Effect of a Standardised Dietary Restriction Protocol on Multiple Laboratory Strains of Drosophila melanogaster

Background

Outcomes of lifespan studies in model organisms are particularly susceptible to variations in technical procedures. This is especially true of dietary restriction, which is implemented in many different ways among laboratories.

Principal Findings

In this study, we have examined the effect of laboratory stock maintenance, genotype differences and microbial infection on the ability of dietary restriction (DR) to extend life in the fruit fly Drosophila melanogaster. None of these factors block the DR effect.

Conclusions

These data lend support to the idea that nutrient restriction genuinely extends lifespan in flies, and that any mechanistic discoveries made with this model are of potential relevance to the determinants of lifespan in other organisms.     

An Analysis of Diet Quality,How It Controls Fatty Acid Profiles,Isotope Signatures and Stoichiometry in the Malaria Mosquito Anopheles arabiensis

Background

Knowing the underlying mechanisms of mosquito ecology will ensure effective vector management and contribute to the overall goal of malaria control. Mosquito populations show a high degree of population plasticity in response to environmental variability. However, the principle factors controlling population size and fecundity are for the most part unknown. Larval habitat and diet play a crucial role in subsequent mosquito fitness. Developing the most competitive insects for sterile insect technique programmes requires a “production” orientated perspective, to deduce the most effective larval diet formulation; the information gained from this process offers us some insight into the mechanisms and processes taking place in natural native mosquito habitats.

Methodology/Principal Findings

Fatty acid profiles and de-novo or direct assimilation pathways, of whole-individual mosquitoes reared on a range of larval diets were determined using pyrolysis gas chromatograph/mass spectrometry. We used elemental analysis and isotope ratio mass spectrometry to measure individual-whole-body carbon, nitrogen and phosphorous values and to assess the impact of dietary quality on subsequent population stoichiometry, size, quality and isotopic signature. Diet had the greatest impact on fatty acid (FA) profiles of the mosquitoes, which exhibited a high degree of dietary routing, characteristic of generalist feeders. De-novo synthesis of a number of important FAs was observed. Mosquito C:N stoichiometry was fixed in the teneral stage. Dietary N content had significant influence on mosquito size, and P was shown to be a flexible pool which limited overall population size.

Conclusions/Significance

Direct routing of FAs was evident but there was ubiquitous de-novo synthesis suggesting mosquito larvae are competent generalist feeders capable of survival on diet with varying characteristics. It was concluded that nitrogen availability in the larval diet controlled teneral mosquito size and that teneral CN ratio is a sex- and species-specific fixed parameter. This finding has significant implications for overall mosquito competitiveness and environmental management.     

Limitations to reproductive output and genetic rescue in populations of the rare shrub Grevillea repens (Proteaceae)

Background and Aims

When conserving rare plant species, managers are often faced with small and/or isolated populations displaying low levels of sexual reproduction and genetic variation. One option for reinvigorating these populations is the introduction of genetic material from other sites, but in some cases fitness may be reduced as a result of outbreeding depression. Here the pollination biology of the rare shrub Grevillea repens is studied across its natural range and reproductive responses following cross-pollination among populations are examined to determine factors that may be limiting sexual reproduction and the potential for genetic rescue.

Methods

Pollen manipulation treatments (self-, autogamous self-, cross- and open pollination) were applied to flowers to examine the breeding system and fruit and seed production in five populations of G. repens. Pollen production, presentation and viability were investigated and interpopulation crosses of increasing genetic distance performed among the populations.

Key Results

The study species is self-incompatible and displayed very low natural seed set over two seasons, due partly to low pollen viability in one of the populations. Within-population crossing increased fruit and seed production at some sites, indicating pollinator limitation. Interpopulation crosses further increased reproductive output in one population, suggesting mate limitation, and for this site there was a positive relationship between genetic distance among populations and the size of genetic rescue benefits. However, in other populations there was a decrease in fruit and seed set with increasing genetic distance.

