Transmission from seed to seedling and elimination of alfalfa viruses.

Introduction: Viral diseases have become a vital factor limiting the development of the alfalfa (Medicago sativa) industry. Six viruses infecting alfalfa with a high incidence rate are Alfalfa mosaic virus (AMV), Medicago sativa alphapartitivirus 1 (MsAPV1), Medicago sativa alphapartitivirus 2 (MsAPV2), Medicago sativa deltapartitivirus 1 (MsDPV1), Medicago sativa amalgavirus 1 (MsAV1), and Cnidium vein yellowing virus 1 (CnVYV1). The purpose of this study was to develop preventive measures against these viruses by investigating their transmission through alfalfa seeds. Methods: In this study, we investigated the transmission rate of alfalfa viruses from seed to seedling by PCR, determined the location of viruses in seed by dissecting seed embryos and seed coat, tracked the changes of viruses in seedlings, and finally discover effective elimination measures for alfalfa viruses from 16 measures. Results and discussion: Our results demonstrated that all these six viruses could be transmitted from alfalfa seeds to seedlings with the transmission rate ranging from 44.44% to 88.89%. For AMV, MsAPV2, and MsAV1, the viral load was significantly higher in the seed coats than in the seed embryos; however, it did not show significant differences between these two parts of the seeds for MsAPV1, MsDPV1, and CnVYV1. Dynamic accumulation analysis of AMV and MsAPV2 indicated that the viral load in plants increased continuously in the early growth stage, making it important to inactivate these viruses prior to their seed-to-seedling transmission. Sixteen treatments including physical, chemical, and combinations of physical and chemical measures were compared in terms of their elimination efficiency on AMV and MsAPV2 and impacts on seed germination. The results showed that soaking alfalfa seeds in sterile distilled water for 2h + 2% NaClO for 1h or 2% NaClO for 1h were more promisingly applicable because it could significantly reduce AMV and MsAPV2 particles in both seeds and seedlings. Our data revealed a route of virus transmission in alfalfa and shed light on the discovery of a highly efficient method for the management of alfalfa viral diseases.

Gene gain and loss from the Asian corn borer W chromosome.

BACKGROUND: Sex-limited chromosomes Y and W share some characteristics, including the degeneration of protein-coding genes, enrichment of repetitive elements, and heterochromatin. However, although many studies have suggested that Y chromosomes retain genes related to male function, far less is known about W chromosomes and whether they retain genes related to female-specific function. RESULTS: Here, we built a chromosome-level genome assembly of the Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Crambidae, Pyraloidea), an economically important pest in corn, from a female, including both the Z and W chromosome. Despite deep conservation of the Z chromosome across Lepidoptera, our chromosome-level W assembly reveals little conservation with available W chromosome sequence in related species or with the Z chromosome, consistent with a non-canonical origin of the W chromosome. The W chromosome has accumulated significant repetitive elements and experienced rapid gene gain from the remainder of the genome, with most genes exhibiting pseudogenization after duplication to the W. The genes that retain significant expression are largely enriched for functions in DNA recombination, the nucleosome, chromatin, and DNA binding, likely related to meiotic and mitotic processes within the female gonad. CONCLUSIONS: Overall, our chromosome-level genome assembly supports the non-canonical origin of the W chromosome in O. furnacalis, which experienced rapid gene gain and loss, with the retention of genes related to female-specific function.

The Efficiency of Pest Control Options against Two Major Sweet Corn Ear Pests in China.

Helicoverpa armigera (Hübner) and Ostrinia furnacalis (Guenée) are the most devastating insect pests at the ear stage of maize, causing significant losses to the sweet corn industry. Pesticide control primarily relies on spraying during the flowering stage, but the effectiveness is inconsistent since larvae are beneath husks within hours to a day, making pesticide treatments simpler to avoid. Insufficient understanding of pest activity patterns impedes precise and efficient pesticide control. H. armigera and O. furnacalis in corn fields were monitored in the last few years in Beijing China, and we observed a higher occurrence of both moths during the R1 stage of sweet corn. Moth captures reached the maximum during this stage, with 555-765 moths per hectare corn field daily. The control efficiency of nine synthetic insecticides and five biopesticides was assessed in the field during this period. Virtako, with mineral oil as the adjuvant, appeared to be the most effective synthetic insecticide, with the efficiencies reaching 88% and 87% on sweet and waxy corn, respectively. Pesticide residue data indicated that the corn is safe after 17 days of its use. The most effective bioinsecticide was Beauveria bassiana combined with mineral oil, with 88% and 80% control efficiency in sweet and waxy corn, respectively. These results suggested that spraying effective insecticides 5 days after corn silking could effectively control corn ear pests H. armigera and O. furnacalis. Our findings provide valuable insights for the development of ear pest management strategies in sweet corn.

