What can reactive oxygen species (ROS) tell us about the action mechanism of herbicides and other phytotoxins?

Reactive oxygen species (ROS) are formed in plant cells continuously. When ROS production exceeds the antioxidant capacity of the cells, oxidative stress develops which causes damage of cell components and may even lead to the induction of programmed cell death (PCD). The levels of ROS production increase upon abiotic stress, but also during pathogen attack in response to elicitors, and upon application of toxic compounds such as synthetic herbicides or natural phytotoxins.

Effects of Phytotoxic Nonenolides, Stagonolide A and Herbarumin I, on Physiological and Biochemical Processes in Leaves and Roots of Sensitive Plants.

Phytotoxic macrolides attract attention as prototypes of new herbicides. However, their mechanisms of action (MOA) on plants have not yet been elucidated. This study addresses the effects of two ten-membered lactones, stagonolide A (STA) and herbarumin I (HBI) produced by the fungus , on , and .

'Regulation of photosynthesis' session of the Russian Photobiology Society 9th Congress (Shepsi, September 12-19, 2021).

The 'Regulation of Photosynthesis' session was one of the largest events of the Congress, with 17 talks and 9 poster presentations. It covered many topics on the cutting edge of modern photosynthesis research: from the electron transport within the cytochrome -complex to the novel role of carbonic anhydrase in the regulation of pH within the thylakoid lumen, the expanding role of retrograde signaling in all aspects of plant life including the regulation of cell-to-cell traffic via plasmodesmata, and the development of new non-invasive techniques to measure photosynthetic response. Here, a short survey of the presented reports is given.

Role of Autophagy in Cell Growth under Salinity.

The microalga (formerly ) is able to accumulate high amounts of the carotenoid astaxanthin in the course of adaptation to stresses like salinity. Technologies aimed at production of natural astaxanthin for commercial purposes often involve salinity stress; however, after a switch to stressful conditions,   experiences massive cell death which negatively influences astaxanthin yield. This study addressed the possibility to improve cell survival in   subjected to salinity via manipulation of the levels of autophagy using AZD8055, a known inhibitor of TOR kinase previously shown to accelerate autophagy in several microalgae.

Structure-Activity Relationship of Phytotoxic Natural 10-Membered Lactones and Their Semisynthetic Derivatives.

Ten-membered lactones (nonenolides) demonstrate phytotoxic, antimicrobial, and fungicidal activity promising for the development of natural product-derived pesticides. The fungus is able to produce phytotoxic stagonolides A (), J (), K () and herbarumin I () with high yield. The aim of this study was to create a set of structurally related nonenolides and to reveal the structural features that affect their biological activity.

Leaf Epidermis: The Ambiguous Symplastic Domain.

The ability to develop secondary (post-cytokinetic) plasmodesmata (PD) is an important evolutionary advantage that helps in creating symplastic domains within the plant body. Developmental regulation of secondary PD formation is not completely understood. In flowering plants, secondary PD occur exclusively between cells from different lineages, e.

Regulation of plasmodesmata in Arabidopsis leaves: ATP, NADPH and chlorophyll b levels matter.

In mature leaves, cell-to-cell transport via plasmodesmata between mesophyll cells links the production of assimilates by photosynthesis with their export to sink organs. This study addresses the question of how signals derived from chloroplasts and photosynthesis influence plasmodesmata permeability. Cell-to-cell transport was analyzed in leaves of the Arabidopsis chlorophyll b-less ch1-3 mutant, the same mutant complemented with a cyanobacterial CAO gene (PhCAO) overaccumulating chlorophyll b, the trxm3 mutant lacking plastidial thioredoxin m3, and the ntrc mutant lacking functional NADPH:thioredoxin reductase C.

Genes in the Development and Evolution of Land Plants.

Mounting evidence from genomic and transcriptomic studies suggests that most genetic networks regulating the morphogenesis of land plant sporophytes were co-opted and modified from those already present in streptophyte algae and gametophytes of bryophytes . However, thus far, no candidate genes have been identified that could be responsible for "planation", a conversion from a three-dimensional to a two-dimensional growth pattern. According to the telome theory, "planation" was required for the genesis of the leaf blade in the course of leaf evolution.

Singlet Oxygen in Plants: Generation, Detection, and Signaling Roles.

Singlet oxygen (O) refers to the lowest excited electronic state of molecular oxygen. It easily oxidizes biological molecules and, therefore, is cytotoxic. In plant cells, O is formed mostly in the light in thylakoid membranes by reaction centers of photosystem II.

Stomata control is changed in a chlorophyll b-free barley mutant.

The barley (Hordeum vulgare L.) chlorina f2 3613 mutant exhibits low photosynthesis and slow growth. This results from downregulation of the levels of photosynthetic antenna proteins caused by the absence of chl b, the major regulator of photosynthetic antennae in land plants.

The levels of peroxisomal catalase protein and activity modulate the onset of cell death in tobacco BY-2 cells via reactive oxygen species levels and autophagy.

In plant cells, peroxisomes participate in the metabolism of reactive oxygen species (ROS). One of the major regulators of cellular ROS levels - catalase (CAT) - occurs exclusively in peroxisomes. CAT activity is required for immunity-triggered autophagic programmed cell death (PCD).

The role of ion disequilibrium in induction of root cell death and autophagy by environmental stresses.

Environmental stresses such as salinity, drought, oxidants, heavy metals, hypoxia, extreme temperatures and others can induce autophagy and necrosis-type programmed cell death (PCD) in plant roots. These reactions are accompanied by the generation of reactive oxygen species (ROS) and ion disequilibrium, which is induced by electrolyte/K+ leakage through ROS-activated ion channels, such as the outwardly-rectifying K+ channel GORK and non-selective cation channels. Here, we discuss mechanisms of the stress-induced ion disequilibrium and relate it with ROS generation and onset of morphological, biochemical and genetic symptoms of autophagy and PCD in roots.

