The OsCPK17-OsPUB12-OsRLCK176 module regulates immune homeostasis in rice.

Plant immunity is fine-tuned to balance growth and defense. However, little is yet known about molecular mechanisms underlying immune homeostasis in rice (Oryza sativa). In this study, we reveal that a rice calcium-dependent protein kinase (CDPK), OsCPK17, interacts with and stabilizes the receptor-like cytoplasmic kinase (RLCK) OsRLCK176, a close homolog of Arabidopsis thaliana BOTRYTIS-INDUCED KINASE 1 (AtBIK1). Oxidative burst and pathogenesis-related gene expression triggered by pathogen-associated molecular patterns are significantly attenuated in the oscpk17 mutant. The oscpk17 mutant and OsCPK17-silenced lines are more susceptible to bacterial diseases than the wild-type plants, indicating that OsCPK17 positively regulates rice immunity. Furthermore, the plant U-box (PUB) protein OsPUB12 ubiquitinates and degrades OsRLCK176. OsCPK17 phosphorylates OsRLCK176 at Ser83, which prevents the ubiquitination of OsRLCK176 by OsPUB12 and thereby enhances the stability and immune function of OsRLCK176. The phenotypes of the ospub12 mutant in defense responses and disease resistance show that OsPUB12 negatively regulates rice immunity. Therefore, OsCPK17 and OsPUB12 reciprocally maintain OsRLCK176 homeostasis and function as positive and negative immune regulators, respectively. This study uncovers positive cross talk between CDPK- and RLCK-mediated immune signaling in plants and reveals that OsCPK17, OsPUB12, and OsRLCK176 maintain rice immune homeostasis.

Rice false smut virulence protein subverts host chitin perception and signaling at lemma and palea for floral infection.

The flower-infecting fungus Ustilaginoidea virens causes rice false smut, which is a severe emerging disease threatening rice (Oryza sativa) production worldwide. False smut not only reduces yield, but more importantly produces toxins on grains, posing a great threat to food safety. U. virens invades spikelets via the gap between the 2 bracts (lemma and palea) enclosing the floret and specifically infects the stamen and pistil. Molecular mechanisms for the U. virens-rice interaction are largely unknown. Here, we demonstrate that rice flowers predominantly employ chitin-triggered immunity against U. virens in the lemma and palea, rather than in the stamen and pistil. We identify a crucial U. virens virulence factor, named UvGH18.1, which carries glycoside hydrolase activity. Mechanistically, UvGH18.1 functions by binding to and hydrolyzing immune elicitor chitin and interacting with the chitin receptor CHITIN ELICITOR BINDING PROTEIN (OsCEBiP) and co-receptor CHITIN ELICITOR RECEPTOR KINASE1 (OsCERK1) to impair their chitin-induced dimerization, suppressing host immunity exerted at the lemma and palea for gaining access to the stamen and pistil. Conversely, pretreatment on spikelets with chitin induces a defense response in the lemma and palea, promoting resistance against U. virens. Collectively, our data uncover a mechanism for a U. virens virulence factor and the critical location of the host-pathogen interaction in flowers and provide a potential strategy to control rice false smut disease.

Ustilaginoidea virens secretes a family of phosphatases that stabilize the negative immune regulator OsMPK6 and suppress plant immunity.

Rice false smut caused by Ustilaginoidea virens is emerging as a devastating disease of rice (Oryza sativa) worldwide; however, the molecular mechanisms underlying U. virens virulence and pathogenicity remain largely unknown. Here we demonstrate that the small cysteine-rich secreted protein SCRE6 in U. virens is translocated into host cells during infection as a virulence factor. Knockout of SCRE6 leads to attenuated U. virens virulence to rice. SCRE6 and its homologs in U. virens function as a novel family of mitogen-activated protein kinase phosphatases harboring no canonical phosphatase motif. SCRE6 interacts with and dephosphorylates the negative immune regulator OsMPK6 in rice, thus enhancing its stability and suppressing plant immunity. Ectopic expression of SCRE6 in transgenic rice promotes pathogen infection by suppressing the host immune responses. Our results reveal a previously unidentified fungal infection strategy in which the pathogen deploys a family of tyrosine phosphatases to stabilize a negative immune regulator in the host plant to facilitate its infection.

