Maedi-visna virus Vif protein uses motifs distinct from HIV-1 Vif to bind zinc and the cofactor required for A3 degradation.

The mammalian apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3 or A3) family of cytidine deaminases restrict viral infections by mutating viral DNA and impeding reverse transcription. To overcome this antiviral activity, most lentiviruses express a viral accessory protein called the virion infectivity factor (Vif), which recruits A3 proteins to cullin-RING E3 ubiquitin ligases such as cullin-5 (Cul5) for ubiquitylation and subsequent proteasomal degradation. Although Vif proteins from primate lentiviruses such as HIV-1 utilize the transcription factor core-binding factor subunit beta as a noncanonical cofactor to stabilize the complex, the maedi-visna virus (MVV) Vif hijacks cyclophilin A (CypA) instead. Because core-binding factor subunit beta and CypA are both highly conserved among mammals, the requirement for two different cellular cofactors suggests that these two A3-targeting Vif proteins have different biochemical and structural properties. To investigate this topic, we used a combination of in vitro biochemical assays and in vivo A3 degradation assays to study motifs required for the MVV Vif to bind zinc ion, Cul5, and the cofactor CypA. Our results demonstrate that although some common motifs between the HIV-1 Vif and MVV Vif are involved in recruiting Cul5, different determinants in the MVV Vif are required for cofactor binding and stabilization of the E3 ligase complex, such as the zinc-binding motif and N- and C-terminal regions of the protein. Results from this study advance our understanding of the mechanism of MVV Vif recruitment of cellular factors and the evolution of lentiviral Vif proteins.

Pest suppression in cultivar mixtures is influenced by neighbor-specific plant-plant communication.

Increased plant genotypic diversity in crop fields can promote ecosystem services including pest control, but understanding of mechanisms behind herbivore population responses to cultivar mixtures is limited. We studied aphid settling on barley plants exposed to volatiles from different cultivars, aphid population development in monocultures and two-cultivar mixtures, and differences in volatile composition between studied cultivars. Aphid responses to one cultivar in a mixture were neighbor-specific and this was more important for pest suppression than the overall mixture effect, aphid colonization patterns, or natural enemy abundance. Aphid populations decreased most in a mixture where both cultivars showed a reduced aphid-plant acceptance after reciprocal volatile exposure in the laboratory, and reduced population growth compared to monocultures in the field. Our findings suggest that herbivore population responses to crop genotypic diversity can depend on plant-plant volatile interactions, which can lead to changes in herbivore response to individual cultivars in a mixture, resulting in slower population growth. The impact of plant-plant interaction through volatiles on associated herbivore species is rarely considered, but improved understanding of these mechanisms would advance our understanding of the ecological consequences of biodiversity and guide development of sustainable agricultural practices. Combining cultivars in mixtures based on how they interact with each other is a promising strategy for sustainable pest management.

Birds differentially prioritize visual and olfactory foraging cues depending on habitat of origin and sex.

Animals interpret their environment by combining information from multiple senses. The relative usefulness of different senses may vary between species, habitats and sexes; yet, how multimodal stimuli are integrated and prioritized is unknown for most taxa. We experimentally assessed foraging preferences of great tits (Parus major) to test whether urban and forest individuals prioritize visual and olfactory cues differently during foraging. We trained 13 wild-caught birds to associate multimodal (colour + odour) cues with a food reward and assessed their foraging preferences in a cue-separation test. In this, the birds could choose between the multimodal training cue and its olfactory or visual components. Our results suggest that the birds did not perceive multimodal cues in an integrated way, as their response was not stronger than for unimodal cue components. Urban birds preferred olfactory cues, while forest birds preferred visual cues. Nevertheless, female birds preferred the multimodal cue, while males foraged more randomly with respect to which cue was present. These findings contribute to our understanding of the relative roles of vision and olfaction in bird foraging behaviour. Future work should focus on how habitat- and sex-specific sensory prioritization modifies bird foraging behaviour and foraging success in the context of urban adaptations across populations.

