Changes In Tail Length Research Articles

Epitranscriptome insights into Riccia fluitans L. (Marchantiophyta) aquatic transition using nanopore direct RNA sequencing

BackgroundRiccia fluitans, an amphibious liverwort, exhibits a fascinating adaptation mechanism to transition between terrestrial and aquatic environments. Utilizing nanopore direct RNA sequencing, we try to capture the complex epitranscriptomic changes undergone in response to land-water transition.ResultsA significant finding is the identification of 45 differentially expressed genes (DEGs), with a split of 33 downregulated in terrestrial forms and 12 upregulated in aquatic forms, indicating a robust transcriptional response to environmental changes. Analysis of N6-methyladenosine (m6A) modifications revealed 173 m6A sites in aquatic and only 27 sites in the terrestrial forms, indicating a significant increase in methylation in the former, which could facilitate rapid adaptation to changing environments. The aquatic form showed a global elongation bias in poly(A) tails, which is associated with increased mRNA stability and efficient translation, enhancing the plant’s resilience to water stress. Significant differences in polyadenylation signals were observed between the two forms, with nine transcripts showing notable changes in tail length, suggesting an adaptive mechanism to modulate mRNA stability and translational efficiency in response to environmental conditions. This differential methylation and polyadenylation underline a sophisticated layer of post-transcriptional regulation, enabling Riccia fluitans to fine-tune gene expression in response to its living conditions.ConclusionsThese insights into transcriptome dynamics offer a deeper understanding of plant adaptation strategies at the molecular level, contributing to the broader knowledge of plant biology and evolution. These findings underscore the sophisticated post-transcriptional regulatory strategies Riccia fluitans employs to navigate the challenges of aquatic versus terrestrial living, highlighting the plant’s dynamic adaptation to environmental stresses and its utility as a model for studying adaptation mechanisms in amphibious plants.

Control of poly(A)-tail length and translation in vertebrate oocytes and early embryos

During oocyte maturation and early embryogenesis, changes in mRNA poly(A)-tail lengths strongly influence translation, but how these tail-length changes are orchestrated has been unclear. Here, we performed tail-length and translational profiling of mRNA reporter libraries (each with millions of 3' UTR sequence variants) in frog oocytes and embryos and in fish embryos. Contrasting to previously proposed cytoplasmic polyadenylation elements (CPEs), we found that a shorter element, UUUUA, together with the polyadenylation signal (PAS), specify cytoplasmic polyadenylation, and we identified contextual features that modulate the activity of both elements. In maturing oocytes, this tail lengthening occurs against a backdrop of global deadenylation and the action of C-rich elements that specify tail-length-independent translational repression. In embryos, cytoplasmic polyadenylation becomes more permissive, and additional elements specify waves of stage-specific deadenylation. Together, these findings largely explain the complex tapestry of tail-length changes observed in early frog and fish development, with strong evidence of conservation in both mice and humans.

Differential Poly(A) Tail Length Analysis Using Nanopore Sequencing.

The poly(A) tail is a sequence of several adenosine nucleotides added to the 3' end of RNA molecules transcribed by polymerase II. The dynamics of poly(A) tail length play a significant role in regulating post-transcriptional gene expression by regulating the stability, translation, and decay of messenger RNAs. As a result, an accurate measurement of poly(A) tail length changes is important for understanding its regulatory function in different cellular contexts. Here, we outline a method for using nanopore sequencing and linear mixed models to analyze differences in poly(A) tail length across conditions.

