Strength of forelimb lateralization predicts motor errors in an insect

Lateralized behaviours are widespread in both vertebrates and invertebrates, suggesting that lateralization is advantageous. Yet evidence demonstrating proximate or ultimate advantages remains scarce, particularly in invertebrates or in species with individual-level lateralization. Desert locusts (Schistocerca gregaria) are biased in the forelimb they use to perform targeted reaching across a gap. The forelimb and strength of this bias differed among individuals, indicative of individual-level lateralization. Here we show that strongly biased locusts perform better during gap-crossing, making fewer errors with their preferred forelimb. The number of targeting errors locusts make negatively correlates with the strength of forelimb lateralization. This provides evidence that stronger lateralization confers an advantage in terms of improved motor control in an invertebrate with individual-level lateralization.     

Thyroid hormone modulation during zebrafish development recapitulates evolved diversity in danionin jaw protrusion mechanics

Protrusile jaws are a highly useful innovation that has been linked to extensive diversification in fish feeding ecology. Jaw protrusion can enhance the performance of multiple functions, such as suction production and capturing elusive prey. Identifying the developmental factors that alter protrusion ability will improve our understanding of fish diversification. In the zebrafish protrusion arises postmetamorphosis. Fish metamorphosis typically includes significant changes in trophic morphology, accompanies a shift in feeding niche and coincides with increased thyroid hormone production. We tested whether thyroid hormone affects the development of zebrafish feeding mechanics. We found that it affected all developmental stages examined, but that effects were most pronounced after metamorphosis. Thyroid hormone levels affected the development of jaw morphology, feeding mechanics, shape variation, and cranial ossification. Adult zebrafish utilize protrusile jaws, but an absence of thyroid hormone impaired development of the premaxillary bone, which is critical to jaw protrusion. Premaxillae from early juvenile zebrafish and hypothyroid adult zebrafish resemble those from adults in the genera Danionella, Devario, and Microdevario that show little to no jaw protrusion. Our findings suggest that evolutionary changes in how the developing skulls of danionin minnows respond to thyroid hormone may have promoted diversification into different feeding niches.     

Isolation and characterization of α‐(1→3)‐glucan‐degrading bacteria from the gut of Diaperis boleti feeding on Laetiporus sulphureus

Bacteria degrading α‐(1→3)‐glucan were sought in the gut of fungivorous insects feeding on fruiting bodies of a polypore fungus Laetiporus sulphureus, which are rich in this polymer. One isolate, from Diaperis boleti, was selected in an enrichment culture in the glucan‐containing medium. The bacterium was identified as Paenibacillus sp. based on the results of the ribosomal DNA analysis. The Paenibacillus showed enzyme activity of 4.97 mU/cm³ and effectively degraded fungal α‐(1→3)‐glucan, releasing nigerooligosaccharides and a trace amount of glucose. This strain is the first reported α‐(1→3)‐glucan‐degrading microorganism in the gut microbiome of insects inhabiting fruiting bodies of polypore fungi.     

Adaptation to Host-Specific Bacterial Pathogens Drives Rapid Evolution of a Human Innate Immune Receptor

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The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri ssp. citri through the regulation of flagellar biosynthesis

Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri ssp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which showed impaired ability to attach to an abiotic substrate. One of these mutants carries the Tn5 insertion in hupB, a gene encoding a bacterial histone-like protein, homologue to the β-subunit of the Heat-Unstable (HU) nucleoid protein of Escherichia coli. These types of protein are necessary to maintain the bacterial nucleoid organization and the global regulation of gene expression. Here, we characterized the influence of the mutation in hupB regarding Xcc biofilm formation and virulence. The mutant strain hupB was incapable of swimming in soft agar, whereas its complemented strain partially recovered this phenotype. Electron microscope imaging revealed that impaired motility of hupB was a consequence of the absence of the flagellum. Comparison of the expression of flagellar genes between the wild-type strain and hupB showed that the mutant exhibited decreased expression of fliC (encoding flagellin). The hupB mutant also displayed reduced virulence compared with the wild-type strain when they were used to infect Citrus lemon plants using different infection methods. Our results therefore show that the histone-like protein HupB plays an essential role in the pathogenesis of Xcc through the regulation of biofilm formation and biosynthesis of the flagellum.     

