RESUMEN
Male and female gametophytes are generated from micro- or megaspore mother cells through consecutive meiotic and mitotic cell divisions. Defects in these divisions often result in gametophytic lethality. Gametophytic lethality was also reported when genes encoding ribosome-related proteins were mutated. Although numerous ribosomal proteins (RPs) have been identified in plants based on homology with their yeast and metazoan counterparts, how RPs are regulated, e.g., through dynamic subcellular targeting, is unknown. We report here that an Arabidopsis (Arabidopsis thaliana) importin ß, KETCH1 (karyopherin enabling the transport of the cytoplasmic HYL1), is critical for gametogenesis. Karyopherins are molecular chaperones mediating nucleocytoplasmic protein transport. However, the role of KETCH1 during gametogenesis is independent of HYPONASTIC LEAVES 1 (HYL1), a previously reported KETCH1 cargo. Instead, KETCH1 interacts with several RPs and is critical for the nuclear accumulation of RPL27a, whose mutations caused similar gametophytic defects. We further showed that knocking down KETCH1 caused reduced ribosome biogenesis and translational capacity, which may trigger the arrest of mitotic cell cycle progression and lead to gametophytic lethality.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Gametogénesis en la Planta , Carioferinas/metabolismo , Proteínas Ribosómicas/metabolismo , Arabidopsis/genética , Arabidopsis/ultraestructura , Puntos de Control del Ciclo Celular , Núcleo Celular/ultraestructura , Regulación hacia Abajo , Regulación de la Expresión Génica de las Plantas , Mutación con Pérdida de Función/genética , Óvulo Vegetal/metabolismo , Óvulo Vegetal/ultraestructura , Polen/crecimiento & desarrollo , Polen/ultraestructura , Unión Proteica , Biosíntesis de Proteínas , Proteínas de Unión al ARN/metabolismo , Ribosomas/metabolismo , Semillas/metabolismo , Semillas/ultraestructuraRESUMEN
Pollen development is a pre-requisite for sexual reproduction of angiosperms, during which various cellular activities are involved. Pollen development accompanies dynamic remodeling of vacuoles through fission and fusion, disruption of which often compromises pollen viability. We previously reported that the Y subunit of adaptor protein 1 (AP1G) mediates synergid degeneration during pollen tube reception. Here, we demonstrate that AP1G is essential for pollen development. AP1G loss-of-function resulted in male gametophytic lethality due to defective pollen development. By ultrastructural analysis and fluorescence labeling, we demonstrate that AP1G loss-of-function compromised dynamic vacuolar remodeling during pollen development and impaired vacuolar acidification of pollen. Results presented here support a key role of vacuoles in gametophytic pollen development.