The functions and consensus motifs of nine types of peptide segments that form different types of nucleotide-binding sites

Genome-wide sequencing identified extrachromosomal circular DNA as a transcription factor-binding motif of the senescence genes that govern replicative senescence in human mesenchymal stem cells

Introduction

Mesenchymal stem cells (MSCs) have long been postulated as an important source cell in regenerative medicine. During subculture expansion, mesenchymal stem cell (MSC) senescence diminishes their multi-differentiation capabilities, leading to a loss of therapeutic potential. Up to date, the extrachromosomal circular DNAs (eccDNAs) have been demonstrated to be involved in senescence but the roles of eccDNAs during MSC.

Methods

Here we explored eccDNA profiles in human bone marrow MSCs (BM-MSCs). EccDNA and mRNA was purified and sequenced, followed by quantification and functional annotation. Moreover, we mapped our datasets with the downloading enhancer and transcription factor-regulated genes to explore the potential role of eccDNAs.

Results

Sequentially, gene annotation analysis revealed that the majority of eccDNA were mapped in the intron regions with limited BM-MSC enhancer overlaps. We discovered that these eccDNA motifs in senescent BMSCs acted as motifs for binding transcription factors (TFs) of senescence-related genes.

Discussion

These findings are highly significant for identifying biomarkers of senescence and therapeutic targets in mesenchymal stem cells (MSCs) for future clinical applications. The potential of eccDNA as a stable therapeutic target for senescence-related disorders warrants further investigation, particularly exploring chemically synthesized eccDNAs as transcription factor regulatory elements to reverse cellular senescence.

Back in time to the Gly-rich prototype of the phosphate binding elementary function

Binding of nucleotides and their derivatives is one of the most ancient elementary functions dating back to the Origin of Life. We review here the works considering one of the key elements in binding of (di)nucleotide-containing ligands - phosphate binding. We start from a brief discussion of major participants, conditions, and events in prebiotic evolution that resulted in the Origin of Life. Tracing back to the basic functions, including metal and phosphate binding, and, potentially, formation of primitive protein-protein interactions, we focus here on the phosphate binding. Critically assessing works on the structural, functional, and evolutionary aspects of phosphate binding, we perform a simple computational experiment reconstructing its most ancient and generic sequence prototype. The profiles of the phosphate binding signatures have been derived in form of position-specific scoring matrices (PSSMs), their peculiarities depending on the type of the ligands have been analyzed, and evolutionary connections between them have been delineated. Then, the apparent prototype that gave rise to all relevant phosphate-binding signatures had also been reconstructed. We show that two major signatures of the phosphate binding that discriminate between the binding of dinucleotide- and nucleotide-containing ligands are GxGxxG and GxxGxG, respectively. It appears that the signature archetypal for dinucleotide-containing ligands is more generic, and it can frequently bind phosphate groups in nucleotide-containing ligands as well. The reconstructed prototype's key signature GxGGxG underlies the role of glycine residues in providing flexibility and interactions necessary for binding the phosphate groups. The prototype also contains other ancient amino acids, valine, and alanine, showing versatility towards evolutionary design and functional diversification.

Genome-wide identification and analysis of the NLR gene family in Medicago ruthenica

Medicago ruthenica, important forage in the legume family, possesses high nutritional value and carries abundant tolerance genes. This study used whole-genome data of M. ruthenica to perform a genome-wide analysis of the nucleotide-binding site-leucine-rich repeat receptor (NLR) gene family, which is the largest family of plant disease resistance genes (R genes). A total of 338 NLR genes were identified in the M. ruthenica genome, including 160 typical genes that contained 80 coiled-coil (CC)-NBS-LRR (CNL) genes, 76 toll/interleukin-1 receptor (TIR)-NBS-LRR (TNL) genes, four resistance to powdery mildew 8 (RPW8)-NBS-LRR (RNL) subclass genes, and 178 atypical NLR genes encoding proteins without at least one important domain. Among its eight chromosomes, M. ruthenica chromosomes 3 and 8 contained most of the NLR genes. More than 40% of all NLR genes were located on these two chromosomes, mainly in multigene clusters. The NLR proteins of M. ruthenica had six highly conserved motifs: P-loop, GLPL, RNBS-D, kinase-2, RNBS-C, and MHDV. Phylogenetic analysis revealed that the NLR genes of M. ruthenica formed three deeply separated clades according to the N-terminal domain of the proteins encoded by these genes. Gene duplication and syntenic analysis suggested four gene duplication types in the NLR genes of M. ruthenica, namely, tandem, proximal, dispersed, and segmental duplicates, which involved 189, 49, 59, and 41 genes, respectively. A total of 41 segmental duplication genes formed 23 NLR gene pairs located on syntenic chromosomal blocks mainly between chromosomes 6 and 7. In addition, syntenic analysis between M. truncatula and M. ruthenica revealed 193 gene pairs located on syntenic chromosomal blocks of the two species. The expression analysis of M. ruthenica NLR genes showed that 303 (89.6%) of the NLR genes were expressed in different varieties. Overall, this study described the full NLR profile of the M. ruthenica genome to provide an important resource for mining disease-resistant genes and disease-resistant breeding.

Genome-wide identification, characterization, and evolutionary analysis of NBS genes and their association with disease resistance in Musa spp

Banana is an important food crop that is susceptible to a wide range of pests and diseases that can reduce yield and quality. The primary objective of banana breeding programs is to increase disease resistance, which requires the identification of resistance (R) genes. Despite the fact that resistant sources have been identified in bananas, the genes, particularly the nucleotide-binding site (NBS) family, which play an important role in protecting plants against pathogens, have received little attention. As a result, this study included a thorough examination of the NBS disease resistance gene family's classification, phylogenetic analysis, genome organization, evolution, cis-elements, differential expression, regulation by microRNAs, and protein-protein interaction. A total of 116 and 43 putative NBS genes from M. acuminata and M. balbisiana, respectively, were identified and characterized, and were classified into seven sub-families. Structural analysis of NBS genes revealed the presence of signal peptides, their sub-cellular localization, molecular weight and pI. Eight commonly conserved motifs were found, and NBS genes were unevenly distributed across multiple chromosomes, with the majority of NBS genes being located in chr3 and chr1 of the A and B genomes, respectively. Tandem duplication occurrences have helped bananas' NBS genes spread throughout evolution. Transcriptome analysis of NBS genes revealed significant differences in expression between resistant and susceptible cultivars of fusarium wilt, eumusae leaf spot, root lesion nematode, and drought, implying that they can be used as candidate resistant genes. Ninety miRNAs were discovered to have targets in 104 NBS genes from the A genome, providing important insights into NBS gene expression regulation. Overall, this study offers a valuable genomic resource and understanding of the function and evolution of NBS genes in relation to rapidly evolving pathogens, as well as providing breeders with selection targets for fast-tracking breeding of banana varieties with more durable resistance to pathogens.

High-quality reference genome sequences of two Cannaceae species provide insights into the evolution of Cannaceae

Canna edulis Ker-Gawl and Canna indica L. are species belonging to the Cannaceae family and both have a very high economic value. Here, we aimed to assemble genomes of C. edulis and C. indica at the chromosome level to generate a reference genome for the Cannaceae family. We also comparatively analyzed the genomes of C. edulis and C. indica and examined the molecular mechanisms responsible for the remarkable differences in plant characteristics in C. edulis varieties. Our results indicated that genome-wide duplication events had recently occurred in C. edulis and C. indica. The comparative analysis of the genomes of C. edulis and C. indica revealed that C. edulis exhibited a remarkable level of replication of genes in the starch and sucrose metabolic pathways, especially during sucrose hydrolysis. This finding is consistent with the fact that the starch content of the C. edulis tuber is higher than that of C. indica. Simplified genome re-sequencing revealed the population structure of 241 C. edulis genes, and a genome-wide association study of leaf traits revealed the location of key genes related to leaf color and morphology. These findings extend our understanding of Cannaceade at the molecular level, and provide an effective theoretical basis for further study and utilization of Cannaceae plants.

