A pair of G-type lectin receptor-like kinases modulates nlp20-mediated immune responses by coupling to the RLP23 receptor complex

Plant cells recognize microbial patterns with the plasma-membrane-localized pattern-recognition receptors consisting mainly of receptor kinases(RKs) and receptor-like proteins(RLPs). RKs, such as bacterial flagellin receptor FLS2, and their downstream signaling components have been studied extensively. However, newly discovered regulatory components of RLP-mediated immune signaling, such as the nlp20 receptor RLP23, await identification. Unlike RKs, RLPs lack a cytoplasmic kinase domain, instead recruiting the receptor-like kinases(RLKs) BAK1 and SOBIR1. SOBIR1 specifically works as an adapter for RLP-mediated immunity. To identify new regulators of RLP-mediated signaling, we looked for SOBIR1-binding proteins(SBPs) in Arabidopsis thaliana using protein immunoprecipitation and mass spectrometry,identifying two G-type lectin RLKs, SBP1 and SBP2, that physically interacted with SOBIR1.SBP1 and SBP2 showed high sequence similarity,were tandemly repeated on chromosome 4, and also interacted with both RLP23 and BAK1. sbp1 sbp2 double mutants obtained via CRISPR-Cas9 gene editing showed severely impaired nlp20-induced reactive oxygen species burst, mitogenactivated protein kinase(MAPK) activation, and defense gene expression, but normal flg22-induced immune responses. We showed that SBP1 regulated nlp20-induced immunity in a kinase activityindependent manner. Furthermore, the nlp20-induced the RLP23–BAK1 interaction, although not the flg22-induced FLS2–BAK1 interaction, was significantly reduced in sbp1 sbp2. This study identified SBPs as new regulatory components in RLP23 receptor complex that may specifically modulate RLP23-mediated immunity by positively regulating the interaction between the RLP23 receptor and the BAK1 co-receptor.

Receptor-like kinases and receptor-like proteins： keys to pathogen recognition and defense signaling in plant innate immunity

Plants have evolved multiple layers of defense against various pathogens in the environment. Receptor-like kinases/proteins （RLKs/RLPs） are on the front lines of the battle between plants and pathogens since they are present at the plasma membrane and perceive signature molecules from either the invading pathogen or damaged plant tissue. With a few notable exceptions, most RLKs/RLPs are positive regulators of plant innate immunity. In this review, we summarize recently discovered RLKs/RLPs that are involved in plant defense responses against various classes of pathogens, We also describe what is currently known about the mechanisms of RLK-mediated initiation of signaling via protein-protein interactions and phosphorylation.

Notes from the Underground:Receptor-Like Kinases in Arabidopsis Root Development

During plant development, the frequency and context of cell division must be controlled, and cells must differentiate properly to perform their mature functions. In addition, stem cell niches need to be maintained as a reservoir for new cells. All of these processes require intercellular signaling, whether it is a cell relaying its position to other cells, or more mature cells signaling to the stem cell niche to regulate the rate of growth. Receptor-like kinases have emerged as a major component in these diverse roles, especially within the Arabidopsis root. In this review, the functions of receptor-like kinase signaling in regulating Arabidopsis root development will be examined in theareas of root apical meristem maintenance, regulation of epidermal cell fate, lateral root development and vascular differentiation.

Receptor-Like Kinases:Key Regulators of Plant Development and Defense

Plants are multi-cellular organisms that live in diverse and fluctuating environments. Cell-cell and cell-environment com- munication are therefore critical to plant growth and develop- ment. In animals, transmembrane receptor protein tyrosine kinases play significant roles in cell-cell signaling. There was a great deal of surprise in the plant community, however, when the first receptor-like protein kinase （RLK） was isolated from maize by John C.

