Category

Plant Science

Plant nutrient detector breakthrough

By | Agriculture, News, Plant Science, Research

Findings from La Trobe University-led research could lead to less fertiliser wastage, saving millions of dollars for Australian farmers.

Published in the journal Plant Physiology, the findings provide a deeper understanding of the mechanisms whereby plants sense how much and when to take in the essential nutrient, phosphorus, for optimal growth.

Lead author Dr Ricarda Jost, from the Department of Plant, Animal and Soil Sciences at La Trobe University said the environmental and economic benefits to farmers could be significant.

“In countries like Australia where soils are phosphorus poor, farmers are using large amounts of expensive, non-renewable phosphorus fertiliser, such as superphosphate or diammonium phosphate (DAP), much of which is not being taken up effectively by crops at the right time for growth,” Dr Jost said.

“Our findings have shown that a protein called SPX4 senses the nutrient status – the ‘amount of fuel in the tank’ of a crop – and alters gene regulation to either switch off or turn on phosphorus acquisition, and to alter growth and flowering time.”

Using Arabidopsis thaliana (thale or mouse-ear cress) shoots, the research team conducted genetic testing by adding phosphorus fertiliser and observing the behaviour of the protein.

For the first time, the SPX4 protein was observed to have both a negative and a positive regulatory effect on phosphorus take-up and resulting plant growth.

“The protein senses when the plant has taken in enough phosphorus and tells the roots to stop taking it up,” Dr Jost said. “If the fuel pump is turned off too early, this can limit plant growth.

“On the other hand, SPX4 seems to have a ‘moonlighting’ activity and can activate beneficial processes of crop development such as initiation of flowering and seed production.”

This greater understanding of how SPX4 operates could lead to a more precise identification of the genes it regulates, and an opportunity to control the protein’s activity using genetic intervention – switching on the positive and switching off the negative responses.

La Trobe agronomist Dr James Hunt said the research findings sit well with the necessity for Australian farmers’ to be as efficient as possible with costly fertiliser inputs.

“In our no-till cropping systems, phosphorus gets stratified in the top layers of soil. When this layer gets dry, crops cannot access these reserves and enter what we a call a phosphorus drought,” Dr Hunt said.

“The phosphorus is there, but crops can’t access it in the dry soil. If we could manipulate crop species to take up more phosphorus when the top soil is wet, we’d be putting more fuel in the tank for later crop growth when the top soil dries out.”

The research team will now be investigating in more detail how SPX4 interacts with gene regulators around plant development and controlling flowering time.

The research was published in Plant Physiology with collaborators from Zhejiang University (China), Ghent University & VIB Center for Plant Systems Biology (Belgium), French Alternative Energies and Atomic Energy Commission (CEA) and the Australian Research Council Centre of Excellence in Plant Energy Biology.

Read the paper: Plant Physiology

Article source: La Trobe University

Image: Free-Photos / Pixabay

Researchers can finally modify plant mitochondrial DNA

By | News, Plant Science

Researchers in Japan have edited plant mitochondrial DNA for the first time, which could lead to a more secure food supply.

Nuclear DNA was first edited in the early 1970s, chloroplast DNA was first edited in 1988, and animal mitochondrial DNA was edited in 2008. However, no tool previously successfully edited plant mitochondrial DNA.

Researchers used their technique to create four new lines of rice and three new lines of rapeseed (canola).

“We knew we were successful when we saw that the rice plant was more polite – it had a deep bow,” said Associate Professor Shin-ichi Arimura, joking about how a fertile rice plant bends under the weight of heavy seeds.

Arimura is an expert in plant molecular genetics at the University of Tokyo and led the research team, whose results were published in Nature Plants. Collaborators at Tohoku University and Tamagawa University also contributed to the research.

Genetic diversity for the food supply

Researchers hope to use the technique to address the current lack of mitochondrial genetic diversity in crops, a potentially devastating weak point in our food supply.

In 1970, a fungal infection arrived on Texas corn farms and was exacerbated by a gene in the corn’s mitochondria. All corn on the farms had the same gene, so none were resistant to the infection. Fifteen percent of the entire American corn crop was killed that year. Corn with that specific mitochondrial gene has not been planted since.

“We still have a big risk now because there are so few plant mitochondrial genomes used in the world. I would like to use our ability to manipulate plant mitochondrial DNA to add diversity,” said Arimura.

