Untapping barley’s grain yield potential by mitigating floral degeneration
IMAGE: THE AIM IS TO BETTER DEVELOP THE YIELD POTENTIAL OF THE CEREAL PLANT. view more
CREDIT: IPK LEIBNIZ INSTITUTE/ T. SCHNURBUSCH
Barley possesses an indeterminate 'spike'-type inflorescence that forms basic floral structures, called spikelets, in a distichous pattern along its central axis (termed rachis). Each rachis node in the barley spike produces three (one central and two lateral) spikelets.
At the end of spikelet primordia initiation along the rachis marks the stage of maximum yield potential. Subsequently, the inflorescence meristem dome starts to collapse, followed by gradual basipetal degeneration of spikelet primordia and spikelets until a specific position along the spike is reached. “We show that up to 50% of the initiated floral primordia are aborted before anthesis, representing an untapped yield potential”, says
Prof. Dr. Thorsten Schnurbusch, head if IPK’s research group “Plant Architecture”. “Understanding the molecular underpinnings of spike PTD may thus help improve grain yield in cereals.”
Due to its quantitative nature and environmental sensitivity, inflorescence PTD constitutes a complex mechanism affecting final grain number. This mechanism appears to be predictable and heritable, consistent with a developmental programme. Photosynthesis, immature spike greening, and energy metabolism appear to be significant contributors to proper spikelet growth and differentiation and were restricted to basal and central spike parts. The researchers discovered, however, that the degenerating apical spike region undergoes sugar and amino acid depletion along with enhanced abscisic acid biosynthesis and signaling.
“Moreover, we functionally validated one of the apically expressed transcription factor genes, barley GRASSY TILLERS1 (HvGT1) an ortholog of maize GT1, as a growth repressor of apical spikelet development”, emphasises Nandhakumar Shanmugaraj, first author of the study. Site-directed Hvgt1 mutants in barley delayed the onset of spike PTD and produced more differentiated apical organs, resulting in significantly more fertile spikelets/florets and increased final spikelet number. “This is the first report on the molecular underpinnings of barley inflorescence PTD; however, here we not only provide a molecular framework for barley but also for related cereals of the Triticeae tribe (e.g., wheat, rye).”
“We believe that the molecular elucidation of PTD in barley will also stimulate future research directions on the evolution of related genes on growth suppression in other plants beyond crop species”, says Prof. Dr. Thorsten Schnurbusch. As barley is amongst the most important cereal crops in the world, better exploiting its spike yield potential can thus contribute to world food security and thereby directly help fight against hunger threats imposed by climate change, and natural or war disasters.
JOURNAL
The Plant Cell
ARTICLE TITLE
Multilayered regulation of developmentally programmed pre-anthesis tip degeneration of the barley inflorescence
ARTICLE PUBLICATION DATE
7-Jun-2023
Scientists map complete genome of millet
New knowledge of ancient grain may enable breeding for climate change adaptation
An international team of researchers has unlocked a large-scale genomic analysis of Setaria or foxtail millet, an important cereal crop. The study, led by researchers at the Chinese Academy of Agricultural Sciences and including scientists at NYU, advances our understanding of the domestication and evolution of foxtail millet, as well as the genetic basis for important agricultural traits.
“Foxtail millet is considered to be the foundation for early Chinese civilization,” said Michael Purugganan, the Silver Professor of Biology at NYU and NYU Abu Dhabi, and the study’s co-senior author. “Moreover, because it is a crop that can grow across a wide range of environments—including arid lands—it has the potential to be important for food security under climate change.”
Foxtail millet is one of the oldest domesticated grain crops in the world and has been grown by humans for roughly 11,000 years. It held a dominant position in Chinese agriculture before the introduction of high-input agricultural practices like irrigation and chemical fertilizers. The protein-rich grain—which employs C4 photosynthesis, a highly efficient form of photosynthesis that helps it adapt to different environments—is resilient to drought and able to thrive in low-nutrient soils.