Development of Loop-Mediated Isothermal Amplification Assays for the Rapid and Accurate Diagnosis of Exserohilum turcicum for Field Applications.

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is one of the most devastating foliar diseases of maize. Rapid and accurate diagnosis for this disease is urgently needed but still limited. Here, we establish a field-deployable diagnostic method to detect E. turcicum based on loop-mediated isothermal amplification (LAMP) assays. A software application called K-mer Elimination by Cross-reference was used to search for the specific sequences belonging to E. turcicum by comparing the whole genome sequence between E. turcicum and other known maize pathogens. Five LAMP primer sets were designed based on specific and single-copy fragments of E. turcicum. Post-LAMP analyses indicated that only the primer set, Et9468_set1, was the most suitable, producing a ladder-like amplification pattern in the agarose gel electrophoresis and a strong fluorescence signal in the presence of SYBR Green I. The LAMP assay using Et9468_set1 primers demonstrated a high level of specificity in distinguishing E. turcicum from six other common fungal pathogens of maize, as well as 12 more fungal and oomycete strains including the epiphytic fungi from maize leaves and other crop pathogens. Moreover, it exhibited remarkable sensitivity by detecting five copies per reaction, which was approximately 104 times more sensitive compared with conventional PCR. The LAMP assay successfully detected E. turcicum in field maize leaves without DNA extraction, demonstrating its suitability for rapid on-spot detection of NCLB. Our study provides a direct LAMP diagnostic method to detect E. turcicum, which enables on-site pathogen detection in the field and the development of preventive strategies for NCLB management.

Genetic Diversity and Pathogenic Variation of the Rice False Smut Pathogen Ustilaginoidea virens from Different Rice Cultivars.

Rice false smut, caused by Ustilaginoidea virens, has become one of the most devastating grain diseases of rice worldwide. Understanding the genetic diversity of U. virens is essential for efficient disease control and breeding for disease resistance. However, little is known about the genetic variation of U. virens from different rice cultivars. We investigated the genetic diversity and pathogenic variation of U. virens isolates from 10 rice cultivars in Zhejiang, China. A total of 260 polymorphic loci and 27 haplotypes were identified based on the 2,137-bp combined DNA fragments of all individuals; hap_4 was the most common haplotype, represented by 41 isolates. Phylogeny indicated that all isolates were divided into four genetic groups. Group I was the largest, with 98 isolates, distributed mainly in eight cultivar populations, whereas 90% of the isolates collected from a Changxiang cultivar were clustered in Group IV. Furthermore, the pairwise FST values exhibited significant genetic differentiation in 27 of the pairwise comparisons between populations, accounting for 23.21% of the total genetic variation. The genetic composition of the isolates of the CX population was distinguishable from that of the other nine populations, and genetic recombination was found in a few isolates. Finally, 27 haplotype representative isolates showed high variation in pathogenicity, and the isolates from the genetic subpopulation I were likely to be more virulent than those from genetic subpopulations II and III. Collectively, these findings suggest that differences in rice cultivars play an important role in the genetic variation of U. virens.

FoRSR1 Is Important for Conidiation, Fusaric Acid Production, and Pathogenicity in Fusarium oxysporum f. sp. ginseng.

