Plant response to drought and hyperosmosis is mediated by the phytohormone abscisic acid (ABA), a sesquiterpene compound widely distributed in various embryophyte groups. Exogenous ABA as well as ...hyperosmosis activates the sucrose nonfermenting 1 (SNF1)-related protein kinase2 (SnRK2), which plays a central role in cellular responses against drought and dehydration, although the details of the activation mechanism are not understood. Analysis of a mutant of the mossPhyscomitrella patenswith reduced ABA sensitivity and reduced hyperosmosis tolerance revealed that a protein kinase designated “ARK” (for “ABA and abiotic stress-responsive Raf-like kinase”) plays an essential role in the activation of SnRK2. ARK encoded by a single gene inP. patensbelongs to the family of group B3 Raf-like MAP kinase kinase kinases (B3-MAPKKKs) mediating ethylene, disease resistance, and salt and sugar responses in angiosperms. Our findings indicate that ARK, as a novel regulatory component integrating ABA and hyperosmosis signals, represents the ancestral B3-MAPKKKs, which multiplied, diversified, and came to have specific functions in angiosperms.
Plants acclimate to environmental stress signals such as cold, drought and hypersalinity, and provoke internal protective mechanisms. Abscisic acid (ABA), a carotenoid‐derived phytohormone, which ...increases in response to the stress signals above, has been suggested to play a key role in the acclimation process in angiosperms, but the role of ABA in basal land plants such as mosses, including its biosynthetic pathways, has not been clarified. Targeted gene disruption of PpABA1, encoding zeaxanthin epoxidase in the moss Physcomitrella patens was conducted to determine the role of endogenous ABA in acclimation processes in mosses. The generated ppaba1 plants were found to accumulate only a small amount of endogenous ABA. The ppaba1 plants showed reduced osmotic acclimation capacity in correlation with reduced dehydration tolerance and accumulation of late embryogenesis abundant proteins. By contrast, cold‐induced freezing tolerance was less affected in ppaba1, indicating that endogenous ABA does not play a major role in the regulation of cold acclimation in the moss. Our results suggest that the mechanisms for osmotic acclimation mediated by carotenoid‐derived synthesis of ABA are conserved in embryophytes and that acquisition of the mechanisms played a crucial role in terrestrial adaptation and colonization by land plant ancestors.
Phytohormone abscisic acid (ABA) plays a key role in stomata closure, osmostress acclimation, and vegetative and embryonic dormancy. Group B3 Raf protein kinases (B3-Rafs) serve as positive ...regulators of ABA and osmostress signaling in the moss
Physcomitrium patens
and the angiosperm
Arabidopsis thaliana
. While
P. patens
has a single B3-Raf called ARK, specific members of B3-Rafs among six paralogs regulate ABA and osmostress signaling in
A. thaliana
, indicating functional diversification of B3-Rafs in angiosperms. However, we found that the liverwort
Marchantia polymorpha
, belonging to another class of bryophytes, has three paralogs of B3-Rafs, Mp
ARK1
, Mp
ARK2
, and Mp
ARK3
, with structural variations in the regulatory domains of the polypeptides. By reporter assays of the
P. patens ark
line and analysis of genome-editing lines of
M. polymorpha
, we found that these B3-Rafs are functionally redundant in ABA response, with respect to inhibition of growth, tolerance to desiccation and expression of stress-associated transcripts, the majority of which are under the control of the PYR/PYL/RCAR-like receptor Mp
PYL1
. Interestingly, gemmae in gemma cups were germinating only in mutant lines associated with Mp
ARK1
, indicating that dormancy in the gametophyte is controlled by a specific B3-Raf paralog. These results indicated not only conservation of the role of B3-Rafs in ABA and osmostress response in liverworts but also functional diversification of B3-Rafs, which is likely to have occurred in the early stages of land plant evolution.
Soil salinity, a major environmental concern, significantly reduces plant growth and production all around the world. Finding solutions to reduce the salinity impacts on plants is critical for global ...food security. In recent years, the priming of plants with organic chemicals has shown to be a viable approach for the alleviation of salinity effects in plants. The current study examined the effects of exogenous ethanol in triggering salinity acclimatization responses in soybean by investigating growth responses, and numerous physiological and biochemical features. Foliar ethanol application to saline water-treated soybean plants resulted in an enhancement of biomass, leaf area, photosynthetic pigment contents, net photosynthetic rate, shoot relative water content, water use efficiency, and K
and Mg
contents, leading to improved growth performance under salinity. Salt stress significantly enhanced the contents of reactive oxygen species (ROS), malondialdehyde, and electrolyte leakage in the leaves, suggesting salt-induced oxidative stress and membrane damage in soybean plants. In contrast, ethanol treatment of salt-treated soybean plants boosted ROS-detoxification mechanisms by enhancing the activities of antioxidant enzymes, including peroxidase, ascorbate peroxidase, catalase, and glutathione
-transferase. Ethanol application also augmented the levels of proline and total free amino acids in salt-exposed plants, implying a role of ethanol in maintaining osmotic adjustment in response to salt stress. Notably, exogenous ethanol decreased Na
uptake while increasing K
and Mg
uptake and their partitioning to leaves and roots in salt-stressed plants. Overall, our findings reveal the protective roles of ethanol against salinity in soybean and suggest that the use of this cost-effective and easily accessible ethanol in salinity mitigation could be an effective approach to increase soybean production in salt-affected areas.
