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.

Diversity, abundance, and sex-specific expression of chemosensory proteins in the reproductive organs of the locust Locusta migratoria manilensis.

Chemosensory proteins (CSPs) are small soluble proteins often associated with chemosensory organs in insects but include members involved in other functions, such as pheromone delivery and development. Although the CSPs of the sensory organs have been extensively studied, little is known on their functions in other parts of the body. A first screening of the available databases has identified 70 sequences encoding CSPs in the oriental locust Locusta migratoria manilensis. Applying proteomic analysis, we have identified 17 of them abundantly expressed in the female reproductive organs, but only one (CSP91) in male organs. Bacterially expressed CSP91 binds fatty acids with a specificity for oleic and linoleic acid, as well as medium-length alcohols and esters. The same acids have been detected as the main gas chromatographic peaks in the dichloromethane extracts of reproductive organs of both sexes. The abundance and the number of CSPs in female reproductive organs indicates important roles for these proteins. We cannot exclude that different functions can be associated with each of the 17 CSPs, including delivery of semiochemicals, solubilization of hormones, direct control of development, or other unknown tasks.

Immunolocalization of odorant-binding proteins on antennal chemosensilla of the peach aphid Myzus persicae (Sulzer).

The antennal sensilla of Myzus persicae were mapped using scanning and transmission electron microscopy. Placoid sensilla and coeloconic sensilla were found on the 6th segments, whereas 2 types of trichoid sensilla were present all through the length of the antenna. A single sensillum placoideum was located on the 5th segment, whereas alate aphids also presented placoid sensilla on the 3rd antennal segment. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of antennal chemosensilla. The antiserum against OBP7 intensively labeled all placoid sensilla from both primary and secondary rhinaria, with gold granules concentrated in the lymph surrounding the dendrite. OBP6 and OBP3 could also be detected in placoid sensilla, but less strongly than OBP7. Barely significant reaction or no reaction was observed with antibodies against OBP8.

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.

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.

Male tarsi specific odorant-binding proteins in the diving beetle Cybister japonicus sharp.

Odorant binding proteins (OBPs) play critical roles in chemical communication of insects, as they recognize and transport environmental chemical signals to receptors. The diving beetle Cybister japonicus Sharp shows a remarkable sexual dimorphism. The foreleg tarsi of males are equipped with large suction cups, believed to help holding the female during underwater courtship and mating. Here, we identified two OBPs highly and specifically expressed in male tarsi, suggesting important functions of these structures in chemical communication. The first protein, CjapOBP1, exhibits the 6 conserved cysteines motif of classic OBPs, while the second, CjapOBP2, contains only four cysteines and can be assigned to the sub-class of C-minus OBPs. Both proteins were expressed in a bacterial system and the purified recombinant proteins were used to for antibodies preparation. Western Blot analysis showed that CjapOBP1 is predominantly expressed in male tarsi and could be also detected in antennae and palpi of both sexes, while CjapOBP2, besides male tarsi, is also present in testis. Ligand-binding experiments showed a good binding affinity between CjapOBP1, CjapOBP2 and citral and coniferyl aldehyde, respectively. These results support a possible function of these two OBPs in the male foreleg tarsi of diving beetles in chemical communication.

Ultrastructure of antennal sensilla of the peach aphid Myzus persicae Sulzer, 1776.

The antennal sensilla of alate Myzus persicae were mapped using transmission electron microscopy and the ultrastructure of sensilla trichoidea, coeloconica, and placoidea are described. Trichoid sensilla, located on the tip of the antennae, are innervated by 2-4 neurons, with some outer dendrites reaching the distal end of the hair. Coeloconic sensilla in primary rhinaria are of two morphological types, both equipped with two dendrites. Dendrites of Type II coeloconic sensilla are enveloped in the dendrite sheath, containing the sensillum lymph. In sensilla coeloconica of Type I, instead, dendrites are enclosed by an electron opaque solid cuticle, with no space left for the sensillum lymph. The ultrastructure of big placoid sensillum reveals the presence of three groups of neurons, with 2-3 dendrites in each neuron group, while both small placoid sensilla are equipped with a single group of neurons, consisting of three dendrites. Both large and small placoid sensilla bear multiple pores on the outer cuticle. The function of these sensilla is also discussed.