The root rot disease caused by Fusarium oxysporum f. sp. ginseng is one of the most destructive diseases of ginseng, an economically important herb. However, little is known about the pathogen's toxin biosynthesis or the molecular mechanisms regulating infection of ginseng. In this study we identified and functionally characterized the FoRSR1 gene that encodes a Ras-related (RSR) small GTPase homologous to yeast Rsr1 in F. oxysporum f. sp. ginseng. Disruption of FoRSR1 resulted in a significant reduction in mycelial dry weight in liquid cultures, although vegetative growth rate was not affected on culture plates. Notably, the Forsr1 mutant exhibited blunted and swollen hyphae with multi-nucleated compartments. It produced fewer and morphologically abnormal conidia and was defective in chlamydospore formation. In infection assays with ginseng roots, the Forsr1 mutant was significantly less virulent and caused only limited necrosis at the wounding sites. Deletion of FoRSR1 also affected pigmentation, autophagy, and production of fusaric acid. Furthermore, the expression of many candidate genes involved in secondary metabolism was significantly downregulated in the mutant, suggesting that FoRSR1 is also important for secondary metabolism. Overall, our results indicated that FoRSR1 plays important roles in conidiation, vacuolar morphology, secondary metabolism, and pathogenesis in F. oxysporum f. sp. ginseng.

Historical evolution of polycyclic aromatic hydrocarbon pollution in Chaihe Reservoir from 1863 to 2018.

Pollution from polycyclic aromatic hydrocarbons (PAHs) spreads and changes worldwide. The pollution evolution in the regional water environment evolves in response to multiple factors, requiring considerable attention. PAH heterogeneity in the sediment core from Chaihe Reservoir was investigated to indicate dynamic changes in PAH pollution levels and sources and propose recommendations for controlling PAHs. Dynamic PAH patterns showed that the overall decline in PAH pollution was in association with local anthropogenic activities, temperature, and precipitation over the period 1863-2018. Nevertheless, coal, oil, and natural gas consumptions still played significant roles in transferring PAHs to the reservoir. Meanwhile, there were dominant local origins, including grass, wood, and coal combustion. The results highlight that the joint action of natural and anthropogenic interventions mitigated PAH pollution in the reservoir. Promoting improved fuels, new energy vehicles, and cleaner energy may further lower PAH pollution.

Arabidopsis RNA polymerase II C-terminal domain phosphatase-like 1 targets mitogen-activated protein kinase cascades to suppress plant immunity.

Mitogen-activated protein kinase (MAPK) cascades play pivotal roles in plant defense against phytopathogens downstream of immune receptor complexes. The amplitude and duration of MAPK activation must be strictly controlled, but the underlying mechanism remains unclear. Here, we identified Arabidopsis CPL1 (C-terminal domain phosphatase-like 1) as a negative regulator of microbe-associated molecular pattern (MAMP)-triggered immunity via a forward-genetic screen. Disruption of CPL1 significantly enhanced plant resistance to Pseudomonas pathogens induced by the bacterial peptide flg22. Furthermore, flg22-induced MPK3/MPK4/MPK6 phosphorylation was dramatically elevated in cpl1 mutants but severely impaired in CPL1 overexpression lines, suggesting that CPL1 might interfere with flg22-induced MAPK activation. Indeed, CPL1 directly interacted with MPK3 and MPK6, as well as the upstream MKK4 and MKK5. A firefly luciferase-based complementation assay indicated that the interaction between MKK4/MKK5 and MPK3/MPK6 was significantly reduced in the presence of CPL1. These results suggest that CPL1 plays a novel regulatory role in suppressing MAMP-induced MAPK cascade activation and MAMP-triggered immunity to bacterial pathogens.

Effects of forest age on soil erosion and nutrient loss in Dianchi watershed, China.

