Cyclic electron flow compensates loss of PGDH3 and concomitant stromal NADH reduction.

In nature plants constantly experience changes in light intensities. Low illumination limits photosynthesis and growth. However, also high light intensities are a threat to plants as the photosynthetic machinery gets damaged when the incoming energy surpasses the capacity of photochemistry.

Homecoming: rewinding the reductive evolution of the chloroplast genome for increasing crop yields.

Developing more productive and sustainable crops will be essential to achieving food security in coming decades. A core process in plant evolution has been the transfer of chloroplast-encoded genes to the nuclear genome. We propose reverting this process as a new approach to improve plant disease resistance and photosynthesis in future crops.

Genome communication in plants mediated by organelle-n-ucleus-located proteins.

An increasing number of eukaryotic proteins have been shown to have a dual localization in the DNA-containing organelles, mitochondria and plastids, and/or the nucleus. Regulation of dual targeting and relocation of proteins from organelles to the nucleus offer the most direct means for communication between organelles as well as organelles and nucleus. Most of the mitochondrial proteins of animals have functions in DNA repair and gene expression by modelling of nucleoid architecture and/or chromatin.

Two dominant boreal conifers use contrasting mechanisms to reactivate photosynthesis in the spring.

Boreal forests are dominated by evergreen conifers that show strongly regulated seasonal photosynthetic activity. Understanding the mechanisms behind seasonal modulation of photosynthesis is crucial for predicting how these forests will respond to changes in seasonal patterns and how this will affect their role in the terrestrial carbon cycle. We demonstrate that the two co-occurring dominant boreal conifers, Scots pine (Pinus sylvestris L.

Spontaneous microscopic hyphema secondary to iris vascular tufts: Case report with video documentation.

A 71-year-old woman presented with spontaneous microhyphema in her left eye, causing blurry vision. Bleeding stopped spontaneously shortly after several cycles of digital compression on the upper eyelid, (which were documented in video), and therefore, did not require laser photocoagulation, a possible approach previously explained to the patient. A microhemangioma at the edge of the iris was identified to be the cause of the condition.

Traumatic corneal flap avulsion and loss 13 years after LASIK.

Postoperative flap displacements after Laser In Situ Keratomileusis (LASIK) are uncommon complications, and flap losses are even less frequent, occurring most commonly within 24 hours after the procedure. Although cases of late subluxation have been reported up to 14 years after the surgery, the longest reported time after surgery for late flap loss is four years after LASIK. We report a case of a 54-year-old man that presented a traumatic total flap avulsion and loss 13 years after LASIK.

Massive Hyphaema Following Laser Iridotomy in a Patient on Dual Antiplatelet Therapy (Aspirin plus Ticagrelor): Case report and literature review.

Massive hyphaema presentation after a laser iridotomy is very rare. We report a 63-year-old man with ischaemic heart disease on dual antiplatelet therapy (aspirin plus ticagrelor) who was diagnosed as a primary angle-closure suspect and was to undergo a neodymium-doped yttrium aluminium garnet laser iridotomy at Centro Oftalmológico Virgilio Galvis, Floridablanca, Colombia in 2016. While performing the iridotomy in the left eye, active bleeding occurred that finally filled approximately 75% of the anterior chamber.

Dual and dynamic intracellular localization of Arabidopsis thaliana SnRK1.1.

Sucrose non-fermenting 1 (SNF1)-related protein kinase 1.1 (SnRK1.1; also known as KIN10 or SnRK1α) has been identified as the catalytic subunit of the complex SnRK1, the Arabidopsis thaliana homologue of a central integrator of energy and stress signalling in eukaryotes dubbed AMPK/Snf1/SnRK1.

Interaction between plastid and mitochondrial retrograde signalling pathways during changes to plastid redox status.

Mitochondria and chloroplasts depend upon each other; photosynthesis provides substrates for mitochondrial respiration and mitochondrial metabolism is essential for sustaining photosynthetic carbon assimilation. In addition, mitochondrial respiration protects photosynthesis against photoinhibition by dissipating excess redox equivalents from the chloroplasts. Genetic defects in mitochondrial function result in an excessive reduction and energization of the chloroplast.

Expression of the minor isoform pea ferredoxin in tobacco alters photosynthetic electron partitioning and enhances cyclic electron flow.

Ferredoxins (Fds) are ferrosulfoproteins that function as low-potential electron carriers in plants. The Fd family is composed of several isoforms that share high sequence homology but differ in functional characteristics. In leaves, at least two isoforms conduct linear and cyclic photosynthetic electron transport around photosystem I, and mounting evidence suggests the existence of at least partial division of duties between these isoforms.

Cyclin-dependent kinase E1 (CDKE1) provides a cellular switch in plants between growth and stress responses.