Surfactin and fengycin contribute to the protection of a Bacillus subtilis strain against grape downy mildew by both direct effect and defence stimulation

Bacillus subtilis GLB191 (hereafter GLB191) is an efficient biological control agent against the biotrophic oomycete Plasmopara viticola, the causal agent of grapevine downy mildew. In this study, we show that GLB191 supernatant is also highly active against downy mildew and that the activity results from both direct effect against the pathogen and stimulation of the plant defences (induction of defence gene expression and callose production). High-performance thin-layer chromatography analysis revealed the presence of the cyclic lipopeptides fengycin and surfactin in the supernatant. Mutants affected in the production of fengycin and/or surfactin were thus obtained and allowed us to show that both surfactin and fengycin contribute to the double activity of GLB191 supernatant against downy mildew. Altogether, this study suggests that GLB191 supernatant could be used as a new biocontrol product against grapevine downy mildew.     

Tracking reveals behavioural coordination driven by environmental constraints in the Black-vented Shearwater Puffinus opisthomelas

During the breeding season, seabird foraging trips are constrained by nest attendance schedule and are necessarily colony centred. Oceanographic cues play a major role in the choice of foraging areas to minimize the time spent away from the nest. Here, we analysed the foraging tracks of Black-vented Shearwaters Puffinus opisthomelas during the incubation and chick-rearing periods of 2016 and 2017 at Isla Natividad (Mexico). We applied expectation-maximization binary clustering to track data to clusterize different behaviour patterns during foraging flights. We then applied binary generalized linear mixed models to characterize of foraging areas based on of environmental variables. We finally used kernel estimation techniques to describe main foraging areas. In 2016, breeding shearwaters used two core areas for foraging and resting on the water; the core area delineated by males was located northward from the colony in the Vizcaino Bay and the core area for females was located southward from the colony at the entrance of San Ignacio Lagoon. In 2017, males and females used the same areas with no evident segregation. Our study provided the first information on Black-vented Shearwater foraging areas during the breeding season and indicated that sexual segregation within coastal waters off the central Baja California Peninsula might be a foraging strategy during years of warmer ocean, likely less productive regimes. Factors including ocean-climate-mediated sexual segregation at sea, leading to interannual variation in foraging areas, should be considered when evaluating management actions intended to protect critical foraging habitats for Black-vented Shearwaters.     

A chromosome-scale assembly of the bilberry genome identifies a complex locus controlling berry anthocyanin composition

Bilberry (Vaccinium myrtillus L.) belongs to the Vaccinium genus, which includes blueberries (Vaccinium spp.) and cranberry (V. macrocarpon). Unlike its cultivated relatives, bilberry remains largely undomesticated, with berry harvesting almost entirely from the wild. As such, it represents an ideal target for genomic analysis, providing comparisons with the domesticated Vaccinium species. Bilberry is prized for its taste and health properties and has provided essential nutrition for Northern European indigenous populations. It contains high concentrations of phytonutrients, with perhaps the most important being the purple colored anthocyanins, found in both skin and flesh. Here, we present the first bilberry genome assembly, comprising 12 pseudochromosomes assembled using Oxford Nanopore (ONT) and Hi-C Technologies. The pseudochromosomes represent 96.6% complete BUSCO genes with an assessed LAI score of 16.3, showing a high conservation of synteny against the blueberry genome. Kmer analysis showed an unusual third peak, indicating the sequenced samples may have been from two individuals. The alternate alleles were purged so that the final assembly represents only one haplotype. A total of 36,404 genes were annotated after nearly 48% of the assembly was masked to remove repeats. To illustrate the genome quality, we describe the complex MYBA locus, and identify the key regulating MYB genes that determine anthocyanin production. The new bilberry genome builds on the genomic resources and knowledge of Vaccinium species, to help understand the genetics underpinning some of the quality attributes that breeding programs aspire to improve. The high conservation of synteny between bilberry and blueberry genomes means that comparative genome mapping can be applied to transfer knowledge about marker-trait association between these two species, as the loci involved in key characters are orthologous.