Soil erosion and nutrient loss are important environmental and ecological problems in the Dianchi watershed in southwestern China. Woodlands-the primary land type in the Dianchi watershed-play an important ecological role in controlling soil and water loss. In this study, we compared soil erosion and loss of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in woodlands of different ages, i.e., young forest, medium forest, and near-mature forest, at the Dongda River catchment in south-western Dianchi watershed. Furthermore, changes in stoichiometries in soil were analyzed. The average degree of erosion of each forest age stage was below moderate. Based on the non-arable soil erosion modulus models of 137Cs and 210Pbex, the soil erosion rates decreased gradually with the increasing forest age. The forest age affected soil nutrient distribution and loss. The losses of TOC and TP gradually decreased, while the losses of TN first increased and then decreased with the growth of forest age. TOC, TN, and TP were enriched in the topsoil. Forest age affected soil stoichiometry and soil nutrient supply level. In general, the forest can effectively reduce soil erosion and nutrient loss in the red soil area with the forest age increasing.

Gap-Free Nuclear and Mitochondrial Genomes of Ustilaginoidea virens JS60-2, a Fungal Pathogen Causing Rice False Smut.

Rice false smut (RFS), caused by Ustilaginoidea virens, has become a major disease in recent years, and mycotoxins produced by U. virens often threaten food safety. To study fungal pathogenesis and identify potential targets for developing new fungicides, gap-free nuclear and complete mitochondrial genomes of U. virens JS60-2 were sequenced and assembled. Using the second and third generation sequencing data, we assembled a 38.02-Mb genome that consists of seven contigs with the contig N50 being 6.32-Mb. In total, 8,486 protein-coding genes were annotated in the genome, including 21 secondary metabolism gene clusters. We also assembled the complete mitochondrial genome, which is 102,498 bp, with 28% GC content. The JS60-2 genomes assembled in this study will facilitate research on U. virens and contribute to RFS control. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

SnRK1A-mediated phosphorylation of a cytosolic ATPase positively regulates rice innate immunity and is inhibited by Ustilaginoidea virens effector SCRE1.

Rice false smut caused by Ustilaginoidea virens is becoming one of the most recalcitrant rice diseases worldwide. However, the molecular mechanisms underlying rice immunity against U. virens remain unknown. Using genetic, biochemical and disease resistance assays, we demonstrated that the xb24 knockout lines generated in non-Xa21 rice background exhibit an enhanced susceptibility to the fungal pathogens U. virens and Magnaporthe oryzae. Consistently, flg22- and chitin-induced oxidative burst and expression of pathogenesis-related genes in the xb24 knockout lines were greatly attenuated. As a central mediator of energy signaling, SnRK1A interacts with and phosphorylates XB24 at Thr83 residue to promote ATPase activity. SnRK1A is activated by pathogen-associated molecular patterns and positively regulates plant immune responses and disease resistance. Furthermore, the virulence effector SCRE1 in U. virens targets host ATPase XB24. The interaction inhibits ATPase activity of XB24 by blocking ATP binding to XB24. Meanwhile, SCRE1 outcompetes SnRK1A for XB24 binding, and thereby suppresses SnRK1A-mediated phosphorylation and ATPase activity of XB24. Our results indicate that the conserved SnRK1A-XB24 module in multiple crop plants positively contributes to plant immunity and uncover an unidentified molecular strategy to promote infection in U. virens and a novel host target in fungal pathogenesis.

Phosphorylation-guarded light-harvesting complex II contributes to broad-spectrum blast resistance in rice.

Environmental conditions are key factors in the progression of plant disease epidemics. Light affects the outbreak of plant diseases, but the underlying molecular mechanisms are not well understood. Here, we report that the light-harvesting complex II protein, LHCB5, from rice is subject to light-induced phosphorylation during infection by the rice blast fungus Magnaporthe oryzae We demonstrate that single-nucleotide polymorphisms (SNPs) in the LHCB5 promoter control the expression of LHCB5, which in turn correlates with the phosphorylation of LHCB5. LHCB5 phosphorylation enhances broad-spectrum resistance of rice to M. oryzae through the accumulation of reactive oxidative species (ROS) in the chloroplast. We also show that LHCB5 phosphorylation-induced resistance is inheritable. Our results uncover an immunity mechanism mediated by phosphorylation of light-harvesting complex II.

