Abiotic stresses including drought, salinity, heat, cold, flooding, and ultraviolet radiation causes crop losses worldwide. In recent times, preventing these crop losses and producing more food and ...feed to meet the demands of ever-increasing human populations have gained unprecedented importance. However, the proportion of agricultural lands facing multiple abiotic stresses is expected only to rise under a changing global climate fueled by anthropogenic activities. Identifying the mechanisms developed and deployed by plants to counteract abiotic stresses and maintain their growth and survival under harsh conditions thus holds great significance. Recent investigations have shown that phytohormones, including the classical auxins, cytokinins, ethylene, and gibberellins, and newer members including brassinosteroids, jasmonates, and strigolactones may prove to be important metabolic engineering targets for producing abiotic stress-tolerant crop plants. In this review, we summarize and critically assess the roles that phytohormones play in plant growth and development and abiotic stress tolerance, besides their engineering for conferring abiotic stress tolerance in transgenic crops. We also describe recent successes in identifying the roles of phytohormones under stressful conditions. We conclude by describing the recent progress and future prospects including limitations and challenges of phytohormone engineering for inducing abiotic stress tolerance in crop plants.
The role of quercetin in plants Singh, Priyanka; Arif, Yamshi; Bajguz, Andrzej ...
Plant physiology and biochemistry,
September 2021, 2021-09-00, 20210901, Volume:
166
Journal Article
Peer reviewed
Flavonoids are a special category of hydroxylated phenolic compounds having an aromatic ring structure. Quercetin is aspecial subclass of flavonoid. It is a bioactive natural compound built upon the ...flavon structure nC6(ring A)-C3(ring C)–C6(ring B). Quercetin facilitates several plant physiological processes, such as seed germination, pollen growth, antioxidant machinery, and photosynthesis, as well as induces proper plant growth and development. Quercetin is a powerful antioxidant, so it potently provides plant tolerance against several biotic and abiotic stresses. This review highlights quercetin's role in increasing several physiological and biochemical processes under stress and non-stress environments. Additionally, this review briefly assesses quercetin's role in mitigating biotic and abiotic stresses (e.g., salt, heavy metal, and UV stress). The biosynthesis of flavonoids, their signaling pathways, and quercetin's role in plant signaling are also discussed.
•Quercetin is a special subclass of flavonoid.•Biosynthesis of flavonoids, their signaling pathways, and quercetin's role in plant signaling is discussed.•Quercetin's role in increasing several physiological and biochemical processes in under stress and non-stress environments.•Quercetin is a powerful antioxidant, so it potently provides plant tolerance against several biotic and abiotic stresses.
The leaves of Festuca arundinacea can excrete cadmium (Cd) out onto the leaf surface, leading to a bio-pump phytoremediation strategy based on “root uptake—root-to-leaf translocation—leaf excretion”. ...However, the bio-bump efficiency of soil Cd is a limiting factor for the implementation of this novel technology. Bio-bump remediation involves the bioprocess of plant root uptake from soil, root-to-leaf translocation, and leaf hydathode excretion. Here we show the significant effects of phytohormones in regulating the bio-pump phytoextraction efficiency. The results showed that salicylic acid and ethylene enhanced the whole process of Cd root uptake, root-to-leaf translocation, and leaf excretion, promoting the bio-pump phytoextraction efficiency by 63.6% and 73.8%, respectively. Gibberellin also greatly promoted Cd translocation, leaf excretion, and phytoextraction, but did not significantly impact Cd root uptake. Our results indicate that salicylic acid and ethylene could be recommended to promote bio-pump phytoextraction efficiency in F. arundinacea. Gibberellin might be used for a short-term promotion of the leaf Cd excretion.
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•Phytohormones performed different impacts on bio-pump phytoextraction.•Salicylic acid promoted bio-pump phytoextraction efficiency by 63.6%.•Ethylene promoted bio-pump phytoextraction efficiency by 73.8%.•Gibberellin promoted leaf Cd excretion but had no impact on root uptake.•Auxin inhibited bio-pump phytoextraction.
