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Plants are exposed to various stress during their growth and development, and abiotic stress is one of the most significant factors. Receptor-like kinases (RLKs) are widely present in plants that can quickly and effectively respond to stress, ultimately leading to a series of biological effects. Lectin receptor-like kinases (LecRLKs) belongs to a subfamily of RLKs, which consisting of three structural domains: extracellular lectin domain, transmembrane domain, and intracellular kinase domain. Based on the different types of extracellular lectin domains, LecRLKs can be classified into three subclasses: L, G and C types. In recent years, numerous studies have shown that plant lectin receptor-like kinases play a vital role in responses to abiotic stress. By recognizing abiotic stress-related signal molecules, LecRLKs can activate downstream signaling pathways, such as the MAPK pathway, the ROS pathway, the calcium signaling pathway, as well as to regulate gene expression and protein translation to enhance plant stress resistance. In this review, we summarize the structural characteristics and classification of LecRLKs. Meanwhile, the functions and mechanisms of LecRLKs in response to abiotic stress such as salt stress, low temperature stress, drought stress, mechanical damage and plant hormones are systematically reviewed. Furthermore, prospects are made for the future research directions of LecRLKs. This review not only provides new insights into the functions and mechanisms of LecRLKs in abiotic stress responses, but also provides a theoretical basis for using LecRLKs to improve crop resistance breeding.

Summary: Plant leaf senescence, caused by multiple internal and environmental factors, has an important impact on agricultural production. The lectin receptor‐like kinase (LecRLK) family members participate in plant development and responses to biotic and abiotic stresses, but their roles in regulating leaf senescence remain elusive. Here, we identify and characterize a rice premature withered leaf 1 (pwl1) mutant, which exhibits premature leaf senescence throughout the plant life cycle. The pwl1 mutant displayed withered and whitish leaf tips, decreased chlorophyll content, and accelerated chloroplast degradation. Map‐based cloning revealed an amino acid substitution (Gly412Arg) in LOC_Os03g62180 (PWL1) was responsible for the phenotypes of pwl1. The expression of PWL1 was detected in all tissues, but predominantly in tillering and mature leaves. PWL1 encodes a G‐type LecRLK with active kinase and autophosphorylation activities. PWL1 is localized to the plasma membrane and can self‐associate, mainly mediated by the plasminogen‐apple‐nematode (PAN) domain. Substitution of the PAN domain significantly diminished the self‐interaction of PWL1. Moreover, the pwl1 mutant showed enhanced reactive oxygen species (ROS) accumulation, cell death, and severe DNA fragmentation. RNA sequencing analysis revealed that PWL1 was involved in the regulation of multiple biological processes, like carbon metabolism, ribosome, and peroxisome pathways. Meanwhile, interfering of biological processes induced by the PWL1 mutation also enhanced heat sensitivity and resistance to bacterial blight and bacterial leaf streak with excessive accumulation of ROS and impaired chloroplast development in rice. Natural variation analysis indicated more variations in indica varieties, and the vast majority of japonica varieties harbour the PWL1Hap1 allele. Together, our results suggest that PWL1, a member of LecRLKs, exerts multiple roles in regulating plant growth and development, heat‐tolerance, and resistance to bacterial pathogens. [ABSTRACT FROM AUTHOR]

Plants are exposed to various stress during their growth and development, and abiotic stress is one of the most significant factors. Receptor-like kinases (RLKs) are widely present in plants that can quickly and effectively respond to stress, ultimately leading to a series of biological effects. Lectin receptor-like kinases (LecRLKs) belongs to a subfamily of RLKs, which consisting of three structural domains: extracellular lectin domain, transmembrane domain, and intracellular kinase domain. Based on the different types of extracellular lectin domains, LecRLKs can be classified into three subclasses: L, G and C types. In recent years, numerous studies have shown that plant lectin receptor-like kinases play a vital role in responses to abiotic stress. By recognizing abiotic stress-related signal molecules, LecRLKs can activate downstream signaling pathways, such as the MAPK pathway, the ROS pathway, the calcium signaling pathway, as well as to regulate gene expression and protein translation to enhance plant stress resistance. In this review, we summarize the structural characteristics and classification of LecRLKs. Meanwhile, the functions and mechanisms of LecRLKs in response to abiotic stress such as salt stress, low temperature stress, drought stress, mechanical damage and plant hormones are systematically reviewed. Furthermore, prospects are made for the future research directions of LecRLKs. This review not only provides new insights into the functions and mechanisms of LecRLKs in abiotic stress responses, but also provides a theoretical basis for using LecRLKs to improve crop resistance breeding. [ABSTRACT FROM AUTHOR]