Identification and Characterization of NBS Resistance Genes in Akebia trifoliata

Akebia trifoliata is an important multiuse perennial plant that often suffers attacks from various pathogens due to its long growth cycle, seriously affecting its commercial value. The absence of research on the resistance (R) genes of A. trifoliata has greatly limited progress in the breeding of resistant varieties. Genes encoding proteins containing nucleotide binding sites (NBSs) and C-terminal leucine-rich repeats (LRRs), the largest family of plant resistance (R) genes, are vital for plant disease resistance. A comprehensive genome-wide analysis showed that there were only 73 NBS genes in the A. trifoliata genome, including three main subfamilies (50 coiled coil (CC)-NBS-LRR (CNL), 19 Toll/interleukin-1 receptor (TIR)-NBS-LRR (TNL) and four resistance to powdery mildew8 (RPW8)-NBS-LRR (RNL) genes). Additionally, 64 mapped NBS candidates were unevenly distributed on 14 chromosomes, most of which were assigned to the chromosome ends; 41 of these genes were located in clusters, and the remaining 23 genes were singletons. Both the CNLs and TNLs were further divided into four subgroups, and the CNLs had fewer exons than the TNLs. Structurally, all eight previously reported conserved motifs were identified in the NBS domains, and both their order and their amino acid sequences exhibited high conservation. Evolutionarily, tandem and dispersed duplications were shown to be the two main forces responsible for NBS expansion, producing 33 and 29 genes, respectively. A transcriptome analysis of three fruit tissues at four developmental stages showed that NBS genes were generally expressed at low levels, while a few of these genes showed relatively high expression during later development in rind tissues. Overall, this research is the first to identify and characterize A. trifoliata NBS genes and is valuable for both the development of new resistant cultivars and the study of molecular mechanisms of resistance.

Genome-Wide Association Mapping of Late Blight Tolerance Trait in Potato (Solanum tuberosum L.)

Uncovering the genetic basis and optimizing the late blight tolerance trait in potatoes (Solanum tuberosum L.) are crucial for potato breeding. Late blight disease is one of the most significant diseases hindering potato production. The traits of late blight tolerance were evaluated for 284 potato cultivars to identify loci significantly associated with the late blight tolerance trait. Of all, 37 and 15 were the most tolerant to disease, and 107 and 30 were the most susceptible. A total of 22,489 high-quality single-nucleotide polymorphisms and indels were identified in 284 potato cultivars. All the potato cultivars were clustered into eight subgroups using population structure analysis and principal component analysis, which were consistent with the results of the phylogenetic tree analysis. The average genetic diversity for all 284 potato cultivars was 0.216, and the differentiation index of each subgroup was 0.025–0.149. Genome-wide linkage disequilibrium (LD) analysis demonstrated that the average LD was about 0.9 kb. A genome-wide association study using a mixed linear model identified 964 loci significantly associated with the late blight tolerance trait. Fourteen candidate genes for late blight tolerance traits were identified, including genes encoding late blight tolerance protein, chitinase 1, cytosolic nucleotide-binding site–leucine-rich repeat tolerance protein, protein kinase, ethylene-responsive transcription factor, and other potential plant tolerance-related proteins. This study provides novel insights into the genetic architecture of late blight tolerance traits and will be helpful for late blight tolerance in potato breeding.

Transcriptomic analysis of pepper plants provides insights into host responses to Fusarium solani infestation

Black pepper is an important commodity crop in Malaysia that generates millions of annual revenue for the country. However, black pepper yield is affected by slow decline disease caused by a soil-borne fungus Fusarium solani. RNA sequencing transcriptomics approach has been employed in this study to explore the differential gene expression in susceptible Piper nigrum L. and resistant Piper colubrinum Link. Gene expression comparative analysis of the two pepper species has yielded 2,361 differentially expressed genes (DEGs). Among them, higher expression of 1,426 DEGs was detected in resistant plant. These DEGs practically demonstrated the major branches of plant-pathogen interaction pathway (Path: ko04626). We selected five groups of defence-related DEGs for downstream qRT-PCR analysis. Cf-9, the gene responsible for recognizing fungal avirulence protein activity was found inexpressible in susceptible plant. However, this gene exhibited promising expression in resistant plant. Inactivation of Cf-9 could be the factor that causes susceptible plant fail in recognition of F. solani and subsequently delay activation of adaptive response to fungal invasion. This vital study advance the understanding of pepper plant defence in response to F. solani and aid in identifying potential solution to manage slow decline disease in black pepper cultivation.

Sequence Composition of Bacterial Chromosome Clones in a Transgressive Root-Knot Nematode Resistance Chromosome Region in Tetraploid Cotton

Plants evolve innate immunity including resistance genes to defend against pest and pathogen attack. Our previous studies in cotton (Gossypium spp.) revealed that one telomeric segment on chromosome (Chr) 11 in G. hirsutum cv. Acala NemX (rkn1 locus) contributed to transgressive resistance to the plant parasitic nematode Meloidogyne incognita, but the highly homologous segment on homoeologous Chr 21 had no resistance contribution. To better understand the resistance mechanism, a bacterial chromosome (BAC) library of Acala N901 (Acala NemX resistance source) was used to select, sequence, and analyze BAC clones associated with SSR markers in the complex rkn1 resistance region. Sequence alignment with the susceptible G. hirsutum cv. TM-1 genome indicated that 23 BACs mapped to TM-1-Chr11 and 18 BACs mapped to TM-1-Chr 21. Genetic and physical mapping confirmed less BAC sequence (53-84%) mapped with the TM-1 genome in the rkn1 region on Chr 11 than to the homologous region (>89%) on Chr 21. A 3.1-cM genetic distance between the rkn1 flanking markers CIR316 and CIR069 was mapped in a Pima S-7 × Acala NemX RIL population with a physical distance ∼1 Mbp in TM-1. NCBI Blast and Gene annotation indicated that both Chr 11 and Chr 21 harbor resistance gene-rich cluster regions, but more multiple homologous copies of Resistance (R) proteins and of adjacent transposable elements (TE) are present within Chr 11 than within Chr 21. (CC)-NB-LRR type R proteins were found in the rkn1 region close to CIR316, and (TIR)-NB-LRR type R proteins were identified in another resistance rich region 10 cM from CIR 316 (∼3.1 Mbp in the TM-1 genome). The identified unique insertion/deletion in NB-ARC domain, different copies of LRR domain, multiple copies or duplication of R proteins, adjacent protein kinases, or TE in the rkn1 region on Chr 11 might be major factors contributing to complex recombination and transgressive resistance.

The Gossypium hirsutum TIR-NBS-LRR gene GhDSC1 mediates resistance against Verticillium wilt

Improving genetic resistance is a preferred method to manage Verticillium wilt of cotton and other hosts. Identifying host resistance is difficult because of the dearth of resistance genes against this pathogen. Previously, a novel candidate gene involved in Verticillium wilt resistance was identified by a genome-wide association study using a panel of Gossypium hirsutum accessions. In this study, we cloned the candidate resistance gene from cotton that encodes a protein sharing homology with the TIR-NBS-LRR receptor-like defence protein DSC1 in Arabidopsis thaliana (hereafter named GhDSC1). GhDSC1 expressed at higher levels in response to Verticillium wilt and jasmonic acid (JA) treatment in resistant cotton cultivars as compared to susceptible cultivars and its product was localized to nucleus. The transfer of GhDSC1 to Arabidopsis conferred Verticillium resistance in an A. thaliana dsc1 mutant. This resistance response was associated with reactive oxygen species (ROS) accumulation and increased expression of JA-signalling-related genes. Furthermore, the expression of GhDSC1 in response to Verticillium wilt and JA signalling in A. thaliana displayed expression patterns similar to GhCAMTA3 in cotton under identical conditions, suggesting a coordinated DSC1 and CAMTA3 response in A. thaliana to Verticillium wilt. Analyses of GhDSC1 sequence polymorphism revealed a single nucleotide polymorphism (SNP) difference between resistant and susceptible cotton accessions, within the P-loop motif encoded by GhDSC1. This SNP difference causes ineffective activation of defence response in susceptible cultivars. These results demonstrated that GhDSC1 confers Verticillium resistance in the model plant system of A. thaliana, and therefore represents a suitable candidate for the genetic engineering of Verticillium wilt resistance in cotton.

