Over 34 million people in the U.S. don’t have enough food. More diverse and adaptable crops are needed to address challenges in food production made worse by climate change. Small, sweet berries called groundcherries may not feed the country, but along with other related “orphan crops,” they could strengthen food supplies. Unfortunately, these distant relatives of tomatoes aren’t ready for large-scale production—at least not yet.
To avoid salt in soil, plants can change their root direction and grow away from saline areas. University of Copenhagen researchers helped find out what makes this possible. The discovery changes our understanding of how plants change their shape and direction of growth and may help alleviate the accelerating global problem of high soil salinity on farmland.
Whereas a bath in the ultra-salty Dead Sea may be a balm for human soul and body, the relationship between most plants and salt is quite the opposite. Plants desperately do whatever they can to steer clear of salinity – as salts can damage and even suffocate them.
Unfortunately, salt in agricultural land is an accelerating global problem, partly due to climate change, which increases the salinity of soil whenever floods sweep coastal zones. Typically, this lowers crop yields.
“The world needs crops that can better withstand salt. If we are to develop plants that are more salt-tolerant, it is important to first understand the mechanisms by which they react to salt,” explains Professor Staffan Persson of the University of Copenhagen’s Department of Plant and Environmental Sciences. He continues:
“To avoid salt in soil, plants can make their roots grow away from saline areas. It is a vital mechanism. Until now, it is unclear how they do this.”
Together with a group of foreign research colleagues, Persson discovered exactly what happens inside plants at a cellular and molecular level as their roots grow away from salt. The results have been published in the scientific journal Developmental Cell.
Stress hormone comes into play
The research group has discovered that when a plant senses local concentrations of salt, the stress hormone ABA (abscisic acid) is activated in the plant. This hormone then sets a response mechanism into motion.
“The plant has a stress hormone triggered by salt. This hormone causes a reorganization of the tiny protein-based tubes in the cell, called the cytoskeleton. The reorganization then causes the cellulose fibers surrounding the root cells to make a similar rearrangement, forcing the root to twist in such a way that it grows away from the salt,” explains Professor Persson.
Changes the understanding of how plants change shape
The leading role played by the stress hormone is what makes the discovery a surprise for the researchers. Until now, it was believed that the hormone auxin controlled a plant’s ability to change directions in response to various environmental influences (known as tropisms).
“That the stress hormone ABA is crucial for plants being able to reorganize their cell walls and change shape and direction of growth is completely new. This could open new avenues in plant research, where there will be a greater focus on the significant role that the hormone seems to play in the ability of plants to cope with various conditions by changing movement,” says Staffan Persson.
By mutating a single amino acid in a protein that drives the twisting of the root, the researchers were able to reverse the twist so that the plant could not grow away from the salt.
Persson believes that it will be some time before the new knowledge is applied in agriculture – not least because GMOs remain banned in the EU. However, the results may open the way for the development of more salt-tolerant crop varieties.
“Plants produce more of the stress hormone when they sense salt. It’s not hard to imagine that if you can speed up a plant’s stress response by changing other aspects of the cytoskeleton, you can probably make its root-twist happen faster. In this way, we can strengthen plants by reducing their exposure to salt,” says Professor Persson.
Read the paper: Developmental Cell
Article source: Copenhagen Plant Science Centre
Author: Staffan Persson
Image credit: Alena Kravchenko/Wikimedia
Scientists have puzzled over the origin of Namibia’s fairy circles for nearly half a century. It boiled down to two main theories: either termites were responsible, or plants were somehow self-organizing. Now, researchers benefitting from two exceptionally good rainfall seasons in the Namib Desert, show that the grasses within the fairy circles died immediately after rainfall, but termite activity did not cause the bare patches. Instead, continuous soil-moisture measurements demonstrate that the grasses around the circles strongly depleted the water within the circles and thereby likely induced the death of the grasses inside the circles.
A mechanism used by a fungal pathogen to promote spread of the devastating cereal crop disease, blast, has been revealed in fine detail.
The Banfield group at the John Innes Centre, in collaboration with the Iwate Biotechnology Research Centre in Japan and The Sainsbury Laboratory in Norwich describes how an effector protein (AVR-Pii) used by the blast fungus Maganaporthe oryzae binds with the rice host receptor protein Exo70.
Using protein structure analysis, the study reveals a tight binding mechanism in which a significant proportion of the effector surface is involved in the interaction with the host target.