Mutualistic association can improve a plant's health and productivity. G-type lectin receptor-like kinase (PtLecRLK1) is a susceptibility factor in Populus trichocarpa that permits root colonization by a beneficial fungus, Laccaria bicolor. Engineering PtLecRLK1 also permits L. bicolor root colonization in non-host plants similar to Populus trichocarpa. The intracellular signaling reprogramed by PtLecRLK1 upon recognition of L. bicolor to allow for the development and maintenance of symbiosis is yet to be determined. In this study, phosphoproteomics was utilized to identify phosphorylation-based relevant signaling pathways associated with PtLecRLK1 recognition of L. bicolor in transgenic switchgrass roots. Our finding shows that PtLecRLK1 in transgenic plants modifies the chitin-triggered plant defense and MAPK signaling along with a significant adjustment in phytohormone signaling, ROS balance, endocytosis, cytoskeleton movement, and proteasomal degradation in order to facilitate the establishment and maintenance of L. bicolor colonization. Moreover, protein–protein interaction data implicate a cGMP-dependent protein kinase as a potential substrate of PtLecRLK1. [ABSTRACT FROM AUTHOR]

Dwarfing is important for the production of wheat (Triticumaestivum L.). In model plants, receptor-like kinases have been implicated in signal transduction, immunity, and development. However, functional roles of lectin receptor-like kinases in wheat are poorly understood. In this study, we identified an L-type lectin receptor-like kinase gene in wheat, designated as TaLecRK-IV.1, and revealed its role in plant height. Real time quantitative PCR analyses indicated that TaLecRK-IV.1 transcript level was lower in a dwarf wheat line harboring the Rht-D1b gene compared to its transcript level detected in a taller wheat line CI12633. Importantly, the virus-induced gene silencing results showed that silencing of TaLecRK-IV.1 in the wheat line CI12633 led to dwarf plants. The results of the disease resistance test performed after the gene silencing experiment suggest no significant role of TaLecRK-IV.1 in the resistance reaction of wheat line CI12633 to sharp eyespot. Gene expression analysis revealed that the transcript abundance of TaLecRK-IV.1 was more up-regulated after the exogenous application of gibberellic acid and auxin, two development-related phytohormones, compared to the gene transcript levels detected in the control plants (mock treatment). These findings support the potential implication of TaLecRK-IV.1 in the pathway controlling plant height rather than the disease resistance role, and suggest that TaLecRK-IV.1 may be a positive regulator of plant height through the gibberellic acid and auxin-signaling pathways. [ABSTRACT FROM AUTHOR]

Lectin receptor-like kinase(LecRLK) is a class of phytokinase with lectin conserved domain, which plays an important role in plant resistance to biological and abiotic stresses, as well as plant growth and development. Cannabis sativa is an important multi-purpose plant, widely used in food, textile, medicine, and other fields. Genome-wide screening and expression analysis of the LecRLK family of C. sativa were performed in this paper, so as to provide scientific reference for functional analysis of the LecRLK family of C. sativa. Based on BLAST and HMM methods, 93 LecRLKs were identified in the whole genome of C. sativa, including 69 G types, 23 L types, and one C types. Subsequently, a series of bioinformatics analyses were performed on the LecRLK family members, and the physicochemical properties of the protein of the LecRLK family members were initially revealed. The prediction of cis-acting elements of promoters in family members showed that family members were regulated by hormones and stress response. The expression analysis showed that some family members were highly expressed in the roots, which may participate in the process of stress resistance. Several members were highly expressed in female flowers and may be involved in female flower development. This study provides a theoretical basis for further study of LecRLK gene function. Meanwhile, the expression analysis screens candidate LecRLK members who may participate in the resistance of C. sativa, which provides a theoretical basis for the subsequent selection of C. sativa varieties against resistance.