BOT-4-one attenuates NLRP3 inflammasome activation: NLRP3 alkylation leading to the regulation of its ATPase activity and ubiquitination

The ATPase activity of NLRP3 has pivotal role in inflammasome activation and is recognized as a good target for the development of the NLRP3 inflammasome-specific inhibitor. However, signals in the vicinity of the ATPase activity of NLRP3 have not been fully elucidated. Here, we demonstrate NLRP3 inflammasome-specific action of a benzoxathiole derivative, BOT-4-one. BOT-4-one exhibited an inhibition of NLRP3 inflammasome activation, which was attributable to its alkylating capability to NLRP3. In particular, the NLRP3 alkylation by BOT-4-one led to an impaired ATPase activity of NLRP3, thereby obstructing the assembly of the NLRP3 inflammasome. Additionally, we found that NLRP3 alkylators, including BOT-4-one, enhance the ubiquitination level of NLRP3, which might also contribute to the inhibition of NLRP3 inflammasome activation. Finally, BOT-4-one appeared to be superior to other known NLRP3 alkylators in inhibiting the functionality of the NLRP3 inflammasome and its resulting anti-inflammatory activity was confirmed in vivo using a monosodium urate-induced peritonitis mouse model. Collectively, the results suggest that NLRP3 alkylators function by inhibiting ATPase activity and increasing the ubiquitination level of NLRP3, and BOT-4-one could be the type of NLRP3 inhibitor that may be potentially useful for the novel development of a therapeutic agent in controlling NLRP3 inflammasome-related diseases.

Molecular cloning of a CC-NBS-LRR gene from Vitis quinquangularis and its expression pattern in response to downy mildew pathogen infection

Downy mildew, caused by Plasmopara viticola, can result in a substantial decrease in grapevine productivity. Vitis vinifera is a widely cultivated grapevine species, which is susceptible to this disease. Repeated pesticide applications are harmful for both the environment and human health. Thus, it is essential to develop varieties/cultivars that are resistant to downy mildew and other diseases. In our previous studies, we investigated the natural resistance of the Chinese wild grapevine V. quinquangularis accession 'PS' against P. viticola and obtained several candidate resistance (R) genes that may play important roles in plant disease resistance. In the present study, we isolated a CC-NBS-LRR-type R gene from 'PS' and designated it VqCN. Its open reading frame is 2676 bp which encodes a protein of 891 amino acids with a predicted molecular mass of 102.12 kDa and predicted isoelectric point of 6.53. Multiple alignments with other disease resistant (R) proteins revealed a conserved phosphate-binding loop (P-loop), resistance nucleotide binding site, a hydrophobic domain (GLPL) and methionine-histidine-aspartate (MHD) motifs, which are typical components of nucleotide-binding site leucine-rich repeat proteins, as well as a coiled-coil region in the N-terminus. Quantitative real-time polymerase chain reaction analysis showed that the transcript of VqCN was rapidly and highly induced after infection with P. viticola in 'PS'. Moreover, the leaves of susceptible 'Cabernet Sauvignon' transiently expressing VqCN manifested increased resistance to P. viticola. The results indicated that VqCN might play a positive role in protecting grapevine against infection with P. viticola. Cloning and functional analysis of a putative resistance gene provide a basis for disease-resistance breeding.

Genome-wide identification and characterization of NB-ARC resistant genes in wheat (Triticum aestivum L.) and their expression during leaf rust infection

NB-ARC domain-containing resistance genes from the wheat genome were identified, characterized and localized on chromosome arms that displayed differential yet positive response during incompatible and compatible leaf rust interactions. Wheat (Triticum aestivum L.) is an important cereal crop; however, its production is affected severely by numerous diseases including rusts. An efficient, cost-effective and ecologically viable approach to control pathogens is through host resistance. In wheat, high numbers of resistance loci are present but only few have been identified and cloned. A comprehensive analysis of the NB-ARC-containing genes in complete wheat genome was accomplished in this study. Complete NB-ARC encoding genes were mined from the Ensembl Plants database to predict 604 NB-ARC containing sequences using the HMM approach. Genome-wide analysis of orthologous clusters in the NB-ARC-containing sequences of wheat and other members of the Poaceae family revealed maximum homology with Oryza sativa indica and Brachypodium distachyon. The identification of overlap between orthologous clusters enabled the elucidation of the function and evolution of resistance proteins. The distributions of the NB-ARC domain-containing sequences were found to be balanced among the three wheat sub-genomes. Wheat chromosome arms 4AL and 7BL had the most NB-ARC domain-containing contigs. The spatio-temporal expression profiling studies exemplified the positive role of these genes in resistant and susceptible wheat plants during incompatible and compatible interaction in response to the leaf rust pathogen Puccinia triticina. Two NB-ARC domain-containing sequences were modelled in silico, cloned and sequenced to analyze their fine structures. The data obtained in this study will augment isolation, characterization and application NB-ARC resistance genes in marker-assisted selection based breeding programs for improving rust resistance in wheat.

Deciphering common recognition principles of nucleoside mono/di and tri-phosphates binding in diverse proteins via structural matching of their binding sites

Nucleoside triphosphate (NTP) ligands are of high biological importance and are essential for all life forms. A pre-requisite for them to participate in diverse biochemical processes is their recognition by diverse proteins. It is thus of great interest to understand the basis for such recognition in different proteins. Towards this, we have used a structural bioinformatics approach and analyze structures of 4677 NTP complexes available in Protein Data Bank (PDB). Binding sites were extracted and compared exhaustively using PocketMatch, a sensitive in-house site comparison algorithm, which resulted in grouping the entire dataset into 27 site-types. Each of these site-types represent a structural motif comprised of two or more residue conservations, derived using another in-house tool for superposing binding sites, PocketAlign. The 27 site-types could be grouped further into 9 super-types by considering partial similarities in the sites, which indicated that the individual site-types comprise different combinations of one or more site features. A scan across PDB using the 27 structural motifs determined the motifs to be specific to NTP binding sites, and a computational alanine mutagenesis indicated that residues identified to be highly conserved in the motifs are also most contributing to binding. Alternate orientations of the ligand in several site-types were observed and rationalized, indicating the possibility of some residues serving as anchors for NTP recognition. The presence of multiple site-types and the grouping of multiple folds into each site-type is strongly suggestive of convergent evolution. Knowledge of determinants obtained from this study will be useful for detecting function in unknown proteins. Proteins 2017; 85:1699-1712. © 2017 Wiley Periodicals, Inc.

Alternative Splicing in Plant Genes: A Means of Regulating the Environmental Fitness of Plants

Gene expression can be regulated through transcriptional and post-transcriptional mechanisms. Transcription in eukaryotes produces pre-mRNA molecules, which are processed and spliced post-transcriptionally to create translatable mRNAs. More than one mRNA may be produced from a single pre-mRNA by alternative splicing (AS); thus, AS serves to diversify an organism’s transcriptome and proteome. Previous studies of gene expression in plants have focused on the role of transcriptional regulation in response to environmental changes. However, recent data suggest that post-transcriptional regulation, especially AS, is necessary for plants to adapt to a changing environment. In this review, we summarize recent advances in our understanding of AS during plant development in response to environmental changes. We suggest that alternative gene splicing is a novel means of regulating the environmental fitness of plants.

De novo transcriptome assembly databases for the butterfly orchid Phalaenopsis equestris

Orchids are renowned for their spectacular flowers and ecological adaptations. After the sequencing of the genome of the tropical epiphytic orchid Phalaenopsis equestris, we combined Illumina HiSeq2000 for RNA-Seq and Trinity for de novo assembly to characterize the transcriptomes for 11 diverse P. equestris tissues representing the root, stem, leaf, flower buds, column, lip, petal, sepal and three developmental stages of seeds. Our aims were to contribute to a better understanding of the molecular mechanisms driving the analysed tissue characteristics and to enrich the available data for P. equestris. Here, we present three databases. The first dataset is the RNA-Seq raw reads, which can be used to execute new experiments with different analysis approaches. The other two datasets allow different types of searches for candidate homologues. The second dataset includes the sets of assembled unigenes and predicted coding sequences and proteins, enabling a sequence-based search. The third dataset consists of the annotation results of the aligned unigenes versus the Nonredundant (Nr) protein database, Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Clusters of Orthologous Groups (COG) databases with low e-values, enabling a name-based search.