A review on potential heterocycles for the treatment of glioblastoma targeting receptor tyrosine kinases

Glioblastoma,the most aggressive form of brain tumor,poses significant challenges in terms of treatment success and patient survival.Current treatment modalities for glioblastoma include radiation therapy,surgical intervention,and chemotherapy.Unfortunately,the median survival rate remains dishearteningly low at 12–15 months.One of the major obstacles in treating glioblastoma is the recurrence of tumors,making chemotherapy the primary approach for secondary glioma patients.However,the efficacy of drugs is hampered by the presence of the blood-brain barrier and multidrug resistance mechanisms.Consequently,considerable research efforts have been directed toward understanding the underlying signaling pathways involved in glioma and developing targeted drugs.To tackle glioma,numerous studies have examined kinase-downstream signaling pathways such as RAS-RAF-MEKERK-MPAK.By targeting specific signaling pathways,heterocyclic compounds have demonstrated efficacy in glioma therapeutics.Additionally,key kinases including phosphatidylinositol 3-kinase(PI3K),serine/threonine kinase,cytoplasmic tyrosine kinase(CTK),receptor tyrosine kinase(RTK)and lipid kinase(LK)have been considered for investigation.These pathways play crucial roles in drug effectiveness in glioma treatment.Heterocyclic compounds,encompassing pyrimidine,thiazole,quinazoline,imidazole,indole,acridone,triazine,and other derivatives,have shown promising results in targeting these pathways.As part of this review,we propose exploring novel structures with low toxicity and high potency for glioma treatment.The development of these compounds should strive to overcome multidrug resistance mechanisms and efficiently penetrate the blood-brain barrier.By optimizing the chemical properties and designing compounds with enhanced drug-like characteristics,we can maximize their therapeutic value and minimize adverse effects.Considering the complex nature of glioblastoma,these novel structures should be rigorously tested and evaluated for their efficacy and safety profiles.

Mouse KL2 is a unique MTSE involved in chromosome-based spindle organization and regulated by multiple kinases during female meiosis

Microtubule-severing enzymes(MTSEs)play important roles in mitosis and meiosis of the primitive organisms.However,their roles in mammalian female meiosis,which accounts for over 80%of gamete-originated human reproductive diseases,remain unexplored.In the current study,we reported that katanin-like 2(KL2)was the only MTSE concentrating at chromosomes.Furthermore,the knockdown of KL2 significantly reduced the chromosome-based increase in the microtubule(MT)polymer,increased aberrant kinetochore-MT(K-MT)attachment,delayed meiosis,and severely affected normal fertility.We demonstrated that the inhibition of aurora B,a key kinase for correcting aberrant K-MT attachment,significantly eliminated KL2 expression from chromosomes.Additionally,KL2 interacted with phosphorylated eukaryotic elongation factor-2 kinase,and they competed for chromosome binding.Phosphorylated KL2 was also localized at spindle poles,with its phosphorylation regulated by extracellular signal-regulated kinase 1/2.In summary,the current study reveals a novel function of MTSEs in mammalian female meiosis and demonstrates that multiple kinases coordinate to regulate the levels of KL2 at chromosomes.

Knights in Action： Lectin Receptor-Like Kinases in Plant Development and Stress Responses

The Receptor-Like Kinase （RLK） is a vast protein family with over 600 genes in Arabidopsis and 1100 in rice. The Lectin RLK （LecRLK） family is believed to play crucial roles in saccharide signaling as well as stress perception. All the LecRLKs possess three domains： an N-terminal lectin domain, an intermediate transmembrane domain, and a C-terminal kinase domain. On the basis of lectin domain variability, LecRLKs have been subgrouped into three subclasses： L-, G-, and C-type LecRLKs. While the previous studies on LecRLKs were dedicated to classification, comparative structural analysis and expression analysis by promoter-based studies, most of the recent studies on LecRLKs have laid special emphasis on the potential of this gene family in regulating biotic/abiotic stress and developmental pathways in plants, thus mak- ing the prospects of studying the LecRLK-mediated regulatory mechanism exceptionally promising. In this review, we have described in detail the LecRLK gene family with respect to a historical, evolutionary, and structural point of view. Furthermore, we have laid emphasis on the LecRLKs roles in development, stress conditions, and hormonal response. We have also discussed the exciting research prospects offered by the current knowledge on the LecRLK gene family. The multitude of the LecRLK gene family members and their functional diversity mark these genes as both interesting and worthy candidates for further analysis, especially in the field of crop improvement.