Antennal Transcriptome Analysis of Olfactory Genes and Characterization of Odorant Binding Proteins in Odontothrips loti (Thysanoptera: Thripidae).

To identify odors in complex environments accurately, insects have evolved multiple olfactory proteins. In our study, various olfactory proteins of Odontothrips loti Haliday, an oligophagous pest that primarily affects Medicago sativa (alfalfa), were explored. Specifically, 47 putative olfactory candidate genes were identified in the antennae transcriptome of O. loti, including seven odorant-binding proteins (OBPs), nine chemosensory proteins (CSPs), seven sensory neuron membrane proteins (SNMPs), eight odorant receptors (ORs), and sixteen ionotropic receptors (IRs). PCR analysis further confirmed that 43 out of 47 genes existed in O. loti adults, and O.lotOBP1, O.lotOBP4, and O.lotOBP6 were specifically expressed in the antennae with a male-biased expression pattern. In addition, both the fluorescence competitive binding assay and molecular docking showed that p-Menth-8-en-2-one, a component of the volatiles of the host, had strong binding ability to the O.lotOBP6 protein. Behavioral experiments showed that this component has a significant attraction to both female and male adults, indicating that O.lotOBP6 plays a role in host location. Furthermore, molecular docking reveals potential active sites in O.lotOBP6 that interact with most of the tested volatiles. Our results provide insights into the mechanism of O. loti odor-evoked behavior and the development of a highly specific and sustainable approach for thrip management.

Identification of CNGCs in Glycine max and Screening of Related Resistance Genes after Fusarium solani Infection.

Cyclic nucleotide-gated channels (CNGCs), non-selective cation channels localised on the plasmalemma, are involved in growth, development, and regulatory mechanisms in plants during adverse stress. To date, CNGC gene families in multiple crops have been identified and analysed. However, there have been no systematic studies on the evolution and development of CNGC gene families in legumes. Therefore, in the present study, via transcriptome analysis, we identified 143 CNGC genes in legumes, and thereafter, classified and named them according to the grouping method used for Arabidopsis thaliana. Functional verification for disease stress showed that four GmCNGCs were specifically expressed in the plasmalemma during the stress process. Further, functional enrichment analysis showed that their mode of participation and coordination included inorganic ion concentration regulation inside and outside the membrane via the transmembrane ion channel and participation in stress regulation via signal transduction. The CNGC family genes in G. max involved in disease stress were also identified and physiological stress response and omics analyses were also performed. Our preliminary results revealed the basic laws governing the involvement of CNGCs in disease resistance in G. max, providing important gene resources and a theoretical reference for the breeding of resistant soybean.

Genome-Wide Scans and Transcriptomic Analyses Characterize Selective Changes as a Result of Chlorantraniliprole Resistance in Plutella xylostella.

Pesticide resistance in insects is an example of adaptive evolution occurring in pest species and is driven by the artificial introduction of pesticides. The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), has evolved resistance to various insecticides. Understanding the genetic changes underpinning the resistance to pesticides is necessary for the implementation of pest control measures. We sequenced the genome of six resistant and six susceptible DBM individuals separately and inferred the genomic regions of greatest divergence between strains using FST and θπ. Among several genomic regions potentially related to insecticide resistance, CYP6B6-like was observed with significant divergence between the resistant and susceptible strains, with a missense mutation located near the substrate recognition site (SRS) and four SNPs in the promoter. To characterize the relative effects of directional selection via insecticide tolerance ('strain') as compared to acute exposure to insecticide ('treatment'), four pairwise comparisons were carried out between libraries to determine the differentially expressed genes. Most resistance-related differentially expressed genes were identified from the comparison of the strains and enriched in pathways for exogenous detoxification including cytochrome P450 and the ABC transporter. Further confirmation came from the weighted gene co-expression network analysis, which indicated that genes in the significant module associated with chlorantraniliprole resistance were enriched in pathways for exogenous detoxification, and that CYP6B6-like represented a hub gene in the "darkred" module. Furthermore, RNAi knock-down of CYP6B6-like increases P. xylostella sensitivity to chlorantraniliprole. Our study thus provides a genetic foundation underlying selection for pesticide resistance and plausible mechanisms to explain fast evolved adaptation through genomic divergence and altered gene expression in insects.