TmcN is involved in ATP regulation of tautomycetin biosynthesis in Streptomyces griseochromogenes

The regulatory mechanism of tautomycetin (TMC) biosynthesis remains largely unknown, although it has been of great interest to the pharmaceutical industry. Our previous study showed that intracellular adenosine triphosphate (inATP) level is negatively correlated with secondary metabolite biosynthesis in various Streptomyces spp. In this study, by exogenous treatment of ATP, we also found a negative correlation between TMC biosynthesis and inATP level in Streptomyces griseochromogenes (S. griseochromogenes). However, the underlying mechanism remains unclear. TmcN, a pathway-specific transcriptional regulator of TMC biosynthetic genes, was previously revealed as a large ATP-binding LuxR (LAL) family protein. The predicted amino acid sequence of TmcN shows highly conserved Walker A and B binding motifs, which suggest an ATPase function of TmcN. We therefore hypothesized that the ATPase domain of TmcN may play a role in sensing endogenous pool of ATP, and is thus involved in the ATP regulation of TMC biosynthesis. To test the hypothesis, we first explored the key residue that affects the ATPase activity of TmcN by amino acid sequence alignment and structural simulation. After that, we disrupted tmcN gene in S. griseochromogenes, and the tmcN or site-direct-mutated tmcN were re-introduced to get the complementary and ATPase domain disrupted strains. The transcription level of tmcN, TMC yield, and inATP, as well as the effect of ATP on TMC production of different mutants were evaluated. Deletion of tmcN or site-direct mutation of ATPase domain of TmcN in S. griseochromogenes significantly reduced the TMC production, and it was not affected by exogenous ATP treatment. In addition, a relatively high level of inATP was detected in tmcN deletion and site-direct mutation strains. Our results here suggested that TmcN, especially its ATPase domain, is involved in consuming of endogenous ATP pool and thus plays pivotal role in connecting the primary and secondary metabolite in S. griseochromogenes.

Nucleotide binding database NBDB--a collection of sequence motifs with specific protein-ligand interactions

NBDB database describes protein motifs, elementary functional loops (EFLs) that are involved in binding of nucleotide-containing ligands and other biologically relevant cofactors/coenzymes, including ATP, AMP, ATP, GMP, GDP, GTP, CTP, PAP, PPS, FMN, FAD(H), NAD(H), NADP, cAMP, cGMP, c-di-AMP and c-di-GMP, ThPP, THD, F-420, ACO, CoA, PLP and SAM. The database is freely available online at http://nbdb.bii.a-star.edu.sg. In total, NBDB contains data on 249 motifs that work in interactions with 24 ligands. Sequence profiles of EFL motifs were derived de novo from nonredundant Uniprot proteome sequences. Conserved amino acid residues in the profiles interact specifically with distinct chemical parts of nucleotide-containing ligands, such as nitrogenous bases, phosphate groups, ribose, nicotinamide, and flavin moieties. Each EFL profile in the database is characterized by a pattern of corresponding ligand–protein interactions found in crystallized ligand–protein complexes. NBDB database helps to explore the determinants of nucleotide and cofactor binding in different protein folds and families. NBDB can also detect fragments that match to profiles of particular EFLs in the protein sequence provided by user. Comprehensive information on sequence, structures, and interactions of EFLs with ligands provides a foundation for experimental and computational efforts on design of required protein functions.

Nucleotides, Nucleosides, and Nucleobases

We review literature on the metabolism of ribo- and deoxyribonucleotides, nucleosides, and nucleobases in Escherichia coli and Salmonella,including biosynthesis, degradation, interconversion, and transport. Emphasis is placed on enzymology and regulation of the pathways, at both the level of gene expression and the control of enzyme activity. The paper begins with an overview of the reactions that form and break the N-glycosyl bond, which binds the nucleobase to the ribosyl moiety in nucleotides and nucleosides, and the enzymes involved in the interconversion of the different phosphorylated states of the nucleotides. Next, the de novo pathways for purine and pyrimidine nucleotide biosynthesis are discussed in detail.Finally, the conversion of nucleosides and nucleobases to nucleotides, i.e.,the salvage reactions, are described. The formation of deoxyribonucleotides is discussed, with emphasis on ribonucleotidereductase and pathways involved in fomation of dUMP. At the end, we discuss transport systems for nucleosides and nucleobases and also pathways for breakdown of the nucleobases.

ATP binding by NLRP7 is required for inflammasome activation in response to bacterial lipopeptides

Nucleotide-binding oligimerization domain (NOD)-like receptors (NLRs) are pattern recognition receptors (PRRs) involved in innate immune responses. NLRs encode a central nucleotide-binding domain (NBD) consisting of the NAIP, CIITA, HET-E and TP1 (NACHT) domain and the NACHT associated domain (NAD), which facilitates receptor oligomerization and downstream inflammasome signaling. The NBD contains highly conserved regions, known as Walker motifs, that are required for nucleotide binding and hydrolysis. The NLR containing a PYRIN domain (PYD) 7 (NLRP7) has been recently shown to assemble an ASC and caspase-1-containing high molecular weight inflammasome complex in response to microbial acylated lipopeptides and Staphylococcus aureus infection. However, the molecular mechanism responsible for NLRP7 inflammasome activation is still elusive. Here we demonstrate that the NBD of NLRP7 is an ATP binding domain and has ATPase activity. We further show that an intact nucleotide-binding Walker A motif is required for NBD-mediated nucleotide binding and hydrolysis, oligomerization, and NLRP7 inflammasome formation and activity. Accordingly, THP-1 cells expressing a mutated Walker A motif display defective NLRP7 inflammasome activation, interleukin (IL)-1β release and pyroptosis in response to acylated lipopeptides and S. aureus infection. Taken together, our results provide novel insights into the mechanism of NLRP7 inflammasome assembly.

Pi64, Encoding a Novel CC-NBS-LRR Protein, Confers Resistance to Leaf and Neck Blast in Rice

Rice blast caused by Magnaporthe oryzae poses a major threat to rice production worldwide. The utilization of host resistance (R) genes is considered to be the most effective and economic means to control rice blast. Here, we show that the japonica landrace Yangmaogu (YMG) displays a broader spectrum of resistance to blast isolates than other previously reported broad-spectrum resistant (BSR) cultivars. Genetic analysis suggested that YMG contains at least three major R genes. One gene, Pi64, which exhibits resistance to indica-sourced isolate CH43 and several other isolates, was mapped to a 43-kb interval on chromosome 1 of YMG. Two open reading frames (NBS-1 and NBS-2) encoding nucleotide-binding site and leucine-rich repeat proteins were short-listed as candidate genes for Pi64. Constructs containing each candidate gene were transformed into three susceptible japonica cultivars. Only transformants with NBS-2 conferred resistance to leaf and neck blast, validating the idea that NBS-2 represents the functional Pi64 gene. Pi64 is constitutively expressed at all development stages and in all tissues examined. Pi64 protein is localized in both the cytoplasm and nucleus. Furthermore, introgression of Pi64 into susceptible cultivars via gene transformation and marker-assisted selection conferred high-level and broad-spectrum leaf and neck blast resistance to indica-sourced isolates, demonstrating its potential utility in breeding BSR rice cultivars.