Receptor-Like Kinases in Plant Innate Immunity

Plants employ a highly effective surveillance system to detect potential pathogens, which is critical for the success of land plants in an environment surrounded by numerous microbes. Recent efforts have led to the identification of a number of immune receptors and components of immune receptor complexes. It is now clear that receptor-like kinases （RLKs） and receptor-like proteins （RLPs） are key pattern-recognition receptors （PRRs） for microbe- and plant-derived molecular patterns that are associated with pathogen invasion. RLKs and RLPs involved in immune signaling belong to large gene families in plants and have undergone lineage specific expansion. Molecular evolution and population studies on phytopathogenic molecular signatures and their receptors have provided crucial insight into the co-evolution between plants and pathogens.

Genome-Wide Expression Pattern Analyses of the Arabidopsis Leucine-Rich Repeat Receptor-Like Kinases

Receptor-like protein kinases （RLKs） are a large group of transmembrane proteins playing critical roles in cell-cell and cell--environment communications. Based on extracellular domain structures, RLKs were classified into more than 21 subfamilies, among which leucine-rich repeat RLKs （LRR-RLKs） belong to the largest subfamily in plants such as Arabidopsis and rice. In Arabidopsis, there are approximately 223 LRR-RLKs, but only about 60 of which have been functionally described to date. To systematically investigate the roles of LRR-RLKs in regulating plant growth, development, and stress adaptations, we generated promoter：：GUS transgenic plants for all 223 LRR-RLK genes in Arabidopsis and analyzed their detailed expression patterns at various developmental stages. The results provide valuable resources for functionally elucidating this large and essential signaling protein subfamily.

SERK Family Receptor-like Kinases Function as Co-receptors with PXY for Plant Vascular Development

In Arabidopsis, the CLAVATA3/EMBRYO SURROUNDING REGION-RELATED （CLE） peptides play important roles in regulating proliferation and differentiation of plant-specific stem cells. Although receptors of CLEs are reported to be leucine-rich repeat receptor kinases, the mechanisms underlying CLE-induced receptor activation remain largely unknown. Here we show that SOMATIC EMBRYOGENESIS RECEPTOR KINASEs （SERKs） serve as co-receptors in CLE41/TDIF-PXY signaling to regulate plant vascular development. TDIF induces interaction of its receptor PXY with SERKs in vitro and in vivo. Furthermore, the serk1-1 serk2-1 bakl-5 mutant plants are less sensitive to TDIF, phenocopying the pxy mutant with a compromised promotion of procambial cell proliferation. Crystal structure of the PXY-TDIF-SERK2 complex reveals that the last amino acid of TDIF conserved among CLEs and other evolutionary-related peptides is important for the interaction between SERK2 and PXY. Taken together, our current study identifies SERKs as signaling components of the TDIF-PXY pathway and suggests a conserved activation mechanism of CLE receptors.

Rapid responses:Receptor-like kinases directly regulate the functions of membrane transport proteins in plants

Receptor-like kinases(RLKs)are a large group of plant-specific transmembrane proteins mainly acting as receptors or co-receptors of various extracellular signals.They usually turn extracellular signals into intracellular responses via altering gene expression profiles.However,recent studies confirmed that many RLKs can physically interact with diverse membrane-localized transport proteins and regulate their activities for speedy responses in limited tissues or cells.In this minireview,we highlight recent discoveries regarding how RLKs can work with membrane transport proteins collaboratively and thereby trigger cellular responses in a precise and rapid manner.It is anticipated that such regulation broadly presents in plants and more examples will be gradually revealed when in-depth analyses are conducted for the functions of RLKs.

Receptor-like Kinases in Root Development:Current Progress and Future Directions

Cell-to-cell and cell-to-environment communications are critical to the growth and development of plants.Cell surface-localized receptor-like kinases(RLKs)are mainly involved in sensing various extracellular signals to initiate their corresponding cellular responses.As important vegetative organs for higher plants to adapt to a terrestrial living situation,roots play a critical role for the survival of plants.It has been demonstrated that RLKs control many biological processes during root growth and development.In this review,we summarize several key regulatory processes during Arabidopsis root developm ent in which RLKs play critical roles.We also put forward a number of relevant questions that are required to be explored in future studies.

