The Road to Sorghum Domestication: Evidence From Nucleotide Diversity and Gene Expression Patterns

Native African cereals (sorghum, millets) ensure food security to millions of low-income people from low fertility and drought-prone regions of Africa and Asia. In spite of their agronomic importance, the genetic bases of their phenotype and adaptations are still not well-understood. Here we focus on Sorghum bicolor, which is the fifth cereal worldwide for grain production and constitutes the staple food for around 500 million people. We leverage transcriptomic resources to address the adaptive consequences of the domestication process. Gene expression and nucleotide variability were analyzed in 11 domesticated and nine wild accessions. We documented a downregulation of expression and a reduction of diversity both in nucleotide polymorphism (30%) and gene expression levels (18%) in domesticated sorghum. These findings at the genome-wide level support the occurrence of a global reduction of diversity during the domestication process, although several genes also showed patterns consistent with the action of selection. Nine hundred and forty-nine genes were significantly differentially expressed between wild and domesticated gene pools. Their functional annotation points to metabolic pathways most likely contributing to the sorghum domestication syndrome, such as photosynthesis and auxin metabolism. Coexpression network analyzes revealed 21 clusters of genes sharing similar expression patterns. Four clusters (totaling 2,449 genes) were significantly enriched in differentially expressed genes between the wild and domesticated pools and two were also enriched in domestication and improvement genes previously identified in sorghum. These findings reinforce the evidence that the combined and intricated effects of the domestication and improvement processes do not only affect the behaviors of a few genes but led to a large rewiring of the transcriptome. Overall, these analyzes pave the way toward the identification of key domestication genes valuable for genetic resources characterization and breeding purposes.

A Morphofunctional Hypothesis for Selection on EDAR V370A and Associated Elements of Sinodonty

The phenomenon of sinodonty refers to a suite of dental characters shared between East Asian and Native American populations, and most prominently to the presence of shoveled incisors. Although this syndrome is a conspicuous aspect of dental differentiation among extant human populations, elements of which have been recent subject of detailed genetic analysis, adaptive consequences of shoveled incisors and related features remains unclear. Here, I hypothesize that many of the associated differences in dentition (along with reduction in mandibular length and increases in salivary gland branching) arose in parallel with the opportunistic consumption of wild rice and millet in central and northern China, respectively, and with their subsequent domestication in the Upper Paleolithic. More efficient mastication and digestion of plant grains (and of other starchy foods obtained via broad-spectrum foraging) would potentially have been enabled by these traits, yielding greater rates of nutritional intake as wild crops were progressively domesticated. This functional hypothesis, although not mutually exclusive relative to other proposed selective factors, matches the estimated timeline in China for both origin and time to fixation of the associated allele (EDAR V370A), and is consistent with chronic energetic gain and fitness benefits independent of any assumptions for concurrent climatic conditions.

Transitions in loneliness in later life: the role of social comparisons and coping strategies

This study explored the coping strategies and social comparisons used by older adults on different loneliness trajectories (decreased loneliness, stable loneliness and degenerating loneliness). The adaptive consequences of social comparison in later life are recognised as an important strategy for preserving life satisfaction regardless of age-related losses. Coping strategies are also important in managing loneliness. Narrative interviews were conducted with lonely older adults (N = 11) who had participated in Wave One of the Maintaining Function and Well-being in Later Life Study Wales (CFAS Wales). The study found key differences in the coping strategies employed by older adults on different loneliness trajectories. Differences in coping styles between those who reported decreased loneliness and those who were chronically lonely stemmed from perceptions as to whether loneliness was modifiable or not. Different types of social comparison were also found to modulate the loneliness experience. The findings indicate that higher-order strategies (problem, emotional and meaning focused) are not distinct entities but are part of a dynamic process. The management of loneliness in later life may be dependent on several factors, including older adults’ interpretations of the cause of loneliness. These interpretations will have implications for interventions aimed at alleviating chronic loneliness, where the focus may have to be on changing older adult's perceptions of unmodifiable loneliness.

Teachers’ Psychological Needs Satisfaction and Thwarting: Can They Explain Students’ Behavioural Engagement in Physical Education? A Multi-Level Analysis

Students’ engagement in Physical Education has been linked to several adaptive consequences. Even though the existing literature suggests that perceived autonomy support can predict engagement, research is scarce on how teachers’ antecedents might influence this behavioural outcome. This study sought to compare the influence of teachers’ basic psychological needs’ satisfaction and basic psychological needs’ thwarting on students’ behavioural engagement and on the relationship between perceived autonomy-support and the students’ behavioural engagement. The sample included 29 Physical Education teachers and 644 students who were taught by the participants teachers. Data were collected using both paper and online surveys and they were analysed using multilevel modelling techniques. The results revealed that, while teachers’ autonomy satisfaction might be significant in the explanation of students’ engagement (β = 0.33, p < 0.01), it seems that needs thwarting could be a better predictor of this outcome (β autonomy thwarting = −0.17, p < 0.01; β competence thwarting = −0.06, p < 0.05). These findings suggest the impact of certain external pressures on teachers’ practices which, in turn, might affect students’ behavioural outcomes.