Mutualistic association can improve a plant’s health and productivity. G-type lectin receptor-like kinase (PtLecRLK1) is a susceptibility factor in Populus trichocarpa that permits root colonization by a beneficial fungus, Laccaria bicolor. Engineering PtLecRLK1 also permits L. bicolor root colonization in non-host plants similar to Populus trichocarpa. The intracellular signaling reprogramed by PtLecRLK1 upon recognition of L. bicolor to allow for the development and maintenance of symbiosis is yet to be determined. In this study, phosphoproteomics was utilized to identify phosphorylation-based relevant signaling pathways associated with PtLecRLK1 recognition of L. bicolor in transgenic switchgrass roots. Our finding shows that PtLecRLK1 in transgenic plants modifies the chitin-triggered plant defense and MAPK signaling along with a significant adjustment in phytohormone signaling, ROS balance, endocytosis, cytoskeleton movement, and proteasomal degradation in order to facilitate the establishment and maintenance of L. bicolor colonization. Moreover, protein–protein interaction data implicate a cGMP-dependent protein kinase as a potential substrate of PtLecRLK1.

BackgroundReceptor-like kinases (RLKs) belong to a large protein family with over 600 members in Arabidopsis and over 1000 in rice. Among RLKs, the lectin receptor-like kinases (LecRLKs) possess a characteristic extracellular carbohydrate-binding lectin domain and play important roles in plant development and innate immunity. There are 75 and 173 LecRLKs in Arabidopsis and rice, respectively. However, little is known about LecRLKs in perennial woody plants.ResultsHere we report the genome-wide analysis of classification, domain architecture and expression of LecRLKs in the perennial woody model plant Populus. We found that the LecRLK family has expanded in Populus to a total of 231, including 180 G-type, 50 L-type and 1 C-type LecRLKs. Expansion of the Populus LecRLKs (PtLecRLKs) occurred partially through tandem duplication. Based on domain architecture and orientation features, we classified PtLecRLKs into eight different classes. RNA-seq-based transcriptomics analysis revealed diverse expression patterns of PtLecRLK genes among leaves, stems, roots, buds and reproductive tissues and organs.ConclusionsThis study offers a comprehensive view of LecRLKs in the perennial woody model plant Populus and provides a foundation for functional characterization of this important family of receptor-like kinases.

• Genome-wide identification and evolutionary analysis of grape LecRLK family. • VvLecRLK genes showed distinct spatiotemporal and temporal expression patterns in multiple biological processes. • This study provides valuable insights into the grape LecRLK gene family and suggests their involvement in multiple biological processes. Lectin receptor kinases (LecRLK s) are critical in plant reactions to biotic and abiotic stresses. Although the genomic organization of LecRLK genes in different plants has gained attention, little research has been done in grapevine (Vitis vinifera L.). Here, we performed genome-wide characterization and expression profiling analysis of VvLecRLKs under different stresses, hormonal treatments, and in different organs. Fifty-one VvLecRLK genes were identified and categorized into three groups. The similarity in the distribution of exon-intron structure and conserved motifs within the same subgroup indicated the conservation of VvLecRLKs during evolution; while the difference in member number and gene structure among subgroups indicated their evolutionary diversity. Cis -acting elements associated with growth and development, hormone response, and stress response were identified in the promoters of VvLecRLK genes. Moreover, VvLecRLK genes showed distinct spatiotemporal and temporal expression patterns in multiple biological processes, including biotic stresses response (Downy mildew, Botrytis cinerea, and Powdery mildew), abiotic stresses response (heat, cold, salt, and drought), hormone treatments (Abscisic acid, Jasmonic acid, Salicylic acid, and Brassinosteroid) response. Further, some VvLecRLKs exhibited a tissue- or stage-specific high expression in different organs at various stages, especially during seed development of seeded and seedless cultivars. qRT-PCR analysis of selected genes further validated the potential role of VvLecRLKs involved in seed phenotype difference between seeded (Vitis labrusca vinifera 'Kyoho' and Vitis vinifera 'Zuijinxiang') and seedless grapes (Vitis vinifera 'Flame Seedless' and Vitis vinifera 'Crimson Seedless'). Our study provides new information on the grape LecRLK family in a systematical and comprehensive way, and for the first time, we propose that VvLecRLKs may play multiple roles in grape growth and development, especially associated with seedlessness in grapes. It provides valuable candidate gene resources for further functional research and benefits grape molecular breeding. [ABSTRACT FROM AUTHOR]

