Genetic and hormonal factors affecting superovulation

Prolific sheep breeds provide the best example of genetic effects on ovarian function that are relevant to the problems of superovulation of domestic livestock. Some of these animals superovulate without any treatment. Their ovaries have been deregulated from the feed-back control systems that normally restrict ovulation rate of sheep and cattle to 1 or 2. The study of prolific sheep highlights the roles of ovarian follicle number, follicle morphology, follicle recruitment, plasma FSH concentrations, inhibin and follicle growth inhibitor in achieving high ovulation rates. These are discussed in relation to the problems of superovulation.Prolific sheep are generally more sensitive to PMSG than other breeds but this may not apply to exogenous FSH. Prolific cattle genotypes, although at an early stage of development, could provide useful guidelines for superovulation in the future. Preliminary data show that they are more sensitive to the ovulatory effect of PMSG and FSH than unselected cattle. Sheep and cattle actively immunized against inhibin or ovarian steriods may be more responsive to treatments designed to induce superovulation. Recent advances in the purification of inhibin and realization of the significance of a locally acting follicle growth inhibitor should result in new developments in this field.     

影响猪肉嫩度的遗传因素

嫩度是猪肉品质的一个重要方面。影响猪肉嫩度的因素很多,遗传因素是改善猪肉嫩度的关键。本对肌纤维性状、钙蛋白酶蛋白水解系统和肌内脂肪的有关基因进行了论述,包括MyoD基因家族、钙调蛋白激酶(CaMK)基因、钙激中性蛋白酶(CAPN)基因、钙蛋白酶抑制蛋白(CAST)基因、心脏脂肪酸结合蛋白(H-FABP)基因、脂肪组织脂肪酸结合蛋白(F一FABP)基因、过氧化氢酶体激活增殖受体（PPARγ)基因以及与肌内脂肪有关的QTL。其中有些已被认为是肉嫩度的候选基因。对改善猪肉嫩度所面临的问题及研究前景进行了讨论。     

Development of ChillPeach genomic tools and identification of cold-responsive genes in peach fruit

The ChillPeach database was developed to facilitate identification of genes controlling chilling injury (CI), a global-scale post-harvest physiological disorder in peach. It contained 7,862 high-quality ESTs (comprising 4,468 unigenes) obtained from mesocarp tissues of two full-sib progeny contrasting for CI, about 48 and 13% of which are unique to Prunus and Arabidopsis, respectively. All ESTs are in the Gateway vector to facilitate functional assessment of the genes. The data set contained several putative SNPs and 184 unigenes with high quality SSRs, of which 42% were novel to Prunus. Microarray slides containing 4,261 ChillPeach unigenes were printed and used in a pilot experiment to identify differentially expressed genes in cold-treated compared to control mesocarp tissues, and in vegetative compared to mesocarp tissues. Quantitative RT-PCR (qRT-PCR) confirmed microarray results for all 13 genes tested. The microarray and qRT-PCR analyses indicated that ChillPeach is rich in putative fruit-specific and novel cold-induced genes. A website ( http://bioinfo.ibmcp.upv.es/genomics/ChillPeachDB ) was created holding detailed information on the ChillPeach database.     

Genetic and environmental factors affecting chiasma formation in locusts

By means of crosses with the African Migratory locust it has been demonstrated that various strains carry different segregations of genes which quantitatively condition the formation of chiasmata during meiosis. These genes occur in polygenic series, and in one low frequency strain the polygenes show an epistatic effect for low chiasma frequency, while another low frequency strain seems to have attained this property through gamma radiation. In reciprocal crosses between the lastnamed low and a medium frequency strain there appears to be a maternal effect, with heterosis and epistasis respectively in the reciprocal crosses. In one strain two lines were selected for plasticity and non-plasticity of hopper colour change in small populations, and this selection has resulted in multiple changes in that the two lines now diverge in the three main physical criteria of phase transformation, viz. hopper colour, adult morphometric ratios and chiasma frequencies; one line is now solitarious for these characteristics, the other more gregarious. The genotypes selected out could be related to the ability to utilize the gregarization pheromone.A 10° rise in temperature above 22° C has the effect of increasing chiasma frequencies significantly, but increase in the carbon dioxide content of the atmosphere has no effect. Male and female hoppers produce equivalent amounts of the chiasma-inducing pheromone, while solitarised hoppers do not lose the ability to produce this pheromone. The crucial stage for the action of this pheromone on chromosomes is during the fifth nymphal instar. The phase status of parents appears to affect chiasma frequencies in the offspring, more specifically that of the mother, so that there is further evidence of maternal effect on chiasma frequency.     

