RESUMEN
Clinostats are instruments that continuously rotate biological specimens along an axis, thereby averaging their orientation relative to gravity over time. Our previous experiments indicated that low-speed clinorotation may itself trigger directional root tip curvature. In this project, we have investigated the root curvature response to low-speed clinorotation using Arabidopsis thaliana and Brachypodium distachyon seedlings as models. We show that low-speed clinorotation triggers root tip curvature in which direction is dictated by gravitropism during the first half-turn of clinorotation. We also show that the angle of root tip curvature is modulated by the speed of clinorotation. Arabidopsis mutations affecting gravity susception (pgm) or gravity signal transduction (arg1, toc132) are shown to affect the root tip curvature response to low-speed clinorotation. Furthermore, low-speed vertical clinorotation triggers relocalization of the PIN3 auxin efflux facilitator to the lateral membrane of Arabidopsis root cap statocytes, and creates a lateral gradient of auxin across the root tip. Together, these observations support a role for gravitropism in modulating root curvature responses to clinorotation. Interestingly, distinct Brachypodium distachyon accessions display different abilities to develop root tip curvature responses to low-speed vertical clinorotation, suggesting the possibility of using genome-wide association studies to further investigate this process.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Brachypodium , Arabidopsis/genética , Gravitropismo/fisiología , Plantones/genética , Brachypodium/genética , Meristema , Rotación , Estudio de Asociación del Genoma Completo , Raíces de Plantas/genética , Proteínas de Arabidopsis/genética , Ácidos IndolacéticosRESUMEN
Sixteen volunteers each drank 700 ml sugar-containing soft drink during two successive periods and the blood sugar was measured at 10 min intervals together with electrical impedance spectroscopy and near infrared spectroscopy (NIR). A maximum correlation of 0.46 was found for the electrical measurements but no clear separation between low and high blood glucose levels were found in the NIR measurements. The latter was attributed to the experimental design where the NIR probe was removed from the skin between each measurement.
RESUMEN
The biological role of the mitochondrial DNA (mtDNA) control region in mtDNA replication remains unclear. In a worldwide survey of mtDNA variation in the general population, we have identified a novel large control region deletion spanning positions 16154 to 16307 (m.16154_16307del154). The population prevalence of this deletion is low, since it was only observed in 1 out of over 120,000 mtDNA genomes studied. The deletion is present in a nonheteroplasmic state, and was transmitted by a mother to her two sons with no apparent past or present disease conditions. The identification of this large deletion in healthy individuals challenges the current view of the control region as playing a crucial role in the regulation of mtDNA replication, and supports the existence of a more complex system of multiple or epigenetically-determined replication origins.