Multi-scale analysis of heat stress acclimation in Arabidopsis seedlings highlights the primordial contribution of energy-transducing organelles.

Much progress has been made in understanding the molecular mechanisms of plant adaptation to heat stress. However, the great diversity of models and stress conditions, and the fact that analyses are often limited to a small number of approaches, complicate the picture. We took advantage of a liquid culture system in which Arabidopsis seedlings are arrested in their development, thus avoiding interference with development and drought stress responses, to investigate through an integrative approach seedlings' global response to heat stress and acclimation.

Brassica napus Drought-Induced 22-kD Protein (BnD22) Acts Simultaneously as a Cysteine Protease Inhibitor and Chlorophyll-Binding Protein.

Class II water-soluble chlorophyll proteins (WSCPs) from Brassicaceae are non-photosynthetic proteins that bind with chlorophyll (Chl) and its derivatives. The physiological function of WSCPs is still unclear, but it is assumed to be involved in stress responses, which is likely related to their Chl-binding and protease inhibition (PI) activities. Yet, the dual function and simultaneous functionality of WSCPs must still be better understood.

High Expression of ALTERNATIVE OXIDASE 2 in Latent Axillary Buds Suggests Its Key Role in Quiescence Maintenance in Rosebush.

Most vegetative axes remain quiescent as dormant axillary buds until metabolic and hormonal signals, driven by environmental changes, trigger bud outgrowth. While the resumption of growth activity is well documented, the establishment and maintenance of quiescence is comparatively poorly understood, despite its major importance in the adaptation of plants to the seasonal cycle or in the establishment of their shape. Here, using the rosebush Rosa hybrida 'Radrazz' as a plant model, we highlighted that the quiescent state was the consequence of an internal and active energy control of buds, under the influence of hormonal factors previously identified in the bud outgrowth process.

A Case of Gene Fragmentation in Plant Mitochondria Fixed by the Selection of a Compensatory Restorer of Fertility-Like PPR Gene.

The high mutational load of mitochondrial genomes combined with their uniparental inheritance and high polyploidy favors the maintenance of deleterious mutations within populations. How cells compose and adapt to the accumulation of disadvantageous mitochondrial alleles remains unclear. Most harmful changes are likely corrected by purifying selection, however, the intimate collaboration between mitochondria- and nuclear-encoded gene products offers theoretical potential for compensatory adaptive changes.

Responses of the Necrotrophic Fungus to the Indolic Phytoalexin Brassinin.

causes black spot disease in . During host infection, this necrotrophic fungus is exposed to various antimicrobial compounds, such as the phytoalexin brassinin which is produced by many cultivated species. To investigate the cellular mechanisms by which this compound causes toxicity and the corresponding fungal adaptive strategies, we first analyzed fungal transcriptional responses to short-term exposure to brassinin and then used additional functional approaches.

Outgrowth of the axillary bud in rose is controlled by sugar metabolism and signalling.

Shoot branching is a pivotal process during plant growth and development, and is antagonistically orchestrated by auxin and sugars. In contrast to extensive investigations on hormonal regulatory networks, our current knowledge on the role of sugar signalling pathways in bud outgrowth is scarce. Based on a comprehensive stepwise strategy, we investigated the role of glycolysis/the tricarboxylic acid (TCA) cycle and the oxidative pentose phosphate pathway (OPPP) in the control of bud outgrowth.

The conundrum of hot mitochondria.

The mitochondrion is often referred as the cellular powerhouse because the organelle oxidizes organic acids and NADH derived from nutriments, converting around 40% of the Gibbs free energy change of these reactions into ATP, the major energy currency of cell metabolism. Mitochondria are thus microscopic furnaces that inevitably release heat as a by-product of these reactions, and this contributes to body warming, especially in endotherms like birds and mammals. Over the last decade, the idea has emerged that mitochondria could be warmer than the cytosol, because of their intense energy metabolism.

Rerouting of ribosomal proteins into splicing in plant organelles.

Production and expression of RNA requires the action of multiple RNA-binding proteins (RBPs). New RBPs are most often created by novel combinations of dedicated RNA-binding modules. However, recruiting existing genes to create new RBPs is also an important evolutionary strategy.