Occurrence, Distribution, and Transmission of Alfalfa Viruses in China.

Alfalfa (Medicago sativa L.) is one of the most important quality forages worldwide and is cultivated throughout China. Alfalfa is susceptible to a variety of viral diseases during its growth, which has caused huge amounts of commercial losses. However, the profile of the alfalfa virus in China remains ambiguous and the viruses transmitted by Odontothrips loti (Haliday), dominant insect pests in alfalfa, are also poorly understood. In the present study, virus diversity was investigated in the primary alfalfa-growing areas in China. A total of 18 alfalfa viruses were identified through RNA-sequencing (RNA-seq) and reverse transcription-polymerase chain reaction (RT-PCR). Two new plant viruses, Medicago sativa virus 1 (MsV1) and Medicago sativa luteovirus 1 (MsLV1), were detected for the first time. Another four viruses, including the Alfalfa ringspot-associated virus (ARaV), Alfalfa virus F (AVF), Alfalfa enamovirus 1 (AEV1), and Alfalfa deltaparitivirus (ADPV), were reported in China for the first time as well. Both Alfalfa mosaic virus (AMV) and Medicago sativa alphapartitivirus 2 (MsAPV2) are the dominant pathogens, with an infection incidence of 91.7-100%, and 74.4-97.2%, respectively. Additionally, O. loti with first- and second-instar nymphs were shown to acquire the AMV within 0.25 h of feeding on a virus-infected alfalfa. Transmission by thrips to healthy alfalfa plants was also demonstrated. Additionally, we clarified the dynamic changes in the AMV in pre-adult stages of O. loti, which indicated that the AMV is propagated in the nymph stage of O. loti. These findings provide valuable information for understanding the alfalfa virome, confirm the role thrips O. loti plays in alfalfa virus transmission, and improve our fundamental knowledge and management of diseases in China.

RNA-seq reveals plant virus composition and diversity in alfalfa, thrips, and aphids in Beijing, China.

Viruses are widespread in alfalfa (Medicago sativa L.), representing a key limitation to the production of this important forage plant. Understanding the diversity of plant viruses in alfalfa and their potential vectors will play an important role in management to minimize the emergence, transmission, and impact of viruses. Next-generation sequencing (NGS) targeting the transcriptome was applied to monitor the virus communities in alfalfa and its two main pests, thrips (Odontothrips loti Haliday and Frankliniella intonsa Trybom) and aphids (Acyrthosiphon pisum Mordvilko and Therioaphis trifolii Monell). A comparison of transcriptome datasets with reference databases revealed the presence of eight candidate viruses. Five out of the eight viruses, alfalfa mosaic virus (AMV), Medicago sativa alphapartitivirus 1 (MsAPV1), Medicago sativa deltapartitivirus 1 (MsDPV1), Medicago sativa amalgavirus 1 (MsAV1), and bean yellow mosaic virus (BYMV), were confirmed by RT-PCR. We identified and determined the presence of four RNA viruses from alfalfa samples, two viruses (AMV and MsAPV1) from thrips samples, and one virus (BYMV) from T. trifolii. All sequences isolated from the insect samples were more than 95% identical to the sequences from the alfalfa samples or to sequences from the National Center for Biotechnology Information (NCBI) reference database. The RNA-seq results of this study suggest that AMV and MsAPV1 are the predominant RNA plant viruses infecting alfalfa and that they are carried by the major pests. This lays the foundation for future research on the vectors and transmission of these viruses. In addition, the sequence data have enabled the assembly of the first complete genome sequence of MsDPV1 from alfalfa.

