Genome-wide association studies in plants: the missing heritability is in the field

Genome-wide association studies (GWAS) have been even more successful in plants than in humans. Mapping approaches can be extended to dissect adaptive genetic variation from structured background variation in an ecological context.     

Comparative studies of the phytochrome system in cell cultures from different plants

Phytochrome contents have been assayed in vivo in cell suspension cultures of Petroselinum hortense, Daucus carota and Glycine max. After transferring the cells to fresh medium phytochrome increased in parallel with the increase in cell number, whereas the amount of phytochrome per cell remained constant. The rate of phytochrome reaccumulation after pretreatment with 15 h red light was very similar in all three systems (2.8–3.6 (e) 10^–5/h). Dark reversion and a fast and slow P_fr destruction were observed in all systems. The rate constants of these reactions varied strongly between the systems. The phytochrome systems of the cell cultures were compared with those of etiolated and light-grown seedlings and it was concluded that the cell suspension cultures of Petroselinum hortense and Daucus carota behaved similarly to light-grown seedlings. In contrast, those of Glycine max behaved similarly to a dark grown seedling.Abbreviations P_r'fr red, far-red absorbing forms of phytochrome - P_tot P_r+P_fr total amount of phytochrome - fwt fresh weight     

Experimental field studies of Asian ape social systems

The Asian apes, orangutans and gibbons, possess unusual social systems among anthropoid primates. Social groups of gibbons consist of mated adult pairs and their offspring; mature orangutans are primarily solitary. Recent experimental field research has begun to yield insights into the behavioral mechanisms employed by these animals to maintain their characteristic patterns of social dispersion. While spatial separation between female orangutans appears to be maintained passively, aggression, which is manifest during direct encounters and long-distance vocal interactions, mediates male asociality. Male-male aggression is the result of intense intrasexual competition occurring between animals for mating access to females. To reduce intrasexual competition, male orangutans have adopted alternative mating tactics. In contrast to female orangutans, female gibbons show marked agonistic tendencies toward conspecifics. Female territoriality contributes to preventing males from becoming polygynous. Male gibbons, restricted to monogamous relationships, attempt to ensure their paternity through intrasexual aggression. These observations suggest that the spatial dispersion of females constrains male mating options in both species. However, variations between orangutan and gibbon social systems can be understood as consequences of the temporal dispersion of sexually receptive females. The temporal clumping of females, due to relatively high operational sex ratios, limits the ability of male gibbons to acquire multiple mates. Conversely, an extremely low operational sex ratio in orangutans creates a strong selection pressure for intrasexual competition and polygamous mating. These considerations provide a novel framework for interpreting the social systems of the African apes.     

Genome-edited plants in the field

1. Download : Download high-res image (82KB)
2. Download : Download full-size image

     

Experimental studies upon a bundle of tonic fibres in the locust extensor tibialis muscle

The bundle of tonic fibres situated at the proximal end of the locust metathoracic extensor tibialis muscle is innervated by the dorsal unpaired median neurone (DUMETi) as well as by the slow excitatory (SETi)) and common inhibitor (CI) neurones. It is not innervated by the fast excitatory neurone (FETi).These fibres contract spontaneously and rhythmically. The myogenic rhythm can be modified by neural stimulation.Spontaneous slow depolarizing potentials resembling the pacemaker potentials of insect cardiac muscle were demonstrated in these fibres.The actions of glutamate on the tonic muscle fibres are not compatible with its being a specific excitatory transmitter. Glutamate can stimulate weak contractions of the muscle, but this action is inhibited when chloride ions are removed from the saline.10^?6 M Octapamine hyperpolarizes the tonic fibre membrane. Octopamine, GABA and glutamate all inhibit the myogenic contractions and reduce the force of the neurally evoked contractions.The tonic muscle is very responsive to proctolin. At 5 × 10^?11 M proctolin enhances the force and increases the frequency of myogenic contractions. At 10^?9 M it depolarizes the muscle membrane potential, and at that and higher concentrations it causes the muscle to contract. At 2 × 10^?7 M proctolin induces contractures which resemble those evoked by sustained high-frequency neural stimulation. Iontophoretic experiments show that proctolin receptors occur at localized sites on the tonic fibre membrane.     

Dependence of synergism of the combined effect of ultrasound and hyperthermia upon intensity of ultrasound

The inactivation of wild-type yeast Saccharomyces cerevisiae was studied after simultaneous treatment with ultrasound and hyperthermia. A temperature range was established within which ultrasound and hyperthermia exert a synergistic action. The effect was shown to depend on ultrasound intensity and the temperature at which the treatment takes place. The temperature range enhancing the ultrasound effect shifted forward higher temperature with increasing ultrasound intensity. For every intensity value, an optimal temperature exists at which the synergetic effect is maximum. The biophysical interpretation of the results obtained is based on the assumption that synergism is due to an additional lethal damage, which arises from the interaction of some sub-lesions induced by both agents. These sublesions are considered non-lethal if the agents are applied separately.     

The theoretical basis and practical application of relationships between different disease intensity measurements in plants

The literature concerning relationships among different measures of plant disease intensity is reviewed. Some previous confusion over the definition of the terms “incidence” and “severity” is noted and clarified. The review highlights the common features of relationships between incidence and severity, incidence and disease density, and incidence at pairs of scales in a spatial hierarchy. These relationships often show a similar saturation curve form that can frequently be described empirically using the complementary log‐log transformation. A catalogue of alternative functional forms is provided. Practical applications in varietal evaluation are discussed.     

Biochemical studies of Aloe vera (Aloe barbadensis Miller) gel of the field grown and micropropagated plants at different developmental stages

The biochemical composition of leaf gel isolated from vegetative and micropropagated Aloe vera plants at different stages of development had been compared. The total sugars, fructose, sucrose and starch were higher in micropropagated leaf gel at all developmental stages. The micropropagated plants have higher α-amylase activity at all stages with maximum at 6 month old. Catalase and peroxidase activities were higher in younger leaves (up to 4 month old) in both types of plants. The calcium and magnesium level increases up to maturity and ranges from 0.19 to 1.12% and 0.02 to 0.10% respectively, in conventionally grown plants whereas it was a little higher in micropropagated plants. Micropropagated plants had 12.5% higher phosphorus levels. The micropropagated plants (1 month old) have 60% higher phenol content as compared to conventional plants. The micropropagated mature plants have 55 and 18.6% higher saponin and sterol contents as compared to conventional plants. The composition of aloe vera gel depends upon the growth stages and method of propagation.