Effects of tail shapes/lengths of Hyperloop pod on aerodynamic characteristics and wave phenomenon

This study provides a view of the primary aerodynamic design of Hyperloop pod considering the influence of tail shape and length on aerodynamic forces (drag and lift) and flow behaviors (pressure, Mach number, and temperature). Numerical simulations are performed considering two tail shapes (i.e., upward and downward tails) and five lengths of the downward tail (i.e., 1.725, 3.45, 6.9, 13.35, and 13.8 m). The dynamic overset mesh method utilizing polyhedral meshes is applied to simulate the movement of the pod. A simplified three-dimensional model is simulated using the unsteady Reynolds-averaged Navier–Stokes shear stress transport k–ω turbulence model, compressible ideal gas, and a pod speed of 300 m/s. The results indicate that the two tail shapes only have a minor effect on aerodynamic drag (i.e., the difference between the upward and downward tails is only 0.75%), generating two tendencies of aerodynamic lift (i.e., the upward tail provides negative lift, and the downward tail yields positive lift). When tail length of the pod increases, it effectively reduces the aerodynamic drag (approximately 7%) and pressure on the pod surface. Meanwhile, the variation of lift observes an intriguing tendency (which the lift is maximum at 6.9 m – tail length). When the tail length is increased over 6.9 m, the lift starts to reduce; however, the lift is increased when the tail is shorter than 6.9 m. The flow fields around and behind the pod tail are significantly affected by the change in tail length, particularly when considering the intensity and generation of the first OS. The highest intensity of the first OS is attained when the tail length is 6.9 m. The increase in tail length considerably reduces the pressure on the pod but slightly affects the pod temperature (exhibiting a maximum difference of 0.4% among the five cases).

Acute and Chronic Effects of Fin Amputation on Behavior Performance of Adult Zebrafish in 3D Locomotion Test Assessed with Fractal Dimension and Entropy Analyses and Their Relationship to Fin Regeneration.

Simple SummaryFin amputation is a routinely conducted procedure for various experiments, especially in zebrafish. However, no study compares the acute and chronic effects of the amputation of each fin on their behaviors. In addition, although some analgesics have been applied after the fin amputation procedure, the long-term effects of these drugs in have not been evaluated yet. In this study, we found that amputation in the caudal fin resulted in the most pronounced behavior alterations and their behavior was fully recovered before the caudal fin was fully regenerated, indicating that these behavioral changes came from pain elicited from the fin amputation. Finally, while lidocaine treatment could ameliorate the behavioral effects after the amputation procedure, it did not accelerate the behavior recovery process; instead, it caused the fish to display some slight side effects.The fin is known to play an important role in swimming for many adult fish, including zebrafish. Zebrafish fins consist of paired pectoral and pelvic with unpaired dorsal, anal, and caudal tail fins with specific functions in fish locomotion. However, there was no study comparing the behavior effects caused by the absence of each fin. We amputated each fin of zebrafish and evaluated their behavior performance in the 3D locomotion test using fractal dimension and entropy analyses. Afterward, the behavior recovery after the tail fin amputation was also evaluated, together with the fin regeneration process to study their relationship. Finally, we conducted a further study to confirm whether the observed behavior alterations were from pain elicited by fin amputation procedure or not by using lidocaine, a pain-relieving drug. Amputation in the caudal fin resulted in the most pronounced behavior alterations, especially in their movement complexity. Furthermore, we also found that their behavior was fully recovered before the caudal fin was fully regenerated, indicating that these behavioral changes were not majorly due to a mechanical change in tail length; instead, they may come from pain elicited from the fin amputation, since treatment with lidocaine could ameliorate the behavioral effects after the amputation procedure. However, lidocaine did not accelerate the behavior recovery process; instead, it caused the fishes to display some slight side effects. This study highlights the potential moderate severity of fin amputation in zebrafish and the importance of analgesia usage. However, side effects may occur and need to be considered since fin amputation is routinely conducted for various research, especially genomic screening.

