A stress recovery signaling network for enhanced flooding tolerance in .

Abiotic stresses in plants are often transient, and the recovery phase following stress removal is critical. Flooding, a major abiotic stress that negatively impacts plant biodiversity and agriculture, is a sequential stress where tolerance is strongly dependent on viability underwater and during the postflooding period. Here we show that in accessions (Bay-0 and Lp2-6), different rates of submergence recovery correlate with submergence tolerance and fecundity.

The effect of auxin (indole-3-acetic acid) on the growth rate and tropism of the sporangiophore of Phycomyces blakesleeanus and identification of auxin-related genes.

The roles of fungal auxins in the regulation of elongation growth, photo-, and gravitropism are completely unknown. We analyzed the effects of exogenous IAA (indole-3-acetic acid), various synthetic auxins including 1-NAA (1-naphthaleneacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid), and the auxin transport inhibitor NPA (N-1-naphtylphtalamic acid) on the growth rate and bending of the unicellular sporangiophore of the zygomycete fungus, Phycomyces blakesleeanus. Sporangiophores that were submerged in an aqueous buffer responded to IAA with a sustained enhancement of the growth rate, while 1-NAA, 2,4-D, and NPA elicited an inhibition.

Protoplast Swelling and Hypocotyl Growth Depend on Different Auxin Signaling Pathways.

Members of the TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX PROTEIN (TIR1/AFB) family are known auxin receptors. To analyze the possible receptor function of AUXIN BINDING PROTEIN1 (ABP1), an auxin receptor currently under debate, we performed different approaches. We performed a pharmacological approach using α-(2,4-dimethylphenylethyl-2-oxo)-indole-3-acetic acid (auxinole), α-(phenylethyl-2-oxo)-indole-3-acetic acid (PEO-IAA), and 5-fluoroindole-3-acetic acid (5-F-IAA) to discriminate between ABP1- and TIR1/AFB-mediated processes in Arabidopsis ().

The Physiology of Adventitious Roots.

Adventitious roots are plant roots that form from any nonroot tissue and are produced both during normal development (crown roots on cereals and nodal roots on strawberry [Fragaria spp.]) and in response to stress conditions, such as flooding, nutrient deprivation, and wounding. They are important economically (for cuttings and food production), ecologically (environmental stress response), and for human existence (food production).

The role of ethylene and ROS in salinity, heavy metal, and flooding responses in rice.

Plant growth and developmental processes as well as abiotic and biotic stress adaptations are regulated by small endogenous signaling molecules. Among these, phytohormones such as the gaseous alkene ethylene and reactive oxygen species (ROS) play an important role in mediating numerous specific growth or cell death responses. While apoplastic ROS are generated by plasma membrane-located respiratory burst oxidase homolog proteins, intracellular ROS are produced mainly in electron transfer chains of mitochondria and chloroplasts.

Reactive oxygen species mediate growth and death in submerged plants.

Aquatic and semi-aquatic plants are well adapted to survive partial or complete submergence which is commonly accompanied by oxygen deprivation. The gaseous hormone ethylene controls a number of adaptive responses to submergence including adventitious root growth and aerenchyma formation. Reactive oxygen species (ROS) act as signaling intermediates in ethylene-controlled submergence adaptation and possibly also independent of ethylene.

The Clubroot Pathogen (Plasmodiophora brassicae) Influences Auxin Signaling to Regulate Auxin Homeostasis in Arabidopsis.

The clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, affects cruciferous crops worldwide. It is characterized by root swellings as symptoms, which are dependent on the alteration of auxin and cytokinin metabolism. Here, we describe that two different classes of auxin receptors, the TIR family and the auxin binding protein 1 (ABP1) in Arabidopsis thaliana are transcriptionally upregulated upon gall formation.

Emerging roots alter epidermal cell fate through mechanical and reactive oxygen species signaling.

A central question in biology is how spatial information is conveyed to locally establish a developmental program. Rice (Oryza sativa) can survive flash floods by the emergence of adventitious roots from the stem. Epidermal cells that overlie adventitious root primordia undergo cell death to facilitate root emergence.