Full-genome identification and characterization of NBS-encoding disease resistance genes in wheat

Host resistance is the most economical, effective and ecologically sustainable method of controlling diseases in crop plants. In bread wheat, despite the high number of resistance loci that have been cataloged to date, only few have been cloned, underlying the need for genomics-guided investigations capable of providing a prompt and acute knowledge on the identity of effective resistance genes that can be used in breeding programs. Proteins with a nucleotide-binding site (NBS) encoded by the major plant disease resistance (R) genes play an important role in the responses of plants to various pathogens. In this study, a comprehensive analysis of NBS-encoding genes within the whole wheat genome was performed, and the genome scale characterization of this gene family was established. From the recently published wheat genome sequence, we used a data mining and automatic prediction pipeline to identify 580 complete ORF candidate NBS-encoding genes and 1,099 partial-ORF ones. Among complete gene models, 464 were longer than 200 aa, among them 436 had less than 70 % of sequence identity to each other. This gene models set was deeply characterized. (1) First, we have analyzed domain architecture and identified, in addition to typical domain combinations, the presence of particular domains like signal peptides, zinc fingers, kinases, heavy-metal-associated and WRKY DNA-binding domains. (2) Functional and expression annotation via homology searches in protein and transcript databases, based on sufficient criteria, enabled identifying similar proteins for 60 % of the studied gene models and expression evidence for 13 % of them. (3) Shared orthologous groups were defined using NBS-domain proteins of rice and Brachypodium distachyon. (4) Finally, alignment of the 436 NBS-containing gene models to the full set of scaffolds from the IWGSC's wheat chromosome survey sequence enabled high-stringence anchoring to chromosome arms. The distribution of the R genes was found balanced on the three wheat sub-genomes. In contrast, at chromosome scale, 50 % of members of this gene family were localized on 6 of the 21 wheat chromosomes and ~22 % of them were localized on homeologous group 7. The results of this study provide a detailed analysis of the largest family of plant disease resistance genes in allohexaploid wheat. Some structural traits reported had not been previously identified and the genome-derived data were confronted with those stored in databases outlining the functional specialization of members of this family. The large reservoir of NBS-type genes presented and discussed will, firstly, form an important framework for marker-assisted improvement of resistance in wheat, and, secondly, open up new perspectives for a better understanding of the evolution dynamics of this gene family in grass species and in polyploid systems.

Alternative splicing in plant immunity

Alternative splicing (AS) occurs widely in plants and can provide the main source of transcriptome and proteome diversity in an organism. AS functions in a range of physiological processes, including plant disease resistance, but its biological roles and functional mechanisms remain poorly understood. Many plant disease resistance (R) genes undergo AS, and several R genes require alternatively spliced transcripts to produce R proteins that can specifically recognize pathogen invasion. In the finely-tuned process of R protein activation, the truncated isoforms generated by AS may participate in plant disease resistance either by suppressing the negative regulation of initiation of immunity, or by directly engaging in effector-triggered signaling. Although emerging research has shown the functional significance of AS in plant biotic stress responses, many aspects of this topic remain to be understood. Several interesting issues surrounding the AS of R genes, especially regarding its functional roles and regulation, will require innovative techniques and additional research to unravel.

Isolation and characterization of NBS-LRR resistance gene analogues from mango

The nucleotide-binding site (NBS)–leucine-rich repeat (LRR) gene family is a class of R genes in plants. NBS genes play a very important role in disease defence. To further study the variation and homology of mango NBS–LRR genes, 16 resistance gene analogues (RGAs) (GenBank accession number HM446507-22) were isolated from the polymerase chain reaction fragments and sequenced by using two degenerate primer sets. The total nucleotide diversity index Pi was 0.362, and 236 variation sites were found among 16 RGAs. The degree of homology between the RGAs varied from 44.4% to 98.5%. Sixteen RGAs could be translated into amino sequences. The high level of this homology in the protein sequences of the P-loop and kinase-2 of the NBS domain between the RGAs isolated in this study and previously characterized R genes indicated that these cloned sequences belonged to the NBS–LRR gene family. Moreover, these 16 RGAs could be classified into the non-TIR–NBS–LRR gene family because only tryptophan (W) could be claimed as the final residual of the kinase-2 domain of all RGAs isolated here. From our results, we concluded that our mango NBS–LRR genes possessed a high level of variation from the mango genome, which may allow mango to recognize many different pathogenic virulence factors.

Characterization of novel wheat NBS domain-containing sequences and their utilization, in silico, for genome-scale R-gene mining

In crop improvement, the isolation, cloning and transfer of disease resistance genes (R-genes) is an ultimate goal usually starting from tentative R-gene analogs (RGAs) that are identified on the basis of their structure. For bread wheat, recent advances in genome sequencing are supporting the efforts of wheat geneticists worldwide. Among wheat R-genes, nucleotide-binding site (NBS)-encoding ones represent a major class. In this study, we have used a polymerase chain reaction-based approach to amplify and clone NBS-type RGAs from a bread wheat cultivar, 'Salambo 80.' Four novel complete ORF sequences showing similarities to previously reported R-genes/RGAs were used for in silico analyses. In a first step, where analyses were focused on the NBS domain, these sequences were phylogenetically assigned to two distinct groups: a first group close to leaf rust Lr21 resistance proteins; and a second one similar to cyst nematode resistance proteins. In a second step, sequences were used as initial seeds to walk up and downstream the NBS domain. This procedure enabled identifying 8 loci ranging in size between 2,115 and 7,653 bp. Ab initio gene prediction identified 8 gene models, among which two had complete ORFs. While GenBank survey confirmed the belonging of sequences to two groups, subsequent characterization using IWGSC genomic and proteomic data showed that the 8 gene models, reported in this study, were unique and their loci matched scaffolds on chromosome arms 1AS, 1BS, 4BS and 1DS. The gene model located on 1DS is a pseudo-Lr21 that was shown to have an NBS-LRR domain structure, while the potential association of the RGAs, here reported, is discussed. This study has produced novel R-gene-like loci and models in the wheat genome and provides the first steps toward further elucidation of their role in wheat disease resistance.

ATPase activity and ATP-dependent conformational change in the co-chaperone HSP70/HSP90-organizing protein (HOP)

Co-chaperones help to maintain cellular homeostasis by modulating the activities of molecular chaperones involved in protein quality control. The HSP70/HSP90-organizing protein (HOP) is a co-chaperone that cooperates with HSP70 and HSP90 in catalysis of protein folding and maturation in the cytosol. We show here that HOP has ATP-binding activity comparable to that of HSP70/HSP90, and that HOP slowly hydrolyzes ATP. Analysis of deletion mutants revealed that the ATPase domain of HOP is in the N-terminal TPR1-DP1-TPR2A segment. In addition, HOP changes its conformation in the presence of ATP. These results indicate that HOP is a unique co-chaperone that undergoes an ATP-dependent conformational change.

In-silico mining, type and frequency analysis of genic microsatellites of finger millet (Eleusine coracana (L.) Gaertn.): a comparative genomic analysis of NBS-LRR regions of finger millet with rice

In recent years, the increased availability of the DNA sequences has given the possibility to develop and explore the expressed sequence tags (ESTs) derived SSR markers. In the present study, a total of 1956 ESTs of finger millet were used to find the microsatellite type, distribution, frequency and developed a total of 545 primer pairs from the ESTs of finger millet. Thirty-two EST sequences had more than two microsatellites and 1357 sequences did not have any SSR repeats. The most frequent type of repeats was trimeric motif, however the second place was occupied by dimeric motif followed by tetra-, hexa- and penta repeat motifs. The most common dimer repeat motif was GA and in case of trimeric SSRs, it was CGG. The EST sequences of NBS-LRR region of finger millet and rice showed higher synteny and were found on nearly same positions on the rice chromosome map. A total of eight, out of 15 EST based SSR primers were polymorphic among the selected resistant and susceptible finger millet genotypes. The primer FMBLEST5 could able to differentiate them into resistant and susceptible genotypes. The alleles specific to the resistant and susceptible genotypes were sequenced using the ABI 3130XL genetic analyzer and found similarity to NBS-LRR regions of rice and finger millet and contained the characteristic kinase-2 and kinase 3a motifs of plant R-genes belonged to NBS-LRR region. The In-silico and comparative analysis showed that the genes responsible for blast resistance can be identified, mapped and further introgressed through molecular breeding approaches for enhancing the blast resistance in finger millet.