Bacteriophage-Derived Double-Stranded RNA Exerts Anti-SARS-CoV-2 Activity In Vitro and in Golden Syrian Hamsters In Vivo.

Bacteriophage-derived dsRNA, known as Larifan, is a nationally well-known broad-spectrum antiviral medication. This study aimed to ascertain the antiviral activity of Larifan against the novel SARS-CoV-2 virus. Larifan's effect against SARS-CoV-2 in vitro was measured in human lung adenocarcinoma (Calu3) and primary human small airway epithelial cells (HSAEC), and in vivo in the SARS-CoV-2 infection model in golden Syrian hamsters. Larifan inhibited SARS-CoV-2 replication both in vitro and in vivo. Viral RNA copy numbers and titer of infectious virus in the supernatant of Calu3 cells dropped significantly: p = 0.0296 and p = 0.0286, respectively. A reduction in viral RNA copy number was also observed in HSAEC, especially when Larifan was added before infection (p = 0.0218). Larifan markedly reduced virus numbers in infected hamsters' lungs post-infection, with a more pronounced effect after intranasal administration (p = 0.0032). The administration of Larifan also reduced the amount of infections virus titer in the lungs (p = 0.0039). Improvements in the infection-induced pathological lesion severity in the lungs of animals treated with Larifan were also demonstrated. The inhibition of SARS-CoV-2 replication in vitro and the reduction in the viral load in the lungs of infected hamsters treated with Larifan alongside the improved lung histopathology suggests a potential use of Larifan in also controlling the COVID-19 disease in humans.

Red Junglefowl Chicks Seek Contact With Humans During Foraging Task.

Contact seeking with humans is documented in some domestic animals, mainly dogs, which have advanced communication skills. Domestication as a companion animal is thought to underlie this ability. However, also domesticated horses and goats display similar human-directed behaviors. This suggests either a broader effect of domestication on contact-seeking behavior, or alternatively, that social interactions with humans can result in the development of human contact seeking. As part of another study, we observed contact-seeking behavior in juvenile red junglefowl (Gallus gallus) chicks exposed to behavioral training since hatching, during a foraging task, where chicks were singly required to collect food rewards in a familiar arena using odor cues. If chicks left the arena, we recorded if they approached and looked up at the experimenter, or if they approached other objects (including another human). Chicks approached the experimenter significantly more often than they approached other objects. This behavior was not linked to a fast performance in the test arena, which gave some birds more time to explore the surroundings, or to learning ability measured in a cognitive task. Yet, the preference for the experimenter was lower for chicks that were handled more prior to the experiment. Also, approach probability was positively correlated with escape attempts in a novel arena test. The observed variation in approach behavior suggests a link to aspects of personality, and exposure to human interactions and experimental procedures. Our observations suggest that, although neither domesticated nor selectively bred, red junglefowl that are socialized with humans can potentially develop behavior used to describe contact seeking. Together with evidence from cognitive and behavioral studies, our results suggest that social experiences, not only domestication, can affect human-animal interactions. We propose how interactions between behavior, cognition and handling could be studied further in controlled settings to validate the preliminary findings of our study and uncover the underlying mechanisms.

Influence of Different Light Spectrums on Behaviour and Welfare in Laying Hens.

Artificial commercial lighting used in animal production facilities can have negative influences on visual abilities, behaviour and welfare of domestic fowl. This study examined the effects of natural-derived light spectrums on behaviour, production and welfare of laying hens reared from hatching into adulthood. Comparisons were made of frequency of a range of behaviours associated with activity, aggression and comfort in birds kept in control light (commercial standard), daylight (full spectrum, including ultraviolet (UV) wavelengths and forest light (forest understorey, including UV). In addition, bird preferences for different lights, feather damage and egg production were monitored. The results showed that the behavioural repertoire of birds changed with age, while the effects of light treatment were subtle. Some evidence was found that birds preferred either daylight or forest light to control light, suggesting that inclusion of UV contributed to the preference. Daylight and forest light were associated with more active behaviours, and daylight with better plumage and later start of lay. Thus natural-like light may have beneficial effects on domestic fowl, but the differences between broad-spectrum light sources are rather small.