The Mitochondrial Small Heat Shock Protein HSP22 from Pea is a Thermosoluble Chaperone Prone to Co-Precipitate with Unfolding Client Proteins.

The small heat shock proteins (sHSPs) are molecular chaperones that share an alpha-crystallin domain but display a high diversity of sequence, expression, and localization. They are especially prominent in plants, populating most cellular compartments. In pea, mitochondrial HSP22 is induced by heat or oxidative stress in leaves but also strongly accumulates during seed development.

Arabidopsis seedlings display a remarkable resilience under severe mineral starvation using their metabolic plasticity to remain self-sufficient for weeks.

During the life cycle of plants, seedlings are considered vulnerable because they are at the interface between the highly stress tolerant seed embryos and the established plant, and must develop rapidly, often in a challenging environment, with limited access to nutrients and light. Using a simple experimental system, whereby the seedling stage of Arabidopsis is considerably prolonged by nutrient starvation, we analysed the physiology and metabolism of seedlings maintained in such conditions up to 4 weeks. Although development was arrested at the cotyledon stage, there was no sign of senescence and seedlings remained viable for weeks, yielding normal plants after transplantation.

Novel Cytonuclear Combinations Modify Seed Physiology and Vigor.

Dormancy and germination vigor are complex traits of primary importance for adaptation and agriculture. Intraspecific variation in cytoplasmic genomes and cytonuclear interactions were previously reported to affect germination in Arabidopsis using novel cytonuclear combinations that disrupt co-adaptation between natural variants of nuclear and cytoplasmic genomes. However, specific aspects of dormancy and germination vigor were not thoroughly explored, nor the parental contributions to the genetic effects.

Decoding the Divergent Subcellular Location of Two Highly Similar Paralogous LEA Proteins.

Many mitochondrial proteins are synthesized as precursors in the cytosol with an N-terminal mitochondrial targeting sequence (MTS) which is cleaved off upon import. Although much is known about import mechanisms and MTS structural features, the variability of MTS still hampers robust sub-cellular software predictions. Here, we took advantage of two paralogous late embryogenesis abundant proteins (LEA) from Arabidopsis with different subcellular locations to investigate structural determinants of mitochondrial import and gain insight into the evolution of the genes.

Water content, adenylate kinase, and mitochondria drive adenylate balance in dehydrating and imbibing seeds.

Water and life are inexorably linked, but some organisms are capable of losing almost all cellular water to enter a non-metabolic state of anhydrobiosis. This raises intriguing questions about how energy metabolism is managed during such transitions. Here, we have investigated adenylate metabolism during seed imbibition and drying using intact or fragmented pea (Pisum sativum L.

New Insights into Phloem Unloading and Expression of Sucrose Transporters in Vegetative Sinks of the Parasitic Plant . (Pomel).

The plant-parasitic plant interaction is a interesting model to study sink-source relationship and phloem unloading. The parasitic plants, such as the achlorophyllous plant , connect to the host phloem through the haustorium and act as supernumerary sinks for the host-derived photoassimilates, primarily sucrose. The application of the fluorescent symplastic tracer, carboxyfluorescein (CF) derived from carboxyfluorescein diacetate (CFDA), to the leaves of the host plant () showed direct phloem connections at the host-parasite interface.

Arabidopsis Seed Mitochondria Are Bioenergetically Active Immediately upon Imbibition and Specialize via Biogenesis in Preparation for Autotrophic Growth.

Seed germination is a vital developmental transition for production of progeny by sexual reproduction in spermatophytes. Quiescent cells in nondormant dry embryos are reawakened first by imbibition and then by perception of germination triggers. Reanimated tissues enter into a germination program requiring energy for expansion growth.

Unraveling the early molecular and physiological mechanisms involved in response to phenanthrene exposure.

Background: Higher plants have to cope with increasing concentrations of pollutants of both natural and anthropogenic origin. Given their capacity to concentrate and metabolize various compounds including pollutants, plants can be used to treat environmental problems - a process called phytoremediation. However, the molecular mechanisms underlying the stabilization, the extraction, the accumulation and partial or complete degradation of pollutants by plants remain poorly understood.