Initial biochemical and functional characterization of a 5'-nucleotidase from Xylella fastidiosa related to the human cytosolic 5'-nucleotidase I

The 5'-nucleotidases constitute a ubiquitous family of enzymes that catalyze either the hydrolysis or the transfer of esterified phosphate at the 5' position of nucleoside monophosphates. These enzymes are responsible for the regulation of nucleotide and nucleoside levels in the cell and can interfere with the phosphorylation-dependent activation of nucleoside analogs used in therapies targeting solid tumors and viral infections. In the present study, we report the initial biochemical and functional characterization of a 5'-nucleotidase from Xylella fastidiosa that is related to the human cytosolic 5'-nucleotidase I. X. fastidiosa is a plant pathogenic bacterium that is responsible for numerous economically important crop diseases. Biochemical assays confirmed the phosphatase activity of the recombinant purified enzyme and revealed metal ion dependence for full enzyme activity. In addition, we investigated the involvement of Xf5'-Nt in the formation of X. fastidiosa biofilms, which are structures that occlude the xylem vessels of susceptible plants and are strictly associated with bacterial pathogenesis. Using polyclonal antibodies against Xf5'-Nt, we observed an overexpression of Xf5'-Nt during the initial phases of X. fastidiosa biofilm formation that was not observed during X. fastidiosa planktonic growth. Our results demonstrate that the de/phosphorylation network catalyzed by 5'-nucleotidases may play an important role in bacterial biofilm formation, thereby contributing novel insights into bacterial nucleotide metabolism and pathogenicity.

Molecular characterization of ZzR1 resistance gene from Zingiber zerumbet with potential for imparting Pythium aphanidermatum resistance in ginger

Soft rot disease caused by the oomycete Pythium aphanidermatum (Edson) Fitzp. is the most economically significant disease of ginger (Zingiber officinale Rosc.) in tropical countries. All available ginger cultivars are susceptible to this pathogen. However a wild ginger relative viz., Zingiber zerumbet L. Smith, was identified as a potential soft rot resistance donor. In the present study, a putative resistance (R) gene designated, ZzR1 was isolated and characterized from Z. zerumbet using sequence information from Zingiber RGCs identified in our earlier experiments. Analysis of the 2280 bp segment revealed a 2157 bp open reading frame (ORF) encoding a putative cytoplasmically localized protein. The deduced ZzR1 protein shared high homology with other known R-genes belonging to the CC-NBS-LRR (coiled coil-nucleotide binding site-leucine rich repeat) class and had a calculated molecular weight of 84.61kDa. Real-time PCR analysis of ZzR1 transcription in Z. zerumbet following pathogen infection demonstrated activation at 3 hpi thus suggesting an involvement of ZzR1 in Z. zerumbet defense mechanism. Although many R-genes have been characterized from different taxa, none of them will help in the development of resistant ginger cultivars owing to the phenomenon of "Restricted Taxonomic Functionality" (RTF). Thus ZzR1 gene characterized from the resistant wild Zingiber accession represents a valuable genomic resource for ginger improvement programs. This first report on R-gene isolation from the Zingiber secondary gene pool is pivotal in designing strategies for engineering resistance in ginger, which is otherwise not amenable to conventional improvement programs owing to sexual reproduction barriers.

Structural and Functional Characterization of RecG Helicase under Dilute and Molecular Crowding Conditions

In an ATP-dependent reaction, the Escherichia coli RecG helicase unwinds DNA junctions in vitro. We present evidence of a unique protein conformational change in the RecG helicase from an α-helix to a β-strand upon an ATP binding under dilute conditions using circular dichroism (CD) spectroscopy. In contrast, under molecular crowding conditions, the α-helical conformation was stable even upon an ATP binding. These distinct conformational behaviors were observed to be independent of Na⁺ and Mg²⁺. Interestingly, CD measurements demonstrated that the spectra of a frayed duplex decreased with increasing of the RecG concentration both under dilute and molecular crowding conditions in the presence of ATP, suggesting that RecG unwound the frayed duplex. Our findings raise the possibility that the α-helix and β-strand forms of RecG are a preactive and an active structure with the helicase activity, respectively.

Pathogen sensing by nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is mediated by direct binding to muramyl dipeptide and ATP

Nucleotide binding and oligomerization domain-containing protein 2 (NOD2/Card15) is an intracellular protein that is involved in the recognition of bacterial cell wall-derived muramyl dipeptide. Mutations in the gene encoding NOD2 are associated with inherited inflammatory disorders, including Crohn disease and Blau syndrome. NOD2 is a member of the nucleotide-binding domain and leucine-rich repeat-containing protein gene (NLR) family. Nucleotide binding is thought to play a critical role in signaling by NLR family members. However, the molecular mechanisms underlying signal transduction by these proteins remain largely unknown. Mutations in the nucleotide-binding domain of NOD2 have been shown to alter its signal transduction properties in response to muramyl dipeptide in cellular assays. Using purified recombinant protein, we now demonstrate that NOD2 binds and hydrolyzes ATP. Additionally, we have found that the purified recombinant protein is able to bind directly to muramyl dipeptide and can associate with known NOD2-interacting proteins in vitro. Binding of NOD2 to muramyl dipeptide and homo-oligomerization of NOD2 are enhanced by ATP binding, suggesting a model of the molecular mechanism for signal transduction that involves binding of nucleotide followed by binding of muramyl dipeptide and oligomerization of NOD2 into a signaling complex. These findings set the stage for further studies into the molecular mechanisms that underlie detection of muramyl dipeptide and assembly of NOD2-containing signaling complexes.

Systematic analysis and comparison of nucleotide-binding site disease resistance genes in maize

Nucleotide-binding site (NBS) disease resistance genes play an integral role in defending plants from a range of pathogens and insect pests. Consequently, a number of recent studies have focused on NBS-encoding genes in molecular disease resistance breeding programmes for several important plant species. Little information, however, has been reported with an emphasis on systematic analysis and a comparison of NBS-encoding genes in maize. In the present study, 109 NBS-encoding genes were identified based on the complete genome sequence of maize (Zea mays cv. B73), classified as four different subgroups, and then characterized according to chromosomal locations, gene duplications, structural diversity and conserved protein motifs. Subsequent phylogenetic comparisons indicated that several maize NBS-encoding genes possessed high similarity to function-known NBS-encoding genes, and revealed the evolutionary relationships of NBS-encoding genes in maize comparede to those in other model plants. Analyses of the physical locations and duplications of NBS-encoding genes showed that gene duplication events of disease resistance genes were lower in maize than in other model plants, which may have led to an increase in the functional diversity of the maize NBS-encoding genes. Various expression patterns of maize NBS-encoding genes in different tissues were observed using an expressed-sequence tags database and, alternatively, after southern leaf blight infection or the application of exogenous salicylic acid. The results reported in the present study contribute to an improved understanding of the NBS-encoding gene family in maize.

A primary survey on bryophyte species reveals two novel classes of nucleotide-binding site (NBS) genes

Due to their potential roles in pathogen defense, genes encoding nucleotide-binding site (NBS) domain have been particularly surveyed in many angiosperm genomes. Two typical classes were found: one is the TIR-NBS-LRR (TNL) class and the other is the CC-NBS-LRR (CNL) class. It is seldom known, however, what kind of NBS-encoding genes are mainly present in other plant groups, especially the most ancient groups of land plants, that is, bryophytes. To fill this gap of knowledge, in this study, we mainly focused on two bryophyte species: the moss Physcomitrella patens and the liverwort Marchantia polymorpha, to survey their NBS-encoding genes. Surprisingly, two novel classes of NBS-encoding genes were discovered. The first novel class is identified from the P. patens genome and a typical member of this class has a protein kinase (PK) domain at the N-terminus and a LRR domain at the C-terminus, forming a complete structure of PK-NBS-LRR (PNL), reminiscent of TNL and CNL classes in angiosperms. The second class is found from the liverwort genome and a typical member of this class possesses an α/β-hydrolase domain at the N-terminus and also a LRR domain at the C-terminus (Hydrolase-NBS-LRR, HNL). Analysis on intron positions and phases also confirmed the novelty of HNL and PNL classes, as reflected by their specific intron locations or phase characteristics. Phylogenetic analysis covering all four classes of NBS-encoding genes revealed a closer relationship among the HNL, PNL and TNL classes, suggesting the CNL class having a more divergent status from the others. The presence of specific introns highlights the chimerical structures of HNL, PNL and TNL genes, and implies their possible origin via exon-shuffling during the quick lineage separation processes of early land plants.