Plants without pollen

Most farmers do not save seeds from their harvest to replant next year. Hybrid plants, the first-generation offspring of two genetically different parent subspecies, are usually hardier and more productive.

To ensure farmers have fresh, first-generation hybrid seeds each season, agricultural supply companies produce seeds through a separate breeding process using two different parent subspecies. One of those parents is male infertile – it cannot make pollen.

Researchers refer to a common type of plant male infertility as cytoplasmic male sterility (CMS). CMS is a rare but naturally occurring phenomenon caused primarily by genes not in the nucleus of the cells, but rather the mitochondria.

Green beans, beets, carrots, corn, onions, petunia, rapeseed (canola) oil, rice, rye, sorghum, and sunflowers can be grown commercially using parent subspecies with CMS-type male infertility.

Beyond green

Plants use sunlight to produce most of their energy, through photosynthesis in green-pigmented chloroplasts. However, chloroplasts’ fame is overrated, according to Arimura.

“Most of a plant isn’t green, only the leaves above the ground. And many plants don’t have leaves for half the year,” said Arimura.

Plants get a significant portion of their energy through the same “powerhouse of the cell” that produces energy in animal cells: the mitochondria.

“No plant mitochondria, no life,” said Arimura.

Mitochondria contain DNA completely separate from the cell’s main DNA, which is stored in the nucleus. Nuclear DNA is the long double-helix genetic material inherited from both parents. The mitochondrial genome is circular, contains far fewer genes, and is primarily inherited only from mothers.

The animal mitochondrial genome is a relatively small molecule contained in a single circular structure with remarkable conservation between species.

“Even a fish’s mitochondrial genome is similar to a human’s,” said Arimura.

Plant mitochondrial genomes are a different story.

“The plant mitochondrial genome is huge in comparison, the structure is much more complicated, the genes are sometimes duplicated, the gene expression mechanisms are not well-understood, and some mitochondria have no genomes at all – in our previous studies, we observed that they fuse with other mitochondria to exchange protein products and then separate again,” said Arimura.

Manipulating plant mitochondrial DNA

To find a way to manipulate the complex plant mitochondrial genome, Arimura turned to collaborators familiar with the CMS systems in rice and rapeseed (canola). Prior research strongly suggested that in both plants, the cause of CMS was a single, evolutionarily unrelated mitochondrial gene in rice and in rapeseed (canola): clear targets in the perplexing maze of plant mitochondrial genomes.

Arimura‘s team adapted a technique that had previously edited mitochondrial genomes of animal cells growing in a dish. The technique, called mitoTALENs, uses a single protein to locate the mitochondrial genome, cut the DNA at the desired gene, and delete it.

“While deleting most genes creates problems, deleting a CMS gene solves a problem for plants. Without the CMS gene, plants are fertile again,” said Arimura.

The fully fertile four new lines of rice and three new lines of rapeseed (canola) that researchers created are a proof of concept that the mitoTALENs system can successfully manipulate even the complex plant mitochondrial genome.

“This is an important first step for plant mitochondrial research,” said Arimura.

Researchers will study the mitochondrial genes responsible for plant male infertility in more detail and identify potential mutations that could add much-needed diversity.

Read the paper: Nature Plants

Article source: University of Tokyo

Image: Tomohiko Kazama

Even in jagged volcanic ice spires, life (i.e. snow algae) finds a way

By | News, Plant Science

High in the Andes Mountains, dagger-shaped ice spires house thriving microbial communities, offering an oasis for life in one of Earth’s harshest environments as well as a possible analogue for life on other planets.

The distinctive icy blade formations known as nieves penitentes (or, “penitent ones”) are named for their resemblance to praying monks in white robes and form in cold, dry conditions at elevations above 13,000 feet. The penitentes, which can range from a few inches to 15 feet high, are found in some of the most hostile conditions on Earth, with extreme winds, temperature fluctuations and high UV radiation exposure due to the thin atmosphere.

And yet, as a recently published study led by CU Boulder student researchers finds, these spires offer shelter for microbes by providing a water source in an otherwise arid, nutrient-poor environment.

In March 2016, CU Boulder students and faculty members traveled to Volcán Llullaillaco in Chile, the world’s second-highest volcano. The two-week expedition into the arid landscape, planned in collaboration with their Chilean colleagues, was no easy feat.

