Researchers have discovered a gene that controls the regulation of iron uptake in plants, according to a new study. With over 2 billion people suffering from iron deficiency around the world, the discovery could be the key to increasing the iron potency of crops.
The oldest living organism on Earth is a plant — Methuselah, a bristlecone pine (Pinus longaeva, pictured above) that is more than 5,000 years old. Conversely, animals only live up to a few hundred years. Can we learn something from plants about longevity and stay young forever — or even recapture lost youth?
Contrary to the long-held belief that plants in the natural world are always in competition, new research has found that in harsh environments mature plants help smaller ones – and thrive as a result.
Atmospheric nitrogen is not directly usable by most living things. In nature, specialized microbes in soils and bodies of water convert nitrogen into ammonia — a crucial form of nitrogen that life can easily access — through a process called nitrogen fixation. In agriculture, soybeans and other legumes that facilitate nitrogen fixation can be planted to restore soil fertility.
An additional obstacle in the process of making nitrogen available to the plants and ecosystems that rely on it is that microbial nitrogen “fixers” incorporate a complex protein called nitrogenase that contains a metal-rich core. Existing research has focused on nitrogenases containing a specific metal, molybdenum.
The extremely small amount of molybdenum found in soil, however, has raised concerns about the natural limits of nitrogen fixation on land. Scientists have wondered what restrictions the scarcity of molybdenum places on nature’s capacity to restore ecosystem fertility in the wake of human-made disturbances, or as people increasingly search for arable land to feed a growing population.
Princeton University researchers have found evidence that nitrogen fixation can be facilitated by metals that are more abundant in soil, which suggests that nitrogen fixation may be more resilient to molybdenum scarcity than previously thought, according to a study published in the journal Proceedings of the National Academy of Science. Working in a 372 mile (600 kilometer) stretch of boreal forest in Canada, the researchers found that nitrogen fixation at an ecosystem scale can also be catalyzed by the metal vanadium, particularly in northern regions with limited natural nitrogen inputs.
“This work prompts a major revision of our understanding of how micronutrients control ecosystem nitrogen status and fertility,” said senior author Xinning Zhang, assistant professor of geosciences and the Princeton Environmental Institute.
“We need to know more about how nitrogen fixation manifests in terms of nutrient budgets, cycling and biodiversity,” she said. “One consequence of this finding is that current estimates of the amount of nitrogen input into boreal forests through fixation may be significantly underestimated. This is a major issue for our understanding of nutrient requirements for forest ecosystems, which currently function as an important sink for anthropogenic carbon.”
First author Romain Darnajoux, a postdoctoral research associate in Zhang’s research group, explained that the findings validate a long-held hypothesis in the scientific community that different metal variants of nitrogenase exist so that organisms can cope with changes in metal availability. The researchers found that vanadium-based nitrogen fixation was only substantive when environmental molybdenum levels were low.
“It would seem that nature evolved backup methods to sustain ecosystem fertility when the environment is variable,” Darnajoux said. “Every nitrogen-cycle step involves an enzyme that requires particular trace metals to work. Molybdenum and iron are typically the focus of scientific study because they’re considered to be essential in the nitrogen-fixing enzyme nitrogenase. However, a vanadium-based nitrogenase also exists, but nitrogen input by this enzyme has been unfortunately largely ignored.”
Darnajoux and Zhang worked with Nicolas Magain and François Lutzoni at Duke University and Marie Renaudin and Jean-Philippe Bellenger at the University of Sherbrooke in Québec.
The researchers’ results suggest that the current estimates of nitrogen input into boreal forests through fixation are woefully low, which would underestimate the nitrogen demand for robust plant growth, Darnajoux said. Boreal forests help mitigate climate change by acting as a sink for anthropogenic carbon. Though these northern forests do not see as many human visitors as even the most lightly populated metropolis, human activities can still have major impacts on forest fertility through the atmospheric transport of air pollution loaded with nitrogen and metals such as molybdenum and vanadium.
“Human activities that substantially change air quality can have a far-reaching influence on how even remote ecosystems function,” Zhang said. “The findings highlight the importance of air pollution in altering micronutrient and macronutrient dynamics. Because air is a global commons, the connection between metals and nitrogen cycling and air pollution has some interesting policy and management dimensions.”
The researchers’ findings could help in the development of more accurate climate models, which do not explicitly contain information on molybdenum or vanadium in simulations of the global flow of nitrogen through the land, ocean and atmosphere.
The importance of vanadium-driven nitrogen fixation extends to other high-latitude regions, and most likely to temperate and tropical systems, Darnajoux and Zhang said. The threshold for the amount of molybdenum an ecosystem needs to activate or deactivate vanadium nitrogen fixation that they found in their study was remarkably similar to the molybdenum requirements of nitrogen fixation found for samples spanning diverse biomes.
The researchers will continue the search for vanadium-based nitrogen fixation in the northern latitudes. They’ve also turned their eyes toward areas closer to home, initiating studies of micro- and macronutrient dynamics in temperate forests in New Jersey, and they plan to expand their work to tropical systems.
Read the paper: Proceedings of the National Academy of Science
Article source: Princeton University
Author: Joseph Albanese
Image credit: Marie Renaudin, University of Sherbrooke
An international team of scientists has made the surprising discovery that a plant’s reaction to rain is close to one of panic. The research revealed complex chemical signals are triggered when water lands on a plant to help it prepare for the dangers of rain.
Vitamin E is a potential antioxidant that could act as a sentinel in plants, sending molecular signs from chloroplast –a cell organelle- to the nucleus. This flow of information reaching the cell nucleus –retrograde signalling- is a molecular mechanism that would ease the adaptive response of plants in physiological stress situation (salinity, lack of nutrients, drought, senescence, etc.).