The disease Fusarium crown and root rot (FCRR), caused mainly by Fusarium oxysporum f. sp. radicis-lycopersici (FORL), seriously affects commercial tomato [ Solanum lycopersicum (Sl)] yields. However, the genes that offer resistance to FORL are limited and the mechanism of resistance to FCRR is poorly understood. Lectin receptor-like kinases (LecRKs) play critical roles in defensive responses and immunity in many plant species; however, whether specific LecRKs are involved in the response of tomato plants to FORL is unclear. Here, we report that the expression of SlLecRK1/Solyc09g011070.1 was obviously induced by the infection of FORL. Biochemical and cell biological data revealed that SlLecRK1 is an active kinase that is located at the cell membrane, while real-time quantitative PCR data suggested that SlLecRK1 is mainly expressed in stems and roots. Genetic studies showed that overexpression of SlLecRK1 significantly improved the resistance of tomato plants to FORL but did not cause visible changes in plant growth and development compared with wild-type control plants. RNA-Seq data suggested that the positive effects of SlLecRK1 on the resistance of tomato plants to FORL occur mainly by triggering the expression of ethylene-responsive transcription factor (ERF) genes. Together, our findings not only identify a new target for the development of FCRR-resistant tomato varieties, they also demonstrate a molecular mechanism linking SlLecRK1 and ERFs in regulating the immune responses of tomato plants to FORL. [ABSTRACT FROM AUTHOR]

The disease Fusarium crown and root rot (FCRR), caused mainly by Fusarium oxysporum f. sp. radicis-lycopersici (FORL), seriously affects commercial tomato [Solanum lycopersicum (Sl)] yields. However, the genes that offer resistance to FORL are limited and the mechanism of resistance to FCRR is poorly understood. Lectin receptor-like kinases (LecRKs) play critical roles in defensive responses and immunity in many plant species; however, whether specific LecRKs are involved in the response of tomato plants to FORL is unclear. Here, we report that the expression of SlLecRK1/Solyc09g011070.1 was obviously induced by the infection of FORL. Biochemical and cell biological data revealed that SlLecRK1 is an active kinase that is located at the cell membrane, while real-time quantitative PCR data suggested that SlLecRK1 is mainly expressed in stems and roots. Genetic studies showed that overexpression of SlLecRK1 significantly improved the resistance of tomato plants to FORL but did not cause visible changes in plant growth and development compared with wild-type control plants. RNA-Seq data suggested that the positive effects of SlLecRK1 on the resistance of tomato plants to FORL occur mainly by triggering the expression of ethylene-responsive transcription factor (ERF) genes. Together, our findings not only identify a new target for the development of FCRR-resistant tomato varieties, they also demonstrate a molecular mechanism linking SlLecRK1 and ERFs in regulating the immune responses of tomato plants to FORL.

Main conclusion: Soybean contains a group of 64 L-type lectin receptor-like kinases. Three LecRKs were involved in the interactions with Phytophthora sojae and Bradyrhizobium diazoefficiens. L-type lectin receptor-like kinases (LecRKs) comprise an important class of membrane-localized receptor-like kinases that are involved in plant adaptation. In this study, we performed an inventory analysis of LecRKs in Glycine max (soybean). In total, 64 GmLecRKs containing the canonical LecRK feature were identified. Phylogenetic analysis revealed that 48 GmLecRKs have close orthologs in Arabidopsis or Solanum lycopersicum, while 16 are likely present only in the leguminous plant species. Transcriptome analyses revealed that expressions of multiple GmLecRK genes are either induced or suppressed during infection by the soybean root rot pathogen Phytophthora sojae. In addition, overexpression of the three LecRKs (Glyma.17G085000, Glyma.05G041300 or Glyma.17G224600) in the soybean hairy roots enhanced resistance to P. sojae. Upon inoculation with Bradyrhizobium diazoefficiens, overexpression of Glyma.17G085000 in the soybean hairy roots does not significantly influence the nodulation, while overexpression of Glyma.05G041300 or Glyma.17G224600 slightly reduced the number and dry weight of nodules. This study highlights the importance of LecRKs in regulating plant–microbe interactions and provides new knowledge on the deployment of LecRKs to increase resistance in soybean. [ABSTRACT FROM AUTHOR]