Morphology and Distribution of Antennal Sensilla in Three Species of Thripidae (Thysanoptera) Infesting Alfalfa Medicago sativa.

Thrips are important pests to alfalfa Medicago sativa. Similar as many other plant-feeding insects, thrips rely on the antennae to receive chemical signals in the environment to locate their hosts. Previous studies indicated that sensilla of different shapes on the surface of insect antenna play an important role in signal recognition. However, morphological analysis of the antennal sensilla in Thysanoptera has been limited to only a few species. To expand the understanding of how antennal sensilla are related to semiochemical detection in thrips, here we compared the morphology and distribution of antennal sensilla in three thrip species, Odontothrips loti, Megalurothrips distalis, and Sericothrips kaszabi, by scanning electron microscope (SEM). The antennae of these three species are all composed of eight segments and share similar types of sensilla which distribute similarly in each segment, despite that their numbers show sexual dimorphism. Specifically, nine major types of sensilla in total were found, including three types of sensilla basiconica (SBI, SBII, and SBIII), two types of sensilla chaetica (SChI and SChII), and one type for each of sensilla coeloconica (SCo), sensilla trichodea (ST), sensilla campaniformia (SCa), and sensilla cavity (SCav). The potential functions of sensilla were discussed according to the previous research results and will lay a morphological foundation for the study of the olfactory mechanism of three species of thrips.

Genome-Wide Selective Signature Analysis Revealed Insecticide Resistance Mechanisms in Cydia pomonella.

The codling moth, Cydia pomonella L. (Lepidoptera, Tortricidae), is a serious invasive pest of pome fruits. Currently, C. pomonella management mainly relies on the application of insecticides, which have driven the development of resistance in the insect. Understanding the genetic mechanisms of insecticide resistance is of great significance for developing new pest resistance management techniques and formulating effective resistance management strategies. Using existing genome resequencing data, we performed selective sweep analysis by comparing two resistant strains and one susceptible strain of the insect pest and identified seven genes, among which, two (glycine receptor and glutamate receptor) were under strong insecticide selection, suggesting their functional importance in insecticide resistance. We also found that eight genes including CYP6B2, CYP307a1, 5-hydroxytryptamine receptor, cuticle protein, and acetylcholinesterase, are potentially involved in cross-resistance to azinphos-methyl and deltamethrin. Moreover, among several P450s identified as positively selected genes, CYP6B2, CYP4C1, and CYP4d2 showed the highest expression level in larva compared to other stages tested, and CYP6B2 also showed the highest expression level in midgut, supporting the roles they may play in insecticide metabolism. Our results provide several potential genes that can be studied further to advance understanding of complexity of insecticide resistance mechanisms in C. pomonella.

Illumina Sequencing of 18S/16S rRNA Reveals Microbial Community Composition, Diversity, and Potential Pathogens in 17 Turfgrass Seeds.

The increasing need for turfgrass seeds is coupled with the high risk of dangerous microbial pathogens being transmitted through the domestic and international trade of seeds. Concerns continue to be raised about seed safety and quality. Here, we show that next-generation sequencing (NGS) of DNA represents an effective and reliable tactic to monitor the microbial communities within turfgrass seeds. A comparison of DNA sequence data with reference databases revealed the presence of 26 different fungal orders. Among them, serious plant disease pathogens such as Bipolaris sorokiniana, Boeremia exigua, Claviceps purpurea, and Rhizoctonia zeae were detected. Seedborne bacteria, including Erwinia persicina and Acidovorax avenae, were identified from different bacterial orders. Our study indicated that the traditional culturing method and the NGS approach for pathogen identification complement each other. The reliability of culturing and NGS methods was further validated by PCR with specific primers. The combination of these different techniques ensures maximum sensitivity and specificity for turfgrass seed pathogen testing assay.

Characterization of Antennal Sensilla and Immunolocalization of Odorant-Binding Proteins on Spotted Alfalfa Aphid, Therioaphis trifolii (Monell).

