BPL3 binds the long non-coding RNA nalncFL7 to suppress FORKED-LIKE7 and modulate HAI1-mediated MPK3/6 dephosphorylation in plant immunity.

RNA-binding proteins (RBPs) participate in a diverse set of biological processes in plants, but their functions and underlying mechanisms in plant-pathogen interactions are largely unknown. We previously showed that Arabidopsis thaliana BPA1-LIKE PROTEIN3 (BPL3) belongs to a conserved plant RBP family and negatively regulates reactive oxygen species (ROS) accumulation and cell death under biotic stress. In this study, we demonstrate that BPL3 suppresses FORKED-LIKE7 (FL7) transcript accumulation and raises levels of the cis-natural antisense long non-coding RNA (lncRNA) of FL7 (nalncFL7). FL7 positively regulated plant immunity to Phytophthora capsici while nalncFL7 negatively regulated resistance. We also showed that BPL3 directly binds to and stabilizes nalncFL7. Moreover, nalncFL7 suppressed accumulation of FL7 transcripts. Furthermore, FL7 interacted with HIGHLY ABA-INDUCED PP2C1 (HAI1), a type 2C protein phosphatase, and inhibited HAI1 phosphatase activity. By suppressing HAI1 activity, FL7 increased the phosphorylation levels of MITOGEN-ACTIVATED PROTEIN KINASE 3 (MPK3) and MPK6, thus enhancing immunity responses. BPL3 and FL7 are conserved in all plant species tested, but the BPL3-nalncFL7-FL7 cascade was specific to the Brassicaceae. Thus, we identified a conserved BPL3-nalncFL7-FL7 cascade that coordinates plant immunity.

A conserved protein family in mirid bug Riptortus pedestris plays dual roles in regulating plant immunity.

The mirid bug (Riptortus pedestris), a major soybean pest, migrates into soybean fields during the pod filling stage and causes staygreen syndrome, which leads to substantial yield losses. The mechanism by which R. pedestris elicits soybean (Glycine max) defenses and counter-defenses remains largely unexplored. In this study, we characterized a protein family from R. pedestris, designated Riptortus pedestris HAMP 1 (RPH1) and its putative paralogs (RPH1L1, 2, 3, 4, and 5), whose members exhibit dual roles in triggering and inhibiting plant immunity. RPH1 and RPH1L1 function as herbivore-associated molecular patterns (HAMPs), activating pattern-triggered immunity (PTI) in tobacco (Nicotiana benthamiana) and G. max. Furthermore, RPH1 stimulates jasmonic acid and ethylene biosynthesis in G. max, thereby enhancing its resistance to R. pedestris feeding. Additionally, RPH1 homologs are universally conserved across various herbivorous species, with many homologs also acting as HAMPs that trigger plant immunity. Interestingly, the remaining RPH1 putative paralogs (RPH1L2-5) serve as effectors that counteract RPH1-induced PTI, likely by disrupting the extracellular perception of RPH1. This research uncovers a HAMP whose homologs are conserved in both chewing and piercing-sucking insects. Moreover, it unveils an extracellular evasion mechanism utilized by herbivores to circumvent plant immunity using functionally differentiated paralogs.

Synthesis of Tetrasubstituted Enamines Using Secondary Amines and In Situ-Generated Allenes from Nitrocyclopropanes.

A novel reaction of cyclic and acyclic secondary amines with in situ-generated allene intermediate species from nitro-substituted donor-acceptor cyclopropanes is reported. In the presence of a simple inorganic base, NaOH, tetrasubstituted enamine derivatives can be obtained in moderate to excellent yields. The reaction is operationally easy, features mild reaction conditions and simple inorganic bases, and is free of transition metals.

A Phytophthora sojae CRN effector mediates phosphorylation and degradation of plant aquaporin proteins to suppress host immune signaling.

