Intensive RNAi with lentiviral vectors in mammalian cells

RNAi is a powerful technology for analyzing gene function in human cells. However, its utility can be compromised by inadequate knockdown of the target mRNA or by interpretation of effects without rigorous controls. We review lentiviral vector-based methods that enable transient or stable knockdowns to trace mRNA levels in human CD4+ T cell lines and other targets. Critical controls are reviewed, including rescue of the pre-knockdown phenotype by re-expression of the targeted gene. The time from thinking about a potential knockdown target to analysis of phenotypes can be as short as a few weeks.     

A Requirement for Argonaute 4 in Mammalian Antiviral Defense

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Evolution of parental care in dart poison frogs (Amphibia: Anura: Dendrobatidae)

Dendrobatid frogs perform a unique mode of parental care, ranging from egg attendance and tadpole transport to tadpole feeding. It is hypothesized that a behaviour in which the egg attending parent remains with the cluch is the most primitive condition. In more advanced forms or parental care, the male is able to attend several clutches of eggs. Tadpole attendance and feeding, finally, started as deceit; the male induced the female to lay eggs into a bromeliad leaf axil already occupied by a larva. Costs and benefits of the different modes of parental care and possible alternative reproductive tactics are discussed.     

Identification of superior parents in a potato breeding programme

Summary An incomplete diallel cross was used to study components of genetic variation in potatoes for a range of characters after early and late harvest. The progenies were also used to evaluate five predictors of progeny performance, namely the mean seedling performance, the mid-parent value and the means of the selfed progenies, of the diploid progenies and of the test-cross progenies. For almost all characters, the general combining ability effects were predominant, although the specific combining ability effects present were greater at late than at early harvests. The seedling performance for tuber yield, number of tubers and average tuber weight did not show any relevant relationship to the field performance. The midparent value provided, in general, satisfactory predictions of the mean progeny performance obtained in the diallel, except for ware tuber yield. The selfed and the diploid progenies did not improve the prediction of progeny means compared to the mid-parent value. The predictions based on the test-crosses surpassed those of the mid-parent value, particularly for tuber yield at ware potato harvest. Methods to identify superior parents are discussed.     

Examination of the influences of density pressure on the pattern of adult emergence with reference to the azuki bean weevil,Callosobruchus chinensis

Summary The effect of competition pressure on the sequential pattern of adult emergence was studied by using the experimental population of the azuki bean weevil. The density and pattern of emergence curves of the parental adult induced the changes in the shape of emergence curve of the progeny as well as the number of progeny individuals. In order to explain these changes, a simple mathematical model which has two independent variables, the population density and the capacity of environment, was introduced. The model generated basically similar patterns of emergene curves as observed in the present experiments. This means that the model displayed well the competition pressure which differentially acted upon early-born and late-born individuals in the populations being at different densities and which were differentially received by individual progeny according to the sequential distributions of parents. This different severity of competition pressure resulted in the difference of time when the pressure compelled influences on the sequential distribution of adult emergence. Therefore, early developed individuals may have good chance to survive, but the competition pressure works as a factor modifying their fundamental superiority, especially in the scramble type of competition. Intense crowding of the azuki bean weevil gave rise to the scramble type of competition in the relation between the numbers of adults emerged in two successive generations. When parental emergence concentrated in a short term and at high density, the competition becomes intense, resulting in the inferiority of early developed individuals, in the decrease in number at the next generation and in the increase of duration for emergence.     