Characterization of Genetic Diversity and Variation in Pathogenicity of the Rice False Smut Pathogen Ustilaginoidea virens from a Single Source.

Rice false smut, caused by Ustilaginoidea virens, is one of the most destructive fungal diseases in rice-growing countries. Studies of the genetic diversity, evolution, and pathogenicity of U. virens can provide more information for disease control and cultivar breeding. Contrary to previous studies on the genetic diversity of different geographical populations of U. virens, this study analyzed the genetic variation of U. virens from different panicles of the same rice cultivar in a field in Yunnan Province using single nucleotide polymorphism molecular markers. A total of 183 polymorphic loci and five haplotypes, hap_1 to hap_5, were identified based on the 1,350-bp combined DNA fragment of 127 isolates, showing some genetic diversity. Hap_1 and hap_3 had the highest occurrence, indicating they were the dominant haplotypes in the field. Further analysis showed that most rice panicles could be coinfected by different haplotypes, and even a few spikelets could be coinfected by multiple haplotypes. The phylogeny indicated that all isolates were divided into five genetic groups. Groups I, II, and III clustered together and were distinguished from Groups IV and V. Significant genetic variations in five pairwise comparisons of panicle populations, accounting for 72.45% of the total variation, were found according to FST values. This variation might be caused by different field microenvironments and the uneven distribution of inoculum sources. An unweighted pair-group method with arithmetic means dendrogram and the population structure revealed that the genetic composition of the isolates collected from YN1, YN2, and YN4, which were dominated by the same genetic subgroup, was different from that collected from YN3. Finally, genetic recombination was found in 11 isolates; hap_2 and hap_5, probably as genetic recombination progenies produced by sexual hybridization between hap_1 and hap_3, acquired a greater virulence than their ancestors according to population structure and pathogenicity analyses. These results will help us understand the genetic diversity, evolution, and infection process of U. virens and aid in the development of more effective management strategies for rice false smut, including new cultivars with improved resistance.

Genetic Diversity and Population Structure of the Rice False Smut Pathogen Ustilaginoidea virens in the Sichuan-Chongqing Region.

Rice false smut caused by Ustilaginoidea virens is one of the most devastating fungal diseases of rice panicles worldwide. In this study, two novel molecular markers derived from single nucleotide polymorphism-rich genomic DNA fragments and a previously reported molecular marker were used for analyzing the genetic diversity and population structure of 167 U. virens isolates collected from nine areas in the Sichuan-Chongqing region, China. A total of 62 haplotypes were identified, and a few haplotypes with high frequency were found and distributed in two to three areas, suggesting gene flow among different geographical populations. All isolates were divided into six genetic groups. Groups I and VI were the largest, with 61 and 48 isolates, respectively. The pairwise FST values showed significant genetic differentiation among all compared geographical populations. Analysis of molecular variance showed that intergroup genetic variation accounted for 40.17% of the total genetic variation, while 59.83% of genetic variation came from intragroup genetic variation. The unweighted pair-group method with arithmetic means dendrogram and population structure revealed that the genetic composition of isolates collected from Santai, Nanchong, Yongchuan, and Wansheng dominated by the same genetic subgroup was different from those collected from other areas. In addition, genetic recombination was found in a few isolates. These findings will help to improve the strategies for rice false smut management and resistance breeding, such as evaluating breeding lines with different isolates or haplotypes at different elevations and landforms.

Ustilaginoidea virens Nuclear Effector SCRE4 Suppresses Rice Immunity via Inhibiting Expression of a Positive Immune Regulator OsARF17.

