PLANT PATHOLOGY
New insights into the immune response of plants
Research team identifies calcium-activated “bi-kinase module” as central molecular switch
University of Münster
Plant pests such as bacteria and fungi lead to significant yield losses in agriculture. In order to develop new strategies against such pathogens, understanding the plant’s immune response is of central importance. A team headed by biologist Prof Jörg Kudla of the University of Münster (Germany) has identified important components and mechanisms of the molecular machinery that transmits information about a pathogen encounter within the plant organism. The study, which has now been published in the journal Science Advances, also provides clues as to how plants manage to transmit immune signals from cell to cell without disrupting other signalling chains in the affected cells.
When plants are infected by pathogens, they mount a two-phase immune response, which first develops directly at the infection site and then spreads throughout the entire organism. This prepares the previously unchallenged parts of the plant for a possible attack. Calcium signals play an essential role in this process. When plant tissue is damaged by a pathogen, it triggers calcium signals which are then passed on from cell to cell. In addition, the cells use an NADPH oxidase (an enzyme in the cell membrane) to release reactive oxygen species as further signalling molecules, which then interact with the calcium signals to enable the systemic propagation of the immune response. Until now, researchers did not fully understand this interplay between calcium and reactive oxygen species and the regulation of NADPH oxidase by calcium-dependent phosphorylation.
Jörg Kudla’s team showed for the first time that two different kinases, both of which are activated by calcium, have to work together in order to facilitate efficient systemic immune signal proliferation. This “bi-kinase module” sensitises the NADPH oxidase to calcium and enables synergistic activation of this enzyme, which then produces more reactive oxygen species. One of the two calcium-dependent kinases was already known, while the second was identified by the team as part of the recently published study. “Such a calcium-activated bi-kinase module has never been described before,” explains Jörg Kudla.
Based on their observations, the biologists proposed a model detailing the mechanisms of systemic immune signalling in plants: Triggered by a pathogen, initially a third kinase inside the infected cell triggers the generation of extracellular reactive oxygen species in the cell, which would then diffuse to the surface of neighbouring cells. Up to this point, the process was understood. The team has now discovered that these reactive oxygen species not only trigger new calcium signals in the neighbouring cells, but also activate the calcium-dependent bi-kinase module, which in turn activates the release of reactive oxygen species.
This causes a renewed influx of calcium into the neighbouring cells. In this way, the signal spreads without the affected cells themselves coming into contact with the pathogen. “Surprisingly, we observed that the intensity of the moving calcium signal is relatively weak and yet sufficient to activate the NADPH oxidase via the bi-kinase module. This is likely caused by sensitisation of this enzyme. We have elucidated the molecular mechanisms of this sensitisation,” says Jörg Kudla. “We also suspect that this enables this weak calcium signal to spread from cell to cell without disrupting other signalling calcium-dependent processes that are occurring simultaneously in these cells.” How exactly the cells regulate the strength of the calcium signal is not yet known.
For their investigation, the team combined various molecular genetic, cell biological and biochemical methods. The investigation of the propagation of calcium signals in tissues was carried out in transgenic plants of thale cress (Arabidopsis thaliana), in which the researchers analysed biosensor proteins for calcium using high-resolution microscopy. For further investigations, human cell cultures were used in which the plant signalling pathway was reconstituted.
Alongside the Kudla research group, Prof Iris Finkemeier’s group from the University of Münster was also involved in the project. The other authors are members of the research group headed by Prof Tina Romeis (formerly at the Free University of Berlin and now at the Leibniz Institute of Plant Biochemistry in Halle).