Effects of the d 2 dwarfing gene in pearl millet

Summary Dwarf varieties have had virtually no impact on the production of pearl millet, in contrast to the case of wheat, rice, and sorghum. This research compared tall and dwarf near-isogenic F₁ hybrids to attempt to determine if there were deleterious effects of the d ₂ dwarfing gene that might account for the lack of release/cultivation of dwarf pearl millet cultivars. Dwarf isohybrids on average yielded less than the tails, because of a smaller average seed size combined with a similar grain number per unit area. There was, however, a larger contribution of background genetic variation (pollinator, male-sterile, and interaction effects) to hybrid variation for nearly all characters measured, including seed size, than there was of the dwarfing gene. Selection of dwarf parents capable of producing hybrids with equal seed size and yield to that of tall parents should not be difficult.Journal article no. 1469 of the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, A.P. 502 324, India     

The benefit to some minnows of spawning in the nests of other species

Synopsis Fishes that act as nest associates spawn simultaneously with nest-building hosts and then abandon their eggs. The proposed benefit for this behavior is increased brood survivorship, arising from the physical environment provided by the nest or the parental care provided by the host. Field and enclosure experiments indicated that associates benefit from the parental care provided by the host, and not from the physical environment provided by the nests of hosts. This information, along with the effect of nest association on host reproductive success, is necessary before the nature of this nesting symbiosis can be characterized.     

Brood size and the cost of provisioning nestlings: interpreting Lack's hypothesis

A recent model of parental provisioning (the tradeoff model) suggests that the maximum delivery rate of food to nestlings represents a tradeoff between parental residual reproductive value and nestling survival. In contrast, Lack's hypothesis suggests that maximum provisioning rate determines brood size and therefore delivery rates are limited by shortages of food or foraging time, not by tradeoffs of parental investment. Several authors have examined the shape of the per-nestling feeding curves to test the tradeoff model against Lack's hypothesis. We show that Lack's hypothesis can produce per-nestling feeding curves consistent with the tradeoff model. Therefore, the shape of the per-nestling feeding curve cannot be used to distinguish between the models.     

植物多基因干扰载体体系构建与效用分析

多数重要的功能基因属于多基因家族,这些家族成员间存在功能冗余,高效的多基因干扰体系对研究多基因家族成员的生物学功能及其分子调控机制具有重要意义。对pCAMBIA1301载体改造,构建了适用于植物的多基因干扰体系pCAMBIA1301m和pCAMBIA1301s。使用该多基因干扰体系构建了四基因的干扰载体pCAMBIA1301m：35S∷SlPP2C1-2-3-4,4个目标基因为来源于番茄PP2C家族A组的PP2C1、PP2C2、PP2C3和PP2C4,并通过遗传转化导入番茄,用GUS染色和PCR检测转基因阳性植株,再利用RT-qPCR技术检测T₁和T₂代转基因植株中目标基因的干扰效率,用T₂代种子分析转基因番茄对ABA敏感性。结果表明,应用该干扰体系成功获得了四基因干扰的转基因植株35S∷SlPP2C1-2-3-4。在转基因番茄中4个目标基因的表达量显著低于野生型,其干扰效率均高于70%,转基因番茄种子萌发具有强烈的ABA不敏感性。多基因干扰体系能高效地同时沉默多个目标基因。     

Reproductive and subsocial behaviour in the ovoviviparous leaf beetle Gonioctena sibirica (Coleoptera: Chrysomelidae)

Abstract.

• 1 In the spring, females of the leaf beetle Gonioctena sibirica deposited larvae on the ventral surface of growing young leaves situated on the apical position of shoots of the willow Salix bakko.
• 2 The parent females remained with the larvae usually on the underside of the basal part of leaves, facing toward the base of shoots. When other arthropods approached, the females temporarily moved towards these intruders, showing aggressive behaviour such as swinging the body or stamping the legs. Many females remained with their larvae until the larvae grew into the final (fourth) instar. No female produced an additional brood in the field.
• 3 Broods from which parent females were experimentally removed suffered higher mortality than those in which females were left intact. Arthropods such as spiders and ants were observed preying on the larvae. In contrast, the survivorship of broods from which females were removed and intruders were excluded with a sticky substance applied to the base of twigs was not different from that of control broods. These results demonstrate that the main mortality factor of offspring is pedestrian arthropod predators and females physically repel the predators.
• 4 Potentially alternative reproductive strategies, such as producing a large number of offspring by iteroparity and/or larger brood(s) with less or no care, seem to be inhibited in G.sibirica by larval dependence on growing young leaves which are temporally limited and by ovoviviparity which may have limited brood size.