Rice false smut caused by the biotrophic fungal pathogen Ustilaginoidea virens has become one of the most important diseases in rice. The large effector repertory in U. virens plays a crucial role in virulence. However, current knowledge of molecular mechanisms how U. virens effectors target rice immune signaling to promote infection is very limited. In this study, we identified and characterized an essential virulence effector, SCRE4 (Secreted Cysteine-Rich Effector 4), in U. virens. SCRE4 was confirmed as a secreted nuclear effector through yeast secretion, translocation assays and protein subcellular localization, as well as up-regulation during infection. The SCRE4 gene deletion attenuated the virulence of U. virens to rice. Consistently, ectopic expression of SCRE4 in rice inhibited chitin-triggered immunity and enhanced susceptibility to false smut, substantiating that SCRE4 is an essential virulence factor. Furthermore, SCRE4 transcriptionally suppressed the expression of OsARF17, an auxin response factor in rice, which positively regulates rice immune responses and resistance against U. virens. Additionally, the immunosuppressive capacity of SCRE4 depended on its nuclear localization. Therefore, we uncovered a virulence strategy in U. virens that transcriptionally suppresses the expression of the immune positive modulator OsARF17 through nucleus-localized effector SCRE4 to facilitate infection.

Versatile effectors of phytopathogenic fungi target host immunity.

Phytopathogenic fungi secrete a large arsenal of effector molecules, including proteinaceous effectors, small RNAs, phytohormones and derivatives thereof. The pathogenicity of fungal pathogens is primarily determined by these effectors that are secreted into host cells to undermine innate immunity, as well as to facilitate the acquisition of nutrients for their in planta growth and proliferation. After conventional and non-conventional secretion, fungal effectors are translocated into different subcellular compartments of the host cells to interfere with various biological processes. In extracellular spaces, apoplastic effectors cope with physical and chemical barriers to break the first line of plant defenses. Intracellular effectors target essential immune components on the plasma membrane, in the cytosol, including cytosolic organelles, and in the nucleus to suppress host immunity and reprogram host physiology, favoring pathogen colonization. In this review, we comprehensively summarize the recent advances in fungal effector biology, with a focus on the versatile virulence functions of fungal effectors in promoting pathogen infection and colonization. A perspective of future research on fungal effector biology is also discussed.

The Conserved Effector UvHrip1 interacts with OsHGW, and Infection of Ustilaginoidea virens Regulates Defense- and Heading Date-Related Signaling Pathway.

Ustilaginoidea virens, which causes rice false smut (RFS), is one of the most detrimental rice fungal diseases and poses a severe threat to rice production and quality. Effectors in U. virens often act as a group of essential virulence factors that play crucial roles in the interaction between host and the pathogen. Thus, the functions of individual effectors in U. virens need to be further explored. Here, we demonstrated a small secreted hypersensitive response-inducing protein (hrip), named UvHrip1, which was highly conserved in U. virens isolates. UvHrip1 was also proven to suppress necrosis-like defense symptoms in N. benthamiana induced by the oomycete elicitor INF1. The localization of UvHrip1 was mainly in the nuclei and cytoplasm via monitoring the UvHrip1-GFP fusion protein in rice cells. Furthermore, Y2H and BiFC assay demonstrated that UvHrip1 interacted with OsHGW, which is a critical regulator in heading date and grain weight signaling pathways in rice. Expression patterns of defense- and heading date-related genes, OsPR1#051 and OsMYB21, were down-regulated over U. virens infection in rice. Collectively, our data provide a theory for gaining an insight into the molecular mechanisms underlying the UvHrip1 virulence function.

Towards understanding the biosynthetic pathway for ustilaginoidin mycotoxins in Ustilaginoidea virens.

