Variations on a theme: plant autophagy in comparison to yeast and mammals

Autophagy is an evolutionary conserved process of bulk degradation and nutrient sequestration that occurs in all eukaryotic cells. Yet, in recent years, autophagy has also been shown to play a role in the specific degradation of individual proteins or protein aggregates as well as of damaged organelles. The process was initially discovered in yeast and has also been very well studied in mammals and, to a lesser extent, in plants. In this review, we summarize what is known regarding the various functions of autopahgy in plants but also attempt to address some specific issues concerning plant autophagy, such as the insufficient knowledge regarding autophagy in various plant species other than Arabidopsis, the fact that some genes belonging to the core autophagy machinery in various organisms are still missing in plants, the existence of autophagy multigene families in plants and the possible operation of selective autophagy in plants, a study that is still in its infancy. In addition, we point to plant-specific autophagy processes, such as the participation of autophagy during development and germination of the seed, a unique plant organ. Throughout this review, we demonstrate that the use of innovative bioinformatic resources, together with recent biological discoveries (such as the ATG8-interacting motif), should pave the way to a more comprehensive understanding of the multiple functions of plant autophagy.     

Shelf-life extension program (SLEP) as a significant contributor to Strategic National Stockpile Maintenance: the Israeli experience with ciprofloxacin

In the past decade, the 2001 anthrax incident in the U.S. and the 2003 SARS epidemic have highlighted the biological threat to civilian populations. The risk posed by the natural or manmade spread of biological agents among the population dictates a need for better national preparedness. One key component of this preparation is the establishment of a Strategic National Stockpile (SNS) of pharmaceuticals that would provide appropriate medical countermeasures in case of an outbreak. However, to reduce the expense of such a stockpile and to make it worthwhile, there is also a need for a shelf-life extension program (SLEP) through which pharmaceuticals could be extended beyond manufacturer-ascribed shelf life, as long as they meet regulation standards. In this article, we review the Israeli experience with the national ciprofloxacin stockpile procurement and shelf-life extension program.     

Selective autophagy in the aid of plant germination and response to nutrient starvation

Selective autophagy, mediated by Atg8 binding proteins, has not been extensively studied in plants. Plants possess a large gene family encoding multiple isoforms of the Atg8 protein. We have recently reported the identification of two new, closely homologous Arabidopsis thaliana plant proteins that bind the Arabidopsis Atg8f protein isoform. These two proteins are specific to plants and have no homologs in nonplant organisms. The expression levels of the genes encoding these proteins are elevated during carbon starvation and also during late stages of seed development. Exposure of young seedlings to carbon starvation induces the production of a newly identified compartment decorated by these Atg8-binding proteins. This compartment dynamically moves along the endoplasmic reticulum membrane and is also finally transported into the vacuole. Enhanced or suppressed expression of these Atg8-binding proteins respectively enhances or suppresses seed germination under suboptimal germination conditions, indicating that they contribute to seed germination vigor.     

A novel fluorescent α-conotoxin for the study of α7 nicotinic acetylcholine receptors

Homomeric α7 nicotinic acetylcholine receptors are a well-established, pharmacologically distinct subtype. The more recently identified α9 subunit can also form functional homopentamers as well as α9α10 heteropentamers. Current fluorescent probes for α7 nicotinic ACh receptors are derived from α-bungarotoxin (α-BgTx). However, α-BgTx also binds to α9* and α1* receptors which are coexpressed with α7 in multiple tissues. We used an analog of α-conotoxin ArIB to develop a highly selective fluorescent probe for α7 receptors. This fluorescent α-conotoxin, Cy3-ArIB[V11L;V16A], blocked ACh-evoked α7 currents in Xenopus laevis oocytes with an IC₅₀ value of 2.0 nM. Observed rates of blockade were minute-scale with recovery from blockade even slower. Unlike FITC-conjugated α-BgTx, Cy3-ArIB[V11L;V16A] did not block α9α10 or α1β1δε receptors. In competition binding assays, Cy3-ArIB[V11L;V16A] potently displaced [¹²⁵I]-α-BgTx binding to mouse hippocampal membranes with a K _i value of 21 nM. Application of Cy3-ArIB[V11L;V16A] resulted in specific punctate labeling of KXα7R1 cells but not KXα3β2R4, KXα3β4R2, or KXα4β2R2 cells. This labeling could be abolished by pre-treatment with α-cobratoxin. Thus, Cy3-ArIB[V11L;V16A] is a novel and selective fluorescent probe for α7 receptors.     

Animal vocal sequences: not the Markov chains we thought they were

Many animals produce vocal sequences that appear complex. Most researchers assume that these sequences are well characterized as Markov chains (i.e. that the probability of a particular vocal element can be calculated from the history of only a finite number of preceding elements). However, this assumption has never been explicitly tested. Furthermore, it is unclear how language could evolve in a single step from a Markovian origin, as is frequently assumed, as no intermediate forms have been found between animal communication and human language. Here, we assess whether animal taxa produce vocal sequences that are better described by Markov chains, or by non-Markovian dynamics such as the ‘renewal process’ (RP), characterized by a strong tendency to repeat elements. We examined vocal sequences of seven taxa: Bengalese finches Lonchura striata domestica, Carolina chickadees Poecile carolinensis, free-tailed bats Tadarida brasiliensis, rock hyraxes Procavia capensis, pilot whales Globicephala macrorhynchus, killer whales Orcinus orca and orangutans Pongo spp. The vocal systems of most of these species are more consistent with a non-Markovian RP than with the Markovian models traditionally assumed. Our data suggest that non-Markovian vocal sequences may be more common than Markov sequences, which must be taken into account when evaluating alternative hypotheses for the evolution of signalling complexity, and perhaps human language origins.     