The spotted alfalfa aphid [Therioaphis trifolii (Monell), Homoptera, Drepanosiphidae] is a well-known destructive pest that can significantly reduce alfalfa yields. Herein, the morphology of antennal sensilla of T. trifolii has been examined by using scanning electron microscopy and the ultrastructure of sensilla stellate and placoidea was described by transmission electron microscopy. Stellate sensilla, placoid sensilla, and coeloconic sensilla were found on the 6th segment, and a single sensillum placoidea was located on the 5th segment. Placoid sensilla were also present on the 3rd antennal segment of alate and apterous aphids, and the number was similar between two morphs. Two types of trichoid sensilla and coeloconic sensilla were found on the antennae, respectively. The results of ultrastructure showed that stellate sensilla are innervated by three neurons, while placoid sensilla present three groups of neurons, equipped with 2-3 dendrites in each neuron group. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of sensilla stellate and placoidea, and we observed that the antiserum against OBP6 intensively labeled all placoid sensilla from both primary and secondary rhinaria. OBP7 and OBP8 could also be detected in placoid sensilla, but less strongly than OBP6. In addition, OBP6, OBP7, and OBP8 were densely labeled in stellate sensilla, suggesting OBP6, OBP7, and OBP8 may sense alarm pheromone germacrene A in T. trifolii.

A genome-wide association study explores the genetic determinism of host resistance to Salmonella pullorum infection in chickens.

BACKGROUND: Salmonella infection is a serious concern in poultry farming because of its impact on both economic loss and human health. Chicks aged 20 days or less are extremely vulnerable to Salmonella pullorum (SP), which causes high mortality. Furthermore, an outbreak of SP infection can result in a considerable number of carriers that become potential transmitters, thus, threatening fellow chickens and offspring. In this study, we conducted a genome-wide association study (GWAS) to detect potential genomic loci and candidate genes associated with two disease-related traits: death and carrier state. METHODS: In total, 818 birds were phenotyped for death and carrier state traits through a SP challenge experiment, and genotyped by using a 600 K high-density single nucleotide polymorphism (SNP) array. A GWAS using a single-marker linear mixed model was performed with the GEMMA software. RNA-sequencing on spleen samples was carried out for further identification of candidate genes. RESULTS: We detected a region that was located between 33.48 and 34.03 Mb on chicken chromosome 4 and was significantly associated with death, with the most significant SNP (rs314483802) accounting for 11.73% of the phenotypic variation. Two candidate genes, FBXW7 and LRBA, were identified as the most promising genes involved in resistance to SP. The expression levels of FBXW7 and LRBA were significantly downregulated after SP infection, which suggests that they may have a role in controlling SP infections. Two other significant loci and related genes (TRAF3 and gga-mir-489) were associated with carrier state, which indicates a different polygenic determinism compared with that of death. In addition, genomic inbreeding coefficients showed no correlation with resistance to SP within each breed in our study. CONCLUSIONS: The results of this GWAS with a carefully organized Salmonella challenge experiment represent an important milestone in understanding the genetics of infectious disease resistance, offer a theoretical basis for breeding SP-resistant chicken lines using marker-assisted selection, and provide new information for salmonellosis research in humans and other animals.

Feather colour affects the aggressive behaviour of chickens with the same genotype on the dominant white (I) locus.

Aggression in chickens is a serious economic and animal welfare issue in poultry farming. Pigmentation traits have been documented to be associated with animal behaviour. Chicken pecking behaviour has been found to be related to feather colour, with premelanosome protein 17 (PMEL17) being one of the candidate genes. In the present study, we performed a genotypic and phenotypic association analysis between chicken plumage colour (red and white) and aggressive behaviour in an F1 hybrid group generated by crossing the autosomal dominant white-feathered breed White Leghorn (WL) and the red-feathered breed Rhode Island Red (RIR). In genetic theory, all the progeny should have white feathers because WL is homozygous autosomal dominant for white feathers. However, we found a few red-feathered female chickens. We compared the aggressiveness between the red and white females to determine whether the feather colour alone affected the behaviour, given that the genetic background should be the same except for feather colour. The aggressiveness was recorded 5 days after sexual maturity at 26 weeks. Generally, white plumage hens showed significantly higher aggressiveness compared to the red ones in chasing, attacking, pecking, and threatening behaviour traits. We assessed three candidate feather colour genes-PMEL17, solute carrier family 45 member 2 (SLC45A2), and SRY-box 10 (SOX10)-to determine the genetic basis for the red and white feather colour in our hybrid population; there was no association between the three loci and feather colour. The distinct behavioural findings observed herein provide clues to the mechanisms underlying the association between phenotype and behaviour in chickens. We suggest that mixing red and white chickens together might reduce the occurrence of aggressive behaviours.