A collaborative research group has succeeded in identifying an important transcription factor, GCAM1, which allows liverwort plants to asexually reproduce through creating clonal progenies. Furthermore, this transcription factor was revealed to have the same origin as those which regulate secondary bud formation in angiosperms.
Most plants have plenty of enemies, from insects and other grazing creatures to various diseases, droughts and many other stressors.
Plants respond to injuries or illnesses by initiating various defense measures. But a viral infection requires a completely different response than desiccation, of course.
To know more about its attacker, the cell relies on mechanical and chemical signals.
Almond and the peach are two well-known tree species, since humans have been eating their fruit (peach) or seed (almond) for thousands of years. New research shows that the movement of the transposons could lie at the origin of the differences between the fruit of both species or the flavour of the almond.
Passion fruit woodiness caused by cowpea aphid-borne mosaic virus (CABMV), the disease that most affects passion fruit (Passiflora edulis) grown in Brazil, can be combated with a relatively simple technique.
A study published in the journal Plant Pathology shows that systematic eradication of plants with symptoms of the disease preserves the crop as a whole and keeps plants producing for at least 25 months.
The technique currently used to combat CABMV entails renewing the entire orchard every year. This is, of course, a costly procedure. According to the authors of the study, economic factors are critical for this crop, which is mostly grown by small producers.
CABMV occurs in all states of Brazil and impairs plant development. Passion fruit woodiness disease causes leaf mosaic, blisters, deformation and reduced fruit size, making the produce unmarketable. Vines are typically eliminated only when the disease is detected in the early stages of their life cycle. The researchers propose systematic roguing – removal of weak, diseased or abnormal plants – throughout the life of the crop.
The study was funded by FAPESP and CAPES, the Brazilian Ministry of Education’s Coordination for the Improvement of Higher Education Personnel. It was conducted by Brazilian researchers affiliated with the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP), the Federal University of São Carlos (UFSCar) at Araras, the University of Southwest Bahia (UESB), and the Semiarid Agriculture Unit of the Brazilian Agricultural Research Corporation (EMBRAPA), as well as colleagues at Argentina’s National Agricultural Technology Institute (INTA).
“Roguing is a technique that has been used to combat papaya disease in Espírito Santo state since the 1980s. After several experiments, it was found to be the best way to control papaya ringspot virus type P [PRSV-P],” said Jorge Alberto Marques Rezende, Full Professor at ESALQ-USP and principal investigator for the study, which began in 2010.
CABMV is transmitted by aphid saliva and spreads throughout an orchard in a few months. The aphid species in question do not colonize the plants but merely visit them, and insecticide is not effective for control purposes.
“Insecticide affects their nervous system but takes hours to kill them. Meanwhile, they’re stimulated to feed on more plants, spreading the virus farther, so insecticide helps propagate the disease instead of controlling it,” said David Marques de Almeida Spadotti, first author of the article. The research was part of Spadotti’s postdoctoral fellowship at ESALQ-USP.
In previous experiments, the use of transgenic passion fruit plants and inoculation with attenuated variants of CABMV as a kind of vaccine also failed to control the disease. In this new study, an experimental orchard was planted in three areas belonging to ESALQ-USP in Piracicaba, São Paulo state, and two areas in Vitória da Conquista, southwestern Bahia. The experiments took place between 2013 and 2018. Approximately 100 healthy seedlings were planted in two areas of each city using trellises or T-shaped arbors connected by wires.
The vines were trained on the trellises and arbors for support but also to separate them so that the disease could easily be observed. Any buds with symptoms were identified and removed in weekly inspections.
In two other areas distant from the others, the same number of vines were planted using trellises and allowed to interlace without roguing, as in commercial plantations. The results of the two strategies were then compared.
In the absence of roguing, the virus spread throughout the crop in 120 days. In the areas submitted to systematic roguing, 8% of the vines were infected and removed after 180 days. In Piracicaba, only 16% had to be removed after 25 months, and the plants remained productive throughout this period.
The presence of CABMV in all infected or preventively removed vines was confirmed by PTA-ELISA serological testing.
“The symptoms appear eight days after inoculation of the virus on average. Roguing enables the grower to identify diseased plants visually and base control on visual inspection. Inspection should ideally be carried out at least once a week”
Spadotti said.
According to the researchers, the next step in the study entails larger pilot plantings of 1,000-2,000 passion fruit vines. In addition to eradicating diseased plants, they plan to replace them with healthy plants. The idea is to maintain the orchard for three to four years and compare it with another orchard maintained in the conventional manner, in which all plants are replaced every year.
“Because passion fruit is semiperennial, this longer production period is more advantageous from an economic standpoint than complete annual substitution,” said Rezende, principal investigator for the Thematic Project “Begomovirus and Crinivirus in Solanaceae”, which also relates to viruses in food crops.
The researchers stress, however, that if the strategy is to succeed, it should be implemented by all passion fruit growers in any given region. In addition to other plantations, the virus can spread from old or abandoned orchards, which should be eliminated.
CABMV-susceptible wild species of passion fruit in forests near plantations may also spread the disease. One of the experimental areas in Vitória da Conquista failed for this reason. When the wild plants were eliminated, the incidence of CABMV was considerably reduced.
According to IBGE, the national statistics and census bureau, Brazil is the world’s leading grower of passion fruit, with more than 550,000 metric tons produced in 2017.
Read the paper: Plant Pathology
Article source: Agência FAPESP
Author: André Julião
Image: Jorge Rezende