Glucosinolate-derived isothiocyanates impact mitochondrial function in fungal cells and elicit an oxidative stress response necessary for growth recovery.

Glucosinolates are brassicaceous secondary metabolites that have long been considered as chemical shields against pathogen invasion. Isothiocyanates (ITCs), are glucosinolate-breakdown products that have negative effects on the growth of various fungal species. We explored the mechanism by which ITCs could cause fungal cell death using Alternaria brassicicola, a specialist Brassica pathogens, as model organism.

The ABA-deficiency suppressor locus HAS2 encodes the PPR protein LOI1/MEF11 involved in mitochondrial RNA editing.

The hot ABA-deficiency suppressor2 (has2) mutation increases drought tolerance and the ABA sensitivity of stomata closure and seed germination. Here we report that the HAS2 locus encodes the mitochondrial editing factor11 (MEF11), also known as lovastatin insensitive1. has2/mef11 mutants exhibited phenotypes very similar to the ABA-hypersensitive mutant, hai1-1 pp2ca-1 hab1-1 abi1-2, which is impaired in four genes encoding type 2C protein phosphatases (PP2C) that act as upstream negative regulators of the ABA signaling cascade.

Variability within a pea core collection of LEAM and HSP22, two mitochondrial seed proteins involved in stress tolerance.

LEAM, a late embryogenesis abundant protein, and HSP22, a small heat shock protein, were shown to accumulate in the mitochondria during pea (Pisum sativum L.) seed development, where they are expected to contribute to desiccation tolerance. Here, their expression was examined in seeds of 89 pea genotypes by Western blot analysis.

Disruption of the CYTOCHROME C OXIDASE DEFICIENT1 gene leads to cytochrome c oxidase depletion and reorchestrated respiratory metabolism in Arabidopsis.

Cytochrome c oxidase is the last respiratory complex of the electron transfer chain in mitochondria and is responsible for transferring electrons to oxygen, the final acceptor, in the classical respiratory pathway. The essentiality of this step makes it that depletion in complex IV leads to lethality, thereby impeding studies on complex IV assembly and respiration plasticity in plants. Here, we characterized Arabidopsis (Arabidopsis thaliana) embryo-lethal mutant lines impaired in the expression of the CYTOCHROME C OXIDASE DEFICIENT1 (COD1) gene, which encodes a mitochondria-localized PentatricoPeptide Repeat protein.

Adjustments of embryonic photosynthetic activity modulate seed fitness in Arabidopsis thaliana.

In this work, we dissect the physiological role of the transient photosynthetic stage observed in developing seeds of Arabidopsis thaliana. By combining biochemical and biophysical approaches, we demonstrate that despite similar features of the photosynthetic apparatus, light absorption, chloroplast morphology and electron transport are modified in green developing seeds, as a possible response to the peculiar light environment experienced by them as a result of sunlight filtration by the pericarp. In particular, enhanced exposure to far-red light, which mainly excites photosystem I, largely enhances cyclic electron flow around this complex at the expenses of oxygen evolution.

FRIENDLY regulates mitochondrial distribution, fusion, and quality control in Arabidopsis.

Mitochondria are defining components of most eukaryotes. However, higher plant mitochondria differ biochemically, morphologically, and dynamically from those in other eukaryotes. FRIENDLY, a member of the CLUSTERED MITOCHONDRIA superfamily, is conserved among eukaryotes and is required for correct distribution of mitochondria within the cell.

The ubiquitous distribution of late embryogenesis abundant proteins across cell compartments in Arabidopsis offers tailored protection against abiotic stress.

Late embryogenesis abundant (LEA) proteins are hydrophilic, mostly intrinsically disordered proteins, which play major roles in desiccation tolerance. In Arabidopsis thaliana, 51 genes encoding LEA proteins clustered into nine families have been inventoried. To increase our understanding of the yet enigmatic functions of these gene families, we report the subcellular location of each protein.