Journal
Science Advances
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
A bi-kinase module sensitizes and potentiates plant immune signaling
Article Publication Date
24-Jan-2025
Unlocking the secrets of tomato's defense mechanisms against insects
Nanjing Agricultural University The Academy of Science
image:
Downregulation of Sl4CLL6 gene expression reduced resistance to mites in tomato plants. Silencing of Sl4CLL6 by TRV-VIGS. A Negative (CK), TRV2-PDS, and TRV2-Sl4CLL6 plants. B Expression of Sl4CLL6 gene in CK and TRV2-4CLL6 plants. C Changes in phenotypes of CK and silenced plants after inoculation with mites for 1, 4, and 7 days. D Average number of mites in CK and silenced plants after inoculation with mites for 0, 1, 4, and 7 days. E–H Changes in the expression of Sl4CLL6 and downstream genes of the phenylpropanoid biosynthesis pathway, SlHCT, SlCAD, and SlCHI, in CK and silenced plants 0, 1, 4, and 7 days after inoculation with mites. I Potential mechanisms by which Sl4CLL6 regulates lignin accumulation and shapes resistance to mites in tomato. Each value indicates the mean ± standard deviation of three biological replicates. *, **, *** and **** indicate significant differences between CK and silenced plants with P < 0.01, P < 0.001, P < 0001, P < 00001, respectively, as determined by t-test.
view moreCredit: Horticulture Research
In a study that could transform agricultural pest management, researchers have uncovered the robust insect resistance mechanisms of Solanum habrochaites, a wild tomato species. By unraveling the genetic and metabolic intricacies of the phenylpropanoid biosynthesis pathway, the study opens new avenues for breeding cultivated tomatoes with enhanced pest resistance. The findings hold the potential to reduce dependency on chemical pesticides, addressing mounting concerns over pesticide resistance and environmental harm.
Tomatoes, a staple crop worldwide, face significant challenges from pests such as aphids and mites, which wreak havoc on yields and quality. Overreliance on chemical pesticides has exacerbated the problem, with pests evolving resistance and the environmental toll of pesticides raising alarm bells. To meet these challenges, scientists are turning to wild tomato species like Solanum habrochaites, which naturally possess robust defense mechanisms. Deciphering these mechanisms is crucial for sustainable agriculture and ensuring food security amid growing pest pressures.
A team from Northeast Agricultural University in China has made a landmark contribution to this endeavor, publishing their findings (DOI: 10.1093/hr/uhad277) in Horticulture Research on January 9, 2024. The study employed cutting-edge metabolomics and transcriptomics techniques to dissect the phenylpropanoid biosynthesis pathway in Solanum habrochaites, identifying its critical role in insect resistance.
The researchers found that Solanum habrochaites produces significantly higher levels of phenylpropanoids and flavonoids, compounds pivotal in deterring phytophagous insects. Comparing the wild species to the cultivated tomato variety ‘Ailsa Craig,’ the study revealed that Solanum habrochaites boasts uniquely structured glandular trichomes capable of storing more anti-insect metabolites. Key genes such as Sl4CLL6 were identified as central players in this defense strategy; silencing these genes resulted in diminished resistance to mites, confirming their critical role. These insights not only deepen our understanding of plant-insect dynamics but also lay the groundwork for breeding pest-resistant crops using wild tomato genetics.
Dr. Aoxue Wang, one of the study’s corresponding authors, emphasized the broader significance of this work: “Our findings offer a significant step forward in understanding the natural defense mechanisms of tomatoes. By harnessing the genetic resources of wild tomato species, we can potentially develop more resilient and sustainable agricultural practices.”