Phytophthora genomes encode a myriad of Crinkler (CRN) effectors, some of which contain putative kinase domains. Little is known about the host targets of these kinase-domain-containing CRNs and their infection-promoting mechanisms. Here, we report the host target and functional mechanism of a conserved kinase CRN effector named CRN78 in a notorious oomycete pathogen, Phytophthora sojae. CRN78 promotes Phytophthora capsici infection in Nicotiana benthamiana and enhances P. sojae virulence on the host plant Glycine max by inhibiting plant H2O2 accumulation and immunity-related gene expression. Further investigation reveals that CRN78 interacts with PIP2-family aquaporin proteins including NbPIP2;2 from N. benthamiana and GmPIP2-13 from soybean on the plant plasma membrane, and membrane localization is necessary for virulence of CRN78. Next, CRN78 promotes phosphorylation of NbPIP2;2 or GmPIP2-13 using its kinase domain in vivo, leading to their subsequent protein degradation in a 26S-dependent pathway. Our data also demonstrates that NbPIP2;2 acts as a H2O2 transporter to positively regulate plant immunity and reactive oxygen species (ROS) accumulation. Phylogenetic analysis suggests that the phosphorylation sites of PIP2 proteins and the kinase domains of CRN78 homologs are highly conserved among higher plants and oomycete pathogens, respectively. Therefore, this study elucidates a conserved and novel pathway used by effector proteins to inhibit host cellular defenses by targeting and hijacking phosphorylation of plant aquaporin proteins.

Cyclophilin effector Al106 of mirid bug Apolygus lucorum inhibits plant immunity and promotes insect feeding by targeting PUB33.

Apolygus lucorum (Meyer-Dur; Heteroptera: Miridae) is a major agricultural pest infesting crops, vegetables, and fruit trees. During feeding, A. lucorum secretes a plethora of effectors into its hosts to promote infestation. However, the molecular mechanisms of these effectors manipulating plant immunity are largely unknown. Here, we investigated the molecular mechanism underlying the effector Al106 manipulation of plant-insect interaction by RNA interference, electrical penetration graph, insect and pathogen bioassays, protein-protein interaction studies, and protein ubiquitination experiment. Expression of Al106 in Nicotiana benthamiana inhibits pathogen-associated molecular pattern-induced cell death and reactive oxygen species burst, and promotes insect feeding and plant pathogen infection. In addition, peptidyl-prolyl cis-trans isomerase (PPIase) activity of Al106 is required for its function to inhibit PTI.Al106 interacts with a plant U-box (PUB) protein, PUB33, from N. benthamiana and Arabidopsis thaliana. We also demonstrated that PUB33 is a positive regulator of plant immunity. Furthermore, an in vivo assay revealed that Al106 inhibits ubiquitination of NbPUB33 depending on PPIase activity. Our findings revealed that a novel cyclophilin effector may interact with plant PUB33 to suppress plant immunity and facilitate insect feeding in a PPIase activity-dependent manner.

Apolygus lucorum effector Al6 promotes insect feeding performance on soybean plants: RNAi analysis and feeding behaviour study with electrical penetration graph.

The mirid bug Apolygus lucorum, a dominant mirid species in northern China, is a notorious polyphagous pest with more than 200 hosts, including several major crops such as cotton and soybean, resulting in massive economic loss. Studies of insect salivary effectors may provide a novel control strategy for A. lucorum. An A. lucorum effector, that is, Al6, that inhibits plant immunity by using glutathione peroxidase to repress reactive oxidase accumulation was previously identified. In this study, we further explored the molecular functions of Al6 associated with feeding behaviour and insect survival on soybean, a major host of A. lucorum, using RNA interference and electrical penetration graph (EPG) techniques. We initially observed the injury symptom of this mirid bug and characterized feeding behaviour on soybean leaves using EPG. Our results revealed that A. lucorum preferred to feed on young plant organs such as tender leaves, shoots and buds. This mirid bug used cell rupture as a feeding strategy to ingest cell contents from plant tissues. Subsequently, we silenced the Al6 gene using RNAi and investigated the feeding behaviour, honeydew excretion, body weight, and survival rates of A. lucorum on soybean after Al6 knockdown. Our results demonstrated that silencing of Al6 significantly reduced feeding duration, amount of honeydew secretion, body weight, and survival rates of A. lucorum. Thus, our findings provide a novel molecular target of plant-mediated RNAi for the control of A. lucorum.