Unravelling the plant signalling machinery: an update on the cellular and genetic basis of plant signal transduction.

Plant signalling is a set of phenomena that serves the transduction of external and internal signals into physiological responses such as modification of enzyme activity, cytoskeleton structure or gene expression. It operates at the level of cell compartments, whole cells, tissues, organs or even plant communities. To achieve this, plants have evolved a network of signalling proteins including plasma membrane receptors and ion transporters, cascades of kinases and other enzymes as well as several second messengers such as cytosolic calcium (Ca2+), reactive oxygen/nitrogen species (ROS/RNS), cyclic nucleotides (cAMP and cGMP) and others.

The Huperzia selago Shoot Tip Transcriptome Sheds New Light on the Evolution of Leaves.

Lycopodiophyta-consisting of three orders, Lycopodiales, Isoetales and Selaginellales, with different types of shoot apical meristems (SAMs)-form the earliest branch among the extant vascular plants. They represent a sister group to all other vascular plants, from which they differ in that their leaves are microphylls-that is, leaves with a single, unbranched vein, emerging from the protostele without a leaf gap-not megaphylls. All leaves represent determinate organs originating on the flanks of indeterminate SAMs.

The absence of chlorophyll b affects lateral mobility of photosynthetic complexes and lipids in grana membranes of Arabidopsis and barley chlorina mutants.

The lateral mobility of integral components of thylakoid membranes, such as plastoquinone, xanthophylls, and pigment-protein complexes, is critical for the maintenance of efficient light harvesting, high rates of linear electron transport, and successful repair of damaged photosystem II (PSII). The packaging of the photosynthetic pigment-protein complexes in the membrane depends on their size and stereometric parameters which in turn depend on the composition of the complexes. Chlorophyll b (Chlb) is an important regulator of antenna size and composition.

Chlorophyllide-a-Oxygenase (CAO) deficiency affects the levels of singlet oxygen and formation of plasmodesmata in leaves and shoot apical meristems of barley.

In plants, organogenesis and specification of cell layers and tissues rely on precise symplastic delivery of regulatory molecules via plasmodesmata. Accordingly, abundance and aperture of plasmodesmata at individual cell boundaries should be controlled by the plant. Recently, studies in Arabidopsis established reactive oxygen species as major regulators of plasmodesmata formation and gating.

Plant peroxisomes are degraded by starvation-induced and constitutive autophagy in tobacco BY-2 suspension-cultured cells.

Very recently, autophagy has been recognized as an important degradation pathway for quality control of peroxisomes in Arabidopsis plants. To further characterize the role of autophagy in plant peroxisome degradation, we generated stable transgenic suspension-cultured cell lines of heterotrophic Nicotiana tabacum L. cv.

Plasmodesmata without callose and calreticulin in higher plants - open channels for fast symplastic transport?

Plasmodesmata (PD) represent membrane-lined channels that link adjacent plant cells across the cell wall. PD of higher plants contain a central tube of endoplasmic reticulum (ER) called desmotubule. Membrane and lumen proteins seem to be able to move through the desmotubule, but most transport processes through PD occur through the cytoplasmic annulus (Brunkard etal.

Evolutionary aspects of non-cell-autonomous regulation in vascular plants: structural background and models to study.

Plasmodesmata (PD) serve for the exchange of information in form of miRNA, proteins, and mRNA between adjacent cells in the course of plant development. This fundamental role of PD is well established in angiosperms but has not yet been traced back to the evolutionary ancient plant taxa where functional studies lag behind studies of PD structure and ontogenetic origin. There is convincing evidence that the ability to form secondary (post-cytokinesis) PD, which can connect any adjacent cells, contrary to primary PD which form during cytokinesis and link only cells of the same lineage, appeared in the evolution of higher plants at least twice: in seed plants and in some representatives of the Lycopodiophyta.

Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes.

The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) raised the questions as to whether these plasmodesmata are functional in phloem loading and how widespread symplasmic loading would be. Analysis of over 800 dicot species allowed the definition of "open" and "closed" types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989, 1990).

Biosynthesis of benzylisoquinoline alkaloids in Corydalis bracteata: compartmentation and seasonal dynamics.

Numerous species of the genus Corydalis (Papaveraceae) produce a large spectrum of benzylisoquinoline alkaloids (BIA), some of which are of potential therapeutic value, but no information on sites of their biosynthesis and compartmentation is available. This study focuses on the biosynthesis, compartmentation and seasonal dynamics of BIA in Corydalis bracteata (Steph. ex Willd) Pers.

Guidelines for the use and interpretation of assays for monitoring autophagy.

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding.

Lignification of cell walls of infected cells in Casuarina glauca nodules that depend on symplastic sugar supply is accompanied by reduction of plasmodesmata number and narrowing of plasmodesmata.

The oxygen protection system for the bacterial nitrogen-fixing enzyme complex nitrogenase in actinorhizal nodules of Casuarina glauca resembles that of legume nodules: infected cells contain large amounts of the oxygen-binding protein hemoglobin and are surrounded by an oxygen diffusion barrier. However, while in legume nodules infected cells are located in the central tissue, actinorhizal nodules are composed of modified lateral roots with infected cells in the expanded cortex. Since an oxygen diffusion barrier around the entire cortex would also block oxygen access to the central vascular system where it is required to provide energy for transport processes, here each individual infected cell is surrounded with an oxygen diffusion barrier.