“This is a very remote area that’s difficult to access,” said Steve Schmidt, a professor in CU Boulder’s Department of Ecology and Evolutionary Biology (EBIO) and a co-author of the study. “The entire back of one of our pickup trucks had to be filled with barrels of drinking water. It’s no trivial thing to go out there, and that’s one of the reasons these formations haven’t been studied much.”

After reaching the penitente fields at 16,000 feet above sea level, the scientists noticed patches of red coloration, a telltale sign of microbial activity that has been previously observed in other snow and ice formations around the world.

Upon bringing back samples for analysis, the researchers confirmed the presence of algal species Chlamydomonas and Chloromonas in the ice, the first documentation of snow algae or any other life forms in the penitentes.

“Snow algae have been commonly found throughout the cryosphere on both ice and snow patches, but our finding demonstrated their presence for the first time at the extreme elevation of a hyper-arid site,” said Lara Vimercati, lead author of the study and a doctoral researcher in EBIO. “Interestingly, most of the snow algae found at this site are closely related to other known snow algae from alpine and polar environments.”

The new findings add to scientists’ understanding of the limits of life on Earth, says Alexandra Krinsky, a co-author of the study and an undergraduate in the Department of Molecular, Cellular and Developmental Biology who helped analyze the samples.

“From looking at the extreme environments of the dry Andes to the aquatic life roaming the sea floor, we have broken the original ideas of where life can and has been found,” she said.

The study may also have implications for the search for alien life. Penitente-like formations have recently been discovered on Pluto and are speculated to exist on Europa, one of Jupiter’s moons. The Atacama region in Chile is also considered to be the best Earth analogue for the soils of Mars.

“We’re generally interested in the adaptations of organisms to extreme environments,” Schmidt said. “This could be a good place to look for upper limits of life.”

“Our study shows how no matter how challenging the environmental conditions, life finds a way when there is availability of liquid water,” Vimercati said.

Additional co-authors of the research include Adam Solon of CU Boulder; John Darcy of the University of Colorado Denver; Dorota Porazinska of the University of Florida; and Pablo Arán and Cristina Dorador of the Universidad de Antofagasta (Chile).

Read the paper: Arctic, Antarctic, and Alpine Research

Article source: University of Colorado at Boulder

Image: Steve Schmidt/CU Boulder

These algae can live inside fungi. It could be how land plants first evolved.

By | News, Plant Science

Picture a typical documentary scene on the evolution of life. It probably starts with little bugs in a murky, primordial soup. Eons of time zip by as bugs turn into fish, fish swim to land as their fins morph into limbs for crawling animals, which then stand up on two legs, to finally end up with walking humans.

The picture is very animal-centric. But what about plants? They also made the jump from water to land. Scientists think that green algae are their water-living ancestors, but we are not sure how the transition to land plants happened.

New research from Michigan State University, and published in the journal eLife, presents evidence that algae could have piggybacked on fungi to leave the water and to colonize the land, over 500 million years ago.

“Fungi are found all over the planet. They create symbiotic relationships with most land plants. That is one reason we think they were essential for evolution of life on land. But until now, we have not seen evidence of fungi internalizing living algae,” says Zhi-Yan Du, study co-author and member of the labs of Christoph Benning, and now, Gregory Bonito.

Researchers selected a strain of soil fungus and marine alga from old lineages, respectively Mortierella elongata and Nannochloropsis oceanica.

When grown together, both organisms form a strong relationship.

“Microscopy images show the algal cells aggregating around and attaching to fungal cells,” Du says. “The algal wall is slightly broken down, and its fibrous extensions appear to grab the surface of the fungus.”

Surprisingly, when they are grown together for a long time – around a month – some algal cells enter the fungal cells. Both organisms remain active and healthy in this relationship.

This is the first time scientists have seen fungi internalize a expand iconeukaryotic, photosynthetic organism. They call it a ‘photosynthetic mycelium’.

“Both organisms get additional benefits from being together,” Du says. “They exchange nutrients, with a likely net flow of carbon from alga to fungus, and a net flow of nitrogen in the other direction. Interestingly, the fungus needs physical contact with living algal cells to get nutrients. Algal cells don’t need physical contact or living fungus to benefit from the interaction. Fungal cells, dead or alive, release nutrients in their surroundings.”