Dwarfing is important for the production of wheat (Triticumaestivum L.). In model plants, receptor-like kinases have been implicated in signal transduction, immunity, and development. However, functional roles of lectin receptor-like kinases in wheat are poorly understood. In this study, we identified an L-type lectin receptor-like kinase gene in wheat, designated as TaLecRK-IV.1, and revealed its role in plant height. Real time quantitative PCR analyses indicated that TaLecRK-IV.1 transcript level was lower in a dwarf wheat line harboring the Rht-D1b gene compared to its transcript level detected in a taller wheat line CI12633. Importantly, the virus-induced gene silencing results showed that silencing of TaLecRK-IV.1 in the wheat line CI12633 led to dwarf plants. The results of the disease resistance test performed after the gene silencing experiment suggest no significant role of TaLecRK-IV.1 in the resistance reaction of wheat line CI12633 to sharp eyespot. Gene expression analysis revealed that the transcript abundance of TaLecRK-IV.1 was more up-regulated after the exogenous application of gibberellic acid and auxin, two development-related phytohormones, compared to the gene transcript levels detected in the control plants (mock treatment). These findings support the potential implication of TaLecRK-IV.1 in the pathway controlling plant height rather than the disease resistance role, and suggest that TaLecRK-IV.1 may be a positive regulator of plant height through the gibberellic acid and auxin-signaling pathways.

Lectin receptor-like kinases (LecRLKs), a plant-specific receptor-like kinase (RLK) sub-family, have been recently found to play crucial roles in plant development and responses to abiotic and biotic stresses. In this review, we first describe the classification and structures of Lectin RLKs. Then we focus on the analysis of functions of LecRLKs in various biological processes and discuss the status of LecRLKs from the ligands they recognize, substrate they target, signaling pathways they are involved in, to the overall regulation of growth-defense tradeoffs. LecRLKs and the signaling components they interact with constitute recognition and protection systems at the plant cell surface contributing to the detection of environmental changes monitoring plant fitness.

Lectin receptor-like kinases (LecRLKs), a plant-specific receptor-like kinase (RLK) sub-family, have been recently found to play crucial roles in plant development and responses to abiotic and biotic stresses. In this review, we first describe the classification and structures of Lectin RLKs. Then we focus on the analysis of functions of LecRLKs in various biological processes and discuss the status of LecRLKs from the ligands they recognize, substrate they target, signaling pathways they are involved in, to the overall regulation of growth-defense tradeoffs. LecRLKs and the signaling components they interact with constitute recognition and protection systems at the plant cell surface contributing to the detection of environmental changes monitoring plant fitness. [ABSTRACT FROM AUTHOR]

Gray leaf spot (GLS) disease in maize, caused by the fungus Cercospora zeina, is a threat to maize production globally. Understanding the molecular basis for quantitative resistance to GLS is therefore important for food security. We developed a de novo assembly pipeline to identify candidate maize resistance genes. Near-isogenic maize lines with and without a QTL for GLS resistance on chromosome 10 from inbred CML444 were produced in the inbred B73 background. The B73-QTL line showed a 20% reduction in GLS disease symptoms compared to B73 in the field (p = 0.01). B73-QTL leaf samples from this field experiment conducted under GLS disease pressure were RNA sequenced. The reads that did not map to the B73 or C. zeina genomes were expected to contain novel defense genes and were de novo assembled. A total of 141 protein-coding sequences with B73-like or plant annotations were identified from the B73-QTL plants exposed to C. zeina. To determine whether candidate gene expression was induced by C. zeina, the RNAseq reads from C. zeina-challenged and control leaves were mapped to a master assembly of all of the B73-QTL reads, and differential gene expression analysis was conducted. Combining results from both bioinformatics approaches led to the identification of a likely candidate gene, which was a novel allele of a lectin receptor-like kinase named L-RLK-CML that (i) was induced by C. zeina, (ii) was positioned in the QTL region, and (iii) had functional domains for pathogen perception and defense signal transduction. The 817AA L-RLK-CML protein had 53 amino acid differences from its 818AA counterpart in B73. A second “B73-like” allele of L-RLK was expressed at a low level in B73-QTL. Gene copy-specific RT-qPCR confirmed that the l-rlk-cml transcript was the major product induced four-fold by C. zeina. Several other expressed defense-related candidates were identified, including a wall-associated kinase, two glutathione s-transferases, a chitinase, a glucan beta-glucosidase, a plasmodesmata callose-binding protein, several other receptor-like kinases, and components of calcium signaling, vesicular trafficking, and ethylene biosynthesis. This work presents a bioinformatics protocol for gene discovery from de novo assembled transcriptomes and identifies candidate quantitative resistance genes.

