A Lateral Flow-Recombinase Polymerase Amplification Method for Colletotrichum gloeosporioides Detection.

The greater yam (Dioscorea alata), a widely cultivated and nutritious food crop, suffers from widespread yield reduction due to anthracnose caused by Colletotrichum gloeosporioides. Latent infection often occurs before anthracnose phenotypes can be detected, making early prevention difficult and causing significant harm to agricultural production. Through comparative genomic analysis of 60 genomes of 38 species from the Colletotrichum genus, this study identified 17 orthologous gene groups (orthogroups) that were shared by all investigated C. gloeosporioides strains but absent from all other Colletotrichum species. Four of the 17 C. gloeosporioides-specific orthogroups were used as molecular markers for PCR primer designation and C. gloeosporioides detection. All of them can specifically detect C. gloeosporioides out of microbes within and beyond the Colletotrichum genus with different sensitivities. To establish a rapid, portable, and operable anthracnose diagnostic method suitable for field use, specific recombinase polymerase amplification (RPA) primer probe combinations were designed, and a lateral flow (LF)-RPA detection kit for C. gloeosporioides was developed, with the sensitivity reaching the picogram (pg) level. In conclusion, this study identified C. gloeosporioides-specific molecular markers and developed an efficient method for C. gloeosporioides detection, which can be applied to the prevention and control of yam anthracnose as well as anthracnose caused by C. gloeosporioides in other crops. The strategy adopted by this study also serves as a reference for the identification of molecular markers and diagnosis of other plant pathogens.

Unraveling the Molecular Basis of Color Variation in Dioscorea alata Tubers: Integrated Transcriptome and Metabolomics Analysis.

Dioscorea alata L. (Dioscoreaceae) is a widely cultivated tuber crop with variations in tuber color, offering potential value as health-promoting foods. This study focused on the comparison of D. alata tubers possessing two distinct colors, white and purple, to explore the underlying mechanisms of color variation. Flavonoids, a group of polyphenols known to influence plant color and exhibit antioxidant properties, were of particular interest. The total phenol and total flavonoid analyses revealed that purple tubers (PTs) have a significantly higher content of these metabolites than white tubers (WTs) and a higher antioxidant activity than WTs, suggesting potential health benefits of PT D. alata. The transcriptome analysis identified 108 differentially expressed genes associated with the flavonoid synthesis pathway, with 57 genes up-regulated in PTs, including CHS, CHI, DFR, FLS, F3H, F3'5'H, LAR, ANS, and ANR. The metabolomics analysis demonstrated that 424 metabolites, including 104 flavonoids and 8 tannins, accumulated differentially in PTs and WTs. Notably, five of the top ten up-regulated metabolites were flavonoids, including 6-hydroxykaempferol-7-O-glucoside, pinocembrin-7-O-(6″-O-malonyl)glucoside, 6-hydroxykaempferol-3,7,6-O-triglycoside, 6-hydroxykaempferol-7-O-triglycoside, and cyanidin-3-O-(6″-O-feruloyl)sophoroside-5-O-glucoside, with the latter being a precursor to anthocyanin synthesis. Integrating transcriptome and metabolomics data revealed that the 57 genes regulated 20 metabolites within the flavonoid synthesis pathway, potentially influencing the tubers' color variation. The high polyphenol content and antioxidant activity of PTs indicate their suitability as nutritious and health-promoting food sources. Taken together, the findings of this study provide insights into the molecular basis of tuber color variation in D. alata and underscore the potential applications of purple tubers in the food industry and human health promotion. The findings contribute to the understanding of flavonoid biosynthesis and pigment accumulation in D. alata tubers, opening avenues for future research on enhancing the nutritional quality of D. alata cultivars.

Features of MR signals of retroplacental basal decidual space and its diagnostic significance.