Ustilaginoidins, toxic to plants, animals and human, are one of major types of mycotoxins produced by Ustilaginoidea virens. In this study, a gene cluster containing the polyketide synthase gene UvPKS1 was analysed via gene replacement and biochemical studies to determine ustilaginoidin biosynthetic pathway in U. virens. UvPKS1 was first proven to be responsible for the first step of ustilaginoidin biosynthesis, since neither ustilaginoidin derivatives nor intermediates were produced when UvPKS1 was deleted. Replacement of ugsO greatly reduced ustilaginoidin production but increased the ratios of dehydrogenated/hydrogenated ustilagioidin derivatives. The enhanced growth rate of the ΔugsO mutant indicates that accumulation of certain ustilaginoidin derivatives may adversely affect mycelial growth in U. virens. Deletion of ugsT encoding a putative MFS transporter disrupted the ability to generate ustilaginoidins. The ustilaginoidin derivatives produced in the ΔugsJ mutant all lack C3-methyl, indicating that UgsJ is responsible for C3-methylation. Only monomeric intermediates, such as 3-methyl-dihydro-nor-rubrofusarin, but no ustilaginoidin derivatives were generated in the ΔugsL mutant, indicating that UgsL is responsible for the dimerization of nor-rubrofusarin derivatives to produce ustilaginoidins. However, ugsR2 deletion had no dramatic effect on ustilaginoidin biosynthesis. Together, biochemical analyses with bioinformatics and chemoinformatics uncover a multiple-step enzyme-catalysed pathway for ustilaginoidin biosynthesis in U. virens.

The Kinase OsCPK4 Regulates a Buffering Mechanism That Fine-Tunes Innate Immunity.

The calcium-dependent protein kinase OsCPK4 has been demonstrated to play important roles in salt and drought tolerance, plant growth, and development in rice (Oryza sativa). However, little is known about molecular mechanisms underlying OsCPK4 function in rice immunity. In this study, we demonstrated that the generation of oxidative burst and pathogenesis-related gene expression triggered by microbe-associated molecular patterns were significantly enhanced in the oscpk4 mutants. These mutant lines are more resistant to bacterial blight and fungal blast diseases than the wild-type plants, indicating that OsCPK4 negatively regulates innate immunity in rice. OsCPK4 was further identified to interact with a receptor-like cytoplasmic kinase OsRLCK176. OsRLCK176 accumulation is negatively regulated by OsCPK4. Interestingly, the kinase-dead OsCPK4 promotes OsRLCK176 degradation more strongly than the wild-type protein. OsCPK4 and OsRLCK176 mutually phosphorylate each other and form a feedback loop. Moreover, the kinase activity and phosphorylation of OsCPK4 and OsRLCK176 contribute to the stability of OsRLCK176. These findings indicate that the kinase-inactive OsCPK4 promotes OsRLCK176 degradation and restricts plant defenses, whereas the activation of OsCPK4-OsRLCK176 phosphorylation circuit invalidates the OsRLCK176 degradation machinery, thus enhancing plant immunity. Collectively, the study proposes a novel defense buffering mechanism mediated by OsCPK4, which fine-tunes microbe-associated molecular pattern-triggered immunity in rice.

Global Proteomic Analysis Reveals Widespread Lysine Succinylation in Rice Seedlings.

Lysine succinylation (Ksu) is a dynamic and reversible post-translational modification that plays an important role in many biological processes. Although recent research has analyzed Ksu plant proteomes, little is known about the scope and cellular distribution of Ksu in rice seedlings. Here, we report high-quality proteome-scale Ksu data for rice seedlings. A total of 710 Ksu sites in 346 proteins with diverse biological functions and subcellular localizations were identified in rice samples. About 54% of the sites were predicted to be localized in the chloroplast. Six putative succinylation motifs were detected. Comparative analysis with succinylation data revealed that arginine (R), located downstream of Ksu sites, is the most conserved amino acid surrounding the succinylated lysine. KEGG pathway category enrichment analysis indicated that carbon metabolism, tricarboxylic acid cycle (TCA) cycle, oxidative phosphorylation, photosynthesis, and glyoxylate and dicarboxylate metabolism pathways were significantly enriched. Additionally, we compared published Ksu data from rice embryos with our data from rice seedlings and found conserved Ksu sites between the two rice tissues. Our in-depth survey of Ksu in rice seedlings provides the foundation for further understanding the biological function of lysine-succinylated proteins in rice growth and development.