The temporary callose layer surrounding the tetrads of microspores is critical for male gametophyte development in flowering plants, as abnormal callose deposition can lead to microspore abortion. A sophisticated signaling network regulates callose biosynthesis but these pathways are poorly understood. In this study, we characterized a rice male-sterile mutant, oslecrk5 , which showed defective callose deposition during meiosis. OsLecRK5 encodes a plasma membrane - localized lectin receptor-like kinase, which can form a dimer with itself. Moreover, normal anther development requires the K-phosphorylation site (a conserved residue at the ATP-binding site) of OsLecRK5. In vitro assay showed that OsLecRK5 phosphorylates the callose synthesis enzyme UGP1, enhancing callose biosynthesis during anther development. Together, our results demonstrate that plasma membrane-localized OsLecRK5 phosphorylates UGP1 and promotes its activity in callose biosynthesis in rice. This is the first evidence that a receptor-like kinase positively regulates callose biosynthesis. [ABSTRACT FROM AUTHOR]

Gray leaf spot (GLS) disease in maize, caused by the fungus Cercospora zeina , is a threat to maize production globally. Understanding the molecular basis for quantitative resistance to GLS is therefore important for food security. We developed a de novo assembly pipeline to identify candidate maize resistance genes. Near-isogenic maize lines with and without a QTL for GLS resistance on chromosome 10 from inbred CML444 were produced in the inbred B73 background. The B73-QTL line showed a 20% reduction in GLS disease symptoms compared to B73 in the field (p = 0.01). B73-QTL leaf samples from this field experiment conducted under GLS disease pressure were RNA sequenced. The reads that did not map to the B73 or C. zeina genomes were expected to contain novel defense genes and were de novo assembled. A total of 141 protein-coding sequences with B73-like or plant annotations were identified from the B73-QTL plants exposed to C. zeina. To determine whether candidate gene expression was induced by C. zeina , the RNAseq reads from C. zeina -challenged and control leaves were mapped to a master assembly of all of the B73-QTL reads, and differential gene expression analysis was conducted. Combining results from both bioinformatics approaches led to the identification of a likely candidate gene, which was a novel allele of a lectin receptor-like kinase named L-RLK-CML that (i) was induced by C. zeina , (ii) was positioned in the QTL region, and (iii) had functional domains for pathogen perception and defense signal transduction. The 817AA L-RLK-CML protein had 53 amino acid differences from its 818AA counterpart in B73. A second "B73-like" allele of L-RLK was expressed at a low level in B73-QTL. Gene copy-specific RT-qPCR confirmed that the l-rlk-cml transcript was the major product induced four-fold by C. zeina. Several other expressed defense-related candidates were identified, including a wall-associated kinase, two glutathione s-transferases, a chitinase, a glucan beta-glucosidase, a plasmodesmata callose-binding protein, several other receptor-like kinases, and components of calcium signaling, vesicular trafficking, and ethylene biosynthesis. This work presents a bioinformatics protocol for gene discovery from de novo assembled transcriptomes and identifies candidate quantitative resistance genes. [ABSTRACT FROM AUTHOR]

Lectin receptor-like kinases (LecRLKs) are a class of membrane proteins found in plants that are involved in diverse functions, including plant development and stress responses. Although LecRLK families have been identified in a variety of plants, a comprehensive analysis has not yet been undertaken in cucumber (Cucumis sativus L.). In this study, 46 putative LecRLK genes were identified in the cucumber genome, including 23 G-type and 22 L-type, and one C-type LecRLK gene. They were unequally distributed on all seven chromosomes, with a clustering tendency. Most of the genes in the cucumber LecRLK (CsLecRLK) gene family lacked introns. In addition, there were many regulatory elements associated with phytohormones and stress on these genes’ promoters. Transcriptome data demonstrated distinct expression patterns of CsLecRLK genes in various tissues. Furthermore, we found that each member of the CsLecRLK family had its own unique expression pattern under hormone and stress treatment by the quantitative real-time PCR (qRT-PCR) analysis. This study provides a better understanding of the character and function of the LecRLK gene family in cucumber and opens up the possibility to exploring the roles that LecRLKs might play in the life cycle of cucumber.