BACKGROUND: With more pregnant women undergoing cesarean section, the number of women with scarring in the uterus undergoing uterine magnetic resonance (MR) examination in the second and third trimesters following a subsequent pregnancy, has increased. OBJECTIVE: To investigate features of MR signals in retroplacental basal decidual space. METHODS: The MR imaging data of patients with clinically and pathologically confirmed placenta implantation and complete placental abruption were retrospectively analyzed. RESULTS: Patients with high-intensity signals in T2-weighted images (T2WI) of the retroplacental basal decidual space did not suffer placenta implantation after delivery, while high-intensity signals in T2WI of the retroplacental basal decidual space was not observed in patients with different degrees of placenta implantation. CONCLUSION: As the retroplacental basal decidual space is the barrier between the placenta and myometrium, high-intensity signals in T2WI can improve the confidence of MR exclusion diagnostics of placenta implantation, and can be used as exclusion criteria for MR diagnosis of placenta implantation.

Low-coverage whole genome sequencing of eleven species/subspecies in Dioscorea sect. Stenophora (Dioscoreaceae): comparative plastome analyses, molecular markers development and phylogenetic inference.

Dioscorea sect. Stenophora (Dioscoreaceae) comprises about 30 species that are distributed in the temperate and subtropical regions of the Northern Hemisphere. Despite being evolutionarily "primitive" and medically valuable, genomic resources and molecular studies of this section are still scarce. Here, we conducted low-coverage whole genome sequencing of 11 Stenophora species/subspecies to retrieve their plastome information (whole plastome characteristics, plastome-divergent hotspots, plastome-derived SSRs, etc.) and polymorphic nuclear SSRs, as well as performed comparative plastome and phylogenetic analyses within this section. The plastomes of Stenophora species/subspecies ranged from 153,691 bp (D. zingiberensis) to 154,149 bp (D. biformifolia) in length, and they all contained the same 114 unique genes. All these plastomes were highly conserved in gene structure, gene order and GC content, although variations at the IR/SC borders contributed to the whole length differences among them. The number of plastome-derived SSRs among Stenophora species/subspecies varied from 74 (D. futschauensis) to 93 (D. zingiberensis), with A/T found to be the most frequent one. Seven highly variable regions and 12 polymorphic nuclear SSRs were identified in this section, thereby providing important information for further taxonomical, phylogenetic and population genetic studies. Phylogenomic analyses based on whole plastome sequences and 80 common protein coding genes strongly supported D. biformifolia and D. banzhuana constituted the successive sister species to the remaining sampled species, which could be furtherly divided into three clades. Overall, this study provided a new perspective for plastome evolution of Stenophora, and proved the role of plastome phylogenomic in improving the phylogenetic resolution in this section. These results also provided an important reference for the protection and utilization of this economically important section.

Pan-Plastome of Greater Yam (Dioscorea alata) in China: Intraspecific Genetic Variation, Comparative Genomics, and Phylogenetic Analyses.

Dioscorea alata L. (Dioscoreaceae), commonly known as greater yam, water yam, or winged yam, is a popular tuber vegetable/food crop worldwide, with nutritional, health, and economical importance. China is an important domestication center of D. alata, and hundreds of cultivars (accessions) have been established. However, genetic variations among Chinese accessions remain ambiguous, and genomic resources currently available for the molecular breeding of this species in China are very scarce. In this study, we generated the first pan-plastome of D. alata, based on 44 Chinese accessions and 8 African accessions, and investigated the genetic variations, plastome evolution, and phylogenetic relationships within D. alata and among members of the section Enantiophyllum. The D. alata pan-plastome encoded 113 unique genes and ranged in size from 153,114 to 153,161 bp. A total of four whole-plastome haplotypes (Haps I-IV) were identified in the Chinese accessions, showing no geographical differentiation, while all eight African accessions shared the same whole-plastome haplotype (Hap I). Comparative genomic analyses revealed that all four whole plastome haplotypes harbored identical GC content, gene content, gene order, and IR/SC boundary structures, which were also highly congruent with other species of Enantiophyllum. In addition, four highly divergent regions, i.e., trnC-petN, trnL-rpl32, ndhD-ccsA, and exon 3 of clpP, were identified as potential DNA barcodes. Phylogenetic analyses clearly separated all the D. alata accessions into four distinct clades corresponding to the four haplotypes, and strongly supported that D. alata was more closely related to D. brevipetiolata and D. glabra than D. cirrhosa, D. japonica, and D. polystachya. Overall, these results not only revealed the genetic variations among Chinese D. alata accessions, but also provided the necessary groundwork for molecular-assisted breeding and industrial utilization of this species.