Conclusions

The results highlight that management strategies involving interpopulation crosses can improve reproductive output in small, isolated populations of rare plants, but guidelines need to be developed on a population by population basis.Key words: Grevillea repens, Proteaceae, genetic rescue, pollination ecology, self-incompatibility, breeding system, interpopulation cross, outbreeding depression, pollinator limitation, mate limitation, resource limitation     

Inherited variability in multiple traits determines fitness in populations of an annual legume from contrasting latitudinal origins

Background and Aims

Variation in fitness depends on corresponding variation in multiple traits which have both genetically controlled and plastic components. These traits are subjected to varying degrees of local adaptation in specific populations and, consequently, are genetically controlled to different extents. In this study it is hypothesized that modulation of different traits would have contrasting relevance for the fitness of populations of diverse origins. Specifically, assuming that environmental pressures vary across a latitudinal gradient, it is suggested that inherited variation in traits differentially determines fitness in annual Lupinus angustifolius populations from contrasting latitudinal origins in western Spain.

Methods

Seeds of L. angustifolius from three contrasting origins were grown in a common garden. Traits related to more plastic vegetative growth and more genetically conserved phenology were measured, together with estimates of reproductive success. Fitness was estimated by the number of viable seeds per plant. Structural Equation Models were used to infer causal relationships among multiple traits and fitness, separating the direct and indirect effects of morphological, phenological and reproductive traits.

Key Results

Phenological, vegetative and reproductive traits accounted for most of the fitness variation. Fitness was highest in plants of southernmost origin, mainly due to earlier flowering. Fitness within each seed origin was controlled by variation in different traits. Southern origin plants that grew to a larger size achieved higher fitness. However, plant size in plants of northernmost origin was irrelevant, but early flowering promoted higher fitness. Variation in fruit and seed set had a greater effect on the fitness of plants of central origin than phenological and size variation.

Conclusions

It is concluded that modulation of a functional trait can be relevant to fitness in a given population (i.e. affecting intensity and direction), but irrelevant in other populations. This points to the need to consider integrated phenotypes when trying to unravel local adaptation effects over single traits.Key words: Lupinus, Structural Equation Models, fitness, phenology, functional traits, reproductive success, SLA, seed size     

Differential costs of reproduction in females and hermaphrodites in a gynodioecious plant

Background and Aims

Plants exhibit a variety of reproductive systems where unisexual (females or males) morphs coexist with hermaphrodites. The maintenance of dimorphic and polymorphic reproductive systems may be problematic. For example, to coexist with hermaphrodites the females of gynodioecious species have to compensate for the lack of male function. In our study species, Geranium sylvaticum, a perennial gynodioecious herb, the relative seed fitness advantage of females varies significantly between years within populations as well as among populations. Differences in reproductive investment between females and hermaphrodites may lead to differences in future survival, growth and reproductive success, i.e. to differential costs of reproduction. Since females of this species produce more seeds, higher costs of reproduction in females than in hermaphrodites were expected. Due to the higher costs of reproduction, the yearly variation in reproductive output of females might be more pronounced than that of hermaphrodites.

Methods

Using supplemental hand-pollination of females and hermaphrodites of G. sylvaticum we examined if increased reproductive output leads to differential costs of reproduction in terms of survival, probability of flowering, and seed production in the following year.

Key Results

Experimentally increased reproductive output had differential effects on the reproduction of females and hermaphrodites. In hermaphrodites, the probability of flowering decreased significantly in the following year, whereas in females the costs were expressed in terms of decreased future seed production.

Conclusions

When combining the probability of flowering and seed production per plant to estimate the multiplicative change in fitness, female plants showed a 56 % and hermaphrodites showed a 39 % decrease in fitness due to experimentally increased reproduction. Therefore, in total, female plants seem to be more sensitive to the cost of reproduction in terms of seed fitness than hermaphrodites.     