The presence of UV wavelengths improves the temporal resolution of the avian visual system.

The ability to perceive rapid movement is an essential adaptation in birds, which are involved in rapid flight, pursuing prey and escaping predators. Nevertheless, the temporal resolution of the avian visual systems has been less well explored than spectral sensitivity. There are indications that birds are superior to humans in their ability to detect movement, as suggested by higher critical flicker frequencies (CFFs). It has also been implied, but not properly tested, that properties of CFF, as a function of light intensity, are affected by the spectral composition of light. This study measured CFF in the chicken, Gallus gallus L., using four different light stimuli - white, full-spectrum (white with addition of UV), yellow (590 nm) and UV (400 nm) - and four light intensity levels, adjusted to relative cone sensitivity. The results showed significantly higher CFF values for full-spectrum compared with white light, as well as a steeper rate of increase with intensity. The presence of UV wavelengths, previously demonstrated to affect mate choice and foraging, appears to be important also for detection of rapid movement. The yellow and UV light stimuli yielded rather similar CFFs, indicating no special role for the double cone in flicker detection.

Disentangling olfactory and visual information used by field foraging birds.

Foraging strategies of birds can influence trophic plant-insect networks with impacts on primary plant production. Recent experiments show that some forest insectivorous birds can use herbivore-induced plant volatiles (HIPVs) to locate herbivore-infested trees, but it is unclear how birds combine or prioritize visual and olfactory information when making foraging decisions. Here, we investigated attraction of ground-foraging birds to HIPVs and visible prey in short vegetation on farmland in a series of foraging choice experiments. Birds showed an initial preference for HIPVs when visual information was the same for all choice options (i.e., one experimental setup had all options with visible prey, another setup with hidden prey). However, if the alternatives within an experimental setup included visible prey (without HIPV) in competition with HIPV-only, then birds preferred the visual option over HIPVs. Our results show that olfactory cues can play an important role in birds' foraging choices when visual information contains little variation; however, visual cues are preferred when variation is present. This suggests certain aspects of bird foraging decisions in agricultural habitats are mediated by olfactory interaction mechanisms between birds and plants. We also found that birds from variety of dietary food guilds were attracted to HIPVs; hence, the ability of birds to use plant cues is probably more general than previously thought, and may influence the biological pest control potential of birds on farmland.

Behavioural assessment of flicker fusion frequency in chicken Gallus gallus domesticus.

To interact with its visual environment, an organism needs to perceive objects in both space and time. High temporal resolution is hence important to the fitness of diurnally active animals, not least highly active aerial species such as birds. However, temporal resolution, as assessed by flicker fusion frequency (FFF; the stimulus frequency at which a flickering light stimulus can no longer be resolved and appears continuous) or critical flicker fusion frequency (CFF; the highest flicker fusion frequency at any light intensity) has rarely been assessed in birds. In order to further our understanding of temporal resolution as a function of light intensity in birds we used behavioural experiments with domestic chickens (Gallus gallus domesticus) from an old game breed 'Gammalsvensk dvärghöna' (which is morphologically and behaviourally similar to the wildtype ancestor, the red jungle fowl, G. gallus), to generate an 'Intensity/FFF curve' (I/FFF curve) across full spectrum light intensities ranging from 0.2 to 2812 cd m⁻². The I/FFF curve is double-branched, resembling that of other chordates with a duplex retina of both rods and cones. Assuming that the branches represent rod and cone mediated responses respectively, the break point between them places the transition between scotopic and photopic vision at between 0.8 and 1.9 cd m⁻². Average FFF ranged from 19.8 Hz at the lowest light intensity to a CFF 87.0 Hz at 1375 cd m⁻². FFF dropped slightly at the highest light intensity. There was some individual variation with certain birds displaying CFFs of 90-100 Hz. The FFF values demonstrated by this non-selected breed appear to be considerably higher than other behaviourally derived FFF values for similar stimuli reported for white and brown commercial laying hens, indicating that the domestication process might have influenced temporal resolution in chicken.