Effect of plant-based enrichment materials on exploration in rearing and fattening pigs (Sus scrofa domesticus)

When pigs cannot perform innate species-specific behaviours (e.g. rooting or chewing), behavioural disorders, like tail biting, can occur. However, it seems that various enrichment materials enhance the pigs to perform exploration behaviour and therefore can help to reduce and prevent tail biting. The aim of this study was to identify such highly explored plant-based enrichment material for undocked pigs during rearing and fattening. Furthermore, we evaluated the impact of the offered enrichment materials on tail length and injuries. Therefore, we continuously recorded the individuals’ exploration durations in 20 groups by using an ultra-high-frequency radio-frequency identification system, installed at material dispensers. Lucerne pellets (LP), straw pellets (SP), chopped hay (CH) and chopped straw (CS) were offered in a systematically alternating order for two-week sections, respectively. At weaning and at days of material change (i.e. eight times in total), animals were weighed and scored for tail length losses and tail injuries. For analysis, the changes in tail length compared to the previous section were calculated as Δ-tail-length losses. Our study revealed that the different offered plant-based enrichment materials affected the duration of exploration behaviour (e.g. rooting, nosing or chewing) during rearing (4 groups, LME, p < 0.0001) and fattening (16 groups, LME, p < 0.0001). In piglets, exploration duration was higher for pelletized materials (LP, SP) than for chopped materials. Fattening pigs explored materials of hay (CH) more often compared to straw-based materials (CS, SP). Daily weight gains of rearing pigs were affected by the type of enrichment material offered in the respective section (LME, p < 0.0001). The highest daily weight gains were achieved when CH was offered. Exploration duration during rearing and fattening was affected by section (LME, both p < 0.0001 for rearing and fattening). Exploration duration during rearing was highest in section 4 and continuously increased from the first section to the last section during fattening. During rearing, the plant-based enrichment materials affected tail injuries (GLMM, p < 0.0001) and Δ-tail-length losses tended to be affected (GLMM, p = 0.057). Fewest tail injuries and Δ-tail-length losses occurred when SP was offered. During fattening, section affected tail injuries (GLMM, p = 0.01). Most injuries occurred during sections 1 and 2. Our results show that pigs of different ages seem to prefer different plant-based enrichment materials. High exploration durations do not necessarily maintain intact tails if material is changed biweekly. However, exploration durations can be maintained at high levels from rearing through fattening period by regularly alternating the provided plant-based enrichment materials.

Genome-wide analysis identifies cis-acting elements regulating mRNA polyadenylation and translation during vertebrate oocyte maturation.

Most cells change patterns of gene expression through transcriptional regulation. In contrast, oocytes are transcriptionally silent and regulate mRNA poly(A) tail length to control protein production. However, the genome-wide relationship of poly(A) tail changes to mRNA translation during vertebrate oocyte maturation is not known. We used Tail-seq and polyribosome analysis to measure poly(A) tail and translational changes during oocyte maturation in Xenopus laevis. We identified large-scale poly(A) and translational changes during oocyte maturation, with poly(A) tail length changes preceding translational changes. Proteins important for completion of the meiotic divisions and early development exhibited increased polyadenylation and translation during oocyte maturation. A family of U-rich sequence elements was enriched near the polyadenylation signal of polyadenylated and translationally activated mRNAs. We propose that changes in mRNA polyadenylation are a conserved mechanism regulating protein expression during vertebrate oocyte maturation and that these changes are controlled by a spatial code of cis-acting sequence elements.

Membrane fusogenic lysine type lipid assemblies possess enhanced NLRP3 inflammasome activation potency

Lysine (K) type cationic lipid with a propyl spacer and ditetradecyl hydrophobic moieties composing liposomes, K3C14, previously studied for gene delivery, were reported to activate the NLRP3 inflammasomes in human macrophages via the conventional phagolysosomal pathway. In this study, K3C16, a propyl spacer bearing lysine type lipids with dihexadecyl moieties (an extension of two hydrocarbon tail length) were compared with K3C14 as liposomes. Such a small change in tail length did not alter the physical properties such as size distribution, zeta potential and polydispersity index (PDI). The NLRP3 activation potency of K3C16 was shown to be 1.5-fold higher. Yet, the toxicity was minimal, whereas K3C14 has shown to cause significant cell death after 24 h incubation. Even in the presence of endocytosis inhibitors, cytochalasin D or dynasore, K3C16 continued to activate the NLRP3 inflammasomes and to induce IL-1β release. To our surprise, K3C16 liposomes were confirmed to fuse with the plasma membrane of human macrophages and CHO-K1 cells. It is demonstrated that the change in hydrophobic tail length by two hydrocarbons drastically changed a cellular entry route and potency in activating the NLRP3 inflammasomes.