Roles of Caloric Restriction,Ketogenic Diet and Intermittent Fasting during Initiation,Progression and Metastasis of Cancer in Animal Models: A Systematic Review and Meta-Analysis

Background

The role of dietary restriction regimens such as caloric restriction, ketogenic diet and intermittent fasting in development of cancers has been detected via abundant preclinical experiments. However, the conclusions are controversial. We aim to review the relevant animal studies systematically and provide assistance for further clinical studies.

Methods

Literatures on associations between dietary restriction and cancer published in PubMed in recent twenty years were comprehensively searched. Animal model, tumor type, feeding regimen, study length, sample size, major outcome, conclusion, quality assessment score and the interferential step of cancer were extracted from each eligible study. We analyzed the tumor incidence rates from 21 studies about caloric restriction.

Results

Fifty-nine studies were involved in our system review. The involved studies explored roles of dietary restriction during initiation, progression and metastasis of cancer. About 90.9% of the relevant studies showed that caloric restriction plays an anti-cancer role, with the pooled OR (95%CI) of 0.20 (0.12, 0.34) relative to controls. Ketogenic diet was also positively associated with cancer, which was indicated by eight of the nine studies. However, 37.5% of the related studies obtained a negative conclusion that intermittent fasting was not significantly preventive against cancer.

Conclusions

Caloric restriction and ketogenic diet are effective against cancer in animal experiments while the role of intermittent fasting is doubtful and still needs exploration. More clinical experiments are needed and more suitable patterns for humans should be investigated.     

Effects of plant size and weather on the flowering phenology of the organ pipe cactus (Stenocereus thurberi)

Background and Aims

Flowering phenology is a critical life-history trait that influences reproductive success. It has been shown that genetic, climatic and other factors such as plant size affect the timing of flowering and its duration. The spatial and temporal variation in the reproductive phenology of the columnar cactus Stenocereus thurberi and its association with plant size and environmental cues was studied.

Methods

Flowering was monitored during 3 years in three populations of S. thurberi along a latitudinal gradient. Plant size was related to phenological parameters. The actual and past weather were used for each site and year to investigate the environmental correlates of flowering.

Key Results

There was significant variation in the timing of flowering within and among populations. Flowering lasted 4 months in the southern population and only 2 months in the northern population. A single flowering peak was evident in each population, but ocurred at different times. Large plants produced more flowers, and bloomed earlier and for a longer period than small plants. Population synchrony increased as the mean duration of flowering per individual decreased. The onset of flowering is primarily related to the variance in winter minimum temperatures and the duration to the autumn–winter mean maximum temperature, whereas spring mean maximum temperature is best correlated with synchrony.

Conclusions

Plant size affects individual plant fecundity as well as flowering time. Thus the population structure strongly affects flowering phenology. Indications of clinal variation in the timing of flowering and reproductive effort suggest selection pressures related to the arrival of migrating pollinators, climate and resource economy in a desert environment. These pressures are likely to be relaxed in populations where individual plants can attain large sizes.Key words: Flowering phenology, optimal timing, plant size, Sonoran Desert, Stenocereus thurberi, temperature     

Cytogeography and genome size variation in the Claytonia perfoliata (Portulacaceae) polyploid complex

Background and Aims

Genome duplication is a central process in plant evolution and contributes to patterns of variation in genome size within and among lineages. Studies that combine cytogeography with genome size measurements contribute to our basic knowledge of cytotype distributions and their associations with variation in genome size.

Methods

Ploidy and genome size were assessed with direct chromosome counts and flow cytometry for 78 populations within the Claytonia perfoliata complex, comprised of three diploid taxa with numerous polyploids that range to the decaploid level. The relationship between genome size and temperature and precipitation was investigated within and across cytotypes to test for associations between environmental factors and nuclear DNA content.