影响柑桔树开花结果性能的生态生理因素

本文报道1988年和1989年春夏之际异常和正常的桔园小气候环境对柑桔树开花结果物候期、抽梢生长、幼果发育、生理落果、当年果实产量和品质等性能的影响。结果表明,柑桔树的座果率受许多生态生理因素制约,但第一次生理落果主要与开花期桔园的小气候环境有关,第二次生理落果则与树体营养生理代谢密切相关。据此提出了预测预报柑桔树第二次生理落果的指标及其防御措施。     

Genetic factors affecting normal growth of testes inDrosophila hydei

Summary A marked growth in the length of testes ofDrosophila hydei males occurred during pupal development. This growth continued over the first 8 days of adult life and in the young adults sperm were not produced until the testes increased approximately threefold in length to about 28 mm. The length of testes is correlated with genetic factors on the X and Y chromosomes. In males lacking a Y chromosome (X/O) or the short arm (Y^S) of the Y chromosome (X/Y^L) the testes were about half the length of testes of control males (X/Y) or double Y males (X/Y/Y). Males with deletions of the distal Y^L chromosome arm had testicular lengths equivalent to the controls. Males with short testes (X/O and X/Y^L) showed disruptions to spermatogenesis at meiosis and an absence of normal spermatid elongation. Reduction of active ribosomal RNA genes on the X chromosome in X/O caused an increased expression ofbobbed (bb) and a corresponding reduction in length of testes. Severelybobbed X/O males had very few cysts of spermatogonia and these cysts did not develop into primary spermatocytes.     

Gender specialization and factors affecting fruit set of the wind-pollinated heterodichogamous Juglans regia

Gender expression, flowering phenology, reproductive performance and factors affecting fruit set (i.e., flowering synchrony, size and distance to the nearest pollen donor) were investigated in a cultivated population of a wind-pollinated self-compatible heterodichogamous Juglans regia (Juglandaceae). Four flowering morphs, (i.e., protandrous, protogynous, male and female) were observed. The sexual functions of the protandrous and protogynous morphs were almost synchronous; however, they were not reciprocal, and the separation of male and female flowering within most monoecious individuals was not complete. Thus, within-morph mating and geitonogamous pollination may be common. The ratio of protandrous versus protogynous morphs was biased towards the protandrous morph, but the fruit set did not differ between the morphs, suggesting that the fruit set of the protandrous morph could be partly compensated by within-morph pollination. The ratio of the female flower number or fruit number to the total male catkin length was higher in the protogynous morph than in the protandrous morph and did not vary with plant size, suggesting that gender variation was not size dependent and that the sexual function of protandrous morphs was more male biased. Fruit set depended on plant size only for protandrous morphs. The fruit set of individual plants decreased with increasing distance to the nearest pollen donor regardless of morph, possibly because of pollen limitation. The fruit set of individual plants increased with flowering synchrony, indicating that flowering synchrony could affect reproductive success.     

Genetic and environmental factors affecting reproductive variation in Allium vineale

Traits related to allocation of resources to sexual and asexual reproduction, together with seed production, were scored on Allium vineale plants sampled from five sites in southern Sweden during a period of 4 years. In addition, random amplified polymorphic DNA (RAPD) fingerprinting of the sampled plants allowed the identification of genets. Integration of genetic and phenotypic data from field and greenhouse provided for the analysis of among‐year, among‐site, and among‐genet variance components. These variance components were taken to represent the influences of short‐term environmental changes, persistent site divergence, and within‐site genet differences, respectively. It was shown that differences among sites and among genets explained a large part of the phenotypic variation of allocation traits, whereas among‐year differences had a larger influence on the variation in seed production. Together, the results support the conclusions of a recent model on the evolution of mixed reproductive systems, that predicts a stable balance between sexual and asexual reproduction because of annual fluctuations in fecundity through the two modes.     