The potential applications of this research extend beyond tomatoes. By leveraging the genetic wealth of wild plants, scientists can pioneer innovative solutions for pest management across diverse crops. This approach promises to benefit farmers by reducing crop losses while fostering environmentally friendly farming practices. The study also invites further exploration of other wild species that may harbor similar genetic treasures, ensuring that agriculture can meet the challenges of a changing world sustainably.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhad277
Funding information
This work was supported by the National Natural Science Foundation of China (grants U22A20495 and 32072588) and the National Natural Science Foundation of Heilongjiang Province (LH2021C032).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2022. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
Integration of metabolomics and transcriptomics reveals the regulation mechanism of the phenylpropanoid biosynthesis pathway in insect resistance traits in Solanum habrochaites
Texas A&M AgriLife Research aims for better control of widespread tomato spotted wilt virus
Federal grants to help wrangle vector-borne disease of tomatoes, peppers, thousands of other plants
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Cracking the code: what makes butterhead lettuce so unique
image:
Genetic mapping of the gene controlling butterhead and compact plant architecture. A Upper panel, the two parents, a stem lettuce (Ws1168, left) and a butterhead lettuce (W6-29885, right). Lower panel, the two phenotypes of individuals from an F3 family derived from the Ws1168 × W6-29885 cross. Scale bar = 10 cm. B BSR analysis of butterhead plant architecture in the segregating F3 family in A. The x-axis represents the nine chromosomes of lettuce. The y-axis represents the Δ(SNP index) between two extreme pools. A single locus on chromosome 1 controls plant architecture in the segregating population. C Upper panel, the two parents, a stem lettuce (Y37, left) and a loose-leaf lettuce (S1, right). Lower panel, the two phenotypes in an F4 family derived from the cross Y37 × S1. Scale bar = 10 cm. D BSR assay of compact plant architecture in the F4 family in C. E Fine mapping of the gene controlling compact plant architecture. Numbers between two neighboring markers refer to the number of recombinants among 4392 individuals in the F4 family. F Gene structure of LG1149597 (LsKIPK), and its sequences in the four parents used in two crosses. The arrow shows the nonsense mutation, converting the codon CGA to TGA.
view moreCredit: Horticulture Research
A recent discovery has unlocked the genetic secrets behind butterhead lettuce’s signature compact structure, a development that could revolutionize crop breeding and agricultural sustainability. Scientists have identified two critical genes, LsKIPK and LsATPase, whose mutations are responsible for the plant’s distinctive architecture. This breakthrough not only deepens our understanding of plant morphology but also offers a path to developing lettuce varieties with improved traits, such as stress resilience and adaptability, potentially transforming farming practices globally.
Butterhead lettuce, prized for its soft leaves and unique, tightly packed structure, is a staple leafy vegetable, especially in Europe. Its compact architecture makes it ideal for mechanized harvesting and efficient storage. However, the genetic factors underpinning this advantageous trait have long eluded researchers. Understanding these factors is crucial for addressing agricultural challenges such as increasing crop yields, improving resistance to environmental stresses, and adapting to modern farming systems. With the growing demand for sustainable agriculture, researchers turned their focus to uncovering the genetic blueprint behind this lettuce’s structure.
Published (DOI: 10.1093/hr/uhad280) in Horticulture Research on December 28, 2023, a study by scientists at Huazhong Agricultural University has identified the genetic drivers behind butterhead lettuce's morphology. Led by Dr. Xin Wang, the team employed cutting-edge genetic mapping and CRISPR/Cas9 technology to pinpoint the roles of LsKIPK and LsATPase. These genes were found to play pivotal roles in regulating cell wall development, resulting in the compact structure unique to butterhead lettuce.
The study revealed that mutations in LsKIPK and LsATPase, specifically the Lskipk and Lsatpase variants, significantly reduced leaf size and angle, key contributors to the plant’s tight form. Researchers demonstrated that the double mutation of these genes is both necessary and sufficient to produce the characteristic butterhead lettuce architecture. The findings mark a departure from the genetic mechanisms observed in other lettuce varieties like crisphead. Using knockout experiments and complementation tests, the team confirmed that manipulating these genes could enable precise control over plant structure, offering exciting possibilities for targeted breeding.
“This study not only unravels the genetic mysteries behind butterhead lettuce’s architecture but also opens up new possibilities for crop improvement,” said Dr. Xin Wang, the study’s lead author. “By understanding and leveraging these genetic pathways, we can potentially develop lettuce varieties that are more efficient to cultivate and harvest, ultimately benefiting both farmers and consumers.”
The implications of this discovery extend far beyond butterhead lettuce. By manipulating the LsKIPK and LsATPase genes, plant breeders could develop crops with compact and resilient architectures suited to mechanized farming, increasing yields while reducing costs. Such innovations could enhance resistance to drought, disease, and other environmental stresses, creating a blueprint for more sustainable agriculture. These advancements promise to meet the growing demands of global food security, transforming how crops are grown, harvested, and stored in the future.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhad280
Funding information
This work was supported by the National Natural Science Foundation of China award no. 31830079 and the scientific research start-up funding (11020102) from Hubei Hongshan Laboratory.