Genome Sequence Resource for Colletotrichum gloeosporioides, an Important Pathogenic Fungus Causing Anthracnose of Dioscorea alata.

Anthracnose disease is one of the most important diseases of Dioscorea alata and many other food yams, which is caused by Colletotrichum gloeosporioides fungus from the Glomerellaceae family of the Sordariomycetes class. In the present study, a C. gloeosporioides starin named CgDa01 was isolated from D. alata, and its genome was sequenced based on Oxford Nanopore technology (ONT) and the Illumina sequencing platform. The high-quality genome of CgDa01 was assembled with a 62.78 Mb genome size and 15,845 predicted protein-coding genes. The proteins of predicted genes were annotated using multiple public databases, including the nonredundant protein database, the InterProScan databases, and Kyoto Encyclopedia of Genes and Genomes. Among the annotated protein-coding genes, 55 were predicted as potential virulence genes by the fungal virulence factor database. The C. gloeosporioides CgDa01 genome assembly described in this study can serve as a resource for better understanding the pathogenic mechanism of C. gloeosporioides on yam hosts.

Genome-Wide Analysis of NBS-LRR Genes From an Early-Diverging Angiosperm Euryale ferox.

NBS-LRR genes are the largest gene family in plants conferring resistance to pathogens. At present, studies on the evolution of NBS-LRR genes in angiosperms mainly focused on monocots and eudicots, while studies on NBS-LRR genes in the basal angiosperms are limited. Euryale ferox represents an early-diverging angiosperm order, Nymphaeales, and confronts various pathogens during its lifetime, which can cause serious economic losses in terms of yield and quality. In this study, we performed a genome-wide identification and analysis of NBS-LRR genes in E. ferox. All 131 identified NBS-LRR genes could be divided into three subclasses according to different domain combinations, including 18 RNLs, 40 CNLs, and 73 TNLs. The E. ferox NBS-LRR genes are unevenly distributed on 29 chromosomes; 87 genes are clustered at 18 multigene loci, and 44 genes are singletons. Gene duplication analysis revealed that segmental duplications acted as a major mechanism for NBS-LRR gene expansions but not for RNL genes, because 18 RNL genes were scattered over 11 chromosomes without synteny loci, indicating that the expansion of RNL genes could have been caused by ectopic duplications. Ancestral gene reconciliation based on phylogenetic analysis revealed that there were at least 122 ancestral NBS-LRR lineages in the common ancestor of the three Nymphaeaceae species, suggesting that NBS-LRR genes expanded slightly during speciation in E. ferox. Transcriptome analysis showed that the majority of NBS-LRR genes were at a low level of expression without pathogen stimulation. Overall, this study characterized the profile of NBS-LRR genes in E. ferox and should serve as a valuable resource for disease resistance breeding in E. ferox.

Genome-wide Identification and Evolutionary Analysis of NBS-LRR Genes From Secale cereale.

Secale cereale is an important crop in the Triticeae tribe of the Poaceae family, and it has unique agronomic characteristics and genome properties. It possesses resistance to many diseases and serves as an important resource for the breeding of other Triticeae crops. We performed a genome-wide study on S. cereale to identify the largest group of plant disease resistance genes (R genes), the nucleotide-binding site-leucine-rich repeat receptor (NBS-LRR) genes. In its genome, 582 NBS-LRR genes were identified, including one from the RNL subclass and 581 from the CNL subclass. The NBS-LRR gene number in the S. cereale genome is greater than that in barley and the diploid wheat genomes. S. cereale chromosome 4 contains the largest number of NBS-LRR genes among the seven chromosomes, which is different from the pattern in barley and the genomes B and D of wheat but similar to that in the genome A of wheat. Further synteny analysis suggests that more NBS-LRR genes on chromosome 4 have been inherited from a common ancestor by S. cereale and the wheat genome A than the wheat genomes B and D. Phylogenetic analysis revealed that at least 740 NBS-LRR lineages are present in the common ancestor of S. cereale, Hordeum vulgare and Triticum urartu. However, most of them have only been inherited by one or two species, with only 65 of them preserved in all three species. The S. cereale genome inherited 382 of these ancestral NBS-LRR lineages, but 120 of them have been lost in both H. vulgare and T. urartu. This study provides the full NBS-LRR profile of the S. cereale genome, which is a resource for S. cereale breeding and indicates that S. cereale can be an important material for the molecular breeding of other Triticeae crops.

