RESUMEN
WHIRLY1 is a chloroplast-nucleus located DNA/RNA-binding protein with functions in development and stress tolerance. By overexpression of HvWHIRLY1 in barley, one line with a 10-fold and two lines with a 50-fold accumulation of the protein were obtained. In these lines, the relative abundance of the nuclear form exceeded that of the chloroplast form. Growth of the plants was shown to be compromised in a WHIRLY1 abundance-dependent manner. Over-accumulation of WHIRLY1 in chloroplasts had neither an evident impact on nucleoid morphology nor on the composition of the photosynthetic apparatus. Nevertheless, oeW1 plants were found to be compromised in the light reactions of photosynthesis as well as in carbon fixation. The reduction in growth and photosynthesis was shown to be accompanied by a decrease in the levels of cytokinins and an increase in the level of jasmonic acid. Gene expression analyses revealed that in nonstress conditions the oeW1 plants had enhanced levels of pathogen response (PR) gene expression indicating activation of constitutive defense. During growth in continuous light of high irradiance PR gene expression increased indicating that under stress conditions oeW1 are capable to further enhance defense.
RESUMEN
In this article a novel mechanism of retrograde signaling by chloroplasts during stress is described. This mechanism involves the DNA/RNA binding protein WHIRLY1 as a regulator of microRNA levels. By virtue of its dual localization in chloroplasts and the nucleus of the same cell, WHIRLY1 was proposed as an excellent candidate coordinator of chloroplast function and nuclear gene expression. Comparison of wild-type and transgenic plants with an RNAi-mediated knockdown of WHIRLY1 showed, that the transgenic plants were unable to cope with continuous high light conditions. They were impaired in production of several microRNAs mediating post-transcriptional responses during stress. The results support a central role of WHIRLY1 in retrograde signaling and also underpin a so far underestimated role of microRNAs in this process.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Hordeum/fisiología , MicroARNs/metabolismo , Proteínas de Plantas/metabolismo , ARN de Planta/metabolismo , Proteínas de Unión al ARN/metabolismo , Estrés Fisiológico/fisiología , Núcleo Celular/metabolismo , Cloroplastos/metabolismo , Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica de las Plantas , Técnicas de Silenciamiento del Gen , Hordeum/genética , MicroARNs/genética , Hojas de la Planta/crecimiento & desarrollo , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente/genética , ARN de Planta/genética , Proteínas de Unión al ARN/genética , Plantones/crecimiento & desarrollo , Plantones/efectos de la radiaciónRESUMEN
Modern solid state nuclear magnetic resonance presents new powerful opportunities for the elucidation of medium range order in glasses in the sub-nanometer region. In contrast to standard chemical shift spectroscopy, the strategy presented here is based on the precise measurement and quantitative analysis of internuclear magnetic dipole-dipole interactions, which can be related to distance information in a straightforward manner. The review discusses the most commonly employed experimental techniques, producing dipolar coupling information in both homo- and heteronuclear spin systems. The approach is particularly powerful in combination with magic-angle sample spinning, producing site-resolved dipolar coupling information. We present new applications to oxide-based network glasses, permitting network connectivities and spatial cation distributions to be elucidated.