A FLASH pipeline for arrayed CRISPR library construction and the gene function discovery of rice receptor-like kinases

Clustered regularly interspaced short palindromic repeats(CRISPR)-CRISPR-associated protein 9(Cas9)-mediated gene editing is revolutionizing plant research and crop breeding.Here,we present an effective and streamlined pipeline for arrayed CRISPR library construction and demonstrate it is suitable for small-to large-scale genome editing in plants.This pipeline introduces artificial PCR fragment-length markers for distinguishing guide RNAs(gRNAs)(FLASH),and a group of 12 constructs harboring different FLASH tags are co-transformed into plants each time.The identities of gRNAs in Agrobacterium mixtures and trans-genic plants can therefore be read out by detecting the FLASH tags,a process that requires only conven-tional PCR and gel electrophoresis rather than sequencing.We generated an arrayed CRISPR library target-ing all 1,072 members of the receptor-like kinase(RLK)family in rice.One-shot transformation generated a mutant population that covers gRNAs targeting 955 RLKs,and 74.3%(710/955)of the target genes had three or more independent T0 lines.Our results indicate that the FLASH tags act as bona fide surrogates for the gRNAs and are tightly(92.1%)associated with frameshift mutations in the target genes.In addition,the FLASH pipeline allows for rapid identification of unintended editing events without corresponding T-DNA integrations and generates high-order mutants of closely related RLK genes.Furthermore,we showed that the RLK mutant library enables rapid discovery of defense-related RLK genes.This study introduces an effective pipeline for arrayed CRISPR library construction and provides genome-wide rice RLK mutant resources for functional genomics.

Receptor-like kinases MDS1 and MDS2 promote SUMM2-mediated immunity

Disruption of the MEKK1-MKK1/MKK2-MPK4 kinase cascade leads to activation of immunity mediated by the nucleotide-binding leucine-rich repeat(NLR)immune receptor SUMM2,which monitors the phosphorylation status of CRCK3.Here we report that two receptor-like kinases(RLKs),MDS1,and MDS2,function redundantly to promote SUMM2-mediated immunity.Activation of SUMM2-mediated immunity is dependent on MDS1,and to a less extent on MDS2.MDS1 associates with CRCK3 in planta and can phosphorylate CRCK3 in vitro,suggesting that it may target CRCK3 to positively regulate SUMM2-mediated signaling.Our finding highlights a new defense mechanism where RLKs promote NLR-mediated immunity.

Screening of Extracellular Binding Proteins of Rice Receptor-like Kinase CR4 by the Yeast Two-hybrid

[Objective] The research aimed to find the extracellular binding proteins of CR4.[Method] The extracellular domain of OsCR4 was as the bait protein,and the yeast two-hybrid was used to screen cDNA library of seedling which was cultivated 14 d.[Result] A lot of proteins which included a peroxide B（D26484）,a methionine thioredoxin reductase（ABF96078）and an unknown function protein were gained.[Conclusion] It provided the theory basis for studying the signal transduction mechanism of CR4.

Cloning and Hybrid Identification of Banana Receptor-like Protein Kinase Gene

[Objective] This study aimed to clone and identify the banana fruit receptor-like protein kinase gene.[Method] The cDNA phage libraries of banana fruit were adopted as the experimental materials to screen positive phage libraries of banana receptor-like protein kinase gene;cloning and sequence analysis of the gene were conducted,and the banana receptor-like protein kinase gene was identified by using in situ hybridization method.[Result] In this study,a 1 698 bp long banana receptor-like protein kinase gene was cloned from banana fruit,encoding 563 amino acids.Southern hybridization result confirmed that the banana receptor-like protein kinase gene was a multiple-copy gene from banana genome.[Conclusion] The study laid the foundation for further investigating the functions of banana receptor-like protein kinase gene in fruit.

Characterization of a S-locus-related Receptor-like Kinase Cluster in Rice Chromosome 4

We have identified 14 S _locus glycoprotein (SLG)_related protein kinase genes in a 323 kb contig of rice (Oryza sativa L.) chromosome 4 and we detected the transcription pattern of this gene cluster by reverse transcription_polymerase reaction (RT_PCR). RT_PCR results revealed that nine putative genes were transcribed in rice and these genes had the different expression patterns: two genes are expressed predominantly in reproductive tissues while the other seven genes are expressed in both reproductive and vegetative tissues. Analysis of the predicted amino acid sequences demonstrated that the extracellular receptor domains are highly homologous to SLG of Brassica, whereas the cytoplasmic kinase domains contain conserved amino acids present in serine/threonine kinases.

