The transcription factor ORA59 represses hypoxia responses during Botrytis cinerea infection and reoxygenation.

Transcription factors belonging to the large ethylene response factor (ERF) family are involved in plant responses to biotic and abiotic stresses. Among the ERFs, OCTADECANOID-RESPONSIVE ARABIDOPSIS 59 (ORA59) integrates ethylene and jasmonic acid signaling to regulate resistance to necrotrophic pathogens. The ERF group ERFVII encodes oxygen-labile proteins that are required for oxygen sensing and are stabilized by hypoxia established at the site of Botrytis (Botrytis cinerea) infection.

Metabolic strategies in hypoxic plants.

Complex multicellular organisms have evolved in an oxygen-enriched atmosphere. Oxygen is therefore essential for all aerobic organisms, including plants, for energy production through cellular respiration. However, plants can experience hypoxia following extreme flooding events and also under aerated conditions in proliferative organs or tissues characterized by high oxygen consumption.

Environmental genome-wide association studies across precipitation regimes reveal that the E3 ubiquitin ligase MBR1 regulates plant adaptation to rainy environments.

In an era characterized by rapidly changing and less-predictable weather conditions fueled by the climate crisis, understanding the mechanisms underlying local adaptation in plants is of paramount importance for the conservation of species. As the frequency and intensity of extreme precipitation events increase, so are the flooding events resulting from soil water saturation. The subsequent onset of hypoxic stress is one of the leading causes of crop damage and yield loss.

Root photosynthesis prevents hypoxia in the epiphytic orchid .

Orchids (Phalaenopsis spp.) growing in tropical and subtropical regions are epiphytes. As such, they grow on trees with the root system utilised to anchor themselves to tree branches.

Spatiotemporal oxygen dynamics in young leaves reveal cyclic hypoxia in plants.

Oxygen is essential for plant growth and development. Hypoxia occurs in plants due to limited oxygen availability following adverse environmental conditions as well in hypoxic niches in otherwise normoxic environments. However, the existence and functional integration of spatiotemporal oxygen dynamics with plant development remains unknown.

ERFVII transcription factors and their role in the adaptation to hypoxia in Arabidopsis and crops.

In this review, we focus on ethylene transcription factors (ERFs), which are a crucial family of transcription factors that regulate plant development and stress responses. ERFVII transcription factors have been identified and studied in several crop species, including rice, wheat, maize, barley, and soybean. These transcription factors are known to be involved in regulating the plant's response to low oxygen stress-hypoxia and could thus improve crop yields under suboptimal growing conditions.

Target of rapamycin signaling couples energy to oxygen sensing to modulate hypoxic gene expression in .

Plants respond to oxygen deprivation by activating the expression of a set of hypoxia-responsive genes (HRGs). The master regulator of this process is a small group of transcription factors belonging to group VII of the ethylene response factors (ERF-VIIs). ERF-VIIs are highly unstable under aerobic conditions due to the continuous oxidation of their characteristic Cys residue at the N terminus by plant cysteine oxidases (PCOs).

The vacuolar H+/Ca transporter CAX1 participates in submergence and anoxia stress responses.

A plant's oxygen supply can vary from normal (normoxia) to total depletion (anoxia). Tolerance to anoxia is relevant to wetland species, rice (Oryza sativa) cultivation, and submergence tolerance of crops. Decoding and transmitting calcium (Ca) signals may be an important component to anoxia tolerance; however, the contribution of intracellular Ca transporters to this process is poorly understood.

Mobile plant microRNAs allow communication within and between organisms.

Plant microRNAs (miRNAs) are small regulatory RNAs that are encoded by endogenous miRNA genes and regulate gene expression through gene silencing, by inducing degradation of their target messenger RNA or by inhibiting its translation. Some miRNAs are mobile molecules inside the plant, and increasing experimental evidence has demonstrated that miRNAs represent molecules that are exchanged between plants, their pathogens, and parasitic plants. It has also been shown that miRNAs are secreted into the external growing medium and that these miRNAs regulate gene expression and the phenotype of nearby receiving plants, thus defining a new concept in plant communication.

Exogenous miRNAs induce post-transcriptional gene silencing in plants.

Plants seem to take up exogenous RNA that was artificially designed to target specific genes, followed by activation of the RNA interference (RNAi) machinery. It is, however, not known whether plants use RNAs themselves as signalling molecules in plant-to-plant communication, other than evidence that an exchange of small RNAs occurs between parasitic plants and their hosts. Exogenous RNAs from the environment, if taken up by some living organisms, can indeed induce RNAi.

RNAi Mediated Hypoxia Stress Tolerance in Plants.

Small RNAs regulate various biological process involved in genome stability, development, and adaptive responses to biotic or abiotic stresses. Small RNAs include microRNAs (miRNAs) and small interfering RNAs (siRNAs). MicroRNAs (miRNAs) are regulators of gene expression that affect the transcriptional and post-transcriptional regulation in plants and animals through RNA interference (RNAi).