PAT-Seq: A Method for Simultaneous Quantitation of Gene Expression, Poly(A)-Site Selection and Poly(A)-Length Distribution in Yeast Transcriptomes.

Next-generation sequencing (NGS) and its application to RNA (RNA-seq) has opened up multiple aspects of RNA processing to deep transcriptome-wide analysis at nucleotide resolution. This has been useful in delineating the transcribed areas of the genome, and in quantitation of RNA isoforms. Such isoforms can diversify the regulatory repertoire of mRNAs. For example, the 3'-end of mRNA can vary in two important ways, in the position chosen for cleavage and polyadenylation, and in the length of the poly(A)-tail. Accordingly, the step-up in resolution made possible by NGS has revealed an unexpectedly high level of alternative polyadenylation (APA). Moreover, it has massively simplified the transcriptome-wide detection of poly(A)-tail length changes. Here we present our approach to the study of 3'-end dynamics using a 3'-focused RNA-seq method called PAT-seq (for poly(A)-test sequencing). The approach records gene expression, APA, and poly(A)-tail changes between transcriptomes to reveal complex interplay between transcriptional and posttranscriptional control mechanisms.

Ontogenetic Changes in Tail-Length and the Possible Relation to Caudal Luring in Northeast Kansas Copperheads, Agkistrodon contortrix

Electronic data capture of the nearly 60 years of field data on northeast Kansas snake populations collected by Henry Fitch enabled review of ontogenetic changes in taillength from birth through adult size in Agkistrodon contortrix. Data from 5084 northeast Kansas Copperhead (Agkistrodon contortrix) records collected by Fitch from 1948–2003 (2287F:2797M) were examined to assess the nature of ontogenetic changes in relative tail length of sexes. We suggest that the longer relative tail length of neonate and juvenile copperheads, combined with tail color, enhances the effectiveness of caudal luring, and offer suggestions for further study.

MRNA poly(A)-tail changes specified by deadenylation broadly reshape translation in Drosophila oocytes and early embryos.

Because maturing oocytes and early embryos lack appreciable transcription, posttranscriptional regulatory processes control their development. To better understand this control, we profiled translational efficiencies and poly(A)-tail lengths throughout Drosophila oocyte maturation and early embryonic development. The correspondence between translational-efficiency changes and tail-length changes indicated that tail-length changes broadly regulate translation until gastrulation, when this coupling disappears. During egg activation, relative changes in poly(A)-tail length, and thus translational efficiency, were largely retained in the absence of cytoplasmic polyadenylation, which indicated that selective poly(A)-tail shortening primarily specifies these changes. Many translational changes depended on PAN GU and Smaug, and these changes were largely attributable to tail-length changes. Our results also revealed the presence of tail-length-independent mechanisms that maintained translation despite tail-length shortening during oocyte maturation, and prevented essentially all translation of bicoid and several other mRNAs before egg activation. In addition to these fundamental insights, our results provide valuable resources for future studies.

Genome-Wide Analysis of PAPS1-Dependent Polyadenylation Identifies Novel Roles for Functionally Specialized Poly(A) Polymerases in Arabidopsis thaliana.