Genome-wide identification of the mitogen-activated protein kinase kinases in pear and their functional analysis in response to black spot

The mitogen-activated protein kinase(MAPK)cascade is crucial to plant growth,development,and stress responses.MAPK kinases(MAPKK)play a vital role in linking upstream MAPKK kinases(MAPKKK)with the downstream MAPK.Black spot is one of the most serious fungal diseases of pear which is an important part of the fruit industry in China.The MAPKK genes have been identified in many plants,however,none has been reported in pear(Pyrus bretschneideri).In order to explore whether MAPK gene of pear is related to black spot disease,we designed this experiment.The present study investigated eight putative PbrMAPKK genes obtained from the Chinese white pear genome.The phylogenetic analysis revealed that PbrMAPKK genes were divided into A,B,C,and D groups.These PbrMAPKK genes are randomly distributed on 7 out of 17 chromosomes and mainly originated from the whole-genome duplication(WGD)event.The expression analysis of PbrMAPKK genes in seven pear tissues and the leaves of susceptible and resistant varieties after Alternaria alternata infection by quantitative real-time PCR(qRT-PCR)identified seven candidate genes associated with resistance.Furthermore,virus-induced gene silencing(VIGS)indicated that PbrMAPKK6 gene enhanced resistance to pear black spot disease in pear.

The wheat receptor-like cytoplasmic kinase TaRLCK1B is required for host immune response to the necrotrophic pathogen Rhizoctonia cerealis

Receptor-like cytoplasmic kinases(RLCKs)represent a large family of proteins in plants.In Arabidopsis and rice,several RLCKs in subfamily VII(RLCKs-VII)have been implicated in pathogen-associated molecular pattern-triggered immunity and basal resistance against bacterial and fungal pathogens.However,little is known about roles of RLCKs-VII of the important crop common wheat(Triticum aestivum)in immune responses.Here,we isolated a RLCK-VII-encoding gene from wheat,designated as TaRLCK1B,and investigated its role in host immune response to infection of a necrotrophic fungus Rhizoctonia cerealis that is a major pathogen of sharp eyespot,a destructive disease of wheat.RNA-sequencing and RT-qPCR analyses showed that transcriptional level of TaRLCK1B was significantly higher in sharp eyespot-resistant wheat cultivars than in susceptible wheat cultivars.The gene transcription was rapidly and markedly elevated in the resistant wheat cultivars by R.cerealis infection.The TaRLCK1B protein was closely related to OsRLCK176,a rice resistance-related RLCKs-VII,with 84.03%identity.Virus-induced gene silencing plus wheat response to R.cerealis assay results indicated that silencing of TaRLCK1 impaired resistance to R.cerealis.Meantime,silencing of TaRLCK1 significantly elevated both the content of H2 O2(a major kind of reactive oxygen species,ROS)and the transcriptional level of the ROS-generating enzyme-encoding gene RBOH,but repressed the expression of the ROS-scavenging enzyme-encoding gene CAT1 at 18 hours after inoculation(hai)with R.cerealis.Taken together,these data suggested that TaRLCK1B was required for the early immune response of wheat to R.cerealis through modulating ROS signaling in wheat.

Cloning and Characterization of a Somatic Embryogenesis Receptor-Like Kinase Gene in Cotton (Gossypium hirsutum)

A novel gene, GhSERK1, was identified in cotton. It encoded a protein belonging to the somatic embryogenesis receptor- like kinase （SERK） family. The genomic sequence of GhSERK1 was 6 920 bp in length, containing a predicted transcriptional start site （TSS）. Its full-length cDNA was 2 502 bp, encoding a protein of 627 amino acids. Sequence analysis of GhSERK1 revealed high levels of similarity to other reported SERKs, as well as a conserved intron/exon structure that was unique to members of the SERK family. Expression analysis showed that GhSERK1 mRNA was present in all organs of cotton plants and at different developmental stages, but its transcripts were most abundant in reproductive organs. Compared with that of the male-fertile line, the level of GhSERK1 mRNA was lower in the anther of the male-sterile cotton line, in which the pollen development was defected. Taken together, these findings illustrated that the GhSERK1 play a critical role during the anther formation, and may also have a broad role in other aspects of plant development.