Plant Responses to Hypoxia: Signaling and Adaptation.

Molecular oxygen deficiency leads to altered cellular metabolism and can dramatically reduce crop productivity. Nearly all crops are negatively affected by lack of oxygen (hypoxia) due to adverse environmental conditions such as excessive rain and soil waterlogging. Extensive efforts to fully understand how plants sense oxygen deficiency and their ability to respond using different strategies are crucial to increase hypoxia tolerance.

Arabidopsis phenotyping reveals the importance of alcohol dehydrogenase and pyruvate decarboxylase for aerobic plant growth.

Alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) are key to the establishment of the fermentative metabolism in plants during oxygen shortage. Most of the evidence that both ADH and PDC are required for plant tolerance to hypoxia comes from experiments performed by limiting oxygen in the environment, such as by exposing plants to gaseous hypoxia or to waterlogging or submergence. However, recent experiments have shown that hypoxic niches might exist in plants grown in aerobic conditions.

Jasmonate Signalling Contributes to Primary Root Inhibition Upon Oxygen Deficiency in .

Plants, including most crops, are intolerant to waterlogging, a stressful condition that limits the oxygen available for roots, thereby inhibiting their growth and functionality. Whether root growth inhibition represents a preventive measure to save energy or is rather a consequence of reduced metabolic rates has yet to be elucidated. In the present study, we gathered evidence for hypoxic repression of root meristem regulators that leads to root growth inhibition.

The Many Facets of Hypoxia in Plants.

Plants are aerobic organisms that require oxygen for their respiration. Hypoxia arises due to the insufficient availability of oxygen, and is sensed by plants, which adapt their growth and metabolism accordingly. Plant hypoxia can occur as a result of excessive rain and soil waterlogging, thus constraining plant growth.

Botrytis cinerea induces local hypoxia in Arabidopsis leaves.

Low oxygen availability often is associated with soil waterlogging or submergence, but may occur also as hypoxic niches in otherwise aerobic tissues. Experimental evidence assigns a role in Botrytis cinerea resistance to a group of oxygen-unstable Ethylene Response Factors (ERF-VII). Given that infection by B.

Energy and sugar signaling during hypoxia.

The major consequence of hypoxia is a dramatic reduction in energy production. At the onset of hypoxia, both oxygen and ATP availability decrease. Oxygen and energy sensing therefore converge to induce an adaptive response at both the transcriptional and translational levels.

ARGONAUTE1 and ARGONAUTE4 Regulate Gene Expression and Hypoxia Tolerance.

In plants, hypoxia can be induced by submergence, and the lack of oxygen impairs mitochondrial respiration, thus affecting the plant's energy status. Hypoxia has major effects on gene expression; these changes induce key responses that help meet the needs of the stressed plant. However, little is known about the possible role of RNA signaling in the regulation of gene expression under limited oxygen availability.

Gene Regulation and Survival under Hypoxia Requires Starch Availability and Metabolism.

Plants respond to hypoxia, often caused by submergence, by expressing a specific set of genes that contribute to acclimation to this unfavorable environmental condition. Genes induced by low oxygen include those encoding enzymes for carbohydrate metabolism and fermentation, pathways that are required for survival. Sugar availability is therefore of crucial importance for energy production under hypoxia.

Seaweed Extract Alleviates Drought Stress in by Affecting Photosynthetic Performance and Related Gene Expression.

Drought represents one of the most relevant abiotic stress affecting growth and yield of crop plants. In order to improve the agricultural productivity within the limited water and land resources, it is mandatory to increase crop yields in presence of unfavorable environmental stresses. The use of biostimulants, often containing seaweed extracts, represents one of the options for farmers willing to alleviate abiotic stress consequences on crops.

Plant responses to flooding stress.

Most plant species cannot survive prolonged submergence or soil waterlogging. Crops are particularly intolerant to the lack of oxygen arising from submergence. Rice can instead germinate and grow even if submerged.

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).

A reassessment of the role of sucrose synthase in the hypoxic sucrose-ethanol transition in Arabidopsis.

Plants under low-oxygen availability adapt their metabolism to compensate for the lower ATP production that arises from the limited respiratory activity in mitochondria. Anaerobic glycolysis requires continuous fuelling of carbon units, also provided from sucrose. The anaerobic catabolism of sucrose is thought to require the activity of sucrose synthase, being this enzymatic reaction more energetically favourable than that of invertase.

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.

Distinct mechanisms regulating gene expression coexist within the fermentative pathways in Chlamydomonas reinhardtii.

Under dark anoxia, the unicellular green algae Chlamydomonas reinhardtii may produce hydrogen by means of its hydrogenase enzymes, in particular HYD1, using reductants derived from the degradation of intercellular carbon stores. Other enzymes belonging to the fermentative pathways compete for the same reductants. A complete understanding of the mechanisms determining the activation of one pathway rather than another will help us engineer Chlamydomonas for fermentative metabolite production, including hydrogen.