Light regulates the degradation of the regulatory protein VE-1 in the fungus Neurospora crassa

BACKGROUND

Fungi use light as an environmental signal to regulate developmental transitions that are key aspects of their biological cycles and that are also relevant for their dispersal and infectivity as plant or animal pathogens. In addition, light regulates the accumulation of photoprotective pigments, like carotenoids, and other secondary metabolites. Most fungal light responses occur after changes in gene transcription and we describe here a novel effect of light in the regulation of degradation of VE-1, a key component of the velvet complex, in the model fungus Neurospora crassa. The velvet complex is a fungal-specific protein complex that coordinates fungal development, secondary metabolism, and light regulation by interacting with other regulators and photoreceptors and modifying gene expression.

RESULTS

We have characterized the role of VE-1 during conidiation in N. crassa. In vegetative mycelia, VE-1 is localized in the cytoplasm and nuclei and is required for light-dependent transcription but does not interact with the photoreceptor and transcription factor WC-1. VE-1 is more stable in light than in darkness during asexual development (conidiation). We have shown that this light effect requires the blue-light photoreceptor WC-1. We have characterized the role of the proteasome, the COP9 signalosome (CSN), and the adaptor component of cullin-RING ubiquitin ligases, FWD-1, in the degradation of VE-1.

CONCLUSIONS

We propose that this new effect of light allows the fungal cell to adapt quickly to changes in light exposure by promoting the accumulation of VE-1 for the regulation of genes that participate in the biosynthesis of photoprotective pigments.

Disability and quality of life in heart failure patients: a cross-sectional study

BACKGROUND

Although both hospitalization and mortality due to heart failure (HF) have been widely studied, less is known about the impact of HF on disability and quality of life.

AIM

To assess the degree of disability and quality of life in HF patients attended at family medicine centres.

DESIGN AND SETTING

Cross-sectional study of a cohort of HF patients attended at family medicine centres.

METHODS

Disability was assessed with the WHODAS 2 questionnaire, which provides a global and six domain scores that is understanding and communication, getting around, self-care, getting along with people, life activities and participation in society. Quality of life was assessed with the Minnesota Living with Heart Failure Questionnaire, which furnishes a global and two domain scores, physical and emotional.

RESULTS

A breakdown of the results showed that 28% of patients had moderate disability and 16.7% had severe disability, with the most important areas affected being: life activities, 8.9% extreme disability and 30.3% severe disability; getting around, 34.6% severe disability and 2% extreme disability; and participation in society, 53.3% moderate-severe disability. Quality of life was mildly affected. New York Heart Association (NYHA) Functional Classification and sex were the major determinants of disability and quality of life. Angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists were associated with better scores in the "getting around" and "life activity" domains.

CONCLUSION

HF patients in primary care show an important degree of disability and an acceptable quality of life.

Control of Development, Secondary Metabolism and Light-Dependent Carotenoid Biosynthesis by the Velvet Complex of Neurospora crassa

Neurospora crassa is an established reference organism to investigate carotene biosynthesis and light regulation. However, there is little evidence of its capacity to produce secondary metabolites. Here, we report the role of the fungal-specific regulatory velvet complexes in development and secondary metabolism (SM) in N. crassa Three velvet proteins VE-1, VE-2, VOS-1, and a putative methyltransferase LAE-1 show light-independent nucleocytoplasmic localization. Two distinct velvet complexes, a heterotrimeric VE-1/VE-2/LAE-1 and a heterodimeric VE-2/VOS-1 are found in vivo The heterotrimer-complex, which positively regulates sexual development and represses asexual sporulation, suppresses siderophore coprogen production under iron starvation conditions. The VE-1/VE-2 heterodimer controls carotene production. VE-1 regulates the expression of >15% of the whole genome, comprising mainly regulatory and developmental features. We also studied intergenera functions of the velvet complex through complementation of Aspergillus nidulans veA, velB, laeA, vosA mutants with their N. crassa orthologs ve-1, ve-2, lae-1, and vos-1, respectively. Expression of VE-1 and VE-2 in A. nidulans successfully substitutes the developmental and SM functions of VeA and VelB by forming two functional chimeric velvet complexes in vivo, VelB/VE-1/LaeA and VE-2/VeA/LaeA, respectively. Reciprocally, expression of veA restores the phenotypes of the N. crassa ve-1 mutant. All N. crassa velvet proteins heterologously expressed in A. nidulans are localized to the nuclear fraction independent of light. These data highlight the conservation of the complex formation in N. crassa and A. nidulans However, they also underline the intergenera similarities and differences of velvet roles according to different life styles, niches and ontogenetic processes.