The poly(A) tail at 3’ ends of eukaryotic mRNAs promotes their nuclear export, stability and translational efficiency, and changes in its length can strongly impact gene expression. The Arabidopsis thaliana genome encodes three canonical nuclear poly(A) polymerases, PAPS1, PAPS2 and PAPS4. As shown by their different mutant phenotypes, these three isoforms are functionally specialized, with PAPS1 modifying organ growth and suppressing a constitutive immune response. However, the molecular basis of this specialization is largely unknown. Here, we have estimated poly(A)-tail lengths on a transcriptome-wide scale in wild-type and paps1 mutants. This identified categories of genes as particularly strongly affected in paps1 mutants, including genes encoding ribosomal proteins, cell-division factors and major carbohydrate-metabolic proteins. We experimentally verified two novel functions of PAPS1 in ribosome biogenesis and redox homoeostasis that were predicted based on the analysis of poly(A)-tail length changes in paps1 mutants. When overlaying the PAPS1-dependent effects observed here with coexpression analysis based on independent microarray data, the two clusters of transcripts that are most closely coexpressed with PAPS1 show the strongest change in poly(A)-tail length and transcript abundance in paps1 mutants in our analysis. This suggests that their coexpression reflects at least partly the preferential polyadenylation of these transcripts by PAPS1 versus the other two poly(A)-polymerase isoforms. Thus, transcriptome-wide analysis of poly(A)-tail lengths identifies novel biological functions and likely target transcripts for polyadenylation by PAPS1. Data integration with large-scale co-expression data suggests that changes in the relative activities of the isoforms are used as an endogenous mechanism to co-ordinately modulate plant gene expression.

Increased sensitivity and accuracy of a single-stranded DNA splint-mediated ligation assay (sPAT) reveals poly(A) tail length dynamics of developmentally regulated mRNAs

Poly(A) tail length is a readout of an mRNA’s translatability and stability, especially in developmental systems. PolyAdenylation Test (PAT) assays attempt to quickly measure the average poly(A) tail length of RNAs of experimental interest. Here we present sPAT, splint-mediated PAT, a procedure that uses a DNA splint to aid in the ligation of an RNA-tag to the poly(A) tail of an mRNA. In comparison to other PAT methodologies, including ePAT, sPAT is highly sensitive to low-abundance mRNAs, gives a more accurate profile of the poly(A) tail distribution, and requires little starting material. To demonstrate its strength, we calibrated sPAT on defined poly(A) tails of synthetic mRNAs, reassessed developmentally regulated poly(A) tail-length changes of known mRNAs from established model organisms, and extended it to the emerging evolutionary developmental nematode model Pristionchus pacificus. Lastly, we used sPAT to analyze the contribution of the two cytoplasmic poly(A) polymerases GLD-2 and GLD-4, and the deadenylase CCR-4, onto Caenorhabditis elegans gld-1 mRNA that encodes a translationally controlled tumor suppressor whose poly(A) tail length measurement proved elusive.

The Ccr4-Not deadenylase complex constitutes the major poly(A) removal activity inC. elegans

Post-transcriptional regulatory mechanisms are widely used to control gene expression programs of tissue development and physiology. Controlled 3' poly(A) tail-length changes of mRNAs provide a mechanistic basis of such regulation, affecting mRNA stability and translational competence. Deadenylases are a conserved class of enzymes that facilitate poly(A) tail removal, and their biochemical activities have been mainly studied in the context of single-cell systems. Little is known about the different deadenylases and their biological role in multicellular organisms. In this study, we identify and characterize all known deadenylases of Caenorhabditis elegans, and identify the germ line as tissue that depends strongly on deadenylase activity. Most deadenylases are required for hermaphrodite fertility, albeit to different degrees. Whereas ccr-4 and ccf-1 deadenylases promote germline function under physiological conditions, panl-2 and parn-1 deadenylases are only required under heat-stress conditions. We also show that the Ccr4-Not core complex in nematodes is composed of the two catalytic subunits CCR-4 and CCF-1 and the structural subunit NTL-1, which we find to regulate the stability of CCF-1. Using bulk poly(A) tail measurements with nucleotide resolution, we detect strong deadenylation defects of mRNAs at the global level only in the absence of ccr-4, ccf-1 and ntl-1, but not of panl-2, parn-1 and parn-2. Taken together, this study suggests that the Ccr4-Not complex is the main deadenylase complex in C. elegans germ cells. On the basis of this and as a result of evidence in flies, we propose that the conserved Ccr4-Not complex is an essential component in post-transcriptional regulatory networks promoting animal reproduction.