Genome-Wide Identification and Evolutionary Analysis of NBS-LRR Genes From Dioscorea rotundata.

Dioscorea rotundata is an important food crop that is mainly cultivated in subtropical regions of the world. D. rotundata is frequently infected by various pathogens during its lifespan, which results in a substantial economic loss in terms of yield and quality. The disease resistance gene (R gene) profile of D. rotundata is largely unknown, which has greatly hampered molecular study of disease resistance in this species. Nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes are the largest group of plant R genes, and they play important roles in plant defense responses to various pathogens. In this study, 167 NBS-LRR genes were identified from the D. rotundata genome. Subsequently, one gene was assigned to the resistance to powdery mildew8 (RPW8)-NBS-LRR (RNL) subclass and the other 166 genes to the coiled coil (CC)-NBS-LRR (CNL) subclass. None of the Toll/interleukin-1 receptor (TIR)-NBS-LRR (TNL) genes were detected in the genome. Among them, 124 genes are located in 25 multigene clusters and 43 genes are singletons. Tandem duplication serves as the major force for the cluster arrangement of NBS-LRR genes. Segmental duplication was detected for 18 NBS-LRR genes, although no whole-genome duplication has been documented for the species. Phylogenetic analysis revealed that D. rotundata NBS-LRR genes share 15 ancestral lineages with Arabidopsis thaliana genes. The NBS-LRR gene number increased by more than a factor of 10 during D. rotundata evolution. A conservatively evolved ancestral lineage was identified from D. rotundata, which is orthologs to the Arabidopsis RPM1 gene. Transcriptome analysis for four different tissues of D. rotundata revealed a low expression of most NBS-LRR genes, with the tuber and leaf displaying a relatively high NBS-LRR gene expression than the stem and flower. Overall, this study provides a complete set of NBS-LRR genes for D. rotundata, which may serve as a fundamental resource for mining functional NBS-LRR genes against various pathogens.

Divergence and Conservative Evolution of XTNX Genes in Land Plants.

The Toll-interleukin-1 receptor (TIR) and Nucleotide-binding site (NBS) domains are two major components of the TIR-NBS-leucine-rich repeat family plant disease resistance genes. Extensive functional and evolutionary studies have been performed on these genes; however, the characterization of a small group of genes that are composed of atypical TIR and NBS domains, namely XTNX genes, is limited. The present study investigated this specific gene family by conducting genome-wide analyses of 59 green plant genomes. A total of 143 XTNX genes were identified in 51 of the 52 land plant genomes, whereas no XTNX gene was detected in any green algae genomes, which indicated that XTNX genes originated upon emergence of land plants. Phylogenetic analysis revealed that the ancestral XTNX gene underwent two rounds of ancient duplications in land plants, which resulted in the formation of clades I/II and clades IIa/IIb successively. Although clades I and IIb have evolved conservatively in angiosperms, the motif composition difference and sequence divergence at the amino acid level suggest that functional divergence may have occurred since the separation of the two clades. In contrast, several features of the clade IIa genes, including the absence in the majority of dicots, the long branches in the tree, the frequent loss of ancestral motifs, and the loss of expression in all detected tissues of Zea mays, all suggest that the genes in this lineage might have undergone pseudogenization. This study highlights that XTNX genes are a gene family originated anciently in land plants and underwent specific conservative pattern in evolution.

Interaction of Ferulic Acid with Glutathione S-Transferase and Carboxylesterase Genes in the Brown Planthopper, Nilaparvata lugens.