Phytosulfokine-α controls hypocotyl length and cell expansion in Arabidopsis thaliana through phytosulfokine receptor 1.

The disulfated peptide growth factor phytosulfokine-α (PSK-α) is perceived by LRR receptor kinases. In this study, a role for PSK signaling through PSK receptor PSKR1 in Arabidopsis thaliana hypocotyl cell elongation is established. Hypocotyls of etiolated pskr1-2 and pskr1-3 seedlings, but not of pskr2-1 seedlings were shorter than wt due to reduced cell elongation.

Aerenchyma formation in the rice stem and its promotion by H2O2.

• Gas spaces (aerenchyma) form as an adaptation to submergence to facilitate gas exchange. In rice (Oryza sativa), aerenchyma develop by cell death and lysis, which are poorly understood at the cellular level. • Aerenchyma formation was studied in rice stems by light microscopy.

G proteins as regulators in ethylene-mediated hypoxia signaling.

Waterlogging or flooding are frequently or constitutively encountered by many plant species. The resulting reduction in endogenous O2 concentration poses a severe threat. Numerous adaptations at the anatomical, morphological and metabolic level help plants to either escape low oxygen conditions or to endure them.

ABP1: an auxin receptor for fast responses at the plasma membrane.

Auxin-binding protein 1 (ABP1) is an auxin receptor for responses not primarily regulated by gene regulation. One fast response is protoplast swelling. By using immunological ABP1 tools we showed that the highly conserved box a is not alone important for auxin binding.

A role for PSK signaling in wounding and microbial interactions in Arabidopsis.

PSK-alpha is a disulfated peptide that acts as a growth factor in plants. PSK-alpha is derived from preproproteins which are encoded by five PSK precursor genes in Arabidopsis thaliana (L.) Heynh and is perceived by leucine-rich repeat receptor kinases.

Epidermal cells that undergo cell death differentially express cell identity genes.

Rice ( L.) is a semiaquatic plant that forms adventitious root primordia at the stem nodes as part of normal development. Upon flooding, roots emerge, preceded by local death of epidermal cells above the root primordia.

The auxin-binding pocket of auxin-binding protein 1 comprises the highly conserved boxes a and c.

The auxin-binding protein 1 (ABP1) has already been proved to be an extracellular receptor of auxin in single cell systems. Protoplasts of maize coleoptiles respond to auxin with an increase in volume. The 2-naphthaleneacetic acid (2-NAA), an inactive auxin analog, acts as an anti-auxin in protoplast swelling, as it suppresses the effect of indole-3-acetic acid (IAA).

Heterotrimeric G protein signaling is required for epidermal cell death in rice.

In rice (Oryza sativa) adventitious root primordia are formed at the nodes as part of normal development. Upon submergence of rice plants, adventitious roots emerge from the nodes preceded by death of epidermal cells above the root primordia. Cell death is induced by ethylene and mediated by hydrogen peroxide (H(2)O(2)).

Epidermal cell death in rice is confined to cells with a distinct molecular identity and is mediated by ethylene and H2O2 through an autoamplified signal pathway.

Rice (Oryza sativa) forms adventitious root primordia at stem nodes during normal development. Root emergence is preceded by ethylene-induced, H(2)O(2)-mediated local death of epidermal cells. Exogenous H(2)O(2) or enhancement of endogenous H(2)O(2) promoted epidermal cell death in a dose-dependent manner.

Interactions between ethylene, gibberellin and abscisic acid regulate emergence and growth rate of adventitious roots in deepwater rice.

Growth of adventitious roots is induced in deepwater rice (Oryza sativa L.) when plants become submerged. Ethylene which accumulates in flooded plant parts is responsible for root growth induction.

The diageotropica mutation of tomato disrupts a signalling chain using extracellular auxin binding protein 1 as a receptor.

The diageotropica ( dgt) mutant of tomato ( Lycopersicon esculentum Mill.) is known to lack a number of typical auxin responses. Here we show that rapid auxin-induced growth of seedling hypocotyls is completely abolished by the mutation over the full range of auxin concentrations tested, and also in early phases of the time course.