Genome-wide identification and mapping of NBS-encoding resistance genes in Solanum tuberosum group phureja

The majority of disease resistance (R) genes identified to date in plants encode a nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain containing protein. Additional domains such as coiled-coil (CC) and TOLL/interleukin-1 receptor (TIR) domains can also be present. In the recently sequenced Solanum tuberosum group phureja genome we used HMM models and manual curation to annotate 435 NBS-encoding R gene homologs and 142 NBS-derived genes that lack the NBS domain. Highly similar homologs for most previously documented Solanaceae R genes were identified. A surprising ∼41% (179) of the 435 NBS-encoding genes are pseudogenes primarily caused by premature stop codons or frameshift mutations. Alignment of 81.80% of the 577 homologs to S. tuberosum group phureja pseudomolecules revealed non-random distribution of the R-genes; 362 of 470 genes were found in high density clusters on 11 chromosomes.

A new class of adenylate kinase in methanogens is related to uridylate kinase

The protein derived from the Methanocaldococcus jannaschii MJ0458 gene is annotated as a δ-1-pyrroline 5-carboxylate synthetase and is predicted to be related to aspartokinase and uridylate kinase. Analysis of the predicted protein sequence indicated that it is a unique kinase with few similarities to either uridylate or adenylate kinase. Here, we report that the MJ0458 gene product is a second type of archaeal adenylate kinase, AdkB. This enzyme is different from the established archaeal-specific adenylate kinase in both sequence and predicted tertiary structure.

Differential Protein Expression in Sugarcane during Sugarcane-Sporisorium scitamineum Interaction Revealed by 2-DE and MALDI-TOF-TOF/MS

To understand the molecular basis of a specific plant-pathogen interaction, it is important to identify plant proteins that respond to the pathogen attack. Two sugarcane varieties, NCo376 and Ya71-374, were used in this study. By applying 2-dimensional electrophoresis (2-DE), the protein expression profile of sugarcane after inoculating with Sporisorium scitamineum was analyzed. In total, 23 differentially expressed proteins were identified by MALDI-TOF-TOF/MS. Bioinformatics analysis revealed that the functions of these 20 differential proteins were associated with such functions as photosynthesis, signal transduction, and disease resistance, while the function of the remaining three proteins was not determined. From above, we can assume that the protein regulatory network during the interaction between sugarcane and S. scitamineum is complicated. This represents the first proteomic investigation focused on highlighting the alterations of the protein expression profile in sugarcane exposed to S. scitamineum, and it provides reference information on sugarcane response to S. scitamineum stress at the protein level.

An autoactive mutant of the M flax rust resistance protein has a preference for binding ATP, whereas wild-type M protein binds ADP

Resistance (R) proteins are key regulators of the plant innate immune system and are capable of pathogen detection and activation of the hypersensitive cell death immune response. To understand the molecular mechanism of R protein activation, we undertook a phenotypic and biochemical study of the flax nucleotide binding (NB)-ARC leucine-rich repeat protein, M. Using Agrobacterium-mediated transient expression in flax cotyledons, site-directed mutations of key residues within the P-loop, kinase 2, and MHD motifs within the NB-ARC domain of M were shown to affect R protein function. When purified using a yeast expression system and assayed for ATP and ADP, these mutated proteins exhibited marked differences in the quantity and identity of the bound nucleotide. ADP was bound to recombinant wild-type M protein, while the nonfunctional P-loop mutant did not have any nucleotides bound. In contrast, ATP was bound to an autoactive M protein mutated in the highly conserved MHD motif. These data provide direct evidence supporting a model of R protein function in which the "off" R protein binds ADP and activation of R protein defense signaling involves the exchange of ADP for ATP.

Over-expression in the nucleotide-binding site-leucine rich repeat gene DEPG1 increases susceptibility to bacterial leaf streak disease in transgenic rice plants

Bacterial leaf streak of rice (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a widely-spread disease in the main rice-producing areas of the world. Investigating the genes that play roles in rice-Xoc interactions helps us to understand the defense signaling pathway in rice. Here we report a differentially expressed protein gene (DEPG1), which regulates susceptibility to BLS. DEPG1 is a nucleotide-binding site (NBS)-leucine rich repeat (LRR) gene, and the deduced protein sequence of DEPG1 has approximately 64% identity with that of the disease resistance gene Pi37. Phylogenetic analysis of DEPG1 and the 18 characterized NBS-LRR genes revealed that DEPG1 is more closely related to Pi37. DEPG1 protein is located to the cytoplasm, which was confirmed by transient expression of DEPG1-GFP (green fluorescent protein) fusion construct in onion epidermal cells. Semi-quantitative PCR assays showed that DEPG1 is widely expressed in rice, and is preferentially expressed in internodes, leaf blades, leaf sheaths and flag leaves. Observation of cross sections of leaves from the transgenic plants with a DEPG1-promoter::glucuronidase (GUS) fusion gene revealed that DEPG1 is also highly expressed in mesophyll tissues where Xoc mainly colonizes. Additionally, Xoc negatively regulates expression of DEPG1 at the early stage of the pathogen infection, and so do the three defense-signal compounds including salicylic acid (SA), methyl jasmonate (MeJA) and 1-aminocyclopropane-1-carboxylic-acid (ACC). Transgenic rice plants overexpressing DEPG1 exhibit enhanced susceptibility to Xoc compared to the wild-type controls. Moreover, enhanced susceptibility to Xoc may be mediated by inhibition of the expression of some SA biosynthesis-related genes and pathogenesis-related genes that may contribute to the disease resistance. Taken together, DEPG1 plays roles in the interactions between rice and BLS pathogen Xoc.

Identification of serine/threonine kinase and nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes in the fire blight resistance quantitative trait locus of apple cultivar 'Evereste'

Fire blight is the most destructive bacterial disease affecting apple (Malus×domestica) worldwide. So far, no resistance gene against fire blight has been characterized in apple, despite several resistance regions having been identified. A highly efficacious resistance quantitative trait locus (QTL) was localized on linkage group 12 (LG12) of the ornamental cultivar 'Evereste'. A marker previously reported to be closely linked to this resistance was used to perform a chromosome landing. A bacterial artificial chromosome (BAC) clone of 189 kb carrying the fire blight resistance QTL was isolated and sequenced. New microsatellite markers were developed, and the genomic region containing the resistance locus was limited to 78 kb. A cluster of eight genes with homologies to already known resistance gene structures to bacterial diseases was identified and the corresponding gene transcription was verified. From this cluster, two genes were recognized in silico as the two most probable fire blight resistance genes showing homology with the Pto/Prf complex in tomato.

Interaction of ATP with fibroblast growth factor 2: biochemical characterization and consequence for growth factor stability

Background

Fibroblast growth factor 2, a well-characterized heparin-binding growth factor, is involved in many biological processes like embryogenesis, cell proliferation and angiogenesis. However, this growth factor is very unstable and shows rapid degradation in aqueous solution. Beside the well-known stabilization of FGF2 by heparin or heparan sulphate, the recently discovered binding to ATP also shows a stabilizing and protective effect on this growth factor.

Results

Here we determined the dissociation constant of ATP on FGF2 by equilibrium microdialysis (K_D: 59.8 μM) and analyzed the impact of this binding on secondary structure by CD-spectroscopy. ATP-binding to FGF2 significantly changed the secondary structure of this growth factor with a shift to random coil structure elements. We also analyzed the influence of this binding on the stability of FGF2 in aqueous solution over a period of 2 h. While the amount of untreated FGF2 is reduced drastically over this period of time, ATP-binding reduces the degradation considerably.

Conclusions

Taken together, our data suggest an important role of ATP in FGF2-stabilization beside the well known-role of heparin and heparan sulphate.

Mining disease-resistance genes in roses: functional and molecular characterization of the rdr1 locus

The interaction of roses with the leaf spot pathogen Diplocarpon rosae (the cause of black spot on roses) is an interesting pathosystem because it involves a long-lived woody perennial, with life history traits very different from most model plants, and a hemibiotrophic pathogen with moderate levels of gene flow. Here we present data on the molecular structure of the first monogenic dominant resistance gene from roses, Rdr1, directed against one isolate of D. rosae. Complete sequencing of the locus carrying the Rdr1 gene resulted in a sequence of 265,477 bp with a cluster of nine highly related TIR-NBS-LRR (TNL) candidate genes. After sequencing revealed candidate genes for Rdr1, we implemented a gene expression analysis and selected five genes out of the nine TNLs. We then silenced the whole TNL gene family using RNAi (Rdr1-RNAi) constructed from the most conserved sequence region and demonstrated a loss of resistance in the normally resistant genotype. To identify the functional TNL gene, we further screened the five TNL candidate genes with a transient leaf infiltration assay. The transient expression assay indicated a single TNL gene (muRdr1H), partially restoring resistance in the susceptible genotype. Rdr1 was found to localize within the muRdr1 gene family; the genes within this locus contain characteristic motifs of active TNL genes and belong to a young cluster of R genes. The transient leaf assay can be used to further analyze the rose black spot interaction and its evolution, extending the analyses to additional R genes and to additional pathogenic types of the pathogen.