Plant phenolics are crucial defense phytochemicals against herbivores and glutathione S-transferase (GST) and carboxylesterase (CarE) in herbivorous insects are well-known detoxification enzymes for such xenobiotics. To understand relationship between a plant phenolic and herbivore GST or CarE genes, we evaluated the relationship between a rice phenolic ferulic acid and resistance to brown planthopper (BPH, Nilaparvata lugens), and investigated the interaction of ferulic acid with GST or CarE genes in BPH. The results indicate that ferulic acid content in tested rice varieties was highly associated with resistance to BPH. Bioassays using artificial diets show that the phenolic acid toxicity to BPH was dose dependent and the LC25 and LC50 were 5.81 and 23.30 µg/ml at 72 hr, respectively. Activities of the enzymes BPH GST and CarE were increased at concentrations below the LC50 of ferulic acid. Moreover, low ferulic acid concentrations (< LC25) upregulated the transcriptional levels of NlGSTD1 and NlGSTE1 of the GST family and NlCE of the CarE family. By using dsRNA-induced gene silencing (DIGS) of GST or CarE, it was shown that suppressed expression levels of NlGSTD1, NlGSTE1 and NlCE were 14.6%-21.2%, 27.8%-34.2%, and 10.5%-19.8%, respectively. Combination of NlGSTD1, NlGSTE1 or NlCE knockdown with ferulic acid increased nymph mortality by 92.9%, 119.9%, or 124.6%, respectively. These results suggest that depletion of detoxification genes in herbivorous insects by plant-mediated RNAi technology might be a new potential resource for improving rice resistance to BPH.

Distinct Patterns of Gene Gain and Loss: Diverse Evolutionary Modes of NBS-Encoding Genes in Three Solanaceae Crop Species.

Plant resistance conferred by nucleotide binding site (NBS)-encoding resistance genes plays a key role in the defense against various pathogens throughout the entire plant life cycle. However, comparative analyses for the systematic evaluation and determination of the evolutionary modes of NBS-encoding genes among Solanaceae species are rare. In this study, 447, 255, and 306 NBS-encoding genes were identified from the genomes of potato, tomato, and pepper, respectively. These genes usually clustered as tandem arrays on chromosomes; few existed as singletons. Phylogenetic analysis indicated that three subclasses [TNLs (TIR-NBS-LRR), CNLs (CC-NBS-LRR), and RNLs (RPW8-NBS-LRR)] each formed a monophyletic clade and were distinguished by unique exon/intron structures and amino acid motif sequences. By comparing phylogenetic and systematic relationships, we inferred that the NBS-encoding genes in the present genomes of potato, tomato, and pepper were derived from 150 CNL, 22 TNL, and 4 RNL ancestral genes, and underwent independent gene loss and duplication events after speciation. The NBS-encoding genes therefore exhibit diverse and dynamic evolutionary patterns in the three Solanaceae species, giving rise to the discrepant gene numbers observed today. Potato shows a "consistent expansion" pattern, tomato exhibits a pattern of "first expansion and then contraction," and pepper presents a "shrinking" pattern. The earlier expansion of CNLs in the common ancestor led to the dominance of this subclass in gene numbers. However, RNLs remained at low copy numbers due to their specific functions. Along the evolutionary process of NBS-encoding genes in Solanaceae, species-specific tandem duplications contributed the most to gene expansions.

Insertion DNA Accelerates Meiotic Interchromosomal Recombination in Arabidopsis thaliana.

Nucleotide insertions/deletions are ubiquitous in eukaryotic genomes, and the resulting hemizygous (unpaired) DNA has significant, heritable effects on adjacent DNA. However, little is known about the genetic behavior of insertion DNA. Here, we describe a binary transgenic system to study the behavior of insertion DNA during meiosis. Transgenic Arabidopsis lines were generated to carry two different defective reporter genes on nonhomologous chromosomes, designated as "recipient" and "donor" lines. Double hemizygous plants (harboring unpaired DNA) were produced by crossing between the recipient and the donor, and double homozygous lines (harboring paired DNA) via self-pollination. The transfer of the donor's unmutated sequence to the recipient generated a functional ß-glucuronidase gene, which could be visualized by histochemical staining and corroborated by polymerase chain reaction amplification and sequencing. More than 673 million seedlings were screened, and the results showed that meiotic ectopic recombination in the hemizygous lines occurred at a frequency >6.49-fold higher than that in the homozygous lines. Gene conversion might have been exclusively or predominantly responsible for the gene correction events. The direct measurement of ectopic recombination events provided evidence that an insertion, in the absence of an allelic counterpart, could scan the entire genome for homologous counterparts with which to pair. Furthermore, the unpaired (hemizygous) architectures could accelerate ectopic recombination between itself and interchromosomal counterparts. We suggest that the ectopic recombination accelerated by hemizygous architectures may be a general mechanism for interchromosomal recombination through ubiquitously dispersed repeat sequences in plants, ultimately contributing to genetic renovation and eukaryotic evolution.