Phytophthora infection signals-induced translocation of NAC089 is required for endoplasmic reticulum stress response-mediated plant immunity.

Plants deploy various immune receptors to recognize pathogen-derived extracellular signals and subsequently activate the downstream defense response. Recently, increasing evidence indicates that the endoplasmic reticulum (ER) plays a part in the plant defense response, known as ER stress-mediated immunity (ERSI), that halts pathogen infection. However, the mechanism for the ER stress response to signals of pathogen infection remains unclear. Here, we characterized the ER stress response regulator NAC089, which was previously reported to positively regulate programed cell death (PCD), functioning as an ERSI regulator. NAC089 translocated from the ER to the nucleus via the Golgi in response to Phytophthora capsici culture filtrate (CF), which is a mixture of pathogen-associated molecular patterns (PAMPs). Plasma membrane localized co-receptor BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 (BAK1) was required for the CF-mediated translocation of NAC089. The nuclear localization of NAC089, determined by the NAC domain, was essential for immune activation and PCD. Furthermore, NAC089 positively contributed to host resistance against the oomycete pathogen P. capsici and the bacteria pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. We also proved that NAC089-mediated immunity is conserved in Nicotiana benthamiana. Together, we found that PAMP signaling induces the activation of ER stress in plants, and that NAC089 is required for ERSI and plant resistance against pathogens.

Infection mechanisms and putative effector repertoire of the mosquito pathogenic oomycete Pythium guiyangense uncovered by genomic analysis.

Pythium guiyangense, an oomycete from a genus of mostly plant pathogens, is an effective biological control agent that has wide potential to manage diverse mosquitoes. However, its mosquito-killing mechanisms are almost unknown. In this study, we observed that P. guiyangense could utilize cuticle penetration and ingestion of mycelia into the digestive system to infect mosquito larvae. To explore pathogenic mechanisms, a high-quality genome sequence with 239 contigs and an N50 contig length of 1,009 kb was generated. The genome assembly is approximately 110 Mb, which is almost twice the size of other sequenced Pythium genomes. Further genome analysis suggests that P. guiyangense may arise from a hybridization of two related but distinct parental species. Phylogenetic analysis demonstrated that P. guiyangense likely evolved from common ancestors shared with plant pathogens. Comparative genome analysis coupled with transcriptome sequencing data suggested that P. guiyangense may employ multiple virulence mechanisms to infect mosquitoes, including secreted proteases and kazal-type protease inhibitors. It also shares intracellular Crinkler (CRN) effectors used by plant pathogenic oomycetes to facilitate the colonization of plant hosts. Our experimental evidence demonstrates that CRN effectors of P. guiyangense can be toxic to insect cells. The infection mechanisms and putative virulence effectors of P. guiyangense uncovered by this study provide the basis to develop improved mosquito control strategies. These data also provide useful knowledge on host adaptation and evolution of the entomopathogenic lifestyle within the oomycete lineage. A deeper understanding of the biology of P. guiyangense effectors might also be useful for management of other important agricultural pests.

Genome-wide association study reveals the genetic architecture of root hair length in maize.

BACKGROUND: Root hair, a special type of tubular-shaped cell, outgrows from root epidermal cell and plays important roles in the acquisition of nutrients and water, as well as interactions with biotic and abiotic stress. Although many genes involved in root hair development have been identified, genetic basis of natural variation in root hair growth has never been explored. RESULTS: Here, we utilized a maize association panel including 281 inbred lines with tropical, subtropical, and temperate origins to decipher the phenotypic diversity and genetic basis of root hair length. We demonstrated significant associations of root hair length with many metabolic pathways and other agronomic traits. Combining root hair phenotypes with 1.25 million single nucleotide polymorphisms (SNPs) via genome-wide association study (GWAS) revealed several candidate genes implicated in cellular signaling, polar growth, disease resistance and various metabolic pathways. CONCLUSIONS: These results illustrate the genetic basis of root hair length in maize, offering a list of candidate genes predictably contributing to root hair growth, which are invaluable resource for the future functional investigation.

