Chromosome-level genome assembly of Bactrocera dorsalis reveals its adaptation and invasion mechanisms

Bactrocera dorsalis is an invasive polyphagous pest causing considerable ecological and economic damage worldwide. We report a high-quality chromosome-level genome assembly and combine various transcriptome data to explore the molecular mechanisms of its rapid adaptation to new environments. The expansions of the DDE transposase superfamily and key gene families related to environmental adaptation and enrichment of the expanded and unique gene families in metabolism and defence response pathways explain its environmental adaptability. The relatively high but not significantly different expression of heat-shock proteins, regardless of the environmental conditions, suggests an intrinsic mechanism underlying its adaptation to high temperatures. The mitogen-activated protein kinase pathway plays a key role in adaptation to new environments. The prevalence of duplicated genes in its genome explains the diversity in the B. dorsalis complex. These findings provide insights into the genetic basis of the invasiveness and diversity of B. dorsalis, explaining its rapid adaptation and expansion.

The Negative Regulative Roles of BdPGRPs in the Imd Signaling Pathway of Bactrocera dorsalis

Peptidoglycan recognition proteins (PGRPs) are key regulators in insects’ immune response, functioning as sensors to detect invading pathogens and as scavengers of peptidoglycan (PGN) to reduce immune overreaction. However, the exact function of PGRPs in Bactrocera dorsalis is still unclear. In this study, we identified and functionally characterized the genes BdPGRP-LB, BdPGRP-SB1 and BdPGRP-SC2 in B. dorsalis. The results showed that BdPGRP-LB, BdPGRP-SB1 and BdPGRP-SC2 all have an amidase-2 domain, which has been shown to have N-Acetylmuramoyl-l-Alanine amidase activity. The transcriptional levels of BdPGRP-LB and BdPGRP-SC2 were both high in adult stages and midgut tissues; BdPGRP-SB1 was found most abundantly expressed in the 2nd instar larvae stage and adult fat body. The expression of BdPGRP-LB and BdPGRP-SB1 and AMPs were significantly up-regulated after injury infected with Escherichia coli at different time points; however, the expression of BdPGRP-SC2 was reduced at 9 h, 24 h and 48 h following inoculation with E. coli. By injection of dsRNA, BdPGRP-LB, BdPGRP-SB1 and BdPGRP-SC2 were knocked down by RNA-interference. Silencing of BdPGRP-LB, BdPGRP-SB1 and BdPGRP-SC2 separately in flies resulted in over-activation of the Imd signaling pathway after bacterial challenge. The survival rate of the ds-PGRPs group was significantly reduced compared with the ds-egfp group after bacterial infection. Taken together, our results demonstrated that three catalytic PGRPs family genes, BdPGRP-LB, BdPGRP-SB1 and BdPGRP-SC2, are important negative regulators of the Imd pathway in B. dorsalis.

The fruit fly fauna (Diptera: Tephritideae: Dacinae) of Papua New Guinea, Indonesian Papua, Associated Islands and Bougainville

