A big part of evolution is competition– when there are limited resources to go around, plants and animals have to duke it out for nutrients, mates, and places to live. That means that the flower-covered meadows of China’s Hengduan mountains were an evolutionary mystery– there are dozens of species of closely-related rhododendrons that all live in harmony. To figure out why, scientists spent a summer carefully documenting the flowering patterns of 34 Rhododendron species, and they discovered the reason why the plants were able to coexist: they burst into bloom at different points in the season so they don’t have to compete for pollinators.
Crops often face harsh growing environments. Instead of using energy for growth, factors such as disease, extreme temperatures, and salty soils force plants to use it to respond to the resulting stress. This is known as the “growth-stress response trade-off”. Now, a group of researchers has discovered a previously unknown pathway that regulates whether a plant uses its resources for growth or stress tolerance. This discovery could enable the stress response to be controlled under agricultural conditions, increasing crop yields.
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.
“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.
Farmers are becoming more involved than ever in the work of developing new, sustainable crop varieties, with a recent Alliance study showing how a “citizen science” approach for on-farm experimentation called tricot, generated agricultural data via local organizations in Central America.
Over the last two centuries, human actions have resulted in rising temperatures, a massive carbon imbalance, and tremendous biodiversity loss. However, there are cases in which human stewardship seems to help remediate this damage. Researchers examined tropical forests across Asia, Africa and the Americas and found that the forests located on protected Indigenous lands were the healthiest, highest functioning, most diverse, and most ecologically resilient.
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.
Biologists have revealed how plants suppress the formation of stomata, the microscopic pores on their surface, to limit water loss during drought conditions.
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.