Double-faced role of Bcl-2-associated athanogene 7 in plant-Phytophthora interaction.

Due to their sessile nature, plants must respond to various environmental assaults in a coordinated manner. The endoplasmic reticulum is a central hub for plant responses to various stresses. We previously showed that Phytophthora utilizes effector PsAvh262-mediated binding immunoglobulin protein (BiP) accumulation for suppressing endoplasmic reticulum stress-triggered cell death. As a BiP binding partner, Bcl-2-associated athanogene 7 (BAG7) plays a crucial role in the maintenance of the unfolded protein response, but little is known about its role in plant immunity. In this work, we reveal a double-faced role of BAG7 in Arabidopsis-Phytophthora interaction in which it regulates endoplasmic reticulum stress-mediated immunity oppositely in different cellular compartments. In detail, it acts as a susceptibility factor in the endoplasmic reticulum, but plays a resistance role in the nucleus against Phytophthora. Phytophthora infection triggers the endoplasmic reticulum-to-nucleus translocation of BAG7, the same as abiotic heat stress; however, this process can be prevented by PsAvh262-mediated BiP accumulation. Moreover, the immunoglobulin/albumin-binding domain in PsAvh262 is essential for both pathogen virulence and BiP accumulation. Taken together, our study uncovers a double-faced role of BAG7; Phytophthora advances its colonization in planta by utilizing an effector to detain BAG7 in the endoplasmic reticulum.

Direct N-alkylation of sulfur-containing amines.

An efficient ruthenium-catalyzed method has been developed for the direct N-alkylation of sulfur-containing amines with alcohols, for the first time, by a step-economical and environmentally friendly hydrogen borrowing strategy. The present methodology features base-free conditions and broad substrate scope, with water being the only by-product. Moreover, this protocol has been applied to the synthesis of the pharmaceutical drug Quetiapine.

Prediction and Characterization of RXLR Effectors in Pythium Species.

RXLR effectors, a class of secreted proteins that are transferred into host cells to manipulate host immunity, have been reported to widely exist in oomycetes, including those from genera Phytophthora, Hyaloperonospora, Albugo, and Saprolegnia. However, in Pythium species, no RXLR effector has yet been characterized, and the origin and evolution of such virulent effectors are still unknown. Here, we developed a modified regular expression method for de novo identification of RXLRs and characterized 359 putative RXLR effectors in nine Pythium species. Phylogenetic analysis revealed that all oomycetous RXLRs formed a single superfamily, suggesting that they might have a common ancestor. RXLR effectors from Pythium and Phytophthora species exhibited similar sequence features, protein structures, and genome locations. In particular, there were significantly more RXLR proteins in the mosquito biological control agent P. guiyangense than in the other eight Pythium species, and P. guiyangense RXLRs might be the result of gene duplication and genome rearrangement events, as indicated by synteny analysis. Expression pattern analysis of RXLR-encoding genes in the plant pathogen P. ultimum detected transcripts of the majority of the predicted RXLR genes, with some RXLR effectors induced in infection stages and one RXLR showing necrosis-inducing activity. Furthermore, all predicted RXLR genes were cloned from two biocontrol agents, P. oligandrum and P. periplocum, and three of the RXLR genes were found to induce a defense response in Nicotiana benthamiana. Taken together, our findings represent the first evidence of RXLR effectors in Pythium species, providing valuable information on their evolutionary patterns and the mechanisms of their interactions with diverse hosts.

The glycoside hydrolase 18 family chitinases are associated with development and virulence in the mosquito pathogen Pythium guiyangense.

