Arabidopsis and genes double knock-out results in a stay-green phenotype during dark-induced senescence.

Yellowing is the first visually observable sign of plant leaf senescence. We found that Arabidopsis double knockout mutant for genes of NAD(H)-dependent glutamate dehydrogenase retains green color of the leaves (stay-green phenotype) during a dark-induced senescence, in contrast to wild-type plants, whose leaves turn yellow. When the plants are exposed to the dark more than four days, they demonstrate slower chlorophyll degradation than in the wild-type plants under the same conditions, as well as dysregulation of chlorophyll breakdown genes encoding chlorophyll reductase, Mg-dechelatase, pheophytinase and pheophorbide oxygenase.

Overexpression of RPOTmp Being Targeted to Either Mitochondria or Chloroplasts in Leads to Overall Transcriptome Changes and Faster Growth.

The transcription of 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 , 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.

Plant mitochondria import DNA via alternative membrane complexes involving various VDAC isoforms.

Mitochondria possess transport mechanisms for import of RNA and DNA. Based on import into isolated Solanum tuberosum mitochondria in the presence of competitors, inhibitors or effectors, we show that DNA fragments of different size classes are taken up into plant organelles through distinct channels. Alternative channels can also be activated according to the amount of DNA substrate of a given size class.

Involvement of Photoprotective Compounds of a Phenolic Nature in the Response of Arabidopsis Thaliana Leaf Tissues to Low-Intensity Laser Radiation.

The influence of low-intensity laser radiation (LILR) on the changes in the content of anthocyanins, kaempferol, quercetin and their glycosides in the leaves of 5-week-old plants of Arabidopsis thaliana L. was studied by means of methods of high-performance liquid chromatography and gas chromatography mass spectrometry (GC-MS). It was found that in the leaves subjected to a stimulating He-Ne laser radiation dose (3.

RPOTmp, an Arabidopsis RNA polymerase with dual targeting, plays an important role in mitochondria, but not in chloroplasts.

In a number of dicotyledonous plants, including Arabidopsis, the transcription of organellar genes is performed by three nuclear-encoded RNA polymerases, RPOTm, RPOTmp, and RPOTp. RPOTmp is a protein with a dual targeting, which is presumably involved in the control of gene expression in both mitochondria and chloroplasts. A previous study of the Arabidopsis insertion rpotmp mutant showed that it has retarded growth and development, altered leaf morphology, changed expression of mitochondrial and probably some chloroplast genes, and decreased activities of the mitochondrial respiratory complexes.

Inhibition of the electron transport strongly affects transcription and transcript levels in Arabidopsis mitochondria.

Mitochondrial transcription rate and RNA steady-state levels were examined in shoots of Arabidopsis seedlings. The shoots were treated with inhibitors of complex III and IV of the cytochrome pathway (CP) and with an inhibitor of the alternative oxidase (AOX) of the mitochondrial electron transport chain. The inhibition of AOX and CP complexes III and IV affected transcription and transcript levels in different ways.

DNA repair in organelles: Pathways, organization, regulation, relevance in disease and aging.

Both endogenous processes and exogenous physical and chemical sources generate deoxyribonucleic acid (DNA) damage in the nucleus and organelles of living cells. To prevent deleterious effects, damage is balanced by repair pathways. DNA repair was first documented for the nuclear compartment but evidence was subsequently extended to the organelles.

Plant mitochondria possess a short-patch base excision DNA repair pathway.

Despite constant threat of oxidative damage, sequence drift in mitochondrial and chloroplast DNA usually remains very low in plant species, indicating efficient defense and repair. Whereas the antioxidative defense in the different subcellular compartments is known, the information on DNA repair in plant organelles is still scarce. Focusing on the occurrence of uracil in the DNA, the present work demonstrates that plant mitochondria possess a base excision repair (BER) pathway.