Philosophical Transactions of the Royal Society B: Biological Sciences最新文献

Congenital mutations in ribosomal proteins (RPs) cause Diamond-Blackfan anaemia (DBA) syndrome. Whereas DBA patients suffer from anaemia and disease symptoms owing to a lack of cell proliferation (hypo-proliferation) early in life, they have a significantly elevated risk of developing cancer (a disease of hyper-proliferation) at a later age. The association between ribosome defects and cancer is further underscored by animal models in which heterozygous RP loss promotes tumourigenesis, as well as by a variety of somatic RP mutations that have been described in haematological and solid malignancies. As discussed in this article, we have gained deeper insight into molecular mechanisms by which RP mutations can be associated with hypo- followed by hyper-proliferation phenotypes. Factors such as oxidative stress and DNA damage, onco-ribosome specialization with hyper-translation of oncogenes and altered extra-ribosomal functions seem essential. However, many questions still remain and more research is needed to explore to what extent different cancer-associated RP mutations can structurally and functionally specialize ribosomes into onco-ribosomes, and what opportunities this can provide to develop innovative cancer therapies.This article is part of the discussion meeting issue 'Ribosome diversity and its impact on protein synthesis, development and disease'.

Plant acclimation occurs through system-wide mechanisms that include proteome shifts, some of which occur at the level of protein synthesis. All proteins are synthesized by ribosomes. Rather than being monolithic, transcript-to-protein translation machines, ribosomes can be selective and cause proteome shifts. In this study, we use apical root meristems of germinating seedlings of the monocotyledonous plant barley as a model to examine changes in protein abundance and synthesis during cold acclimation. We measured metabolic and physiological parameters that allowed us to compare protein synthesis in the cold to optimal rearing temperatures. We demonstrated that the synthesis and assembly of ribosomal proteins are independent processes in root proliferative tissue. We report the synthesis and accumulation of various macromolecular complexes and propose how ribosome compositional shifts may be associated with functional proteome changes that are part of successful cold acclimation. Our study indicates that translation initiation is limiting during cold acclimation while the ribosome population is remodelled. The distribution of the triggered ribosomal protein heterogeneity suggests that altered compositions may confer 60S subunits selective association capabilities towards translation initiation complexes. To what extent selective translation depends on heterogeneous ribo-proteome compositions in barley proliferative root tissue remains a yet unresolved question.This article is part of the discussion meeting issue 'Ribosome diversity and its impact on protein synthesis, development and disease'.

The common avian origin of many zoonotic infections and epidemics warrants investigation into the mechanism of respiratory surface protection in reservoir species such as birds. Our recent molecular investigations on the evolution and pulmonary expression of an ancient family of proteins, the C-type lectins, have revealed unique molecular adaptations in the surfactant proteins avian SP-A1 (aSP-A1), aSP-A2 and aSP-C coupled with the loss of surfactant protein-D (SP-D) in the avian lineage. As surfactant proteins are members of the collectin family, a subgroup of the C-type lectins, an in silico search for related non-surfactant collectin proteins (Collectin-10 (CL-10) and Collectin-11 (CL-11)) in the NCBI genome database was conducted to understand their evolution in the avian lineage. In addition, both CL-10 and CL-11 gene expression in the lungs and other organs of zebra finches and turkeys was confirmed by PCR. These PCR-confirmed zebra finch and turkey CL-10 and CL-11 sequences were compared with sequenced and in silico-predicted vertebrate homologues to develop a phylogenetic tree. Compared with avian surfactant proteins, CL-10 and CL-11 are highly conserved among vertebrates, suggesting a critical role in development and innate immune protection. The conservation of CL-11 EPN and collagen domain motifs may compensate to some extent for the loss of SP-D in the avian lineage.This article is part of the theme issue 'The biology of the avian respiratory system'.

Respiration plays a central role in avian vocal behaviour by providing the airstream that induces vibration of vocal folds. In this role, respiratory movements dictate the coarse temporal pattern of song, while simultaneously fulfilling its vital functions. Whereas these aspects have been investigated in oscines, little information exists in other taxa. Broad taxonomic information is, however, necessary for addressing questions regarding evolutionary specializations of the respiratory system. Acoustic recordings of unstudied taxa suggest that rapid action by respiratory muscles is a basal trait within birds. In addition to controlling the timing of vocalization, respiratory activity also influences acoustic features such as sound amplitude and frequency. The latter is more strongly influenced by respiratory driving pressure in non-vocal learners. Singing, as a highly dynamic respiratory activity presents an opportunity for studying detailed ventilation patterns and thus could give insight into the basic control of airflow in the avian lung-air sac system. Although we have learned many details of how respiratory control is tied into cortical song control, many open questions remain. Control of respiratory pacemaker circuitry by upstream vocal control centres, respiratory input in initiation of vocalization and the use of online feedback from the respiratory system are all incompletely understood.This article is part of the theme issue 'The biology of the avian respiratory system'.

The respiratory biology of birds has been of interest to researchers for centuries, particularly owing to its dramatically heterogeneous structure, unusual ability for non-ventilatory structures to invade nearly all parts of the body (including the skeleton) in many taxa, and its exceptional efficiency under high-altitude hypoxia. Advances in imaging, experimental and developmental techniques, as well as recent palaeontological specimens have facilitated new discoveries, analyses and progress in the field. Comprehensively, this theme issue shows the origin of the modern avian respiratory system, current controversies and how the evolution of respiratory structures in birds has impacted their biology from the molecular, to the cellular, to the phylogenetic level. This collection of articles addresses progress the field has made, gaps in our knowledge and where the field needs to go, with a primary focus on adult and embryonic form and function but also touching on vocalization and clinical aspects of avian respiratory biology.This article is part of the theme issue 'The biology of the avian respiratory system'.