Chitinases, the enzymes responsible for the biological degradation of chitin, participate in numerous physiological processes such as nutrition, parasitism, morphogenesis and immunity in various organisms. However, the genome-wide distribution, evolution and biological functions of chitinases are rarely reported in oomycetes. This study systematically investigated the glycoside hydrolase 18 (GH18) family of chitinases from the mosquito pathogenic oomycete, Pythium guiyangense using bioinformatics and experimental assays. A total of 3 pairs of GH18 chitinase genes distributed in three distinct phylogenic clusters were identified from P. guiyangense genome, which is consistent with the ones in plant pathogenic oomycetes. Further transcriptional analysis revealed that Pgchi1/2 was highly expressed at the development stages, while Pgchi3/4 and Pgchi5/6 were up-regulated at the infection stages. The biological function analysis of chitinase genes using genetic transformation silencing method showed that silencing of Pgchi1/2 resulted in reduced zoospore production, without affecting the virulence. However, attenuation of Pgchi3/4 and Pgchi5/6 genes regulated not only oxidative stress responses, but also led to decreased infection rates to mosquito larvae. Taken together, this study provides a comprehensive overview of P. guiyangense chitinase family and reveals their diverse roles in the development, stress response, and virulence, which would elucidate insightful information on the molecular mechanism of chitinase in entomopathogenic pathogens.

The mirid bug Apolygus lucorum deploys a glutathione peroxidase as a candidate effector to enhance plant susceptibility.

The mirid bug Apolygus lucorum has become a major agricultural pest since the large-scale cultivation of Bt-cotton. It was assumed that A. lucorum, similarly to other phloem sap insects, could secrete saliva that contains effector proteins into plant interfaces to perturb host cellular processes during feeding. However, the secreted effectors of A. lucorum are still uncharacterized and unstudied. In this study, 1878 putative secreted proteins were identified from the transcriptome of A. lucorum, which either had homology with published aphid effectors or shared common features with plant pathogens and insect effectors. One hundred and seventy-two candidate effectors were used for cell death-inducing/suppressing assays, and a putative salivary gland effector, Apolygus lucorum cell death inhibitor 6 (Al6), was characterized. The mRNAs of Al6 were enriched at feeding stages (nymph and adult) and, in particular, in salivary glands. Moreover, we revealed that the secreted Al6 encoded an active glutathione peroxidase that reduced reactive oxygen species (ROS) accumulation induced by INF1 or Flg22. Expression of the Al6 gene in planta altered insect feeding behavior and promoted plant pathogen infections. Inhibition of cell death and enhanced plant susceptibility to insect and pathogens are dependent on glutathione peroxidase activity of Al6. Thus, this study shows that a candidate salivary gland effector, Al6, functions as a glutathione peroxidase and suppresses ROS induced by pathogen-associated molecular pattern to inhibit pattern-triggered immunity (PTI)-induced cell death. The identification and molecular mechanism analysis of the Al6 candidate effector in A. lucorum will provide new insight into the molecular mechanisms of insect-plant interactions.

Genome-wide and functional analyses of tyrosine kinase-like family genes reveal potential roles in development and virulence in mosquito pathogen Pythium guiyangense.

The tyrosine kinase-like (TKL) gene family is widely existed in most eukaryotes and participates in many biological processes, however, has been rarely studied in oomycetes. In this study we performed bioinformatic and experimental analyses to characterize TKLs in Pythium guiyangense, a promising mosquito biological control agent. Our results revealed that TKLs were widely distributed in all the detected oomycetes, but were largely expanded in P. guiyangense in a species-specific expansion manner. The expansion was mostly driven by whole-genome duplication and tandem duplication. Domain distributions and exon-intron structures were highly conserved in the same group while diverse in different groups, suggesting of functional divergence. Transcriptional analysis revealed that over one fourth of TKLs were differentially expressed after infection of mosquito larvae, implying that these genes might participate in the infection process. Furthermore, subgroup A TKLs were functionally investigated using genetic transformation silencing method. Our findings demonstrated that subgroup A TKLs were up-regulated at the early infection stages and silencing of subgroup A TKLs led to reduced mycelia growth, zoospore production and alteration of stress responses. Pathogenicity assays also revealed that silencing of subgroup A TKLs reduced P. guiyangense virulence to mosquito larvae. Taken together, this study provides a comprehensive overview of P. guiyangense TKL family and reveals their potential roles in growth, development, stress response, and especially virulence.

Decrease in DNA methylation 1 (DDM1) is required for the formation of m CHH islands in maize.

