RESUMEN
Light is the most influential environmental stimulus for plant growth. In response to deficient light, plants reprogram their development to adjust their growth in search for a light source. A fine reprogramming of gene expression orchestrates this adaptive trait. Here we show that plants alter microRNA (miRNA) biogenesis in response to light transition. When plants suffer an unusual extended period of light deprivation, the miRNA biogenesis factor HYPONASTIC LEAVES 1 (HYL1) is degraded but an inactive pool of phosphorylated protein remains stable inside the nucleus. Degradation of HYL1 leads to the release of gene silencing, triggering a proper response to dark and shade. Upon light restoration, a quick dephosphorylation of HYL1 leads to the reactivation of miRNA biogenesis and a switch toward a developmental program that maximizes the light uptake. Our findings define a unique and fast regulatory mechanism controlling the plant silencing machinery during plant light response.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Regulación de la Expresión Génica de las Plantas/genética , MicroARNs/metabolismo , Proteínas de Unión al ARN/metabolismo , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Silenciador del Gen , Luz , MicroARNs/genética , Mutación , Fosforilación , Hojas de la Planta/metabolismo , Procesamiento Postranscripcional del ARN/fisiologíaRESUMEN
Root hairs are single cells that develop by tip growth and are specialized in the absorption of nutrients. Their cell walls are composed of polysaccharides and hydroxyproline-rich glycoproteins (HRGPs) that include extensins (EXTs) and arabinogalactan-proteins (AGPs). Proline hydroxylation, an early posttranslational modification of HRGPs that is catalyzed by prolyl 4-hydroxylases (P4Hs), defines the subsequent O-glycosylation sites in EXTs (which are mainly arabinosylated) and AGPs (which are mainly arabinogalactosylated). We explored the biological function of P4Hs, arabinosyltransferases, and EXTs in root hair cell growth. Biochemical inhibition or genetic disruption resulted in the blockage of polarized growth in root hairs and reduced arabinosylation of EXTs. Our results demonstrate that correct O-glycosylation on EXTs is essential for cell-wall self-assembly and, hence, root hair elongation in Arabidopsis thaliana.