Among the extant air-breathing vertebrates, the avian respiratory system is the most efficient gas exchanger. Novel morphological and physiological adaptations and specializations largely explain its exceptional functional superiority. Anatomically, the avian respiratory system is separated into lungs that serve as gas exchangers and air sacs that operate as ventilators. Utterly rigid, the avian lungs are deeply fixed to the ribs and the vertebrae. A thin blood-gas barrier (BGB), vast respiratory surface area and large pulmonary capillary blood volume generate high total pulmonary morphometric diffusing capacity of O₂. The weak allometric scaling of the thickness of the BGB indicates optimization for gas exchange; the negative scaling and strong correlation between the surface density of the respiratory surface area and body mass show the extreme subdivision of the gas exchange tissue; and the respiratory surface area, the pulmonary capillary blood volume and the total pulmonary morphometric diffusing capacity of O₂ correlate strongly and positively with body mass. The arrangement of the structural components of the exchange tissue form crosscurrent-, countercurrent-like- and multicapillary serial arterialization gas exchange designs. By synchronized actions of the air sacs, the palaeopulmonic part of the of the avian lung is efficiently ventilated continuously and unidirectionally in a caudocranial direction.This article is part of the theme issue 'The biology of the avian respiratory system'.

Avian embryos have been at the core of embryological, morphological, physiological and biochemical/molecular research, especially involving research in three primary areas: developmental, biomedical and agricultural research. As developmental models, the avian embryo-especially that of the chicken-has been the single most used embryo model, perhaps in part from the combination of large size, ease of access and prior knowledge base. Developmental research with avian embryos has included organ system studies of the heart, vasculature, lungs, kidneys, nervous system, etc., as well as integrated physiological processes including gas-exchange, acid-base and ion/water regulation. In terms of translational research, avian embryos have modelled vascular development, based on the easily accessible chorioallantoic membrane under the eggshell. This same respiratory organ has enabled toxicological studies of how pollutants affect vertebrate development. Investigation of the transition to pulmonary breathing and the associated emergence of respiratory control has also relied heavily upon the avian embryo. In addition to developmental and biomedical investigations, the avian embryo has been studied intensively due to the huge importance of domesticated birds as a food source. Consequently, the effects of environment (including temperature, humidity, noise levels and photoperiod) during incubation on subsequent post-hatch phenotype are being actively investigated.This article is part of the theme issue 'The biology of the avian respiratory system'.

The avian respiratory system is composed of an exchange structure (parabronchi) and a pump (air sacs) to perform gas exchange. While there are many studies dealing with the morphology and function of the palaeopulmonic parabronchi, the air sacs and the neopulmo have been somewhat neglected from a comparative and functional point of view, not always receiving a closer examination that they deserve. While a decent amount of data are available regarding air sac and neopulmo morphology on a family level or for domestic species, several orders of birds have yet to be investigated. Owing to the lack of detailed specific data, we did not perform a comparative phylogenetic analysis but compiled data regarding air sac and neopulmo morphology and analysed them from the viewpoint of current phylogenetic relations while also discussing aspects of these structures regarding avian physiology.This article is part of the theme issue 'The biology of the avian respiratory system'.

Air space proportion (ASP), the volume fraction in bone that is occupied by air, is frequently applied as a measure for quantifying the extent of skeletal pneumaticity in extant and fossil archosaurs. Nonetheless, ASP estimates rely on a key assumption: that the soft tissue mass within pneumatic bones is negligible, an assumption that has rarely been explicitly acknowledged or tested. Here, we provide the first comparisons between estimated air space proportion (where the internal cavity of a pneumatic bone is assumed to be completely air-filled) and true air space proportion (ASPt, where soft tissues present within the internal cavities of fresh specimens are considered). Using birds as model archosaurs exhibiting postcranial skeletal pneumaticity, we find that estimates of ASPt are significantly lower than estimates of ASP, raising an important consideration that should be acknowledged in investigations of the evolution of skeletal pneumaticity and bulk skeletal density in extinct archosaurs, as well as in volume-based estimates of archosaur body mass. We advocate for the difference between ASP and ASPt to be explicitly acknowledged in studies seeking to quantify the extent of skeletal pneumaticity in extinct archosaurs, to avoid the risk of systematically overestimating the volume fraction of pneumatic bones composed of air.This article is part of the theme issue 'The biology of the avian respiratory system'.

Postcranial skeletal pneumaticity is a phenomenon in birds in which epithelial extensions of the lung-air sac system aerate bones. Detailed development of this phenotype remains largely unknown. Here, we investigate changes in bone, soft tissue and air space volume in the developing humerus of turkeys using computed tomography and micro-computed tomography. Employing a two-phase approach, we first tracked humeral air space development in vivo in domesticated turkeys between week 10 (W10) and W18 post-hatch. In phase 2, we analysed air space and marrow volume change through the first 22 weeks of post-hatch development. Our results indicate that pneumatization of the humerus begins between W2 and W4 post-hatch, with air spaces expanding distally from the proximal humerus. Internal air space expands most rapidly between W7 and W9, with maximal volume reached at W15. Increased marrow growth occurs between W13 and W19, coincident with stabilization and a potential decline in relative air space volume. Our study highlights a dynamic relationship between bone, marrow and pneumatic epithelium, suggesting pneumaticity expression is likely impacted by both within-bone tissue growth dynamics and extrinsic factors related to forelimb function. This work provides the necessary gross anatomical framework for subsequent analyses of tissue-level and cellular mechanisms related to the pneumatization process.This article is part of the theme issue 'The biology of the avian respiratory system'.