Landscape influences on dispersal behaviour: a theoretical model and empirical test using the fire salamander,Salamandra infraimmaculata

When populations reside within a heterogeneous landscape, isolation by distance may not be a good predictor of genetic divergence if dispersal behaviour and therefore gene flow depend on landscape features. Commonly used approaches linking landscape features to gene flow include the least cost path (LCP), random walk (RW), and isolation by resistance (IBR) models. However, none of these models is likely to be the most appropriate for all species and in all environments. We compared the performance of LCP, RW and IBR models of dispersal with the aid of simulations conducted on artificially generated landscapes. We also applied each model to empirical data on the landscape genetics of the endangered fire salamander, Salamandra infraimmaculata, in northern Israel, where conservation planning requires an understanding of the dispersal corridors. Our simulations demonstrate that wide dispersal corridors of the low-cost environment facilitate dispersal in the IBR model, but inhibit dispersal in the RW model. In our empirical study, IBR explained the genetic divergence better than the LCP and RW models (partial Mantel correlation 0.413 for IBR, compared to 0.212 for LCP, and 0.340 for RW). Overall dispersal cost in salamanders was also well predicted by landscape feature slope steepness (76 %), and elevation (24 %). We conclude that fire salamander dispersal is well characterised by IBR predictions. Together with our simulation findings, these results indicate that wide dispersal corridors facilitate, rather than hinder, salamander dispersal. Comparison of genetic data to dispersal model outputs can be a useful technique in inferring dispersal behaviour from population genetic data.     

Measuring acoustic complexity in continuously varying signals: how complex is a wolf howl?

Communicative complexity is a key behavioural and ecological indicator in the study of animal cognition. Much attention has been given to measures such as repertoire size and syntactic structure in both bird and mammal vocalizations, as large repertoires and complex call combinations may give an indication of the cognitive abilities both of the sender and receiver. However, many animals communicate using a continuous vocal signal that does not easily lend itself to be described by concepts such as ‘repertoire’. For example, dolphin whistles and wolf howls both have complex patterns of frequency modulation, so that no two howls or whistles are quite the same. Is there a sense in which some of these vocalizations may be more ‘complex’ than others? Can we arrive at a quantitative metric for complexity in a continuously varying signal? Such a metric would allow us to extend familiar analyses of communicative complexity to those species where vocal behaviour is not restricted to sequences of stereotyped syllables. We present four measures of complexity in continuous signals (Wiener Entropy, Autocorrelation, Inflection Point Count, and Parsons Entropy), and examine their relevance using example data from members of the genus Canis. We show that each metric can lead to different conclusions regarding which howls could be considered complex or not. Ultimately, complexity is poorly defined and researchers must compare metrics to ensure that they reflect the properties for which the hypothesis is being tested.     

Exposure by males to light emitted from media devices at night is linked with decline of sperm quality and correlated with sleep quality measures

ABSTRACT

The last several decades have been characterized by the widespread usage of digital devices, especially smartphones. At the same time, there have been reports of both decline in sleep duration and quality and male fertility decline. The aim of this study was to assess the relationship between evening exposure to the light-emitting screens of digital media devices and measures of both sleep and sperm quality. Semen samples were obtained from 116 men undergoing fertility evaluation for the following sperm variables: volume (mL), pH, sperm concentration (million/mL), motility percentage (progressive% + non-progressive motility%), and total sperm count. Exposure to the screens of electronic devices and sleep habits was obtained by means of a questionnaire. Smartphone and tablet usage in the evening and after bedtime was negatively correlated with sperm motility (?0.392; ?0.369; p < .05), sperm progressive motility (?0.322; ?0.299; p < .05), and sperm concentration (?0.169; p < .05), and positively correlated with the percentage of immotile sperm (0.382; 0.344; p < .05). In addition, sleep duration was positively correlated with sperm total and progressive motility (0.249; 0.233; p < .05) and negatively correlated with semen pH (?0.349; p < .05). A significant negative correlation was observed between subjective sleepiness and total and progressive motility (?0.264; p < .05) as well as total motile sperm number (?0.173; p < .05). The results of this study support a link between evening and post-bedtime exposure to light-emitting digital media screens and sperm quality. Further research is required to establish the proposed causative link and may lead to the future development of relevant therapeutic and lifestyle interventions.     

Syntactic structure and geographical dialects in the songs of male rock hyraxes

Few mammalian species produce vocalizations that are as richly structured as bird songs, and this greatly restricts the capacity for information transfer. Syntactically complex mammalian vocalizations have been previously studied only in primates, cetaceans and bats. We provide evidence of complex syntactic vocalizations in a small social mammal: the rock hyrax (Procavia capensis: Hyracoidea). We adopted three algorithms, commonly used in genetic sequence analysis and information theory, to examine the order of syllables in hyrax calls. Syntactic dialects exist, and the syntax of hyrax calls is significantly different between different regions in Israel. Call syntax difference is positively correlated to geographical distance over short distances. No correlation is found over long distances, which may reflect limited dispersal movement. These findings indicate that rich syntactic structure is more common in the vocalizations of mammalian taxa than previously thought and suggest the possibility of vocal production learning in the hyrax.