The role of intragestational ghrelin on postnatal development and reproductive programming in mice

The purpose of this study was to evaluate the intragestational role of ghrelin in offspring development and reproductive programming in a mouse model of ghrelin imbalance during pregnancy. Female mice were injected with ghrelin (supraphysiological levels: 4 nmol/animal/day), antagonist (endogenous ghrelin inhibition with (D-Lys3)GHRP-6, 6 nmol/animal/day) or vehicle (control = normal ghrelin levels) throughout the pregnancy. Parameters evaluated in litters were growth, physical, neurobiological and sexual development and, at adulthood, reproductive function. Litter size and initial weight did not vary between treatments. Male pups from dams treated with ghrelin showed higher body weight increase until adulthood (31.7 ± 0.8 vs control = 29.7 ± 0.7, n = 11–14 litters/treatment; P < 0.05). Postnatal physical and neurobiological development was not modified by treatments. The antagonist accelerated male puberty onset, evidenced as earlier testis descent and increased relative testicular weight (antagonist = 0.5 ± 0.0% vs ghrelin = 0.4 ± 0.0% and control = 0.4 ± 0.0%, n = 5–10 litters/treatment; P < 0.05). At adulthood, these males exhibited lower relative testicular weight and reduced sperm motility (63.9 ± 3.6% vs control = 70.9 ± 3.3 and ghrelin = 75.6 ± 3.0, n = 13–15 animals; P < 0.05), without changes in plasma testosterone or fertility. Female pups intragestationally exposed to the antagonist showed earlier vaginal opening (statistically significant only at Day 25) and higher ovarian volume (antagonist = 1085.7 ± 64.0 mm3 vs ghrelin = 663.3 ± 102.8 mm3 and control = 512.3 ± 116.4 mm3; n = 4–6 animals/treatment; P < 0.05), indicating earlier sexual maturation. At adulthood, these females and those exposed to ghrelin showed a tendency to higher percentages of embryo loss and/or foetal atrophy. In conclusion, ghrelin participates in reproductive foetal programming: alterations in ghrelin activity during pregnancy modified body weight increase and anticipated puberty onset, exerting (or tending to) negative effects on adult reproductive function.

A Ras GTPase associated protein is involved in the phototropic and circadian photobiology responses in fungi

Light is an environmental signal perceived by most eukaryotic organisms and that can have major impacts on their growth and development. The MadC protein in the fungus Phycomyces blakesleeanus (Mucoromycotina) has been postulated to form part of the photosensory input for phototropism of the fruiting body sporangiophores, but the madC gene has remained unidentified since the 1960s when madC mutants were first isolated. In this study the madC gene was identified by positional cloning. All madC mutant strains contain loss-of-function point mutations within a gene predicted to encode a GTPase activating protein (GAP) for Ras. The madC gene complements the Saccharomyces cerevisiae Ras-GAP ira1 mutant and the encoded MadC protein interacts with P. blakesleeanus Ras homologs in yeast two-hybrid assays, indicating that MadC is a regulator of Ras signaling. Deletion of the homolog in the filamentous ascomycete Neurospora crassa affects the circadian clock output, yielding a pattern of asexual conidiation similar to a ras-1 mutant that is used in circadian studies in N. crassa. Thus, MadC is unlikely to be a photosensor, yet is a fundamental link in the photoresponses from blue light perceived by the conserved White Collar complex with Ras signaling in two distantly-related filamentous fungal species.

Expansion of Signal Transduction Pathways in Fungi by Extensive Genome Duplication

Plants and fungi use light and other signals to regulate development, growth, and metabolism. The fruiting bodies of the fungus Phycomyces blakesleeanus are single cells that react to environmental cues, including light, but the mechanisms are largely unknown [1]. The related fungus Mucor circinelloides is an opportunistic human pathogen that changes its mode of growth upon receipt of signals from the environment to facilitate pathogenesis [2]. Understanding how these organisms respond to environmental cues should provide insights into the mechanisms of sensory perception and signal transduction by a single eukaryotic cell, and their role in pathogenesis. We sequenced the genomes of P. blakesleeanus and M. circinelloides and show that they have been shaped by an extensive genome duplication or, most likely, a whole-genome duplication (WGD), which is rarely observed in fungi [3-6]. We show that the genome duplication has expanded gene families, including those involved in signal transduction, and that duplicated genes have specialized, as evidenced by differences in their regulation by light. The transcriptional response to light varies with the developmental stage and is still observed in a photoreceptor mutant of P. blakesleeanus. A phototropic mutant of P. blakesleeanus with a heterozygous mutation in the photoreceptor gene madA demonstrates that photosensor dosage is important for the magnitude of signal transduction. We conclude that the genome duplication provided the means to improve signal transduction for enhanced perception of environmental signals. Our results will help to understand the role of genome dynamics in the evolution of sensory perception in eukaryotes.

A global multilocus analysis of the model fungus Neurospora reveals a single recent origin of a novel genetic system

The large diversity of mating systems observed in the fungal kingdom underlines the importance of mating system change in fungal evolution. The selfing species Neurospora tetrasperma has evolved a novel method of achieving self-fertility by a mating system referred to as pseudohomothallism. However, little is known about the origin of N. tetrasperma and its relationship to the self-sterile, heterothallic, Neurospora species. In this study, we used a combination of phylogenetic and population genetic analyses to reconstruct the evolutionary history of N. tetrasperma and its heterothallic relatives. We sequenced 9 unlinked nuclear loci from 106 strains of N. tetrasperma sampled from across the globe, and a sample of 28 heterothallic strains of Neurospora. Our analyses provide strong support for monophyly of N. tetrasperma, but reject the monophyly of N. crassa. We estimate that N. tetrasperma is of a recent origin and that it diverged from the heterothallic species ∼1 million years ago. We also extend previous findings on the diversification within the N. tetrasperma clade, with 10 lineages identified. Taken together, these findings indicate that N. tetrasperma is younger than has been previously reported and that a rapid diversification of lineages has occurred within the N. tetrasperma clade.