“Even better, when nutrients are scarce, algal and fungal cells grown together fend off starvation by feeding each other. They do better than when they are grown separately.”

Perhaps this increased hardiness explains how algae survived the trek onto land.

“In nature, similar symbiotic events might be going on, more than we realize,” Du adds. “We now have a system to study how a expand iconphotosynthetic organism can live inside a non-photosynthetic one and how this symbiosis evolves and functions.”

Both organisms are biotech related strains because they produce high amounts of oil. Du is testing them as a platform to produce high-value compounds, such as biofuels or Omega 3 fatty acids.

“Because the two organisms are more resilient together, they might better survive the stresses of bioproduction,” Du says. “We could also lower the cost of harvesting algae, which is a large reason biofuel costs are still prohibitive.”

Read the paper: eLife

Article source: MSU-DOE Plant Research Laboratory

Image: Zhi-Yan Du, colored by Igor Houwat; from eLife

Improved model could help scientists better predict crop yield, climate change effects

By | Climate change, News, Plant Science

A new computer model incorporates how microscopic pores on leaves may open in response to light—an advance that could help scientists create virtual plants to predict how higher temperatures and rising levels of carbon dioxide will affect food crops, according to a study published in a special issue of the journal Photosynthesis Research.

“This is an exciting new computer model that could help us make much more accurate predictions across a wide range of conditions,” said Johannes Kromdijk, who led the work as part of an international research project called Realizing Increased Photosynthetic Efficiency RIPE.

RIPE, which is led by the University of Illinois, is engineering crops to be more productive without using more water by improving photosynthesis, the natural process all plants utilize to convert sunlight into energy to fuel growth and crop yields. RIPE is supported by the Bill & Melinda Gates Foundation, the U.S. Foundation for Food and Agriculture Research (FFAR), and the U.K. Government’s Department for International Development (DFID).

The current work focused on simulating the behavior of what are known as stomata—microscopic pores in leaves that, in response to light, open to allow water, carbon dioxide, and oxygen to enter and exit the plant. In 2018, the RIPE team published a paper in Nature Communications that showed increasing one specific protein could prompt plants to close their stomata partially—to a point where photosynthesis was unaffected, but water loss decreased significantly. This study’s experimental data was used to create the newly improved stomata model introduced today.

“We’ve known for decades that photosynthesis and stomatal opening are closely coordinated, but just how this works has remained uncertain,” said Stephen Long, Ikenberry Endowed University Chair of Crop Sciences and Plant Biology at the University of Illinois. “With this new computer model, we have a much better tool for calculating stomatal movements in response to light.”

The ultimate goal, Long said, is to identify opportunities to control these stomatal gatekeepers to make drought-tolerant crops. “Now we’re closing in on the missing link: How photosynthesis tells stomates when to open.”

Computer modeling has been a major advance in crop breeding. The father of modern genetics, Gregor Mendel, made his breakthrough discovery that pea plants inherit traits from their parents by growing and breeding more than 10,000 pea plants over eight years. Today, plant scientists can virtually grow thousands of crops in a matter of seconds using these complex computer models that simulate plant growth.

Stomatal models are used together with models for photosynthesis to make wide-ranging predictions from future crop yields to crop management, such as how crops respond when there is a water deficit. In addition, these models can give scientists a preview of how crops like wheat, maize, or rice could be affected by rising carbon dioxide levels and higher temperatures.

“The previous version of the stomatal model used a relationship that wasn’t consistent with our current understanding of stomatal movements,” said Kromdijk, now a University Lecturer at the University of Cambridge. “We found that our new version needs far less tuning to make highly accurate predictions.”

Still, there’s a lot of work to be done to show that this modified model functions in a wide variety of applications and to underpin the relationship between stomata and photosynthesis further.

“We have to show that this model works for a diverse range of species and locations,” said former RIPE member Katarzyna Glowacka, now an assistant professor at the University of Nebraska-Lincoln. “Large-scale simulation models string together models for atmospheric turbulence, light interception, soil water availability, and others—so we have to convince several research communities that this is an improvement that is worth making.”

Read the paper: Photosynthesis Research

Article source: University of Illinois College of Agricultural, Consumer and Environmental Sciences ACES

Image: Brian Stauffer/University of Illinois