RESUMEN
In plants, aerial organs originate continuously from stem cells in the center of the shoot apical meristem. Descendants of stem cells in the subepidermal layer are progenitors of germ cells, giving rise to male and female gametes. In these cells, mutations, including insertions of transposable elements or viruses, must be avoided to preserve genome integrity across generations. To investigate the molecular characteristics of stem cells in Arabidopsis, we isolated their nuclei and analyzed stage-specific gene expression and DNA methylation in plants of different ages. Stem cell expression signatures are largely defined by developmental stage but include a core set of stem cell-specific genes, among which are genes implicated in epigenetic silencing. Transiently increased expression of transposable elements in meristems prior to flower induction correlates with increasing CHG methylation during development and decreased CHH methylation, before stem cells enter the reproductive lineage. These results suggest that epigenetic reprogramming may occur at an early stage in this lineage and could contribute to genome protection in stem cells during germline development.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Metilación de ADN , Elementos Transponibles de ADN/genética , Brotes de la Planta/metabolismo , Células Madre/metabolismo , Células Madre Germinales Adultas/metabolismo , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/genética , Núcleo Celular/genética , Núcleo Celular/metabolismo , Epigénesis Genética , Epigenómica , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas/genética , Ontología de Genes , Silenciador del Gen , Estudio de Asociación del Genoma Completo , Meristema/genética , Meristema/crecimiento & desarrollo , Meristema/metabolismo , Brotes de la Planta/crecimiento & desarrollo , Análisis de Componente Principal , RNA-SeqRESUMEN
Maintenance of blood vessel integrity is crucial for vascular homeostasis and is mainly controlled at the level of endothelial cell (EC) junctions. Regulation of endothelial integrity has largely been investigated in the mature quiescent vasculature. Less is known about how integrity is maintained during vascular growth and remodeling involving extensive junctional reorganization. Here, we show that embryonic mesenteric blood vascular remodeling is associated with a transient loss of venous integrity and concomitant extravasation of red blood cells (RBCs), followed by their clearance by the developing lymphatic vessels. In wild-type mouse embryos, we observed activated platelets extending filopodia at sites of inter-EC gaps. In contrast, embryos lacking the activatory C-type lectin domain family 1, member b (CLEC1B) showed extravascular platelets and an excessive number of RBCs associated with and engulfed by the first lymphatic EC clusters that subsequently form lumenized blood-filled vessels connecting to the lymphatic system. These results uncover novel functions of platelets in maintaining venous integrity and lymphatic vessels in clearing extravascular RBCs during developmental remodeling of the mesenteric vasculature. They further provide insight into how vascular abnormalities characterized by blood-filled lymphatic vessels arise.