RESUMEN
The transcription of Arabidopsis organellar genes is performed by three nuclear-encoded RNA polymerases: RPOTm, RPOTmp, and RPOTp. The RPOTmp protein possesses ambiguous transit peptides, allowing participation in gene expression control in both mitochondria and chloroplasts, although its function in plastids is still under discussion. Here, we show that the overexpression of RPOTmp in Arabidopsis, targeted either to mitochondria or chloroplasts, disturbs the dormant seed state, and it causes the following effects: earlier germination, decreased ABA sensitivity, faster seedling growth, and earlier flowering. The germination of RPOTmp overexpressors is less sensitive to NaCl, while rpotmp knockout is highly vulnerable to salt stress. We found that mitochondrial dysfunction in the rpotmp mutant induces an unknown retrograde response pathway that bypasses AOX and ANAC017. Here, we show that RPOTmp transcribes the accD, clpP, and rpoB genes in plastids and up to 22 genes in mitochondria.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Cloroplastos , Regulación de la Expresión Génica de las Plantas , Germinación , Mitocondrias , Transcriptoma , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Mitocondrias/metabolismo , Mitocondrias/genética , Cloroplastos/metabolismo , Cloroplastos/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Germinación/genética , ARN Polimerasas Dirigidas por ADN/genética , ARN Polimerasas Dirigidas por ADN/metabolismo , Plantones/genética , Plantones/crecimiento & desarrollo , Plantas Modificadas Genéticamente/crecimiento & desarrollo , Plantas Modificadas Genéticamente/genéticaRESUMEN
Short interrupted repeat cassette (SIRC)-a novel DNA element found throughout the A. thaliana nuclear genome. SIRCs are represented by short direct repeats interrupted by diverse DNA sequences. The maxima of SIRC's distribution are located within pericentromeric regions. We suggest that originally SIRC was a special case of the complex internal structure of the miniature inverted repeat transposable element (MITE), and further MITE amplification, transposition, and loss of terminal inverted repeats gave rise to SIRC as an independent DNA element. SIRC sites were significantly enriched with several histone modifications associated with constitutive heterochromatin and mobile genetic elements. The majority of DNA-binding proteins, strongly associated with SIRC, are related to histone modifications for transcription repression. A part of SIRC was found to overlap highly inducible protein-coding genes, suggesting a possible regulatory role for these elements, yet their definitive functions need further investigation.