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2022. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
Lskipk Lsatpase double mutants are necessary and sufficient for the compact plant architecture of butterhead lettuce
New discovery paves the way for more resistant soybeans to combat $1.5 billion crop loss from nematode infection
American Phytopathological Society
Soybean growers across the globe face a silent but devastating threat: the soybean cyst nematode (SCN). This microscopic pathogen attacks soybean roots, jeopardizing crop yields and causing more than $1.5 billion in annual losses in the United States alone. Despite decades of effort, effective solutions to protect soybeans from SCN remain elusive, as the pathogen is often detected only in later stages because its early symptoms are subtle. However, new research offers hope for a sustainable solution to this agricultural challenge.
A recent study published in the journal Molecular Plant-Microbe Interactions (MPMI), led by the graduate student Alexandra Margets and other researchers from the Roger Innes Laboratory at Indiana University Bloomington, in collaboration with the Baum Lab at Iowa State University, has identified and characterized a key protein behind SCN infection. Their findings could revolutionize how farmers protect their crops from this pervasive threat.
The team of researchers identified an effector protein called CPR1 (“cysteine protease 1”), which SCN secretes into soybean roots during infection. CPR1 disrupts the plant’s immune system, paving the way for the pathogen to establish itself. Using a cutting-edge technique called “proximity labeling,” the team identified a soybean protein, GmBCAT1 (branched-chain amino acid aminotransferase), as a target of CPR1. Further experiments revealed that CPR1 prevents the accumulation of GmBCAT1, suggesting cleavage. This discovery could enable the team to engineer “decoy” proteins that trick SCN effectors into cleaving them, thereby triggering a robust plant immune response that prevents further infection.
“This work has broad impacts on our understanding of SCN parasitism and the development of a novel resistance strategy. If shown to be successful, we can develop plants that are resistant to SCN and deliver a new solution for soybean farmers to use in their fields,” said Roger Innes, head of the Innes Lab. “If this technology works for SCN resistance in soybeans, it will almost certainly work for other crop plants and respective plant diseases.”
These insights could have far-reaching implications for global agriculture. By developing SCN-resistant soybeans, this research aims to reduce the reliance on chemical pesticides, lowering agriculture’s environmental impact while increasing crop yields. The complementary expertise of the Innes Lab in decoy protein engineering and the Baum Lab in soybean and nematode biology underscores the potential for transformative advancements in sustainable farming. Both labs hope this research will benefit farmers and promote sustainable agriculture by developing a new generation of SCN-resistant soybeans.
For additional details, read “The Soybean Cyst Nematode Effector Cysteine Protease 1 (CPR1) Targets a Mitochondrial Soybean Branched-Chain Amino Acid Aminotransferase (GmBCAT1),” published in MPMI.
Follow the research team on X, Bluesky, and LinkedIn
Alexandra Margets
X: @_acmargets
LinkedIn: https://www.linkedin.com/in/alexandra-margets/
Bluesky: acmargets.bsky.social
Jessica Foster
X: @JFplantstuff
Bluesky: jfplantstuff.bsky.social
Anil Kumar
X: @Anilm58
LinkedIn: https://www.linkedin.com/in/anil-kumar-9766b222/
Thomas J. Baum
X: @BaumLabISU
Roger W. Innes
X: @RogerInnes1
Bluesky: inneslab.bsky.social
About Molecular Plant-Microbe Interactions (MPMI)
Molecular Plant-Microbe Interactions® (MPMI) is a gold open access journal that publishes fundamental and advanced applied research on the genetics, genomics, molecular biology, biochemistry, and biophysics of pathological, symbiotic, and associative interactions of microbes, insects, nematodes, or parasitic plants with plants.
Follow MPMI on X and Bluesky and visit https://apsjournals.apsnet.org/journal/mpmi to learn more.