The escalating global temperatures associated with climate change are detrimental to plant growth and development, leading to significant reductions in crop yields worldwide. Our research ...demonstrates that salicylic acid (SA), a phytohormone known for its growth-promoting properties, is crucial in enhancing heat tolerance in cotton (Gossypium hirsutum). This enhancement is achieved through modifications in various biochemical, physiological, and growth parameters. Under heat stress, cotton plants typically show significant growth disturbances, including leaf wilting, stunted growth, and reduced biomass. However, priming cotton plants with 1 mM SA significantly mitigated these adverse effects, evidenced by increases in shoot dry mass, leaf-water content, and chlorophyll concentrations in the heat-stressed plants. Heat stress also prompted an increase in hydrogen peroxide levels—a key reactive oxygen species—resulting in heightened electrolyte leakage and elevated malondialdehyde concentrations, which indicate severe impacts on cellular membrane integrity and oxidative stress. Remarkably, SA treatment significantly reduced these oxidative stresses by enhancing the activities of critical antioxidant enzymes, such as catalase, glutathione S-transferase, and ascorbate peroxidase. Additionally, the elevated levels of total soluble sugars in SA-treated plants enhanced osmotic regulation under heat stress. Overall, our findings reveal that SA-triggered protective mechanisms not only preserve photosynthetic pigments but also ameliorate oxidative stress and boost plant resilience in the face of elevated temperatures. In conclusion, the application of 1 mM SA is highly effective in enhancing heat tolerance in cotton and is recommended for field trials before being commercially used to improve crop resilience under increasing global temperatures.
Liverwort
Marchantia polymorpha
is considered as the key species for addressing a myriad of questions in plant biology. Exploration of drought tolerance mechanism(s) in this group of land plants ...offers a platform to identify the early adaptive mechanisms involved in drought tolerance. The current study aimed at elucidating the drought acclimation mechanisms in liverwort’s model
M. polymorpha
. The gemmae, asexual reproductive units of
M. polymorpha
, were exposed to sucrose (0.2 M), mannitol (0.5 M) and polyethylene glycol (PEG, 10%) for inducing physiological drought to investigate their effects at morphological, physiological and biochemical levels. Our results showed that drought exposure led to extreme growth inhibition, disruption of membrane stability and reduction in photosynthetic pigment contents in
M. polymorpha
. The increased accumulation of hydrogen peroxide and malondialdehyde, and the rate of electrolyte leakage in the gemmalings of
M. polymorpha
indicated an evidence of drought-caused oxidative stress. The gemmalings showed significant induction of the activities of key antioxidant enzymes, including superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase and glutathione
S
-transferase, and total antioxidant activity in response to increased oxidative stress under drought. Importantly, to counteract the drought effects, the gemmalings also accumulated a significant amount of proline, which coincided with the evolutionary presence of proline biosynthesis gene
Δ
1
-pyrroline-5-carboxylate synthase 1
(
P5CS1
) in land plants. Furthermore, the application of exogenous abscisic acid (ABA) reduced drought-induced tissue damage and improved the activities of antioxidant enzymes and accumulation of proline, implying an archetypal role of this phytohormone in
M. polymorpha
for drought tolerance. We conclude that physiological drought tolerance mechanisms governed by the cellular antioxidants, proline and ABA were adopted in liverwort
M. polymorpha
, and that these findings have important implications in aiding our understanding of osmotic stress acclimation processes in land plants.