Lectins are fundamental to plant life and have important roles in cell-to-cell communication; development and defence strategies. At the cell surface; lectins are present both as soluble proteins (LecPs) and as chimeric proteins: lectins are then the extracellular domains of receptor-like kinases (LecRLKs) and receptor-like proteins (LecRLPs). In this review; we first describe the domain architectures of proteins harbouring G-type; L-type; LysM and malectin carbohydrate-binding domains. We then focus on the functions of LecPs; LecRLKs and LecRLPs referring to the biological processes they are involved in and to the ligands they recognize. Together; LecPs; LecRLKs and LecRLPs constitute versatile recognition systems at the cell surface contributing to the detection of symbionts and pathogens; and/or involved in monitoring of the cell wall structure and cell growth. [ABSTRACT FROM AUTHOR]

Lectins are fundamental to plant life and have important roles in cell-to-cell communication; development and defence strategies. At the cell surface; lectins are present both as soluble proteins (LecPs) and as chimeric proteins: lectins are then the extracellular domains of receptor-like kinases (LecRLKs) and receptor-like proteins (LecRLPs). In this review; we first describe the domain architectures of proteins harbouring G-type; L-type; LysM and malectin carbohydrate-binding domains. We then focus on the functions of LecPs; LecRLKs and LecRLPs referring to the biological processes they are involved in and to the ligands they recognize. Together; LecPs; LecRLKs and LecRLPs constitute versatile recognition systems at the cell surface contributing to the detection of symbionts and pathogens; and/or involved in monitoring of the cell wall structure and cell growth.

Lectin receptor-like kinases (LecRLKs) are members of RLK family composed of lectin-like extracellular recognition domain, transmembrane domain and cytoplasmic kinase domain. LecRLKs are plasma membrane proteins believed to be involved in signal transduction. However, most of the members of the protein family even in plants have not been functionally well characterized. Herein, we show that Pisum sativum LecRLK (PsLecRLK) localized in plasma membrane systems and/or other regions of the cell and its transcript upregulated under salinity stress. Overexpression of PsLecRLK in transgenic tobacco plants confers salinity stress tolerance by alleviating both the ionic as well the osmotic component of salinity stress. The transgenic plants show better tissue compartmentalization of Na and higher ROS scavenging activity which probably results in lower membrane damage, improved growth and yield maintenance even under salinity stress. Also, expression of several genes involved in cellular homeostasis is perturbed by PsLecRLK overexpression. Alleviation of osmotic and ionic components of salinity stress along with reduced oxidative damage and upregulation of stress-responsive genes in transgenic plants under salinity stress conditions could be possible mechanism facilitating enhanced stress tolerance. This study presents PsLecRLK as a promising candidate for crop improvement and also opens up new avenue to investigate its signalling pathway. [ABSTRACT FROM AUTHOR]

Seed germination and innate immunity both have significant effects on plant life spans because they control the plant's entry into the ecosystem and provide defenses against various external stresses, respectively. Much ecological evidence has shown that seeds with high vigor are generally more tolerant of various environmental stimuli in the field than those with low vigor. However, there is little genetic evidence linking germination and immunity in plants. Here, we show that the rice lectin receptor-like kinase Oslec RK contributes to both seed germination and plant innate immunity. We demonstrate that knocking down the Oslec RK gene depresses the expression of α-amylase genes, reducing seed viability and thereby decreasing the rate of seed germination. Moreover, it also inhibits the expression of defense genes, and so reduces the resistance of rice plants to fungal and bacterial pathogens as well as herbivorous insects. Yeast two-hybrid and co-immunoprecipitation experiments revealed that Oslec RK interacts with an actin-depolymerizing factor ( ADF) in vivo via its kinase domain. Moreover, the rice adf mutant exhibited a reduced seed germination rate due to the suppression of α-amylase gene expression. This mutant also exhibited depressed immune responses and reduced resistance to biotic stresses. Our results thus provide direct genetic evidence for a common physiological pathway connecting germination and immunity in plants. They also partially explain the common observation that high-vigor seeds often perform well in the field. The dual effects of Oslec RK may be indicative of progressive adaptive evolution in rice. [ABSTRACT FROM AUTHOR]

