Germ Granules Govern Small RNA Inheritance

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Molecular insights into the transgenerational inheritance of stress memory

There is accumulating evidence to show that environmental stressors can regulate a variety of phenotypes in descendants through germline-mediated epigenetic inheritance. Studies of model organisms exposed to environmental cues (e.g., diet, heat stress, toxins) indicate that altered DNA methylations, histone modifications, or non-coding RNAs in the germ cells are responsible for the transgenerational effects. In addition, it has also become evident that maternal provision could provide a mechanism for the transgenerational inheritance of stress adaptations that result from ancestral environmental cues. However, how the signal of environmentally-induced stress response transmits from the soma to the germline, which may influence offspring fitness, remains largely elusive. Small RNAs could serve as signaling molecules that transmit between tissues and even across generations. Furthermore, a recent study revealed that neuronal mitochondrial perturbations induce a transgenerational induction of the mitochondrial unfolded protein response mediated by a Wnt-dependent increase in mitochondrial DNA levels. Here, we review recent work on the molecular mechanism by which parental experience can affect future generations and the importance of soma-to-germline signaling for transgenerational inheritance.     

The significance of specific distributions and functions in models of quantitative inheritance

The main purpose of this paper is to attract attention to the fact that a mathematical model of quantitative inheritance can lead to qualitatively different results, if distributions and functions which in the model represent biological processes are assumed to take analytically different (even though qualitatively similar) forms. A simple model of the effect of environmental variation on the post-selection genotypic variance in a population under phenotypic stabilizing selection is considered. It is demonstrated that this model leads to qualitatively different conclusions depending on whether the phenotypic fitness function is assumed in a Gaussian or in a quadratic form.     

Quantitative cytology of the alfalfa generative cell and its relation to male plastid inheritance patterns in three genotypes

Summary Studies utilizing restriction analysis of plastid DNA, as well as those employing chlorophyll-deficient mutants, have shown a high frequency of paternal plastid transmission in alfalfa. Recent research has also shown that plastid inheritance patterns among alfalfa genotypes and are under genetic control. In a previous study we were unable to detect any correlations between qualitative, three-dimensional ultrastructure of generative cells and male plastid transmission strength in certain genotypes. In the present study we used serial ultrathin sectioning, computerized reconstruction and quantitation, and stereology to further analyze generative cells within mature pollen. Measurements included volumes and surface areas of cells, nuclei, and organelles, as well as organelle number and distribution. Three genotypes were investigated, one that is a strong transmitter of male plastids (genotype 301), one that is a weaker transmitter of male plastids (genotype 7W), and a third that is an even weaker male plastid transmitter (genotype MS-5). Our results show that genotype MS-5 has significantly fewer plastids/generative cell than either of the other genotypes, which may account for it being a relatively poor transmitter of male plastids. However, plastid number does not explain known differences in male plastid inheritance between genotypes 301 and 7W, since plastid number does not differ significantly between these two genotypes. Regarding the other features of generative cells measured in this study, no consistent correlations were found that might account for differences in male plastid inheritance patterns between genotypes. Plastid distribution is equal in each end of the spindle-shaped generative cell in all genotypes studied. Similar relative results were found with regard to mitochondria within generative cells; however, comparative genetic data are not available on mitochondrial transmission patterns in alfalfa genotypes.     

云南松半同胞家系初期子代测定

对收集的云南松（Ｐｉｎｕｓ　ｙｕｎｎａｎｅｎｓｉｓ）２９２个半同胞家系进行栽培试验,经方差分析知各家系子代间高生长有极显著差异,真正的优树占参试总数的２９．７％（广西）;树高广义遗传力为５８．０％,遗传增益为３８．８９％;同一林分内家系间高生长变异幅度小于林分之间的变异幅度。     

Muscle determinants in the ascidian egg are inactivated by UV irradiation and the inactivation is partially rescued by injection of maternal mRNAs

The ascidian egg contains cytoplasmic determinants that specify the fate of larval muscle cells. In a previous study, we developed an experimental system to identify the molecular nature of muscle determinants, in which unfertilized Ciona savignyi eggs were fragmented into four pieces by centrifugation. When inseminated, only nucleated fragments (red fragments) develop into partial embryos that only show differentiation of epidermal cells. One type of enucleated fragment (black fragment) has the remarkable ability to promote muscle differentiation when fused with red fragments. In the present study, using this experimental system, we investigated the molecular nature of muscle determinants. UV irradiation of black fragments suppressed the ability to promote expression of the muscle-specific protein, myosin heavy chain. The wavelength of UV light responsible for the inactivation (250–275 nm) suggested that UV-sensitive targets are nucleic acids. Injection of poly(A)⁺ RNA isolated from an un-irradiated black-fragment-rich fraction into UV-irradiated black fragments partially recovered the ability to promote the expression of myosin heavy chain protein. Poly(A)⁺ RNA from a red-fragment-rich fraction did not rescue the suppression of UV-irradiated black fragments. These results suggest that maternal mRNAs enriched in black fragments are closely associated with muscle determinants in the ascidian egg.     

Pre-laying nutrition mediates maternal effects on offspring immune capacity and growth in the pied flycatcher

We have aimed at detecting prelaying maternal effects on nestling antibody defences and growth through experimental food supplementation of female pied flycatchers Ficedula hypoleuca and subsequent exchange of whole clutches with control nests. The levels of immunoglobulins and the mass and size of chicks at 12 days of age were ascertained. This is the first study controlling for maternal incubation effects by exchanging eggs rather than nestlings. Our prediction is that the females' availability of pre-laying nutritional resources affects offspring immune capacity and growth through maternal effects in the eggs when conditions during incubation and rearing are controlled for. Nestling immunoglobulin Y (IgY) levels and tarsus length were indeed positively associated with maternal food supplementation at laying. The only rearing environmental effect detected was that of mite infestation which affected both IgY levels and growth of nestlings. Nestlings that recruited to the population in the subsequent 2 years had higher IgY levels than those that did not. Maternal adaptations for allocating resources to eggs play an important role in moulding offspring phenotypes and may affect their survival prospects.     

Childhood influences on youth obesity

We develop a model to estimate the influence of child and parental characteristics on the likelihood that a child will become an obese or overweight youth. We use this model to test whether it is possible to forecast obesity and overweight among youth. Comparing Receiver Operating Characteristic (ROC) scores from these forecasts, we find that a model using childhood covariates does as well in forecasting youth obesity and overweight as a model using the covariate values contemporaneous with the youth obesity and overweight outcomes. The datasets used in this paper, the National Longitudinal Survey of Youth (NLSY79) and the NLSY79 Children and Young Adults, provide data from 1986 to 2002, allowing for the study of a child's transition to and from obesity or overweight over a long period. Explanatory variables that significantly influence the likelihood of youth obesity or overweight outcomes include the mother's obesity status and education, the youth's mental health, and certain demographic features including race, sex, and family size. These factors provide potential targets for policies that could be implemented early in life among children most likely to become obese or overweight.