Key Results

A euploid series (n = 6) of diploids to octoploids was documented through chromosome counts, and decaploids were suggested by flow cytometry. Increased variation in genome size among populations was found at higher ploidy levels, potentially associated with differential contributions of diploid parental genomes, variation in rates of genomic loss or gain, or undetected hybridization. Several accessions were detected with atypical genome sizes, including a diploid population of C. parviflora ssp. grandiflora with an 18 % smaller genome than typical, and hexaploids of C. perfoliata and C. parviflora with genomes 30 % larger than typical. There was a slight but significant association of larger genome sizes with colder winter temperature across the C. perfoliata complex as a whole, and a strong association between lower winter temperatures and large genome size for tetraploid C. parviflora.

Conclusions

The C. perfoliata complex is characterized by polyploids ranging from tetraploid to decaploid, with large magnitude variation in genome size at higher ploidy levels, associated in part with environmental variation in temperature.     

Kinship between parents reduces offspring fitness in a natural population of Rhododendron brachycarpum

Background and Aims

A reduction in offspring fitness resulting from mating between neighbours is interpreted as biparental inbreeding depression. However, little is known about the relationship between the parents'' genetic relatedness and biparental inbreeding depression in their progeny in natural populations. This study assesses the effect of kinship between parents on the fitness of their progeny and the extent of spatial genetic structure in a natural population of Rhododendron brachycarpum.

Methods

Kinship coefficients between 11 858 pairs of plants among a natural population of 154 R. brachycarpum plants were estimated a priori using six microsatellite markers. Plants were genotyped, and pairs were selected from among 60 plants to vary the kinship from full-sib to unrelated. After a hand-pollination experiment among the 60 plants, offspring fitness was measured at the stages of seed maturation (i.e. ripening) under natural conditions, and seed germination and seedling survival under greenhouse conditions. In addition, spatial autocorrelation was used to assess the population''s genetic structure.

Key Results

Offspring fitness decreased significantly with increasing kinship between parents. However, the magnitude and timing of this effect differed among the life-cycle stages. Measures of inbreeding depression were 0·891 at seed maturation, 0·122 (but not significant) at seed germination and 0·506 at seedling survival. The local population spatial structure was significant, and the physical distance between parents mediated the level of inbreeding between them.

Conclusions

The level of inbreeding between individuals determines offspring fitness in R. brachycarpum, especially during seed maturation. Genetic relatedness between parents caused inbreeding depression in their progeny. Therefore, biparental inbreeding contributes little to reproduction and instead acts as a selection force that promotes outcrossing, as offspring of more distant (less related) parents survive better.     

Clonal growth is enhanced in the absence of a mating morph: a comparative study of fertile stylar polymorphic and sterile monomorphic populations of Nymphoides montana (Menyanthaceae)

Background and Aims

Many aquatic species with stylar polymorphisms have the capacity for clonal and sexual reproduction and are sensitive to the balance of the two reproductive modes when there are a limited number of mating morphs within a population. This study asked how the clonal and sexual reproductive modes perform in populations that contain only a single morph and where fitness gain through sexual reproduction is rare. In clonal aquatic Nymphoides montana, polymorphic populations normally contain two mating morphs in equal frequencies. Populations are sexually fertile and appear to be maintained by pollen transfer between the two partners. However, in a monomorphic population of N. montana where mating opportunities are unavailable, female and male function is impaired and clonality maintains the population. Here, the consequences of intraspecific variation in sexuality were explored between monomorphic and polymorphic N. montana populations in eastern Australia.

Methods

Comparative measurements of male and female fertility, total dry mass and genotypic diversity using ISSR markers were made between populations with variable sexuality.

Key Results and Conclusions

Very few seeds were produced in the monomorphic population under natural and glasshouse conditions due to dysfunctional pollen and ovules. Stigma–anther separation was minimal in the monomorphic population, which may be a consequence of the relaxed selective pressures that regulate the maintenance of sexual function. However, clonal reproduction was favoured at the expense of sexual reproduction in the monomorphic population; this may facilitate the establishment of sterility throughout the population via resource reallocation or pleiotropic effects. The ISSR results showed that the monomorphic population was one large, single genotype, unlike the multi-genotypic fertile polymorphic populations. Evolutionary loss of sex in a clonal population in which a mating morph is absent was evident; under these conditions clonal growth may assure reproduction and expand the population via spreading stolons.     