(E)-ß-farnesene synthase gene affects aphid behavior in transgenic Medicago sativa.

BACKGROUND: Pea aphid (Acyrthosiphon pisum Harris) is one of the major pests in alfalfa crops, causing significant yield losses. (E)-ß-farnesene (EßF), an alarm pheromone released by pea aphid, is generic to many species of aphids, and is used to minimize potential danger from predators and parasitoids by avoiding the source of the pheromone. RESULTS: In this study, EßF synthase gene was constructed into a plant expression vector, and overexpressed in alfalfa (Medicago sativa L.), with expression among transgenic lines confirmed by qRT-PCR. Subcellular localization analysis showed that EßF synthase gene was expressed in the plasma membrane and nucleus of the leaf. GC/MS of extraction from transgenic alfalfa indicated emission of EßF ranging from 5.92 to 13.09 ng day-1 g-1 fresh tissue. Behavior assays in Y-olfactometers demonstrated that transgenic alfalfa expressing AaEßF gene could repel pea aphids, with aphids taking a significantly longer time to select a transgenic line compared with the control line (P < 0.01). CONCLUSION: We have demonstrated a potentially valuable strategy of using EßF synthase genes for aphid control in alfalfa. © 2018 Society of Chemical Industry.

iTRAQ-Based Comparative Proteomic Analysis Reveals Molecular Mechanisms Underlying Wing Dimorphism of the Pea Aphid, Acyrthosiphon pisum.

Wing dimorphism is a widespread phenomenon in insects with an associated trade-off between flight capability and fecundity. Despite the molecular underpinnings of phenotypic plasticity that has already been elucidated, it is still not fully understood. In this study, we focused on the differential proteomics profiles between alate and apterous morphs of the pea aphid, Acyrthosiphon pisum at the fourth instar nymph and adult stages, using isobaric tags for relative and absolute quantitation (iTRAQ) in a proteomic-based approach. A total of 5,116 protein groups were identified and quantified in the three biological replicates, of which 836 were differentially expressed between alate and apterous morphs. A bioinformatics analysis of differentially expressed protein groups (DEPGs) was performed based on gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). KEGG enrichment analysis showed that DEPGs mainly participated in energy metabolism, amino acid biosynthesis and metabolism, and signal sensing and transduction. To verify the reliability of proteomics data, the transcriptional expression of 29 candidates of differentially expressed proteins were analyzed by quantitative real-time PCR (qRT-PCR), showing that 26 genes were consistent with those at proteomic levels. In addition, differentially expressed proteins between winged and wingless morphs that were linked to olfactory sense were investigated. Quantitative real-time PCR revealed the tissue- and morph-biased expression profiles. These results suggested that olfactory sense plays a key role in wing dimorphism of aphids. The comparative proteomic analysis between alate and apterous morphs of the pea aphid provides a novel insight into wing development and dimorphism in aphids and will help facilitate our understanding of these concepts at molecular levels.

Niemann-Pick C2 Proteins: A New Function for an Old Family.

Niemann-Pick proteins type C2 (NPC2) are carriers of cholesterol in vertebrates, with a single member in each species. The high sequence conservation between mammals and across vertebrates is related to their common function. In contrast, NPC2 proteins in arthropods have undergone extensive duplication and differentiation, probably under environmental pressure, and are likely to have different functions. Recent studies have suggested that in arthropods these proteins might act as carriers for semiochemicals and other hydrophobic compounds. In this study we focused on the function of a specific NPC2 gene in the moth Helicoverpa armigera (HarmNPC2-1). This protein binds several flavonoids with micromolar dissociation constants. The best ligand was gossypol, present in cotton, one of the main host plants for H. armigera. Western blot revealed the presence of HarmNPC2-1 in different parts of the body, including the antennae, proboscis, and abdomen. In the antennae, in situ hybridization experiments produced strong staining in auxiliary cells at the base of sensilla trichodea, basiconica, coeloconica, and chaetica. Immunocytochemistry confirmed the expression of the protein in sensilla chaetica. Our results support a role of semiochemical carriers for NPC2 proteins in insects and indicate such proteins as new targets for insecticide-free pest population control.