Bacteria-assisted phytoremediation uses bacteria to promote plant health and improve its ability to remediate toxic heavy metals like Arsenic (As). Here, we isolated rhizobacteria and identified them ...as Bacillus subtilis strain IU31 using 16S rDNA sequencing. IU31 showed phosphate solubilization potential on Pikovskaya agar medium and produced siderophores, which were detected on Chromium Azurol-S (CAS) agar medium. Indole-3-acetic acid (IAA) and gibberellins (GAs), namely GA1, GA3, GA4, GA7, GA9, GA12, GA15, and GA24, were quantified by GC/MS-SIM analysis. The expression levels of genes involved in GA and IAA biosynthesis, such as cyp112, cyp114, trpA, and trpB, were assessed using semi-quantitative RT-PCR. Plant bioassays showed that As at a 15 mg/kg concentration reduced plant growth, chlorophyll content, and biomass. However, IU31 inoculation significantly improved plant growth dynamics, enhancing As accumulation by up to 50% compared with uninoculated plants. IU31 inoculation induced the bioconcentration factor (BCF) and bioaccumulation factor (BAF) of As in plants compared to uninoculated plants, but the translocation factor (TF) of As was unaffected by IU31 inoculation. IU31 inoculation effectively restored glutathione-S-transferase (GST) and catalase (CAT) enzyme activities, as well as glutathione (GSH) and hydrogen peroxide concentrations to nearly normal levels, which were significantly elevated in plants exposed to As stress. These results show that IU31 improves plant health and growth by producing IAA and GAs, which might contribute to the uptake and detoxification of As.
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•Plant growth-promoting Bacillus subtilis strain IU31 was isolated from the rhizosphere.•The IU31 produced phytohormones and siderophores and solubilized phosphate.•Gibberellins and IAA of bacteria were quantified by GC-MS.•Semiquantitative RT-PCR was used to measure the expression of trpA, trpB, cyp112, and cyp114 genes.•Infection of rice plants with IU31 results in increased growth and biomass.
Summary
Carotenoids are isoprenoid compounds synthesized by all photosynthetic and some non‐photosynthetic organisms. They are essential for photosynthesis and contribute to many other aspects of a ...plant's life. The oxidative breakdown of carotenoids gives rise to the formation of a diverse family of essential metabolites called apocarotenoids. This metabolic process either takes place spontaneously through reactive oxygen species or is catalyzed by enzymes generally belonging to the CAROTENOID CLEAVAGE DIOXYGENASE family. Apocarotenoids include the phytohormones abscisic acid and strigolactones (SLs), signaling molecules and growth regulators. Abscisic acid and SLs are vital in regulating plant growth, development and stress response. SLs are also an essential component in plants’ rhizospheric communication with symbionts and parasites. Other apocarotenoid small molecules, such as blumenols, mycorradicins, zaxinone, anchorene, β‐cyclocitral, β‐cyclogeranic acid, β‐ionone and loliolide, are involved in plant growth and development, and/or contribute to different processes, including arbuscular mycorrhiza symbiosis, abiotic stress response, plant–plant and plant–herbivore interactions and plastid retrograde signaling. There are also indications for the presence of structurally unidentified linear cis‐carotene‐derived apocarotenoids, which are presumed to modulate plastid biogenesis and leaf morphology, among other developmental processes. Here, we provide an overview on the biology of old, recently discovered and supposed plant apocarotenoid signaling molecules, describing their biosynthesis, developmental and physiological functions, and role as a messenger in plant communication.
Significance Statement
Apocarotenoids are carotenoid‐derived small molecules with regulatory functions, including cellular signaling, growth regulation and communication with surrounding organisms. Owing to these functions, apocarotenoids can influence plant physiology, development and plant–plant/plant–microorganisms interactions, making them a major focus of study in agriculture and fundamental research.
Plants are subjected to various abiotic stresses, such as drought, extreme temperature, salinity, and heavy metals. Abiotic stresses have negative impact on the physiology and morphology of plants ...through defects in the genetic regulation of cellular pathways. Plants employ several tolerance mechanisms and pathways to avert the effects of stresses that are triggered whenever alterations in metabolism are encountered. Phytohormones are among the most important growth regulators; they are known for having a prominent impact on plant metabolism, and additionally, they play a vital role in the stimulation of plant defense response mechanisms against stresses. Exogenous phytohormone supplementation has been adopted to improve growth and metabolism under stress conditions. Recent investigations have shown that phytohormones produced by root-associated microbes may prove to be important metabolic engineering targets for inducing host tolerance to abiotic stresses. Phytohormone biosynthetic pathways have been identified using several genetic and biochemical methods, and numerous reviews are currently available on this topic. Here, we review current knowledge on the function of phytohormones involved in the improvement of abiotic stress tolerance and defense response in plants exposed to different stressors. We focus on recent successes in identifying the roles of microbial phytohormones that induce stress tolerance, especially in crop plants. In doing so, this review highlights important plant morpho-physiological traits that can be exploited to identify the positive effects of phytohormones on stress tolerance. This review will therefore be helpful to plant physiologists and agricultural microbiologists in designing strategies and tools for the development of broad spectrum microbial inoculants supporting sustainable crop production under hostile environments.