Tryptophanyl-tRNA synthetase Urzyme: a model to recapitulate molecular evolution and investigate intramolecular complementation

We substantiate our preliminary description of the class I tryptophanyl-tRNA synthetase minimal catalytic domain with details of its construction, structure, and steady-state kinetic parameters. Generating that active fragment involved deleting 65% of the contemporary enzyme, including the anticodon-binding domain and connecting peptide 1, CP1, a 74-residue internal segment from within the Rossmann fold. We used protein design (Rosetta), rather than phylogenetic sequence alignments, to identify mutations to compensate for the severe loss of modularity, thus restoring stability, as evidenced by renaturation described previously and by 70-ns molecular dynamics simulations. Sufficient solubility to enable biochemical studies was achieved by expressing the redesigned Urzyme as a maltose-binding protein fusion. Michaelis-Menten kinetic parameters from amino acid activation assays showed that, compared with the native full-length enzyme, TrpRS Urzyme binds ATP with similar affinity. This suggests that neither of the two deleted structural modules has a strong influence on ground-state ATP binding. However, tryptophan has 10(3) lower affinity, and the Urzyme has comparably reduced specificity relative to the related amino acid, tyrosine. Molecular dynamics simulations revealed how CP1 may contribute significantly to cognate amino acid specificity. As class Ia editing domains are nested within the CP1, this finding suggests that this module enhanced amino acid specificity continuously, throughout their evolution. We call this type of reconstructed protein catalyst an Urzyme (Ur prefix indicates original, primitive, or earliest). It establishes a model for recapitulating very early steps in molecular evolution in which fitness may have been enhanced by accumulating entire modules, rather than by discrete amino acid sequence changes.

Isolation and characterization of NBS-LRR- resistance gene candidates in turmeric (Curcuma longa cv. surama)

Turmeric (Curcuma longa), an important asexually reproducing spice crop of the family Zingiberaceae is highly susceptible to bacterial and fungal pathogens. The identification of resistance gene analogs holds great promise for development of resistant turmeric cultivars. Degenerate primers designed based on known resistance genes (R-genes) were used in combinations to elucidate resistance gene analogs from Curcuma longa cultivar surama. The three primers resulted in amplicons with expected sizes of 450-600 bp. The nucleotide sequence of these amplicons was obtained through sequencing; their predicted amino acid sequences compared to each other and to the amino acid sequences of known R-genes revealed significant sequence similarity. The finding of conserved domains, viz., kinase-1a, kinase-2 and hydrophobic motif, provided evidence that the sequences belong to the NBS-LRR class gene family. The presence of tryptophan as the last residue of kinase-2 motif further qualified them to be in the non-TIR-NBS-LRR subfamily of resistance genes. A cluster analysis based on the neighbor-joining method was carried out using Curcuma NBS analogs together with several resistance gene analogs and known R-genes, which classified them into two distinct subclasses, corresponding to clades N3 and N4 of non-TIR-NBS sequences described in plants. The NBS analogs that we isolated can be used as guidelines to eventually isolate numerous R-genes in turmeric.

Unique features of the rice blast resistance Pish locus revealed by large scale retrotransposon-tagging

BACKGROUND

R gene-mediated resistance is one of the most effective mechanisms of immunity against pathogens in plants. To date some components that regulate the primary steps of plant immunity have been isolated, however, the molecular dissection of defense signaling downstream of the R proteins remains to be completed. In addition, R genes are known to be highly variable, however, the molecular mechanisms responsible for this variability remain obscure.

RESULTS

To identify novel factors required for R gene-mediated resistance in rice, we used rice insertional mutant lines, induced by the endogenous retrotransposon Tos17, in a genetic screening involving the rice blast fungus Magnaporthe oryzae. We inoculated 41,119 mutant lines with the fungus using a high throughput procedure, and identified 86 mutant lines with diminished resistance. A genome analysis revealed that 72 of the 86 lines contained mutations in a gene encoding a nucleotide binding site (NBS) and leucine rich repeat (LRR) domain-containing (NBS-LRR) protein. A genetic complementation analysis and a pathogenesis assay demonstrated that this NBS-LRR gene encodes Pish, which confers resistance against races of M. oryzae containing avrPish. The other 14 lines have intact copies of the Pish gene, suggesting that they may contain mutations in the signaling components downstream of Pish. The genome analysis indicated that Pish and its neighboring three NBS-LRR genes are high similar to one another and are tandemly located. An in silico analysis of a Tos17 flanking sequence database revealed that this region is a "hot spot" for insertion. Intriguingly, the insertion sites are not distributed evenly among these four NBS-LRR genes, despite their similarity at the sequence and expression levels.

CONCLUSIONS

In this work we isolated the R gene Pish, and identified several other mutants involved in the signal transduction required for Pish-mediated resistance. These results indicate that our genetic approach is efficient and useful for unveiling novel aspects of defense signaling in rice. Furthermore, our data provide experimental evidence that R gene clusters have the potential to be highly preferred targets for transposable element insertions in plant genomes. Based on this finding, a possible mechanism underlying the high variability of R genes is discussed.

Modular architecture of nucleotide-binding pockets

Recently, modularity has emerged as a general attribute of complex biological systems. This is probably because modular systems lend themselves readily to optimization via random mutation followed by natural selection. Although they are not traditionally considered to evolve by this process, biological ligands are also modular, being composed of recurring chemical fragments, and moreover they exhibit similarities reminiscent of mutations (e.g. the few atoms differentiating adenine and guanine). Many ligands are also promiscuous in the sense that they bind to many different protein folds. Here, we investigated whether ligand chemical modularity is reflected in an underlying modularity of binding sites across unrelated proteins. We chose nucleotides as paradigmatic ligands, because they can be described as composed of well-defined fragments (nucleobase, ribose and phosphates) and are quite abundant both in nature and in protein structure databases. We found that nucleotide-binding sites do indeed show a modular organization and are composed of fragment-specific protein structural motifs, which parallel the modular structure of their ligands. Through an analysis of the distribution of these motifs in different proteins and in different folds, we discuss the evolutionary implications of these findings and argue that the structural features we observed can arise both as a result of divergence from a common ancestor or convergent evolution.

PolY, a transcriptional regulator with ATPase activity, directly activates transcription of polR in polyoxin biosynthesis in Streptomyces cacaoi

polY, a transcriptional regulatory gene in the polyoxin biosynthetic cluster of Streptomyces cacaoi, was analysed, and its deduced product (PolY) showed amino acid sequence homology to AfsR from Streptomyces coelicolor A3(2). PolY contains an OmpR-like DNA binding domain at its N-terminal and an ATPase domain in the middle of the protein. Disruption of polY abolished polyoxin biosynthesis, which could be restored by the integration of a single copy of polY into the chromosome of the disruption mutant. Transcription of polR, a pathway-specific regulatory gene of polyoxin biosynthesis, was controlled by polY. Electrophoretic mobility shift assay and DNase I protection experiments indicated that PolY bound to the promoter region of polR, and the binding site contained a direct nucleotide repeat typical of Streptomyces antibiotic regulatory protein binding sites. PolY exhibited ATPase activity in vitro. Additionally, binding of ADP/ATPgammaS to ATPase domain triggered the oligomerization of PolY and enhanced its DNA binding activity. Consistently, further experiments in vivo demonstrated that changes of ADP/ATP concentrations significantly affected PolY activity in the cell. These results suggested that the ATPase domain might be a sensor of endogenous pool of ADP/ATP, whose change modulated PolY activity under the physiological conditions.