“C4 plants constitute only about 3% of flowering plant species, but they surprisingly contribute to approximately 25-30% of global biomass production. The complexity of the genomes of most C4 species has posed challenges for fundamental studies and breeding, but Setaria serves as an ideal model system for studying C4 photosynthetic plants in genomics and genetics research,” said Xianmin Diao, a professor in the Institute of Crop Sciences at the Chinese Academy of Agricultural Sciences, the study’s co-senior author, and the scientist who organized the study.
In their study published in the journal Nature Genetics, the researchers established the Setaria pan-genome—the entire set of the species’ genes—by assembling 110 representative genomes from a worldwide collection of 1,844 Setaria species. They performed large-scale genetic studies for 68 traits across 22 environments in 13 geographical locations, each with distinct climactic conditions, identifying potential genes and marker-panels for how foxtail millet has evolved and improved at different geographic sites. For instance, the researchers found that the gene SiGW3 regulates grain yield of foxtail millet.
They also constructed the first graph-based genome sequence of Setaria, offering insights into genomic variation across wild and cultivated Setaria. This deeper understanding of the comprehensive genomic variation equips researchers with valuable genetic tools to pursue biological research and breeding efforts.
“This paper is a significant milestone, as it paves the way for the next generation of comparative genomics studies that can help to decipher the molecular mechanism of C4 photosynthesis. The large-scale comparative genomics, genome-wide association study, and genomic selection studies of Setaria not only provide opportunities for gene discovery and breeding advancements in foxtail millet itself, but also offer insights for other crops to enhance global food security,” added Diao.
“Understanding the genetic basis underlying the domestication and improvement of foxtail millet, along with these important agricultural characteristics, holds significant potential for its enhancement. With our graph-based genome, we can estimate grain quality-related traits and potential yield, providing avenues for foxtail millet breeding for climate change adaptation,” said Qiang He, a postdoctoral researcher in the Institute of Crop Sciences at the Chinese Academy of Agricultural Sciences and the study’s first author.
Purugganan’s research was supported by grants from the National Science Foundation Plant Genome Research Program (IOS-1546218 and 2204374), the Zegar Family Foundation, and the NYU Abu Dhabi Research Institute.
JOURNAL
Nature Genetics
ARTICLE TITLE
A graph-based genome and pan-genome variation of the model plant Setaria
ARTICLE PUBLICATION DATE
8-Jun-2023
Scientists discover how plants fight major root disease
IMAGE: WTS ENCODES AN ER-LOCALIZED CA2+ RELEASE CHANNEL, TRIGGERING IMMUNE RESPONSE TO PROTECT STELE FROM P. BRASSICAE INVASION view more
CREDIT: CHENG HANGYUAN
Researchers led by CHEN Yuhang and ZHOU Jianmin from the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences have shown how plants resist clubroot, a major root disease that threatens the productivity of Brassica crops such as rape.
The study, which uncovers novel mechanisms underlying plant immunity and promises a new avenue for crop breeding, was published in Cell.
Clubroot, a soil-borne disease, is the most devastating disease of Brassica crops. In China, approximately 3.2–4 million hm2 of agricultural land is affected by clubroot each year, resulting in a 20%–30% yield loss. Resting spores of Plasmodiophora brassicae (Pb), the causal pathogen of clubroot, are viable in soil for up to 20 years, making contaminated soil unsuitable for Brassica crops.
To date, only two clubroot resistance genes have been cloned, and their resistance has broken down as a result of newly evolved virulent Pb isolates.
In this study, the newly identified resistance gene WTS confers resistance to all Pb isolates tested, including isolates that are virulent toward existing resistant rape varieties. Thus, WTS is a broad-spectrum resistance gene and offers great potential for breeding clubroot disease resistance in crops.
WTS is not expressed in the absence of the pathogen. However, upon Pb infection, WTS is strongly induced exclusively in the pericycle, a critical layer of root cells surrounding the stele. The stele is the cylindrical central vascular portion of root containing critical tissues, including xylem and phloem that are essential for nutrient and water transport.
In susceptible plants, Pb invades and colonizes the stele, blocking nutrient and water transport. Expression of WTS in the pericycle activates plant defenses and prevents Pb from colonizing the stele. WTS thus defines a defense mechanism that is specifically activated at the right place and right time to ensure normal plant growth and development.