The road to sorghum domestication: evidence from nucleotide diversity and gene expression patterns

Native African cereals (sorghum, millets) ensure food security to millions of low-income people from low fertility and drought-prone regions of Africa and Asia. In spite of their agronomic importance, the genetic bases of their phenotype and adaptations are still not well understood. Here we focus on Sorghum bicolor, which is the fifth cereal worldwide for grain production and constitutes the staple food for around 500 million people. We leverage transcriptomic resources to address the adaptive consequences of the domestication process. A clear domestication syndrome is visible in cultivated sorghum (plant architecture, shattering, dormancy and seed weight). Gene expression and nucleotide variability were analyzed in 11 crop and 9 wild accessions. We showed a reduction of diversity in the crop pool both in nucleotide polymorphism (30%) and gene expression levels (18%), which supports the occurrence of a genetic bottleneck in the domestication history of sorghum. Nine hundred and forty nine genes were significantly differentially expressed between the two compartments. Among them, genes involved in internode elongation and auxin metabolism were upregulated in the crop, while genes linked to photosynthesis and reduction-oxidation processes were downregulated in the same pool. Coexpression network analyses revealed 21 clusters of genes sharing similar expression patterns. Four clusters (totalizing 2449 genes) were significantly enriched in differentially expressed genes between the wild and crop pools and two were also enriched in domestication and improvement genes previously identified in sorghum. These results reinforce the evidence that domestication and improvement do not only affect the behaviors of a few genes but led to a large rewiring of the transcriptome during the domestication event and the improvement process. Overall, these analyses pave the way towards the identification of key domestication genes valuable for genetic resources characterization and breeding purposes.

Substantial intraspecific genome size variation in golden-brown algae and its phenotypic consequences

Background and Aims While nuclear DNA content variation and its phenotypic consequences have been well described for animals, vascular plants and macroalgae, much less about this topic is known regarding unicellular algae and protists in general. The dearth of data is especially pronounced when it comes to intraspecific genome size variation. This study attempts to investigate the extent of intraspecific variability in genome size and its adaptive consequences in a microalgal species. Methods Propidium iodide flow cytometry was used to estimate the absolute genome size of 131 strains (isolates) of the golden-brown alga Synura petersenii (Chrysophyceae, Stramenopiles), identified by identical internal transcribed spacer (ITS) rDNA barcodes. Cell size, growth rate and genomic GC content were further assessed on a sub-set of strains. Geographic location of 67 sampling sites across the Northern hemisphere was used to extract climatic database data and to evaluate the ecogeographical distribution of genome size diversity. Key Results Genome size ranged continuously from 0.97 to 2.02 pg of DNA across the investigated strains. The genome size was positively associated with cell size and negatively associated with growth rate. Bioclim variables were not correlated with genome size variation. No clear trends in the geographical distribution of strains of a particular genome size were detected, and strains of different genome size occasionally coexisted at the same locality. Genomic GC content was significantly associated only with genome size via a quadratic relationship. Conclusions Genome size variability in S. petersenii was probably triggered by an evolutionary mechanism operating via gradual changes in genome size accompanied by changes in genomic GC content, such as, for example, proliferation of transposable elements. The variation was reflected in cell size and relative growth rate, possibly with adaptive consequences.

Shifting Paradigms in the Mechanics of Nectar Extraction and Hummingbird Bill Morphology

As functional morphologists, we aim to connect structures, mechanisms, and emergent higher-scale phenomena (e.g., behavior), with the ulterior motive of addressing evolutionary patterns. The fit between flowers and hummingbird bills has long been used as an example of impressive co-evolution, and hence hummingbirds’ foraging behavior and ecological associations have been the subject of intense study. To date, models of hummingbird foraging have been based on the almost two-centuries-old assumption that capillary rise loads nectar into hummingbird tongue grooves. Furthermore, the role of the bill in the drinking process has been overlooked, instead considering it as the mere vehicle with which to traverse the corolla and access the nectar chamber. As a scientific community, we have been making incorrect assumptions about the basic aspects of how hummingbirds extract nectar from flowers. In this article, we summarize recent advances on drinking biomechanics, morphological and ecological patterns, and selective forces involved in the shaping of the hummingbird feeding apparatus, and also address its modifications in a previously unexpected context, namely conspecific and heterospecific fighting. We explore questions such as: how do the mechanics of feeding define the limits and adaptive consequences of foraging behaviors? Which are the selective forces that drive bill and tongue shape, and associated sexually dimorphic traits? And finally, what are the proximate and ultimate causes of their foraging strategies, including exploitative and interference competition? Increasing our knowledge of morphology, mechanics, and diversity of hummingbird feeding structures will have implications for understanding the ecology and evolution of these remarkable animals.