Evolution of the KCS gene family in plants: the history of gene duplication, sub/neofunctionalization and redundancy.

Very long-chain fatty acids (VLCFAs) play an important role in the survival and development of plants, and VLCFA synthesis is regulated by ß-ketoacyl-CoA synthases (KCSs), which catalyze the condensation of an acyl-CoA with malonyl-CoA. Here, we present a genome-wide survey of the genes encoding these enzymes, KCS genes, in 28 species (26 genomes and two transcriptomes), which represents a large phylogenetic scale, and also reconstruct the evolutionary history of this gene family. KCS genes were initially single-copy genes in the green plant lineage; duplication resulted in five ancestral copies in land plants, forming five fundamental monophyletic groups in the phylogenetic tree. Subsequently, KCS genes duplicated to generate 11 genes of angiosperm origin, expanding up to 20-30 members in further-diverged angiosperm species. During this process, tandem duplications had only a small contribution, whereas polyploidy events and large-scale segmental duplications appear to be the main driving force. Accompanying this expansion were variations that led to the sub- and neofunctionalization of different members, resulting in specificity that is likely determined by the 3-D protein structure. Novel functions involved in other physiological processes emerged as well, though redundancy is also observed, largely among recent duplications. Conserved sites and variable sites of KCS proteins are also identified by statistical analysis. The variable sites are likely to be involved in the emergence of product specificity and catalytic power, and conserved sites are possibly responsible for the preservation of fundamental function.

Protective effect of epimedium combined with oligomeric proanthocyanidins on exercise-induced renal ischemia-reperfusion injury of rats.

OBJECTIVE: This paper studied the protective effect and mechanism of epimedium combined with oligomeric proanthocyanidins on exercise-induced renal ischemia-reperfusion injury of rats. METHODS: In the experiment, the rats were given exhaustive swimming training and then their blood urea nitrogen (BUN) and other biochemical indexes were measured after they were given gastric perfusion with 6.01 g/kg doze of epimedium and 50 mg/kg doze of oligomeric proanthocyanidins for 56 days. RESULTS: The result indicated that 8 weeks of over training led to ischemia-reperfusion injury of rats. Moreover, their kidney tissues were significantly changed pathologically and renal functions drastically damaged. BUN and serum creatinine increased and EOM group (P < 0.05), OPCOM group (P < 0.05) and EOPCOM group (P < 0.01) were lower than OM group. EOPCOM group was lower than OPCOM group. SOD activity decreased, EOM group (P < 0.05), OPCOM group (P < 0.05), EOPCOM group (P < 0.01) higher than OM group, and EOPCOM group (P < 0.05) higher than OPCOM group. The content of MDA increased, EOM group (P < 0.05), OPCOM group (P < 0.05), EOPCOM group (P < 0.01) lower than OM group, and EOPCOM group (P < 0.05) lower than OPCOM group. CONCLUSION: Both epimedium and oligomeric proanthocyanidins can boost SOD activity, clean oxygen radicals, clean and alleviate peroxidation of lipids, which exert protection on exercise-induced renal ischemia-reperfusion. The two combined yield a much better result.

Effects of neurolytic celiac plexus block on liver regeneration in rats with partial hepatectomy.