Female reproductive success decreases with display size in monkshood, Aconitum kusnezoffii (Ranunculaceae)

Background and Aims

Reduction in female fitness in large clones can occur as a result of increased geitonogamous self-fertilization and its influence through inbreeding depression. This possibility was investigated in the self-compatible, bee-pollinated perennial herb Aconitum kusnezoffii which varies in clone size.

Methods

Field investigations were conducted on pollinator behaviour, flowering phenology and variation in seed set. The effects of self-pollination following controlled self- and cross-pollination were also examined. Selfing rates of differently sized clones were assessed using allozyme markers.

Key Results

High rates of geitonogamous pollination were associated with large display size. Female fitness at the ramet level decreased with clone size. Fruit and seed set under cross-pollination were significantly higher than those under self-pollination. The pre-dispersal inbreeding depression was estimated as 0·502 based on the difference in seed set per flower between self- and cross-pollinated flowers. Selfing rates of differently sized clones did not differ.

Conclusions

It is concluded that in A. kusnezoffii the negative effects of self-pollination causing reduced female fertility with clone size arise primarily from a strong early-acting inbreeding depression leading to the abortion of selfed embryos prior to seed maturation.Key words: Early-acting inbreeding depression, Aconitum kusnezoffii, clone size, female reproductive success, geitonogamy     

Floral display size,conspecific density and florivory affect fruit set in natural populations of Phlox hirsuta,an endangered species

Background and Aims

Natural variation in fruit and seed set may be explained by factors that affect the composition of pollen grains on stigmas. Self-incompatible species require compatible outcross pollen grains to produce seeds. The siring success of outcross pollen grains, however, can be hindered if self (or other incompatible) pollen grains co-occur on stigmas. This study identifies factors that determine fruit set in Phlox hirsuta, a self-sterile endangered species that is prone to self-pollination, and its associated fitness costs.

Methods

Multiple linear regressions were used to identify factors that explain variation in percentage fruit set within three of the five known populations of this endangered species. Florivorous beetle density, petal colour, floral display size, local conspecific density and pre-dispersal seed predation were quantified and their effects on the ability of flowers to produce fruits were assessed.

Key Results

In all three populations, percentage fruit set decreased as florivorous beetle density increased and as floral display size increased. The effect of floral display size on fruit set, however, often depended on the density of nearby conspecific plants. High local conspecific densities offset – even reversed – the negative effects of floral display size on percentage fruit set. Seed predation by mammals decreased fruit set in one population.

Conclusions

The results indicate that seed production in P. hirsuta can be maximized by selectively augmenting populations in areas containing isolated large plants, by reducing the population sizes of florivorous beetles and by excluding mammals that consume unripe fruits.     

Host genetics and diet,but not immunoglobulin A expression,converge to shape compositional features of the gut microbiome in an advanced intercross population of mice

Background

Individuality in the species composition of the vertebrate gut microbiota is driven by a combination of host and environmental factors that have largely been studied independently. We studied the convergence of these factors in a G₁₀ mouse population generated from a cross between two strains to search for quantitative trait loci (QTLs) that affect gut microbiota composition or ileal Immunoglobulin A (IgA) expression in mice fed normal or high-fat diets.

Results

We found 42 microbiota-specific QTLs in 27 different genomic regions that affect the relative abundances of 39 taxa, including four QTL that were shared between this G₁₀ population and the population previously studied at G₄. Several of the G₁₀ QTLs show apparent pleiotropy. Eight of these QTLs, including four at the same site on chromosome 9, show significant interaction with diet, implying that diet can modify the effects of some host loci on gut microbiome composition. Utilization patterns of IghV variable regions among IgA-specific mRNAs from ileal tissue are affected by 54 significant QTLs, most of which map to a segment of chromosome 12 spanning the Igh locus. Despite the effect of genetic variation on IghV utilization, we are unable to detect overlapping microbiota and IgA QTLs and there is no significant correlation between IgA variable pattern utilization and the abundance of any of the taxa from the fecal microbiota.