Translational control by changes in poly(A) tail length: recycling mRNAs.

Beyond the well-known function of poly(A) tail length in mRNA stability, recent years have witnessed an explosion of information about how changes in tail length and the selection of alternative polyadenylation sites contribute to the translational regulation of a large portion of the genome. The mechanisms and factors mediating nuclear and cytoplasmic changes in poly(A) tail length have been studied in great detail, the targets of these mechanisms have been identified--in some cases by genome-wide screenings--and changes in poly(A) tail length are now implicated in a number of physiological and pathological processes. However, in very few cases have all three levels--mechanisms, targets and functions--been studied together.

Designing and surface modification of zinc oxide nanoparticles for biomedical applications

The present study aimed to work out a simple and high yield procedure for the immobilization of β galactosidase on bioaffinity support, concanavalin A (Con A) layered zinc oxide nanoparticles (ZnO-NP). Thermogravimetric analysis of bioaffinity support revealed 4% loss in weight at 600°C whereas its thermal decomposition was observed at 530°C by differential thermal analysis. No significant change was noticed in the band intensity of pUC19 plasmid after its treatment with Con A layered ZnO-NP. Comet assay further exhibited negligible change in tail length of comet after treating the lymphocytes by bioaffinity matrix. The bioaffinity matrix binds 89% of the enzyme activity. Atomic force microscopy analysis showed that the prepared matrix has an advantageous microenvironment and large surface area for binding significant amount of the enzyme. The functional groups present in native and parent compound were monitored by Fourier transform-infrared spectroscopy. Michaelis constant, Km was 2.38 and 5.88mM for free and immobilized β galactosidase, respectively. Vmax for the soluble and immobilized enzyme was 0.520mM/min and 0.460mM/min, respectively. Concanavalin A layered ZnO-NP bound β galactosidase exhibited a shift in the temperature-optima and retained nearly 86% activity even after its 6th repeated use.

Immobilization of Kluyveromyces lactis β galactosidase on concanavalin A layered aluminium oxide nanoparticles—Its future aspects in biosensor applications

Abstract Several new types of carrier and technology have been implemented in the recent past to improve traditional enzyme immobilization which aims to enhance enzyme loading, activity and stability in order to decrease the cost of enzyme in industrial processes. Thus, the present study aimed to work out a simple and high yield procedure for the immobilization of Kluyveromyces lactis β galactosidase on a bioaffinity support, concanavalin A layered Al 2 O 3 nanoparticles (Con A layered Al 2 O 3 -NPs). Thermogravimetric analysis of bioaffinity support revealed 6% loss in weight at 600 °C whereas its thermal decomposition was observed at 350 °C by differential thermal analysis. No significant change was noticed in the band intensity of pUC19 plasmid upon its treatment with Con A layered Al 2 O 3 -NPs. Comet assay further exhibited negligible change in tail length of comet after treating the lymphocytes by bioaffinity matrix. Atomic force microscopy revealed large surface area of Con A layered Al 2 O 3 -NPs for binding higher amounts of enzyme. Moreover, Fourier transform-infrared spectroscopy confirmed binding of β galactosidase on bioaffinity support by exhibiting broadening in peaks at 3220.61 cm −1 and 3447.27 cm −1 . Soluble and immobilized β galactosidase showed same pH-optima at pH 7.0. However, immobilized enzyme exhibited enhanced pH stability and broad spectrum temperature optimum than soluble β galactosidase. Immobilized β galactosidase was found to be highly stable against product inhibition by galactose and retained 85% activity after its sixth repeated use.