Abstract
The formation of adventitious roots (ARs) is a complex process. It plays an important role in the successful production of elite clones since it is a key step in the vegetative propagation ...of economically important horticultural woody species. The American chestnut (Castanea dentata) is a heritage species and is notoriously recalcitrant to stem rooting. As part of the efforts to understand American chestnut cuttings’ recalcitrance, we examined AR formation via histology and compared the phytohormone level profile between American chestnut and easy-to-root poplar cuttings (Populus x euramericana). It was found that ARs could be induced directly from American chestnut cuttings without callus formation. Adventitious roots of American chestnut were initiated from cambial derivatives and developed a vascular system connected with that of the stem. Compared to easy-to-root poplar, American chestnut cuttings had a low level of indole-3-acetic acid (IAA) and a high level of cytokinin (CK), abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), and oxylipin 12-oxo-phytodienoic acid (OPDA). Hormone distribution between leaves and stems also differed between American chestnut and poplar. This unfavorite endogenous hormone profile may contribute to American chestnut cuttings’ recalcitrance to rooting.
Species used in this study: American chestnut Castanea dentata (Marsh.) Borkh., poplar (Populus x euramericana).
Chemicals used in this study: 1-Naphthaleneacetic acid (NAA).
New eco-friendly approaches are required to improve plant biomass production. Beneficial plant growth-promoting (PGP) bacteria may be exploited as excellent and efficient biotechnological tools to ...improve plant growth in various – including stressful – environments. We present an overview of bacterial mechanisms which contribute to plant health, growth, and development. Plant growth promoting rhizobacteria (PGPR) can interact with plants directly by increasing the availability of essential nutrients (e.g. nitrogen, phosphorus, iron), production and regulation of compounds involved in plant growth (e.g. phytohormones), and stress hormonal status (e.g. ethylene levels by ACC-deaminase). They can also indirectly affect plants by protecting them against diseases via competition with pathogens for highly limited nutrients, biocontrol of pathogens through production of aseptic-activity compounds, synthesis of fungal cell wall lysing enzymes, and induction of systemic responses in host plants. The potential of PGPR to facilitate plant growth is of fundamental importance, especially in case of abiotic stress, where bacteria can support plant fitness, stress tolerance, and/or even assist in remediation of pollutants. Providing additional evidence and better understanding of bacterial traits underlying plant growth-promotion can inspire and stir up the development of innovative solutions exploiting PGPR in times of highly variable environmental and climatological conditions.
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•Bacteria facilitate plant growth under stressful environmental conditions.•Direct and indirect mechanisms are involved in improvement of plant growth and development.•Plant-growth promoting rhizobacteria and host-plant interaction under stress•Agriculture and phytoremediation efficiency may be significantly improved by using plant-growth promoting bacteria.
The complex juvenile/maturity transition during a plant's life cycle includes growth, reproduction, and senescence of its fundamental organs: leaves, flowers, and fruits. Growth and senescence of ...leaves, flowers, and fruits involve several genetic networks where the phytohormone ethylene plays a key role, together with other hormones, integrating different signals and allowing the onset of conditions favorable for stage progression, reproductive success and organ longevity. Changes in ethylene level, its perception, and the hormonal crosstalk directly or indirectly regulate the lifespan of plants. The present review focused on ethylene's role in the development and senescence processes in leaves, flowers and fruits, paying special attention to the complex networks of ethylene crosstalk with other hormones. Moreover, aspects with limited information have been highlighted for future research, extending our understanding on the importance of ethylene during growth and senescence and boosting future research with the aim to improve the qualitative and quantitative traits of crops.
Microbial plant biostimulants (MPBs) are capable of improving the productivity and quality of crops by activating plant physiological and molecular processes, representing an efficient tool in ...sustainable agriculture. Through phytohormone production, MPBs are capable of regulating plant physiological processes, increasing the productivity and quality of crops, in addition to being an efficient alternative in the industrial production of phytohormones.
Bacillus
is a bacterial genus with various species on the market being used as biopesticides, due to their ability to produce antimicrobial, nematicidal and insecticidal compounds. The capability of
Bacillus
species to protect plants against pests and/or pathogens also entails the triggering or increase of plant defense responses. Furthermore, a relevant number of species from the genus
Bacillus
provoke plant growth promotion by different mechanisms such as increasing the tolerance of their host plants under abiotic stress conditions or improving plant nutrition. In several cases, the plant response is mediated by the bacterial production of phytohormones. In the present work, all studies from recent decades where the production of phytohormones by
Bacillus
species are reported, highlighting their role in host plants and the mechanisms by which they are capable of increasing plant growth, promoting their development, and improving their response to different stresses.
Key points
•
Different Bacillus-species are known as agricultural biopesticides.
•
Bacillus role as biostimulants is being increasingly addressed.
•
Bacillus represents a good source of phytohormones of agricultural interest.
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