Fruit characteristics and factors affecting fruit removal in a Panamanian community of strangler figs

We describe fruiting characteristics for 12 species in a community of strangler figs (Moraceae: Urostigma) studied in Panama. We quantify diurnal and nocturnal removal rates and proportions of fruits removed, and relate them to the activities of the main dispersers of the figs: bats and birds. These results combined with previous studies show that there are clear differences between fig species with fruit that ripen red and those with fruit that remain green(ish). In the red-fruited species, the fruit are small, ripen asynchronously over relatively long periods, produce little scent, and are mainly taken during the day by birds. In contrast, in the green(ish)-fruited species, the fruits are larger, span a range of sizes, ripen relatively synchronously, produce very distinctive aromas, and are mainly taken at night by bats. This dichotomy in fruiting characteristics suggests coadaptive links between groups of dispersers and different species within the genus Ficus. All fig species produce a range of fruit crop sizes (10–155 fuits/m² canopy area) of which a high proportion were removed by seed dispersers (>80%). Removal rates (fruit removed per day) were positively correlated with crop size, suggesting that trees with large crop size attract more frugivores. Removal rates of green-fruited figs were significantly lower and persistence and abortion of ripe fruit were significant higher around full moon, apparently due to the reduced activity of bats. We further estimate the number of bats that are sustained by a tree fruit crop and account for the observed fruit removal. We then discuss the evidence for coadaptation between different groups of figs and their seed dispersers, Finally, we consider the conservation implications for figs as keystone resources in tropical forests. Received: 26 April 1999 / Accepted: 10 January 2000     

Genetic factors affecting HDL levels, structure, metabolism and function

PURPOSE OF REVIEW: HDL is a recognized negative risk factor for the cardiovascular diseases. Establishing the genetic determinants of HDL concentration and functions would add to the prediction of cardiovascular risk and point to the biochemical mechanisms underlying this risk. The present review focuses on various approaches to establish genetic determinants of the HDL concentration, structure and function. RECENT FINDINGS: While many genes contribute to the HDL concentration and collectively account for half of the variability, polymorphism of individual candidate genes contributes little. There are strong interactions between environmental and genetic influences. Recent findings have confirmed that APOA1 and ABCA1 exert the strongest influence on HDL concentrations and risk of atherosclerosis. CETP and lipases also affect the HDL concentration and functionality, but their connection to the atherosclerosis risk is conditional on the interaction between environmental and genetic factors. SUMMARY: Analysis of genetic determinants of HDL-cholesterol in patients with specific disease states or in response to the environmental condition may be a more accurate way to assess variations in HDL concentration. This may result in defining the rules of interaction between genetic and environmental factors and lead to understanding the mechanisms responsible for the variations in HDL concentration and functionality.     

Genetic and non-genetic factors affecting birth-weight and adult Body Mass Index.

Birthweight affects neonatal mortality and morbidity and has been used as a marker of foetal undernutrition in studies of prenatal effects on adult characteristics. It is potentially influenced by genetic and environmental influences on the mother, and effects of foetal genotype, which is partially derived from the maternal genotype. Interpretations of variation in birthweight and associated characteristics as being due to prenatal environment ignore other possible modes of materno-foetal transmission. Subjects were adult twins recruited through the Australian Twin Registry, aged 17 to 87 years, and the sample comprised 1820 men and 4048 women. Twins reported their own birthweight as part of a health questionnaire. Body Mass Index (BMI) was calculated from self-reports of height and weight. Correlations between co-twins' birthweights were high for both monozygotic (r = 0.77) and dizygotic (r = 0.67) pairs, leading to substantial estimates of shared environmental effects (56% of variance) with significant additive genetic (23%) and non-shared environmental (21%) components. Adult BMI was mainly influenced by genetic factors, both additive (36% of variance) and nonadditive (35%). The correlation between birthweight and BMI was positive, in that heavier babies became on average more obese adults. A bivariate model of birthweight and adult BMI showed significant positive genetic (r(g) = 0.16, p = 0.005) and environmental (r(e) = 0.08, p = 0.000011) correlations. Intra-uterine environmental or perinatal influences shared by cotwins exercise a strong influence on birthweight, but the factors which affect both birthweight and adult BMI are partly genetic and partly non-shared environmental.     