Potassium (K) is an integral part of plant nutrition, playing essential roles in plant growth and development. Despite its abundance in soils, the limitedly available form of K ion (K+) for plant ...uptake is a critical factor for agricultural production. Plants have evolved complex transport systems to maintain appropriate K+ levels in tissues under changing environmental conditions. Adequate stimulation and coordinated actions of multiple K+-channels and K+-transporters are required for nutrient homeostasis, reproductive growth, cellular signaling and stress adaptation responses in plants. Various contemporary studies revealed that K+-homeostasis plays a substantial role in plant responses and tolerance to abiotic stresses. The beneficial effects of K+ in plant responses to abiotic stresses include its roles in physiological and biochemical mechanisms involved in photosynthesis, osmoprotection, stomatal regulation, water-nutrient absorption, nutrient translocation and enzyme activation. Over the last decade, we have seen considerable breakthroughs in K research, owing to the advances in omics technologies. In this aspect, omics investigations (e.g., transcriptomics, metabolomics, and proteomics) in systems biology manner have broadened our understanding of how K+ signals are perceived, conveyed, and integrated for improving plant physiological resilience to abiotic stresses. Here, we update on how K+-uptake and K+-distribution are regulated under various types of abiotic stress. We discuss the effects of K+ on several physiological functions and the interaction of K+ with other nutrients to improve plant potential against abiotic stress-induced adverse consequences. Understanding of how K+ orchestrates physiological mechanisms and contributes to abiotic stress tolerance in plants is essential for practicing sustainable agriculture amidst the climate crisis in global agriculture.
•Potassium ion (K+) is the most abundant cation required for plant growth and survival.•K+-transport and -signaling play crucial roles in plant abiotic stress responses.•K+ controls multiple physiological processes, such as stomatal regulation and osmoprotection.•K+ interacts with phytohormones and other nutrients for plant adaptation to abiotic stresses.•K+-use-efficiency is requisite to enhance crop performance under stressful conditions.
One of the most important abiotic factors that hinder plant development, growth, and production is salt stress. In recent years, there has been a lot of interest in the biological treatment of salt ...stress in plants using beneficial microbes. The fungal endophyte Beauveria bassiana provides a wide variety of ecosystem services, like suppressing insect pests and pathogens and enhancing plant growth. However, the role of B. bassiana in reducing salt stress in plants has not yet been clarified. This study was undertaken to evaluate the performance of B. bassiana isolate BeauA1 primed rice under salt stress by estimating rice growth, stress parameters, and mitigator characteristics. Primarily, rice seeds were primed with BeauA1 and placed in an agar medium with 120 mM NaCl (≈12 dS m−1 salt solution) to observe the role of BeauA1 in the early establishment of rice seedlings in salt conditions. Seed priming with BeauA1 resulted in an enhancement of rice growth attributes under both control and NaCl stress conditions. In the pot experiment, the BeauA1 primed rice seedlings were planted in soil with different concentrations of salt, viz. 8, 10, and 12 dS m−1. The BeauA1 primed rice plants showed improvement in leaf succulence, leaf area, photosynthetic pigments, and shoot relative water content (RWC), leading to enhanced growth under both salt stress and control conditions. The biochemical study found that BeauA1 considerably increased proline content, total soluble sugars, total carbohydrates, and K+/Na+ in leaves. The antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), glutathione S-transferase (GST), and nonenzymatic antioxidants phenol and flavonoid were upregulated in BeauA1-primed plants under both control and stressed conditions. Further significant reductions of the lipid peroxidation products malondialdehyde (MDA) and hydrogen peroxide (H2O2) by BeauA1 under salt stress were consistent with higher antioxidant activities in salt stress conditions. Principal component analysis (PCA) further validated BeauA1-primed plants' modulation of growth, antioxidant defense, and reduction of MDA and H2O2 in rice under salt-stress conditions. Our findings indicated that utilizing BeauA1 to reduce salt stress would be a useful strategy to increase rice yield in salt-affected regions.
•Seed priming with B. bassiana isolate BeauA1 improved rice growth under both salinated and non-salinated environments.•B. bassiana improved salt stress tolerance by elevating osmoprotectants and the K+/Na+ ratio.•B. bassiana reduced ROS-induced oxidative damage by modulating antioxidant defense in rice plants under salt stress.
The foraging of honeybees is one of the most well-organized and admirable behaviors that exists among social insects and being greatly influenced by nectarine sources and habitat adaptability. In ...Bangladesh, apiculture is mostly confined to rearing of European honeybee Apis mellifera L. despite of having the native A. cerana F. due to lack of information about comparative foraging efficiency and productibility of two species in Asian cropland ecosystem. The present study aimed to molecular characterization of two honeybee species in apiary and their foraging performance on litchi orchard. The genetic identity was revealed thorough phylogenetic analysis with >90% bootstrap value using mitochondrial cytochrome oxidase sub unit- 1 (CO1) gene and nucleotide sequence data deposited to NCBI GenBank with accession number ON680900- ON680902 for A. mellifera and ON703291-ON703293 of A. cerana. Upon placing the identified bee hives in litchi orchard, the foraging efficiency were studied based on egression and ingression rate, number of bees visited flowers per minutes, and nectar and pollen collection efficiency in varied time series of the day. Principal component analysis (PCA) for measuring the contribution of different foraging parameters and the species wise PCA biplot revealed the better foraging efficiency by A. mellifera L. compared to A. cerana F. in litchi blooms. However, foraging efficiency of other nectarine sources should be analyzed for suggesting best performing bee species in apiculture.
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