Conclusions

We conclude that host genetics and diet can converge to shape the gut microbiota, but host genetic effects are not manifested through differences in IgA production.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0552-6) contains supplementary material, which is available to authorized users.     

The Effects of Exercise Training in Addition to Energy Restriction on Functional Capacities and Body Composition in Obese Adults during Weight Loss: A Systematic Review

Background

Obesity is associated with impairments of physical function, cardiovascular fitness, muscle strength and the capacity to perform activities of daily living. This review examines the specific effects of exercise training in relation to body composition and physical function demonstrated by changes in cardiovascular fitness, and muscle strength when obese adults undergo energy restriction.

Methods

Electronic databases were searched for randomised controlled trials comparing energy restriction plus exercise training to energy restriction alone. Studies published to May 2013 were included if they used multi-component methods for analysing body composition and assessed measures of fitness in obese adults.

Results

Fourteen RCTs met the inclusion criteria. Heterogeneity of study characteristics prevented meta-analysis. Energy restriction plus exercise training was more effective than energy restriction alone for improving cardiovascular fitness, muscle strength, and increasing fat mass loss and preserving lean body mass, depending on the type of exercise training.

Conclusion

Adding exercise training to energy restriction for obese middle-aged and older individuals results in favourable changes to fitness and body composition. Whilst weight loss should be encouraged for obese individuals, exercise training should be included in lifestyle interventions as it offers additional benefits.     

Integrating multiple disturbance aspects: management of an invasive thistle,Carduus nutans

Background and Aims

Disturbances occur in most ecological systems, and play an important role in biological invasions. We delimit five key disturbance aspects: intensity, frequency, timing, duration and extent. Few studies address more than one of these aspects, yet interactions and interdependence between aspects may lead to complex outcomes.

Methods

In a two-cohort experimental study, we examined how multiple aspects (intensity, frequency and timing) of a mowing disturbance regime affect the survival, phenology, growth and reproduction of an invasive thistle Carduus nutans (musk thistle).

Key Results

Our results show that high intensity and late timing strongly delay flowering phenology and reduce plant survival, capitulum production and plant height. A significant interaction between intensity and timing further magnifies the main effects. Unexpectedly, high frequency alone did not effectively reduce reproduction. However, a study examining only frequency and intensity, and not timing, would have erroneously attributed the importance of timing to frequency.

Conclusions

We used management of an invasive species as an example to demonstrate the importance of a multiple-aspect disturbance framework. Failure to consider possible interactions, and the inherent interdependence of certain aspects, could result in misinterpretation and inappropriate management efforts. This framework can be broadly applied to improve our understanding of disturbance effects on individual responses, population dynamics and community composition.     

Characteristics of nutrient intakes,basal physical fitness and serum markers in elderly women with osteopenia

Purpose

This study investigated the correlations among BMD, nutrient intake, basal physical fitness and serum markers in elderly women with osteopenia.

Methods

Bone Mineral Density (BMD) was measured in 54 elderly women (60–77yrs) by using dual energy X-ray absorptiometry (DEXA). The subjects were divided into an osteopenia group (OG; n = 29) and a normal group (NG; n = 25). A physical fitness test was conducted to determine muscle strength, muscle endurance, flexibility, agility, and balance. The dietary nutrient intake for one day was analyzed. The serum Ca, Pi and Mg concentration was also analyzed.

Results

There was significant correlation between All subject’s weight and their total-BMD as well as the T-score (p < .01). There was also significant correlation between the fat free mass and Total-BMD (p < .01). There was significant positive correlation between energy intake and dietary carbohydrate with Total-BMD and T-score in the OG (p < .05). The Serum Pi of the OG was significantly lower than that of the NG (p < .05), and there was significant correlation with the BMD in most regions as well as with the Total-BMD and T-score (p < .05, p < .01).