Effects of chilling on tomato fruit texture

The effects of chilling on tomato ( Lycopersicon esculentum Mill cv. Caruso) texture were investigated using fruit stored at 22°C (nonchilled) or 5°C (chilled) for 28 days. or at 5°C for 15 days before transfer to 22°C to facilitate ripening during and additional 13 days (prechilled). Prechilled fruit exhibited symptoms of slight chilling injury, i.e. development of mealiness, accelerated softening relative to that of nonchilled fruit and nonuniform surface colour development. The firmness of all fruit decreased during ripening and chilled storage when measured by flat plate compression and puncture, especially during the early stages of ripening of nonchilled and prechilled fruit. The compression firmness of pericarp tissue similarly decreased during ripening of nonchilled and prechilled fruit, but was maintained during chilling. Total moisture content (ca 94%) of tissue, uronide content (32-35% w/w) and extracted β-galactosidase activity did not differ significantly ( P > 0.05) among fruit during ripening and chilled storage. The degree of uronide methyl esterification in ethanol-insoluble solids prepared from pericarp tissue (EIS) was relatively low for all fruit. i.e. <40%. EIS from which greater levels of pectinesterase were extracted (i.e. nonchilled>chilled>prechilled) exhibited decreased levels of uronide methyl esterification. Markedly elevated levels of β-glucosidase activity were extracted from prechilled EIS. Total polygalacturonase activity (mainly as PGI) and autolysis of enzyme-extracted EIS were inversely correlated ( P ≤ 0.05) only with the loss of nonchilled fruit and tissue firmness and prechilled fruit firmness. Results suggest a possible role for β-glucosidase in textural changes of prechilled fruit and tissue (e.g. loss of firmness, development of mealiness) and also implicate loss of skin strength in the softening of whole fruit during chilling.     

Genetic factors affecting maize tolerance to low temperatures at emergence and germination

Summary On the basis of the percentage of plants emerging under laboratory cold-test conditions, inbred lines were divided into tolerant (T), semi-tolerant (I) and sensitive (S) to low temperatures. Tolerance to low temperature is, then, an inheritable and varietal plant characteristic.On average, local varieties showed the best emergence, followed by double crosses, single crosses and inbred lines in that order. Some tolerant hybrids and inbred lines had quite high emergence after 27 days at 6 °C. Thus the tolerant inbred lines Bc-130 E-5 and T-193/II had more emerged seeds (78 and 75% with embryo roots and 52 and 47% with stalk apices, respectively) with longer embryo roots and stalk apices than the sensitive inbred lines T-145/11 and W-8 at the end of this treatment.The two-year average emergence of 56 reciprocal single crosses and their parental inbred lines cold-tested at 6 °C and 8 °C indicates that the degree of tolerance to low temperatures is strongly dependent on the germination ability of the maternal parent of the cross, i. e. on maternal effect. The genetic mechanism of this inheritance is rather complex. The higher stand density of single crosses over inbred lines may be explained by complementary gene action in the seed embryo. The characteristics of the maternal parent were important in determining not only the percentage of germinated plants, but also the speed of germination and growth of the embryo root and stalk apex. With each parental inbred line the percentage emergence differed according to whether the line was used as the maternal or pollen parent in the crosses.     

Genetic and epigenetic factors affecting blastomere fragmentation in two-cell stage mouse embryos

We report here that mouse embryos can exhibit a significant incidence of blastomere fragmentation at the two-cell stage. The incidence of this is influenced by both the maternal and paternal genotype. Embryos from C57BL/6 mothers exhibit a very low incidence of fragmentation at the two-cell stage in crosses involving males of C57BL/6, DBA/2, AKR/J, or SJL strains but exhibit a significantly increased incidence of fragmentation in crosses involving C3H/HeJ males. Increased fragmentation is seen in embryos from C3H/HeJ females crossed with C57BL/6 males but not with C3H/HeJ males. Embryos obtained from reciprocal (C57BL/6 x C3H/HeJ) F1 hybrid females also exhibit an increased incidence of fragmentation at the two-cell stage when the hybrid females are mated to either C57BL/6 or C3H/HeJ males. Interestingly, the results differ significantly between reciprocal F1 hybrid females, indicating a parental origin effect, possibly a result of either genomic imprinting or differences in mitochondrial origin. We conclude that the incidence of blastomere fragmentation at the two-cell stage in the mouse is under the control of more than one genetic locus. We also conclude that blastomere fragmentation is affected by both parental genotypes. These results are relevant to understanding the genetic control blastomere fragmentation, which may contribute to evolutionary processes, affect the success of procedures such as cloning, and affect the outcome of assisted reproduction techniques.