Liver regeneration is the basic physiological process after partial hepatectomy (PH), and is important for the functional rehabilitation of the liver after acute hepatic injury. This study was designed to explore the effects of neurolytic celiac plexus block (NCPB) on liver regeneration after PH. We established a model of PH in rats, assessing hepatic blood flow, liver function, and serum CRP, TNF-α, IL-1ß and IL-6 concentrations of the residuary liver after PH. Additionally, histopathological studies, immunohistochemistry, and western blotting were also performed. Our results indicated that NCPB treatment after PH improved liver regeneration and survival rates, increased hepatic blood flow, reduced hepatocyte damage, decreased the secretion and release of inflammatory cytokines, increased the expression of B cell lymphoma/leukemia-2 (Bcl-2), and decreased the expression of Bcl-2 associated X protein (Bax). Additionally, Western blotting revealed that the expression of NF-κB p65 and c-Jun were decreased in liver after NCPB. In conclusion, the results of our present study indicate that NCPB treatment has a favorable effect on liver regeneration after PH. We suggest that NCPB can be utilized as an effective therapeutic method to help the functional rehabilitation of the liver after acute hepatic injury or liver cancer surgery.

Glutathione S-transferase of brown planthoppers (Nilaparvata lugens) is essential for their adaptation to gramine-containing host plants.

Plants have evolved complex processes to ward off attacks by insects. In parallel, insects have evolved mechanisms to thwart these plant defenses. To gain insight into mechanisms that mediate this arms race between plants and herbivorous insects, we investigated the interactions between gramine, a toxin synthesized by plants of the family Gramineae, and glutathione S transferase (GST), an enzyme found in insects that is known to detoxify xenobiotics. Here, we demonstrate that rice (Oryza sativa), a hydrophytic plant, also produces gramine and that rice resistance to brown planthoppers (Nilaparvata lugens, BPHs) is highly associated with in planta gramine content. We also show that gramine is a toxicant that causes BPH mortality in vivo and that knockdown of BPH GST gene nlgst1-1 results in increased sensitivity to diets containing gramine. These results suggest that the knockdown of key detoxification genes in sap-sucking insects may provide an avenue for increasing their sensitivity to natural plant-associated defense mechanisms.

Non-random arrangement of synonymous codons in archaea coding sequences.

Non-random arrangement of synonymous codons in coding sequences has been recently reported in eukaryotic and bacterial genomes, but the case in archaeal genomes is largely undetermined. Here, we systematically investigated 122 archaeal genomes for their synonymous codon co-occurrence patterns. We found that in most archaeal coding sequences, the order of synonymous codons is not arranged randomly, but rather some successive codon pairs appear significantly more often than expected. Importantly, such codon pairing bias (CPB) pattern in archaea does not seem to completely follow the co-tRNA codon pairing (CCP) rule previously reported for eukaryotes, but largely obeys an identical codon pairing (ICP) rule. Further, synonymous codon permutation test demonstrated that in many archaeal genomes, random mutation alone is unable to cause the observed high level of ICP bias, which strongly indicates that selection force has been involved to shape synonymous codon orders, potentially meeting a global requirement to optimize translation rate.

DNA barcoding the Dioscorea in China, a vital group in the evolution of monocotyledon: use of matK gene for species discrimination.

BACKGROUND: Dioscorea is an important plant genus in terms of food supply and pharmaceutical applications. However, its classification and identification are controversial. DNA barcoding is a recent aid to taxonomic identification and uses a short standardized DNA region to discriminate plant species. In this study, the applicability of three candidate DNA barcodes (rbcL, matK, and psbA-trnH) to identify species within Dioscorea was tested. METHODOLOGY/PRINCIPAL FINDINGS: One-hundred and forty-eight individual plant samples of Dioscorea, encompassing 38 species, seven varieties and one subspecies, representing majority species distributed in China of this genus, were collected from its main distributing areas. Samples were assessed by PCR amplification, sequence quality, extent of specific genetic divergence, DNA barcoding gap, and the ability to discriminate between species. matK successfully identified 23.26% of all species, compared with 9.30% for rbcL and 11.63% for psbA-trnH. Therefore, matK is recommended as the best DNA barcoding candidate. We found that the combination of two or three loci achieved a higher success rate of species discrimination than one locus alone. However, experimental cost would be much higher if two or three loci, rather than a single locus, were assessed. CONCLUSIONS: We conclude that matK is a strong, although not perfect, candidate as a DNA barcode for Dioscorea identification. This assessment takes into account both its ability for species discrimination and the cost of experiments.