A relationship between carotenoid accumulation and the distribution of species of the fungus Neurospora in Spain

The ascomycete fungus Neurospora is present in many parts of the world, in particular in tropical and subtropical areas, where it is found growing on recently burned vegetation. We have sampled the Neurospora population across Spain. The sampling sites were located in the region of Galicia (northwestern corner of the Iberian peninsula), the province of Cáceres, the city of Seville, and the two major islands of the Canary Islands archipelago (Tenerife and Gran Canaria, west coast of Africa). The sites covered a latitude interval between 27.88° and 42.74°. We have identified wild-type strains of N. discreta, N. tetrasperma, N. crassa, and N. sitophila and the frequency of each species varied from site to site. It has been shown that after exposure to light Neurospora accumulates the orange carotenoid neurosporaxanthin, presumably for protection from UV radiation. We have found that each Neurospora species accumulates a different amount of carotenoids after exposure to light, but these differences did not correlate with the expression of the carotenogenic genes al-1 or al-2. The accumulation of carotenoids in Neurospora shows a correlation with latitude, as Neurospora strains isolated from lower latitudes accumulate more carotenoids than strains isolated from higher latitudes. Since regions of low latitude receive high UV irradiation we propose that the increased carotenoid accumulation may protect Neurospora from high UV exposure. In support of this hypothesis, we have found that N. crassa, the species that accumulates more carotenoids, is more resistant to UV radiation than N. discreta or N. tetrasperma. The photoprotection provided by carotenoids and the capability to accumulate different amounts of carotenoids may be responsible, at least in part, for the distribution of Neurospora species that we have observed across a range of latitudes.

Inhibitory effects of ghrelin on sexual behavior: role of the peptide in the receptivity reduction induced by food restriction in mice

Ghrelin (Ghr) is a gut/hypothalamus peptide with inhibitory actions on reproductive physiology; however, there are no previous reports of its role on estrous behavior. Under the hypothesis that the increase of plasma Ghr during food restriction (FR) is responsible for receptivity reduction, we intended to evaluate the receptivity percentage of female mice subjected to: exp. 1) acute and chronic FR and Ghr administration (3 nmol/animal/day, s. c.) and exp. 2) the co-administration of a ghrelin antagonist [ant=(d-Lys3)-GHRP-6; 6 nmol/animal/day s. c.]. All females were ovariectomized, primed with steroids, trained, and randomly subjected every week to each one of several protocols, followed by a behavioral test. Experiment 1 (n=8): basal, no treatment; acute FR (aFR), 24-h fasting; chronic FR (cFR), 50% FR for 5 days; acute ghrelin (aGhr), Ghr 30 min before test and chronic ghrelin (cGhr), Ghr for 5 days. Except for cGhr, all treatments significantly decreased the percentage of receptivity (mean±SEM): basal 61.9±6.0, aFR 33.1±8.1, cFR 18.8±7.7, aGhr 45.6±10.6, p<0.05 vs. basal. In exp. 2 (n=11), except for cFR+ant (55.0±6.4) the co-administration of the antagonist reversed the deleterious effects detected in exp. 1: basal 70.9±5.4; aFR+ant 72.3±7.6; aGhr+ant 73.6±4.7. As expected, the administration of vehicle or antagonist alone did not modify receptivity. Besides, we found a significant correlation between percentage of body weight loss and percentage of receptivity reduction (r=0.62, p=0.0004). This is the first study demonstrating that ghrelin is able to inhibit female mice sexual behavior and that is involved, at least in part, in receptivity reduction after food scarcity.

A complex photoreceptor system mediates the regulation by light of the conidiation genes con-10 and con-6 in Neurospora crassa

Genes con-10 and con-6 in Neurospora crassa are activated during conidiation or after illumination of vegetative mycelia. Light activation requires the white-collar complex (WCC), a transcription factor complex composed of the photoreceptor WC-1 and its partner WC-2. We have characterized the photoactivation of con-10 and con-6, and we have identified 300bp required for photoactivation in the con-10 promoter. A complex stimulus-response relationship for con-10 and con-6 photoactivation suggested the activity of a complex photoreceptor system. The WCC is the key element for con-10 activation by light, but we suggest that other photoreceptors, the cryptochrome CRY-1, the rhodopsin NOP-1, and the phytochrome PHY-2, modify the activity of the WCC for con-10 photoactivation, presumably through a repressor. In addition we show that the regulatory protein VE-1 is required for full photocarotenogenesis. We propose that these proteins may modulate the WCC in a gene-specific way.