Plant quiescence strategy and seed dormancy under hypoxia.

Plant quiescence and seed dormancy can be triggered by reduced oxygen availability. Under water, oxygen depletion caused by flooding can culminate in a quiescent state, which is a plant strategy for energy preservation and survival. In adult plants, a quiescent state can be activated by sugar starvation, leading to metabolic depression.

Seed bacterial microbiota in post-submergence tolerant and sensitive barley genotypes.

Flooding is a predominant abiotic stress for cultivated plants, including barley. This cereal crop shows a large adaptability to different environmental conditions, suggesting the presence of key traits to tolerate adverse conditions. During germination, genetic variations account for dissimilarities in flooding tolerance.

Recent progress in understanding the cellular and genetic basis of plant responses to low oxygen holds promise for developing flood-resilient crops.

With recent progress in active research on flooding and hypoxia/anoxia tolerance in native and agricultural crop plants, vast knowledge has been gained on both individual tolerance mechanisms and the general mechanisms of flooding tolerance in plants. Research on carbohydrate consumption, ethanolic and lactic acid fermentation, and their regulation under stress conditions has been accompanied by investigations on aerenchyma development and the emergence of the radial oxygen loss barrier in some plant species under flooded conditions. The discovery of the oxygen-sensing mechanism in plants and unravelling the intricacies of this mechanism have boosted this very international research effort.

The inability of barley to germinate after submergence depends on hypoxia-induced secondary dormancy.

Global climate change has dramatically increased flooding events, which have a strong impact on crop production. Barley (Hordeum vulgare) is one of the most important cereals and its cultivation includes a broad range of different environments. We tested the capacity to germinate of a large barley panel after a short period of submergence followed by a period of recovery.

Turning earthworms into moonworms: Earthworms colonization of lunar regolith as a bioengineering approach supporting future crop growth in space.

The earthworms beneficial effects on soils may be promising to improve lunar soil fertility, enabling the use of local substrates for space farming. Herein, we investigated the effects of the lunar regolith simulant (LHS-1) at different concentrations in cow manure mixtures on the survival and fitness of . During 14 and 60-day experiments, although showed an increased mortality with LHS-1 alone, most of the population survived.

Group VII ethylene response factors, MtERF74 and MtERF75, sustain nitrogen fixation in Medicago truncatula microoxic nodules.

Group VII ethylene response factors (ERF-VII) are plant-specific transcription factors (TFs) known for their role in the activation of hypoxia-responsive genes under low oxygen stress but also in plant endogenous hypoxic niches. However, their function in the microaerophilic nitrogen-fixing nodules of legumes has not yet been investigated. We investigated regulation and the function of the two Medicago truncatula ERF-VII TFs (MtERF74 and MtERF75) in roots and nodules, MtERF74 and MtERF75 in response to hypoxia stress and during the nodulation process using an RNA interference strategy and targeted proteolysis of MtERF75.

Bacterial Endophytes Contribute to Rice Seedling Establishment Under Submergence.

Flooding events caused by severe rains and poor soil drainage can interfere with plant germination and seedling establishment. Rice is one of the cereal crops that has unique germination strategies under flooding. One of these strategies is based on the fast coleoptile elongation in order to reach the water surface and re-establish the contact with the air.

Screening for Abiotic Stress Response in Rice.

Rice (Oryza sativa L.) is the staple food for over half of the world population. However, most rice varieties are severely injured by abiotic stresses, with strong social and economic impacts.

Cereal Germination under Low Oxygen: Molecular Processes.

Cereal crops can differ greatly in tolerance to oxygen shortage under germination and seedling establishment. Rice is able to germinate and elongate the coleoptile under submergence and anoxia. This capacity has been attributed to the successful use of starchy reserves through a molecular pathway activated by sugar starvation and low oxygen.

The Oxidative Paradox in Low Oxygen Stress in Plants.

Reactive oxygen species (ROS) are part of aerobic environments, and variations in the availability of oxygen (O) in the environment can lead to altered ROS levels. In plants, the O sensing machinery guides the molecular response to low O, regulating a subset of genes involved in metabolic adaptations to hypoxia, including proteins involved in ROS homeostasis and acclimation. In addition, nitric oxide (NO) participates in signaling events that modulate the low O stress response.

Molecular Mechanisms Supporting Rice Germination and Coleoptile Elongation under Low Oxygen.

Rice germinates under submergence by exploiting the starch available in the endosperm and translocating sugars from source to sink organs. The availability of fermentable sugar under water allows germination with the protrusion of the coleoptile, which elongates rapidly and functions as a snorkel toward the air above. Depending on the variety, rice can produce a short or a long coleoptile.

Auxin is required for the long coleoptile trait in japonica rice under submergence.

Rice coleoptile elongation under submergence guarantees fast seedling establishment in the field. We investigated the role of auxin in influencing the capacity of rice to produce a long coleoptile under water. In order to explore the complexity of auxin's role in coleoptile elongation, we used gene expression analysis, confocal microscopy of an auxin-responsive fluorescent reporter, gas chromatography coupled to tandem mass spectrometry (GC-MS/MS), and T-DNA insertional mutants of an auxin transport protein.