Bax, Bcl-xl Exert their Regulation on Different Sites on the Ceramide Channel

Ceramide is a sphingolipid that has been shown to play a vital role in the commitment of a cell to apoptosis. There is increasing evidence that ceramide channels may be the pathway through which cytochrome c is released from mitochondria, a critical step in the apoptotic process. Ceramide content increases in mitochondria upon an apoptotic signal and can form stable channels in mitochondrial membranes which are large enough for the passage of proteins. The Bcl-2 family of proteins regulate apoptosis and have pro-apoptotic members, like Bax, and anti-apoptotic members, like Bcl-xL. These proteins have been shown to directly interact with ceramide channels; Bax directly enlarges ceramide channels and Bcl-xL directly disassembles ceramide channels. The molecular site of interaction of Bax and Bcl-xL with ceramide was probed using structural analogs of ceramide which retain channel forming ability. Mitochondrial outer membrane permeability, and thus channel formation, was assessed using the dynamic cytochrome c accessibility assay. The results indicate that Bax was most sensitive to changes in the head group of ceramide while Bcl-xL was most sensitive to changes in tail length. These changes were not simply an effect of kinetics as longer incubations did not yield different results. Furthermore, when we tested known inhibitors of Bcl-xL, 2-methoxyantimycin A3 and ABT-737, the inhibitory effects of Bcl-xL on ceramide could be reversed. The results obtained in this study paint a very novel picture of how proteins may indeed be able to identify and regulate ceramide channels during apoptosis. Supported by a grant from NSF (MCB-0641208).

Rapid change in nest size of a bird related to change in a secondary sexual character

Among bird species in which males contribute to nest building, sexual selection has favored larger nests. I investigated determinants of nest size in the barn swallow Hirundo rustica and how nest size changed during the period 1977–2003, when tail length (a male secondary sexual character) increased by more than 1.2 standard deviations. Males with short tails contributed more to nest building than long-tailed males, signaling their future investment in food provisioning of offspring. Pairs of barn swallows were consistent in nest size when build ing new nests the same or different years, and level of phenotypic plasticity in nest size was small and could not account for temporal patterns in nest size. Offspring resembled their parents with respect to nest size, indicating a significant heritability of nest size, independent of whether offspring were reared by their parents or by foster parents, and there was a significant negative genetic correlation between male tail length and outer nest volume and amount of nest material. The temporal increase in male tail length was associated with a decrease in nest size, with the amount of nest material in 2003 on average being less than a third of the amount used in 1977. Temporal change in nest size could be accounted for by indirect selection on tail length causing change in nest size to match that predicted from change in tail length and the genetic correlation between male tail length and nest size.

Rapid evolutionary change in a secondary sexual character linked to climatic change

The ability of organisms to respond evolutionarily to rapid climatic change is poorly known. Secondary sexual characters show the potential for rapid evolutionary change, as evidenced by strong divergence among species and high evolvability. Here we show that the length of the outermost tail feathers of males of the socially monogamous barn swallow Hirundo rustica, feathers that provide a mating advantage to males, has increased by more than 1 standard deviation during the period from 1984 to 2003. Barn swallows from the Danish population studied here migrate through the Iberian Peninsula to South Africa in fall, and return along the same route in spring. Environmental conditions on the spring staging grounds in Algeria, as indexed by the Normalized Difference Vegetation Index, predicted tail length and change in tail length across generations. However, conditions in the winter quarters and at the breeding grounds did not predict change in tail length. Environmental conditions in Algeria in spring showed a temporal deterioration during the study period, associated with a reduction in annual survival rate of male barn swallows. Phenotypic plasticity in tail length of males, estimated as the increase in tail length from the age of 1 to 2 years, decreased during the course of the study. Estimates of directional selection differentials for male tail length with respect to mating success, breeding date, fecundity, survival and total selection showed temporal variation, with the intensity of breeding date selection, survival selection and total selection declining during the study. Response to selection as estimated from the product of heritability and total selection was very similar to the observed temporal change in tail length. These findings provide evidence of rapid micro-evolutionary change in a secondary sexual character during a very short time period, which is associated with a rapid change in environmental conditions.