Journal
Molecular Plant-Microbe Interactions
Article Title
The Soybean Cyst Nematode Effector Cysteine Protease 1 (CPR1) Targets a Mitochondrial Soybean Branched-Chain Amino Acid Aminotransferase (GmBCAT1)
Harnessing nature to defend soybean roots
Using novel Cry protein to control the number-one soybean pest
American Phytopathological Society
image:
Comparison of anterior midgut ultrastructure in soybean cyst nematode (SCN) fed on A, wild-type or B, GMB151 (Cry14Ab-expressing) plants. Intestine lumen is expanded in size in the GMB151-fed worm, and it is filled with fibrillar material that is lysate from the microvillus-like structure (MvL) (Figs. 5, 6, and 7). In GMB151 plant-fed nematodes, the loss of MvL cytoplasm by ruptured MvL membranes causes cytoplasm density to be lower compared with MvL lacking ruptured membranes and cytoplasm density in the ground cytoplasm of the epithelial cell to which they are attached (as quantified in Fig. 5B). Scale bars are 0.5 µm.
view moreCredit: R. Howard Berg, Theodore W. Kahn, Michael T. McCarville, Jayme Williams, Kirk J. Czymmek, and Julia Daum
The microscopic soybean cyst nematode (SCN) may be small, but it has a massive impact. This pest latches onto soybean roots, feeding on their nutrients and leaving a trail of destruction that costs farmers billions in yield losses each year. Unfortunately, current methods to combat SCN are faltering as the pest grows resistant to traditional controls. But new research is now offering a glimmer of hope.
A collaborative team of scientists from BASF Agricultural Solutions and the Advanced Bioimaging Laboratory at the Donald Danforth Plant Science Center are working on a potential solution: a special protein known as Cry14. Published in the journal Molecular Plant-Microbe Interactions (MPMI), this innovative study details how Cry14 could revolutionize the fight against SCN. Lead author R. Howard Berg and his team have developed a way to genetically equip soybean plants with this special protein. This approach, long used in other crops such as corn and cotton to combat insect pests, has now been implemented successfully to prevent SCN from feeding on soybean roots.
This study addresses key scientific questions about the Cry14 protein, including its function and its potential to enhance existing agricultural products for farmers. The study demonstrates that combining Cry14 with current treatment options reduces the SCN population in soybean roots, ultimately leading to higher soybean yields. The research team also investigated how Cry14 provides this protection. Conflicting data in the scientific literature have raised questions about what size is “too large” for SCN to ingest. The Cry14 protein exceeds the previously assumed size limit. However, using state-of-the-art electron microscopy and imaging equipment, the team captured groundbreaking images of the Cry14 protein inside the guts of SCNs feeding on soybean plants expressing the protein. These images provide direct evidence that Cry14 can be ingested by nematodes.
And for the first time, high-resolution electron microscopy was used to document Cry-induced damage, revealing membrane lysis in intestinal cells, which leads to cell death. This finding confirms the expected mode of action for Cry proteins.
This groundbreaking research creates a path for the use of other Cry proteins to control SCN and other nematodes. Until now, conflicting literature and challenges working with Cry proteins had all but closed the door on this as a viable approach for nematode control in plants.
This technology comes along at a critical time: when SCN is developing resistance to control by native soybean traits. The new cell biology information on how Cry14 affects the intestine could stimulate other researchers to apply this technology in novel ways.
For additional details, read “Immunolocalization and ultrastructure show ingestion of Cry protein expressed in Glycine max by Heterodera glycines and its mode of action,” published in MPMI.
About Molecular Plant-Microbe Interactions (MPMI)
Molecular Plant-Microbe Interactions® (MPMI) publishes peer-reviewed fundamental and advanced applied research on the genetics, genomics, molecular biology, biochemistry, and biophysics of pathological, symbiotic, and associative interactions of microbes, insects, nematodes, or parasitic plants with plants.
Follow MPMI on X and Bluesky and visit https://apsjournals.apsnet.org/journal/mpmi to learn more.
Journal
Molecular Plant-Microbe Interactions
Article Title
Immunolocalization and Ultrastructure Show Ingestion of Cry Protein Expressed in Glycine max by Heterodera glycines and Its Mode of Action
COI Statement
R.H.B. worked on this project as a paid consultant for the BASF Corporation (BASF). M.T.M., J.W., and J.D. are employed by BASF, whose products are evaluated in this study. The remaining authors declare no conflict of interest.