Plants must deal effectively with unfavorable growth conditions that necessitate a coordinated response to integrate cellular signals with mitochondrial retrograde signals. A genetic screen was carried out to identify regulators of alternative oxidase (rao mutants), using AOX1a expression as a model system to study retrograde signaling in plants. Two independent rao1 mutant alleles identified CDKE1 as a central nuclear component integrating mitochondrial retrograde signals with energy signals under stress.

Flavodoxin displays dose-dependent effects on photosynthesis and stress tolerance when expressed in transgenic tobacco plants.

Ferredoxins are iron-sulfur proteins involved in various one-electron transfer pathways. Ferredoxin levels decrease under adverse environmental conditions in photosynthetic organisms. In cyanobacteria, this decline is compensated by induction of flavodoxin, an isofunctional flavoprotein.

Plastid-to-nucleus communication, signals controlling the running of the plant cell.

The presence of genes encoding organellar proteins in both the nucleus and the organelle necessitates tight coordination of expression by the different genomes, and this has led to the evolution of sophisticated intracellular signaling networks. Organelle-to-nucleus signaling, or retrograde control, coordinates the expression of nuclear genes encoding organellar proteins with the metabolic and developmental state of the organelle. Complex networks of retrograde signals orchestrate major changes in nuclear gene expression and coordinate cellular activities and assist the cell during plant development and stress responses.

The plastid redox insensitive 2 mutant of Arabidopsis is impaired in PEP activity and high light-dependent plastid redox signalling to the nucleus.

The photosynthetic apparatus is composed of proteins encoded by genes from both the nuclear and the chloroplastic genomes. The activities of the nuclear and chloroplast genomes must therefore be closely coordinated through intracellular signalling. The plastids produce multiple retrograde signals at different times of their development, and in response to changes in the environment.

Stress response of transgenic tobacco plants expressing a cyanobacterial ferredoxin in chloroplasts.

Expression of the chloroplast electron shuttle ferredoxin is induced by light through mechanisms that partially depend on sequences lying in the coding region of the gene, complicating its manipulation by promoter engineering. Ferredoxin expression is also down-regulated under virtually all stress situations, and it is unclear if light-dependent induction and stress-dependent repression proceed through the same or similar mechanisms. Previous reports have shown that expression of a cyanobacterial flavodoxin in tobacco plastids results in plants with enhanced tolerance to adverse environmental conditions such as drought, chilling and xenobiotics (Tognetti et al.

Cyanobacterial flavodoxin complements ferredoxin deficiency in knocked-down transgenic tobacco plants.

Ferredoxins are the main electron shuttles in chloroplasts, accepting electrons from photosystem I and delivering them to essential oxido-reductive pathways in the stroma. Ferredoxin levels decrease under adverse environmental conditions in both plants and photosynthetic micro-organisms. In cyanobacteria and some algae, this decrease is compensated for by induction of flavodoxin, an isofunctional flavoprotein that can replace ferredoxin in many reactions.

Perennial stream discharge in the hyperarid Atacama Desert of northern Chile during the latest Pleistocene.

A large fraction of the vital groundwater in the Atacama Desert of northern Chile is likely composed of "fossil" or "ancient" reserves that receive little or no recharge in today's hyperarid climate. Here, we present evidence for latest Pleistocene perennial streamflow in canyons from the hyperarid core of the Atacama Desert in northern Chile. Fluvial terraces in the Pampa del Tamarugal (PdT) basin (21 degrees S) contain widespread fossil wood, in situ roots, and well preserved leaf litter deposits indicative of perennial surface flow currently absent in these channels.

Synthesis of 4-hydroxy-7,8-dimethoxyisochroman-3-one and its plant growth-regulating properties on tobacco (Nicotiana tabacum cv. Petit Havana).

The synthesis of 6,7-dimethoxy-4-hydroxyisochroman-3-one 10 from 2,3-dimethoxytoluene (11) via glyoxylate 12 is reported. Compound 10 strongly inhibited vegetative growth of tobacco plants, whereas developmental patterns (protein levels, protein profile, pigments, and chlorophylls) were not affected. Morphological changes were observed in the leaves of the treated plants.

Transgenic tobacco plants expressing antisense ferredoxin-NADP(H) reductase transcripts display increased susceptibility to photo-oxidative damage.

Ferredoxin-NADP(H) reductase (FNR) catalyses the final step of the photosynthetic electron transport in chloroplasts. Using an antisense RNA strategy to reduce expression of this flavoenzyme in transgenic tobacco plants, it has been demonstrated that FNR mediates a rate-limiting step of photosynthesis under both limiting and saturating light conditions. Here, we show that these FNR-deficient plants are abnormally prone to photo-oxidative injury.