In addition, WTS encodes a novel protein. Structural analysis by cryo-EM has revealed that WTS self-assembles into a previously unknown pentameric architecture with a central pore.
Further studies have also shown that the WTS protein complex functions as an endoplasmic reticulum-localized calcium release channel that increases cytosolic calcium ions, a critical secondary signal for the activation of plant defenses.
The intriguing disease resistance mechanisms uncovered by the researchers represent a new paradigm in plant immunity against soil-borne pathogens. The cloned WTS gene offers new hope for breeding Brassica crops resistant to a devastating disease that is otherwise difficult to control.
JOURNAL
Cell
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
WeiTsing, a pericycle-expressed ion channel, safeguards the stele to confer clubroot resistance
ARTICLE PUBLICATION DATE
8-Jun-2023
Team finds reliable predictor of plant species persistence, coexistence
IMAGE: U. OF I. PLANT BIOLOGY PROFESSOR JAMES O’DWYER, PICTURED, AND GRADUATE STUDENT KENNETH JOPS DEVELOPED A METHOD FOR PREDICTING WHETHER PAIRS OR GROUPS OF PLANTS ARE LIKELY TO PERSIST TOGETHER IN A HABITAT OVER TIME. view more
CREDIT: PHOTO BY MICHELLE HASSEL
CHAMPAIGN, Ill. — Like many ecological scientists, University of Illinois Urbana-Champaign plant biology professor James O’Dwyer has spent much of his career searching for ways to measure and predict how specific plant communities will fare over time. Which species in a diverse population will persist and coexist? Which will decline? What factors might contribute to continuing biodiversity?
In a new study reported in the journal Nature, O’Dwyer and his colleague, U. of I. graduate student Kenneth Jops, report the development of a method for determining whether pairs or groups of plant species are likely to coexist over time. Using data from published studies, their approach reliably predicts the complementary life histories of pairs of plants that – while competing for many of the same resources – manage to thrive in a shared habitat.
The method relies on the painstaking collection of years of data about each species, O’Dwyer said.
“Over the last 50 or so years, people have gathered more and more data about plant life histories, your death rates, your reproductive rates, how many seeds you’re producing, how quickly you grow into the next life stage – and all of that can be changing throughout your lifespan,” he said. “And we write this as a matrix that roughly describes all those aspects of life history – and it’s different for every species.”
Certain elements of the matrix are plugged into an equation that yields the “effective population size,” a number that is recorded in units of years. The key finding in the new study is that if two plant species have roughly equivalent effective population sizes, they are more likely to coexist over time.
Jops first saw patterns in the data gathered for species found in the same habitat, “but it took us a while to make sense of the patterns,” O’Dwyer said.
An equal or near-equal EPS means that “there’s something about the way that the life histories jigsaw together that makes it more likely that they will persist,” O’Dwyer said.
The EPS equation reflects a mathematical relationship between the number of new individuals “born” each year, the average age of the parents, and the plant’s reproductive success over its lifetime, the researchers said.
The team found that a larger EPS also coincided with a better outcome for the species.
The data set the team used in the new study is relatively small, O’Dwyer said.
“There are around 800 to 1,000 plant species in the database we use – a drop in the ocean of plant diversity,” he said. Further research will test the new method on larger data sets involving more plants in more types of habitats, the researchers said.
“Plant biodiversity is a huge and complex question and I’m glad we were able to shed some light on how life history fits into that puzzle,” Jops said. “I hope this will encourage researchers to collect life history data across larger communities so we can apply our theory along with niche, fitness differences and environmental factors to better explain biodiversity patterns across the globe.”
The Simons Foundation and James S. McDonnell Foundation supported this research.
Editor’s note:
To reach James O’Dwyer, email jodwyer@illinois.edu
To reach Kenneth Jops, email kjops2@illinois.edu
The paper “Life history complementarity and the maintenance of biodiversity” is available online or from the U. of I. News Bureau.
JOURNAL
Nature
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Life history complementarity and the maintenance of biodiversity
ARTICLE PUBLICATION DATE
7-Jun-2023
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