In revealing the structure of AVR-Pii, the research group have also shown that this effector belongs to a new protein family in the blast pathogen, termed “Zifs”, as they are based on a Zinc-finger motif.
This research is published in Proceedings of the National Academy of Sciences (PNAS).
“We have identified a new family of Zif effectors, a finding which has implications for understanding the molecular mechanisms of blast disease. These proteins could be useful in our quest to engineer new disease resistance properties against blast,” said Professor Mark Banfield a group leader at the John Innes and corresponding author of the study.
Image: The crystal structure of OsExo70F2 in complex with AVR-Pii reveals hydrophobic residues dominate the interaction interface. (A) Schematic representation of OsExo70F2 in complex with AVR-Pii. Both molecules are represented as cartoon ribbons, with the molecular surface also shown and colored as labeled in green and yellow for OsExo70F2 and AVR-Pii, respectively. (B) Close-up view of the interaction interface between OsExo70F2 and AVR-Pii. OsExo70F2 is presented as a solid surface, with the effector as cartoon ribbons and side chains displayed as a cylinder for AVR-Pii–interacting residues (Asp45, Tyr48, His49, Tyr64, Phe65, and Asn66) in addition to the residues coordinating the Zn2+ atom (Cys51, Cys54, His67, and Cys69). (C) OsExo70F2 surface hydrophobicity representation at the AVR-Pii interaction interface; residues are colored depending on their hydrophobicity from light blue (low) to yellow (high). (D) Representation of OsExo70F2 surface electrostatic potential at the AVR-Pii interaction interface; residues are colored depending on their electrostatic potential from dark blue (positive) to red (negative). AVR-Pii residues 20 to 43 were not observed in the electron density used to derive the structure. Credit: Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2210559119
Previously, all effector structures in the blast pathogen were from a family known as the MAX fold. The team hypothesised that AVR-Pii would not be a MAX effector, and speculated the research could discover a novel protein family.
This AVR-Pii – Exo70 interaction was already known to support disease resistance in rice plants expressing the NLR immune receptor protein pair Pii. But how the interaction underpinned resistance was unknown.
Future research will explore how the association between AVR-Pii and Exo70 leads to immune recognition by the NLR receptor. NLR receptors belong to a family of proteins that enable plants to sense the presence of pathogen effector molecules and mount an immune response to resist disease.
Plant diseases destroy up to 30% of annual crop production, contributing to global food insecurity, and blast is a major disease of cereal crops.
Discovering how pathogens target plant hosts to promote virulence is essential if we are to understand how diseases develop, in addition to engineering immunity.
“A blast fungus zinc-finger fold effector binds to a hydrophobic pocket in host Exo70 proteins to modulate immune recognition in rice”, appears in PNAS.
Read the paper: Proceedings of the National Academy of Sciences
Article source: John Innes Centre
Image credit: Pixabay
The central biocatalyst in photosynthesis, Rubisco, is the most abundant enzyme on earth. By reconstructing billion-year-old enzymes, a team of Max Planck Researchers has deciphered one of the key adaptations of early photosynthesis. Their results not only provide insights into the evolution of modern photosynthesis but also offer new impulses for improving it.
A research team has measured the dynamic leakiness of CO2 from C4 plants. Previous studies had measured the leakiness under steady-state conditions, but this group took the measurements to prove that leakiness can and should be measured as a dynamic parameter.
Flower and seed coat colour are important agronomic traits in chickpea that influence consumer preference. Based on their cultivation globally, this legume crop is categorized as “desi” or “kabuli”. Seeds of desi-type chickpeas are generally dark brown and angular with a rough seed coat, while the kabuli type produces light-brown coloured and rounded seeds with smooth seed coats. Recently, a group of scientists in India successfully developed a new genetically engineered selection marker-free stable chickpea line.
Biologists often use green fluorescent protein (GFP) to see what happens inside cells. GFP, which scientists first isolated in jellyfish, is a protein that changes light from one color into another. Attaching it to other proteins allows researchers to find out if cells produce those proteins and where within cells to find them. This in turn shows how cells deliver and use genes.
Plant leaves can cope with much higher salt concentrations than roots. The underlying mechanism may help to develop more salt-tolerant crops. When there is a lack of water, heat or intensive irrigation, the level of common salt (sodium chloride) in the soil increases. However, most crops are sensitive to salt. They react to the increasing soil salinity by greatly reducing their growth. This leads to a reduction in the harvest.