The species within the Tribe Dacini from Papua New Guinea, Indonesian Papua (West Papua, Central Papua, Papua), associated islands and Bougainville are recorded. In all, 296 species are recorded including 65 new species described herein. The new species are treated under two genera, Bactrocera Macquart (eight subgenera) and Dacus Fabricius (three subgenera). The following new species are described and illustrated: Bactrocera (Bactrocera) atriscuta, B. (B.) bisianumu, B. (B.) bogiae, B. (B.) bubiae, B. (B.) bukaensis, B. (B.) caccabata, B. (B.) centraliae, B (B.) dysoxyli, B. (B.) expandosa, B. (B.) fumica, B. (B.) gabensiae, B. (B.) kaiauiae, B. (B.) kauiae, B. (B.) keravatiae, B. (B.) kokodiae, B. (B.) kunvawaensis, B. (B.) labubulu, B. (B.) laensis, B. (B.) manusiae, B. (B.) meraiensis, B. (B.) monostriata, B. (B.) neoabdonigella, B. (B.) neoaeroginosa, B. (B.) ohuiae, B. (B.) paraendiandrae, B. (B.) paraochracea, B. (B.) pometiae, B. (B.) raunsepnaensis, B. (B.) rounaensis, B (B.) rutilana, B. (B.) saramandiae, B. (B.) sari, B. (B.) sylvania, B. (B.) tikelingiae, B. (B.) trivirgulata, B. (B.) waidoriae, B. (B.) yayamiae, Bactrocera (Bulladacus) curiosa, Bactrocera (Calodacus) insolita, Bactrocera (Hemizeugodacus) neoaglaiae, B. (H.) wilhelmiae, Bactrocera (Neozeugodacus) leblanci, Bactrocera (Semicallantra) cerberae, B. (S.) malasaitiae, Bactrocera (Tetradacus) arbuscula, B. (T.) novotnyi, B. (T.) procera, Bactrocera (Zeugodacus) aiyurae, B. (Z.) anglimpiae, B. (Z.) bainingsiae, B. (Z.) madangiae, B. (Z.) magiae, B. (Z.) mitparingii, B. (Z.) oiyaripensis, B. (Z.) parasepikae, B. (Z.) rufoscutella, B. (Z.) xanthovelata, Dacus (Callantra) nigrolobus, D. (Mellesis) alatifuscatus, Dacus (Neodacus) asteriscus, D. (N.) bimaculosus, D. (N.) curvabilis, D. (N.) kreeriae, D. (N.) lalokiae and D. (N.) neosignatifrons. Females of B. (Bactrocera) daruensis Drew, B. (Bactrocera) nigella (Drew) and B. (Bactrocera) thistletoni Drew are described and a revised description of B. (Bactrocera) torresiae Huxham & Hancock is presented. Bactrocera (Bactrocera) denigrata (Drew) is withdrawn from synonymy with B. longicornis Macquart, and a full description of B. longicornis is presented from a study of the holotype and 27 newly collected specimens. New geographical distribution, host plant and male lure records are presented for some species. The major pest species that occur in the geographical region covered by this publication are reviewed and their biosecurity risks to other regional countries discussed. The land mass of Papua New Guinea and Indonesian Papua contains a richer fauna than any other from South-east Asia to the eastern Pacific, presumably resulting from speciation in the rich rainforest ecosystem. Differences of opinion on the status of some species in the Bactrocera dorsalis complex and on the supraspecific classification within the genus Bactrocera are evident in the literature. We have acknowledged and discussed these differences and, as authors, have presented conclusions based on our own research data.

The Fungus Metarhizium sp. BCC 4849 Is an Effective and Safe Mycoinsecticide for the Management of Spider Mites and Other Insect Pests

Five isolates of Metarhizium sp. were evaluated for their pathogenicity against the spider mite (Tetranychus truncatus Ehara) (Acari: Tetranychidae) and Metarhizium sp. BCC 4849 resulted in the highest mortality (82%) on the 5th day post-inoculation (DPI). Subsequent insect bioassay data indicated similar high virulence against five other insects: African red mites (Eutetranychus africanus Tucker) (Acari: Tetranychidae), bean aphid (Aphis craccivora Koch) (Hemiptera: Aphididae), cassava mealybug (Phenacoccus manihoti Matile-Ferrero) (Hemiptera: Pseudococcidae), sweet potato weevil (Cylas formicarius Fabricius) (Coleoptera: Brentidae), and oriental fruit fly (Bactrocera dorsalis Hendel) (Diptera: Tephritidae), at mortalities of 92–99%, on 3rd–6th DPI, and in laboratory conditions. The pathogenicity assay against E. africanus in hemp plants under greenhouse conditions indicated 85–100% insect mortality on 10th DPI using the fungus alone or in combination with synthetic acaricide. Genome sequencing of Metarhizium sp. BCC 4849 revealed the high abundance of proteins associated with zinc-, heme-, and iron-binding; oxidation-reduction; and transmembrane transport, implicating its versatile mode of interaction with the environment and adaptation to various ion homeostasis. The light and scanning electron microscopy indicated that at 24 h post inoculation (PI), adhesion and appressorial formation occurred, notably near the setae. Most infected mites had stopped moving and started dying by 48–72 h PI. Elongated hyphal bodies and oval blastospores were detected in the legs. At 96–120 h PI or longer, dense mycelia and conidial mass had colonized the interior and exterior of dead mites, primarily at the bottom than the upper part. The shelf-life study also indicated that conidial formulation combined with an oxygen-moisture absorber markedly enhanced the viability and germination after storage at 35 °C for four months. The fungus was tested as safe for humans and animals, according to our toxicological assays.