The Lectin Receptor-Like Kinase (LecRLK) family is known for its role in plant stress and developmental pathways. The review captures information on the historical, evolutionary, structural, and functional aspect of the LecRLK family with special emphasis on the future directions of study.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 making 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. [ABSTRACT FROM AUTHOR]

Lectin receptor-like kinases (LecRLKs) are class of membrane proteins found in higher plants that are involved in diverse functions ranging from plant growth and development to stress tolerance. The basic structure of LecRLK protein comprises of a lectin and a kinase domain, which are interconnected by transmembrane region. Here we have identified LecRLKs from Arabidopsis and rice and studied these proteins on the basis of their expression profile and phylogenies. We were able to identify 32 G-type, 42 L-type and 1 C-type LecRLKs from Arabidopsis and 72 L-type, 100 G-type and 1 C-type LecRLKs from rice on the basis of their annotation and presence of lectin as well kinase domains. The whole family is rather intron-less. We have sub-grouped the gene family on the basis of their phylogram. Although on the basis of sequence the members of each group are closely associated but their functions vary to a great extent. The interacting partners and coexpression data of the genes revealed the importance of gene family in physiology and stress related responses. An in-depth analysis on gene-expression suggested clear demarcation in roles assigned to each gene. To gain additional knowledge about the LecRLK gene family, we searched for previously unreported motifs and checked their importance structurally on the basis of homology modelling. The analysis revealed that the gene family has important roles in diverse functions in plants, both in the developmental stages and in stress conditions. This study thus opens the possibility to explore the roles that LecRLKs might play in life of a plant. [ABSTRACT FROM AUTHOR]

The plant lectin receptor-like kinases (LecRLKs) are involved in various signaling pathways but their role in salinity stress tolerance has not heretofore been well described. Salinity stress negatively affects plant growth/productivity and threatens food security worldwide. Based on functional gene-mining assay, we have isolated 34 salinity tolerant genes out of one million Escherichia coli (SOLR) transformants containing pea cDNAs grown in 0.8 M NaCl. Sequence analysis of one of these revealed homology to LecRLK, which possesses N-myristilation and N-glycosylation sites thus corroborating the protein to be a glycoconjugate. The homology based computational modeling of the kinase domain suggested high degree of conservation with the protein already known to be stress responsive in plants. The NaCl tolerance provided by PsLecRLK to the above bacteria was further confirmed in E. coli (DH5α). In planta studies showed that the expression of PsLecRLK cDNA was significantly upregulated in response to NaCl as compared to K+ and Li+ ions, suggesting the Na+ ion specific response. Transcript of the PsLecRLK gene accumulates mainly in roots and shoots. The purified 47 kDa recombinant PsLecRLK-KD (kinase domain) protein has been shown to phosphorylate general substrates like MBP and casein. This study not only suggests the conservation of the cellular response to high salinity stress across prokaryotes and plant kingdom but also provides impetus to develop novel concepts for better understanding of mechanism of stress tolerance in bacteria and plants. It also opens up new avenues for studying practical aspects of plant salinity tolerance for enhanced agricultural productivity. [ABSTRACT FROM AUTHOR]

Lectin receptor-like kinases (LecRLKs) are a class of membrane proteins found in plants that are involved in diverse functions, including plant development and stress responses. Although LecRLK families have been identified in a variety of plants, a comprehensive analysis has not yet been undertaken in cucumber (Cucumis sativus L.). In this study, 46 putative LecRLK genes were identified in the cucumber genome, including 23 G-type and 22 L-type, and one C-type LecRLK gene. They were unequally distributed on all seven chromosomes, with a clustering tendency. Most of the genes in the cucumber LecRLK (CsLecRLK) gene family lacked introns. In addition, there were many regulatory elements associated with phytohormones and stress on these genes' promoters. Transcriptome data demonstrated distinct expression patterns of CsLecRLK genes in various tissues. Furthermore, we found that each member of the CsLecRLK family had its own unique expression pattern under hormone and stress treatment by the quantitative real-time PCR (qRT-PCR) analysis. This study provides a better understanding of the character and function of the LecRLK gene family in cucumber and opens up the possibility to exploring the roles that LecRLKs might play in the life cycle of cucumber. [ABSTRACT FROM AUTHOR]