DNA methylation plays a crucial role in suppressing mobilization of transposable elements and regulation of gene expression. A number of studies have indicated that DNA methylation pathways and patterns exhibit distinct properties in different species, including Arabidopsis, rice, and maize. Here, we characterized the function of DDM1 in regulating genome-wide DNA methylation in maize. Two homologs of ZmDDM1 are abundantly expressed in the embryo and their simultaneous disruption caused embryo lethality with abnormalities in cell proliferation from the early stage of kernel development. We establish that ZmDDM1 is critical for DNA methylation, at CHG sites, and to a lesser extent at CG sites, in heterochromatic regions, and unexpectedly, it is required for the formation of m CHH islands. In addition, ZmDDM1 is indispensable for the presence of 24-nt siRNA, suggesting its involvement in the RdDM pathway. Our results provide novel insight into the role of ZmDDM1 in regulating the formation of m CHH islands, via the RdDM pathway maize, suggesting that, in comparison to Arabidopsis, maize may have adopted distinct mechanisms for regulating m CHH.

Comparative physical genome mapping of malaria vectors Anopheles sinensis and Anopheles gambiae.

BACKGROUND: Anopheles sinensis is a dominant natural vector of Plasmodium vivax in China, Taiwan, Japan, and Korea. Recent genome sequencing of An. sinensis provides important insights into the genomic basis of vectorial capacity. However, the lack of a physical genome map with chromosome assignment and orientation of sequencing scaffolds hinders comparative analyses with other genomes to infer evolutionary changes relevant to the vector capacity. RESULTS: Here, a physical genome map for An. sinensis was constructed by assigning 52 scaffolds onto the chromosomes using fluorescence in situ hybridization (FISH). This chromosome-based genome assembly composes approximately 36% of the total An. sinensis genome. Comparisons of 3955 orthologous genes between An. sinensis and Anopheles gambiae identified 361 conserved synteny blocks and 267 inversions fixed between these two lineages. The rate of gene order reshuffling on the X chromosome is approximately 3.2 times higher than that on the autosomes. CONCLUSIONS: The physical map will facilitate detailed genomic analysis of An. sinensis and contribute to understanding of the patterns and mechanisms of large-scale genome rearrangements in anopheline mosquitoes.

Tryptophan/copper-catalyzed aromatization reaction of chiral cyclohexanones to phenols.

By merging organocatalysis with copper catalysis, a highly efficient stereospecific approach for the synthesis of chiral phenols from cyclohexanones has been developed for the first time. The aromatization reaction proceeds through the in situ formation of enone intermediates and further subsequent bromination/dehydrobromination reactions. And a series of functionalized phenol derivatives are obtained in good yields (up to 89%) and good to excellent enantioselectivities (up to 99% ee).

One-pot asymmetric synthesis of a spiro[dihydrofurocoumarin/pyrazolone] scaffold by a Michael addition/I2-mediated cyclization sequence.

An asymmetric formal one-pot reaction of 4-hydroxycoumarins with unsaturated pyrazolones has been developed by merging a chiral bifunctional organocatalyst with molecular iodine, which furnished a series of optically active spiro[dihydrofurocoumarin/pyrazolone] heterocycles with spiro quaternary stereogenic centers in moderate to excellent yields (up to 99%) with excellent diastereoselectivities (up to >99 : 1 dr) and good to excellent enantioselectivities (up to 99% ee). The application in the gram-scale synthesis of chiral spiro[dihydrofurocoumarin/pyrazolone] compounds was also successfully realized.

Jørgensen-Hayashi catalysts supported on poly(ethylene glycol)s as highly efficient and reusable organocatalysts for the enamine-catalyzed asymmetric Michael reaction.

A new kind of recyclable and reusable PEG-supported Jørgensen-Hayashi catalyst is synthesized for the first time and proven to be efficient for the enamine-catalyzed asymmetric Michael reaction with generally moderate to good diastereoselectivity and high to excellent enantioselectivity (up to 6 : 1 dr, 99% ee). The prepared PEG-supported catalyst can be recovered eight times and was found to provide similar diastereoselectivity and enantioselectivity to unsupported functional catalysts.