Ultrastructure and morphology of antennal sensilla of the adult diving beetle Cybister japonicus Sharp.

The morphology and distribution of the antennal sensilla of adult diving beetle Cybister japonicus Sharp (Dytiscidae, Coleoptera), have been examined. Five types of sensilla on the antennae were identified by scanning electron microscope (SEM) and transmission electron microscope (TEM). Sensilla placodea and elongated s. placodea are the most abundant types of sensilla, distributing only on the flagellum. Both these types of sensilla carry multiple pore systems with a typical function as chemoreceptors. Three types of s. coeloconica (Type I-III) were also identified, with the characterization of the pit-in-pit style, and carrying pegs externally different from each other. Our data indicated that both type I and type II of s. coleconica contain two bipolar neurons, while the type III of s. coleconica contains three dendrites in the peg. Two sensory dendrites in the former two sensilla are tightly embedded inside the dendrite sheath, with no space left for sensilla lymph. There are no specific morphological differences in the antennal sensilla observed between males and females, except that the males have longer antennae and more sensilla than the females.

P-HYDROXYPHENYLPYRUVATE DIOXYGENASE from Medicago sativa is involved in vitamin E biosynthesis and abscisic acid-mediated seed germination.

P-HYDROXYPHENYLPYRUVATE DIOXYGENASE (HPPD) is the first committed enzyme involved in the biosynthesis of vitamin E, and is characterized by catalyzing the conversion of p-hydroxyphenyl pyruvate (HPP) to homogentisic acid (HGA). Here, an HPPD gene was cloned from Medicago sativa L. and designated MsHPPD, which was expressed at high levels in alfalfa leaves. PEG 6000 (polyethylene glycol), NaCl, abscisic acid and salicylic acid were shown to significantly induce MsHPPD expression, especially in the cotyledons and root tissues. Overexpression of MsHPPD was found to significantly increase the level of ß-tocotrienol and the total vitamin E content in Arabidopsis seeds. Furthermore, these transgenic Arabidopsis seeds exhibited an accelerated germination time, compared with wild-type seeds under normal conditions, as well as under NaCl and ABA treatments. Meanwhile, the expression level of several genes associated with ABA biosynthesis (NCED3, NCED5 and NCED9) and the ABA signaling pathway (RAB18, ABI3 and ABI5) were significantly down-regulated in MsHPPD-overexpressing transgenic lines, as well as the total free ABA content. Taken together, these results demonstrate that MsHPPD functions not only in the vitamin E biosynthetic pathway, but also plays a critical role in seed germination via affecting ABA biosynthesis and signaling.

Functional characterization of a gibberellin receptor and its application in alfalfa biomass improvement.

Bioactive gibberellins (GAs) are essential phytohormones involved in the regulation of many aspects of plant development. GA receptors are crucial in GA signal transduction in plants. The GA receptor GoGID1 promotes plant elongation and improves biomass production when ectopically expressed in tobacco. Here, we discovered that GoGID1 can interact with the DELLA proteins of Arabidopsis in the presence of gibberellic acid. GoGID1 partially or completely functionally rescued the phenotypes of the Arabidopsis double-mutants atgid1a/atgid1c and atgid1a/atgid1b. The overexpression of GoGID1 led to increases in plant height and biomass production in transgenic Arabidopsis plants. The GoGID1 gene enhanced GA sensitivity of the transgenic plants. More importantly, transgenic alfalfa plants overexpressing GoGID1 exhibited increased growth rates, heights and biomass and produced larger leaves when compared with the control plants. Thus, GoGID1 functions as a GA receptor, playing multiple roles in plant growth and development. The GoGID1 gene has the potential to be used in the genetic engineering of forage crops for biomass improvement.