Conclusion

These results suggested that the fat free mass in elderly women plays an important role in maintaining their BMD and that sufficient caloric intake would be likely to improve BMD in elderly women with osteopenia. In addition, the results suggested the possibility of a decrease in bone mass by hypophosphatemia in elderly women.     

Paternity of subordinates raises cooperative effort in cichlids

Background

In cooperative breeders, subordinates generally help a dominant breeding pair to raise offspring. Parentage studies have shown that in several species subordinates can participate in reproduction. This suggests an important role of direct fitness benefits for cooperation, particularly where groups contain unrelated subordinates. In this situation parentage should influence levels of cooperation. Here we combine parentage analyses and detailed behavioural observations in the field to study whether in the highly social cichlid Neolamprologus pulcher subordinates participate in reproduction and if so, whether and how this affects their cooperative care, controlling for the effect of kinship.

Methodology/Principal Findings

We show that: (i) male subordinates gained paternity in 27.8% of all clutches and (ii) if they participated in reproduction, they sired on average 11.8% of young. Subordinate males sharing in reproduction showed more defence against experimentally presented egg predators compared to subordinates not participating in reproduction, and they tended to stay closer to the breeding shelter. No effects of relatedness between subordinates and dominants (to mid-parent, dominant female or dominant male) were detected on parentage and on helping behaviour.

Conclusions/Significance

This is the first evidence in a cooperatively breeding fish species that the helping effort of male subordinates may depend on obtained paternity, which stresses the need to consider direct fitness benefits in evolutionary studies of helping behaviour.     

ADI1, a methionine salvage pathway enzyme,is required for Drosophila fecundity

Background

Methionine, an essential amino acid, is required for protein synthesis and normal cell metabolism. The transmethylation pathway and methionine salvage pathway (MTA cycle) are two major pathways regulating methionine metabolism. Recently, methionine has been reported to play a key role in Drosophila fecundity.

Results

Here, we revealed that the MTA cycle plays a crucial role in Drosophila fecundity using the mutant of aci-reductone dioxygenase 1 (DADI1), an enzyme in the MTA cycle. In dietary restriction condition, the egg production of adi1 mutant flies was reduced compared to that of control flies. This fecundity defect in mutant flies was rescued by reintroduction of Dadi1 gene. Moreover, a functional homolog of human ADI1 also recovered the reproduction defect, in which the enzymatic activity of human ADI1 is required for normal fecundity. Importantly, methionine supply rescued the fecundity defect in Dadi1 mutant flies. The detailed analysis of Dadi1 mutant ovaries revealed a dramatic change in the levels of methionine metabolism. In addition, we found that three compounds namely, methionine, SAM and Methionine sulfoxide, respectively, may be required for normal fecundity.

Conclusions

In summary, these results suggest that ADI1, an MTA cycle enzyme, affects fly fecundity through the regulation of methionine metabolism.     

Do plants adjust their sex allocation and secondary sexual morphology in response to their neighbours?

Background and aims

Changes in the sex allocation (i.e. in pollen versus seed production) of hermaphroditic plants often occur in response to the environment. In some homosporous ferns, gametophytes choose their gender in response to chemical cues sent by neighbours, such that spores develop as male gametophytes if they perceive a female or hermaphrodite nearby. Here it is considered whether a similar process might occur in the androdioecious angiosperm species Mercurialis annua, in which males co-occur with hermaphrodites; previous work on a Spanish population of M. annua found that individuals were more likely to develop as males at high density.

Methods

Using a novel approach to treat plants with leachate from pots containing males or hermaphrodites of M. annua, the hypothesis that individuals assess their mating opportunities, and adjust their sex expression accordingly, was tested through an exchange of chemical cues through the soil.

Key Results

For the population under study, from Morocco, no evidence was found for soil-signal-dependent sex expression: neither sex ratios nor sex allocation differed among experimental treatments.

Conclusions

The results imply either that the Moroccan population under study behaves differently from that previously studied in Spain (pointing to potential geographical variation in plasticity for sex expression), or that our method failed to capture the signals used by M. annua for adjustment of sex expression.