The Genetic Basis of a Rare Flower Color Polymorphism in Mimulus lewisii Provides Insight into the Repeatability of Evolution

A long-standing question in evolutionary biology asks whether the genetic changes contributing to phenotypic evolution are predictable. Here, we identify a genetic change associated with segregating variation in flower color within a population of Mimulus lewisii. To determine whether these types of changes are predictable, we combined this information with data from other species to investigate whether the spectrum of mutations affecting flower color transitions differs based on the evolutionary time-scale since divergence. We used classic genetic techniques, along with gene expression and population genetic approaches, to identify the putative, loss-of-function mutation that generates rare, white flowers instead of the common, pink color in M. lewisii. We found that a frameshift mutation in an anthocyanin pathway gene is responsible for the white-flowered polymorphism found in this population of M. lewisii. Comparison of our results with data from other species reveals a broader spectrum of flower color mutations segregating within populations relative to those that fix between populations. These results suggest that the genetic basis of fixed differences in flower color may be predictable, but that for segregating variation is not.     

Diverse aerobic anoxygenic phototrophs synthesize bacteriochlorophyll in oligotrophic rather than copiotrophic conditions,suggesting ecological niche

While investigating aerobic anoxygenic phototrophs (AAP) from Lake Winnipeg's bacterial community, over 500 isolates were obtained. Relatives of 20 different species were examined simultaneously, identifying conditions for optimal growth or pigment production to determine features that may unify this group of phototrophs. All were distributed among assorted α-Proteobacterial families including Erythrobacteraceae, Sphingomonadaceae, Sphingosinicellaceae, Acetobacteraceae, Methylobacteriaceae, and Rhodobacteraceae. Major phenotypic characteristics matched phylogenetic association, including pigmentation, morphology, metal transformations, tolerances, lipid configurations, and enzyme activities, which distinctly separated each taxonomic family. While varying pH and temperature had a limited independent impact on pigment production, bacteriochlorophyll synthesis was distinctly promoted under low nutrient conditions, whereas copiotrophy repressed its production but enhanced carotenoid yield. New AAP diversity was also reported by revealing strains related to non-phototrophic Rubellimicrobium and Sphingorhabdus, as well as spread throughout Roseomonas, Sphingomonas, and Methylobacterium/Methylorubrum, which previously only had a few known photosynthetic members. This study exemplified the overwhelming diversity of AAP in a single aquatic environment, confirming cultivation continues to be of importance in microbial ecology to discover functionality in both new and previously reported cohorts of bacteria as specific laboratory conditions were required to promote aerobic bacteriochlorophyll production.     

Insulin and Leptin Signaling Interact in the Mouse Kiss1 Neuron during the Peripubertal Period

Reproduction requires adequate energy stores for parents and offspring to survive. Kiss1 neurons, which are essential for fertility, have the potential to serve as the central sensors of metabolic factors that signal to the reproductive axis the presence of stored calories. Paradoxically, obesity is often accompanied by infertility. Despite excess circulating levels of insulin and leptin, obese individuals exhibit resistance to both metabolic factors in many neuron types. Thus, resistance to insulin or leptin in Kiss1 neurons could lead to infertility. Single deletion of the receptors for either insulin or the adipokine leptin from Kiss1 neurons does not impair adult reproductive dysfunction. However, insulin and leptin signaling pathways may interact in such a way as to obscure their individual functions. We hypothesized that in the presence of genetic or obesity-induced concurrent insulin and leptin resistance, Kiss1 neurons would be unable to maintain reproductive function. We therefore induced a chronic hyperinsulinemic and hyperleptinemic state in mice lacking insulin receptors in Kiss1 neurons through high fat feeding and examined the impact on fertility. In an additional, genetic model, we ablated both leptin and insulin signaling in Kiss1 neurons (IR/LepR^Kiss mice). Counter to our hypothesis, we found that the addition of leptin insensitivity did not alter the reproductive phenotype of IR^Kiss mice. We also found that weight gain, body composition, glucose and insulin tolerance were normal in mice of both genders. Nonetheless, leptin and insulin receptor deletion altered pubertal timing as well as LH and FSH levels in mid-puberty in a reciprocal manner. Our results confirm that Kiss1 neurons do not directly mediate the critical role that insulin and leptin play in reproduction. However, during puberty kisspeptin neurons may experience a critical window of susceptibility to the influence of metabolic factors that can modify the onset of fertility.     

Prey capture efficiency in brown capuchin monkeys (Cebus apella) is influenced by sex and corpus callosum morphology

The diet of capuchin monkeys consists largely of fruits, but these monkeys commonly prey upon insects and other invertebrates as well as vertebrates such as lizards, birds, and fish. Capturing small fast‐moving prey requires the ability to process complex visuospatial information such as motion detection, shape, and pursuit. Here we report the results of an experimental investigation into whether capuchins display sex differences in prey capture efficiency, and whether these differences are associated with the morphology of regions of the corpus callosum (CC) involved in visuospatial ability. We examined the prey capture behavior of seven capuchin subjects (four female, three male) in the laboratory by providing subjects opportunities to fish. Additionally, we obtained structural magnetic resonance images from these subjects to determine if spatial‐ability was related to CC anatomy. Over 30 fishing trials, we recorded the number of prey capture attempts, success rate in capturing fish, and hand techniques used in these attempts. Males were significantly faster and more successful than females at capturing prey. In addition, males had smaller total CC:brain ratios than females. Males displayed a left hand bias, as well as significant unimanual usage, whereas females displayed no significant preference for hand usage. Individual capture times were correlated with total CC:brain ratio. Taken together, our results suggest a relationship between prey capture efficiency, sex, and the degree of brain lateralization. Am. J. Primatol. 72:502–508, 2010. © 2010 Wiley‐Liss, Inc.     

Cdc37/Hsp90 protein complex disruption triggers an autophagic clearance cascade for TDP-43 protein

The RNA-binding protein, trans-active response DNA-binding protein 43 (TDP-43), is normally found in the nucleus, but in amyotrophic lateral sclerosis, frontal temporal dementia, and some cases of Alzheimer disease it is cleaved and mislocalized to the cytosol, leading to accumulation. The mechanisms contributing to this are largely unknown. Here, we show that part of the normal clearance cascade for TDP-43 involves the Cdc37/Hsp90 complex. An Hsp90 inhibitor that disrupts the Cdc37/Hsp90 complex reduced TDP-43 levels to a greater extent than a standard Hsp90 ATPase inhibitor. When Cdc37 was depleted, TDP-43 underwent proteolytic clearance that was dependent on nuclear retrotranslocation and autophagic uptake. Accumulation of the microtubule-associated protein tau prevented the clearance of cleaved TDP-43, but not its production. This caused cleaved TDP-43 to accumulate, a feature observed in the brain of persons with Alzheimer disease. Clearance of cleaved TDP-43 was also prevented by knockdown of the autophagic inducer beclin1. Thus, in cells where TDP-43 clearance is normally needed, a system that employs manipulation of the Hsp90 complex and autophagy exists. But when tau accumulation is occurring, cleaved TDP-43 can no longer be cleared, perhaps explaining the emergence of these co-pathologies.