The calcineurin β-like interacting protein kinase CIPK25 regulates potassium homeostasis under low oxygen in Arabidopsis.

Hypoxic conditions often arise from waterlogging and flooding, affecting several aspects of plant metabolism, including the uptake of nutrients. We identified a member of the CALCINEURIN β-LIKE INTERACTING PROTEIN KINASE (CIPK) family in Arabidopsis, CIPK25, which is induced in the root endodermis under low-oxygen conditions. A cipk25 mutant exhibited higher sensitivity to anoxia in conditions of potassium limitation, suggesting that this kinase is involved in the regulation of potassium uptake.

Exploring Legume-Rhizobia Symbiotic Models for Waterlogging Tolerance.

Unexpected and increasingly frequent extreme precipitation events result in soil flooding or waterlogging. Legumes have the capacity to establish a symbiotic relationship with endosymbiotic atmospheric dinitrogen-fixing rhizobia, thus contributing to natural nitrogen soil enrichment and reducing the need for chemical fertilization. The impact of waterlogging on nitrogen fixation and legume productivity needs to be considered for crop improvement.

Dissection of coleoptile elongation in japonica rice under submergence through integrated genome-wide association mapping and transcriptional analyses.

Rice is unique among cereals for its ability to germinate not only when submerged but also under anoxic conditions. Rice germination under submergence or anoxia is characterized by a longer coleoptile and delay in radicle emergence. A panel of temperate and tropical japonica rice accessions showing a large variability in coleoptile length was used to investigate genetic factors involved in this developmental process.

Transcriptome profiling of short-term response to chilling stress in tolerant and sensitive Oryza sativa ssp. Japonica seedlings.

Low temperature is a major factor limiting rice growth and yield, and seedling is one of the developmental stages at which sensitivity to chilling stress is higher. Tolerance to chilling is a complex quantitative trait, so one of the most effective approaches to identify genes and pathways involved is to compare the stress-induced expression changes between tolerant and sensitive genotypes. Phenotypic responses to chilling of 13 Japonica cultivars were evaluated, and Thaibonnet and Volano were selected as sensitive and tolerant genotypes, respectively.

A calcineurin B-like protein participates in low oxygen signalling in rice.

Following the identification of the calcineurin B-like interacting protein kinase 15 (CIPK15), which is a regulator of starch degradation, the low O2 signal elicited during rice germination under submergence has been linked to the sugar sensing cascade and calcium (Ca2+) signalling. CIPK proteins are downstream effectors of calcineurin B-like proteins (CBLs), which act as Ca2+ sensors, whose role under low O2 has yet to be established. In the present study we describe CBL4 as a putative CIPK15 partner, transcriptionally activated under low O2 in rice coleoptiles.

New insights into reactive oxygen species and nitric oxide signalling under low oxygen in plants.

Plants produce reactive oxygen species (ROS) when exposed to low oxygen (O ). Much experimental evidence has demonstrated the existence of an oxidative burst when there is an O shortage. This originates at various subcellular sites.

Universal stress protein HRU1 mediates ROS homeostasis under anoxia.

Plant survival is greatly impaired when oxygen levels are limiting, such as during flooding or when anatomical constraints limit oxygen diffusion. Oxygen sensing in Arabidopsis thaliana is mediated by Ethylene Responsive Factor (ERF)-VII transcription factors, which control a core set of hypoxia- and anoxia-responsive genes responsible for metabolic acclimation to low-oxygen conditions. Anoxic conditions also induce genes related to reactive oxygen species (ROS).

Quiescence in rice submergence tolerance: an evolutionary hypothesis.

Rice (Oryza sativa) varieties differ considerably in their tolerance to submergence, a trait that has been associated with the SUB1A gene. Recently, this gene was found in some wild rice species and landraces, which along with O. sativa, belong to the AA genome type group.

Low oxygen response mechanisms in green organisms.

Low oxygen stress often occurs during the life of green organisms, mostly due to the environmental conditions affecting oxygen availability. Both plants and algae respond to low oxygen by resetting their metabolism. The shift from mitochondrial respiration to fermentation is the hallmark of anaerobic metabolism in most organisms.

New role for an old rule: N-end rule-mediated degradation of ethylene responsive factor proteins governs low oxygen response in plants(F).

The N-end rule pathway regulates protein degradation, which depends on exposed N-terminal sequences in prokaryotes and eukaryotes. In plants, conserved and specific enzymes stimulate selective proteolysis. Although a number of developmental and growth phenotypes have been reported for mutants in the N-end rule, its function has remained unrelated to specific physiological pathways.

How plants sense low oxygen.

The recent identification of the oxygen-sensing mechanism in plants is a breakthrough in plant physiology. The presence of a conserved N-terminal motif on some ethylene responsive factors (ERFs), targets the protein for post-translational modifications finally leading to degradation under normoxia and thus providing a mechanism for sensing the presence of oxygen. The stabilization of the N-terminus under low oxygen activates these ERFs, which regulate low oxygen core genes that enable plants to tolerate abiotic stress such as flooding.