxide than normal, without any ill effect on the plants.

 

If scientists could add a trait like this to crops or drug-producing plants, it could help them produce more chemicals naturally while reducing greenhouse gases in the atmosphere.

 

“We’ve long been interested in this aromatic amino acid pathway because it’s one of the major plant pathways that transform carbon fixed by photosynthesis into medicines, food, fuels, and materials,” says Hiroshi Maeda, a UW–Madison professor of botany who led the new research. “Now for the first time, we’ve discovered how to regulate the key control knob plants use to turn up production of this pathway.”

 

Maeda and his team, led by postdoctoral researchers Ryo Yokoyama and Marcos Vinicius Viana de Oliveira, published their findings June 8 in Science Advances.

 

Normally, plants tightly control the production of aromatic amino acids by building in natural brakes to the process. When plants have produced enough amino acids, the whole system grinds to a halt.

 

The mutated plants Maeda’s team discovered using the model plant Arabidopsis have much less sensitive brakes thanks to mutations in a gene called DHS, which starts the production of aromatic amino acids. The upshot is the plant doesn’t know when to stop and keeps churning out these compounds.

 

The scientists were surprised to discover that the plants put photosynthesis into overdrive, taking in significantly more carbon dioxide into the plant to fuel this new production boom.

 

“We think that the increased photosynthesis does two things. One is to provide additional energy to operate this energetically expensive pathway. The second is to supply more carbon building blocks to make energetically dense aromatic chemicals,” says Maeda.

Some of these energy dense compounds, like lignin, find their way into the cell wall, where they make useful biofuel fodder.

 

Arabidopsis is simply a tiny mustard plant. While a useful model in the lab, it produces nothing of value. Co-author de Oliveira has his sights set on testing similar mutations in crops — which take in huge amounts of carbon dioxide every year — or in plants that produce valuable aromatic chemicals.

 

“These brakes we identified look very similar among different plants. So, expanding this discovery to crops opens up many possibilities, such as enriching our food with essential nutrients or improving bioenergy production, while capturing more carbon dioxide from atmosphere to slow down the global warming,” says de Oliveira.

 

This work was supported in part by the National Science Foundation grant MCB-1818040. 

David Zaruk in The Genetic Literacy Project

 

he world is teetering on the brink of multiple food security crises which will lead to famines, political and social unrest and economic collapse across a wide range of regions. A perfect storm of war in the Ukraine (leading to lost food exports and reduced planting this spring), high energy costs, export restrictions on a large number of fertilisers, food commodity price speculation, logistic bottlenecks, financial and economic vulnerabilities following two years of a global pandemic and persistent droughts in many key agricultural regions means that food stresses are baked into world markets before the first crop failure of 2022.

 

Against this backdrop, the European Commission produced a document last month: “Safeguarding food security and reinforcing the resilience of food systems“. This EU strategy on how to mitigate the coming food security crisis, famines and increased malnutrition is to promote more organic food production, agroecology, reduced fertiliser use, subsistence farming, social justice theories, Farm2Fork and increased food-related aid (to countries ready to adopt some food cult ideology shared by a minority of activists in Brussels). The EU is serving up a recipe for famine, civil strife and economic collapse across large sections of the developing world… and their Communication celebrates this.

 

This official EU report is written by people with full bellies, ideological dreams of food purity and no idea of how challenging it can be to secure a harvest. Painful to read but more painful to ignore, I have provided my commentary on selected passages. I keep pinching myself when I say that this is the state of thinking of our European leadership. It would be funny if so many were not at risk of dying or malnutrition, to a large part, due to their ignorant food cult ideology.