Silicon regulates phosphate deficiency through involvement of auxin and nitric oxide in barley roots.

MAIN CONCLUSION: Silicon application mitigates phosphate deficiency in barley through an interplay with auxin and nitric oxide, enhancing growth, photosynthesis, and redox balance, highlighting the potential of silicon as a fertilizer for overcoming nutritional stresses. Silicon (Si) is reported to attenuate nutritional stresses in plants, but studies on the effect of Si application to plants grown under phosphate (Pi) deficiency are still very scarce, especially in barley. Therefore, the present work was undertaken to investigate the potential role of Si in mitigating the adverse impacts of Pi deficiency in barley Hordeum vulgare L. (var. BH902). Further, the involvement of two key regulatory signaling molecules--auxin and nitric oxide (NO)--in Si-induced tolerance against Pi deficiency in barley was tested. Morphological attributes, photosynthetic parameters, oxidative stress markers (O2·-, H2O2, and MDA), antioxidant system (enzymatic--APX, CAT, SOD, GR, DHAR, MDHAR as well as non-enzymatic--AsA and GSH), NO content, and proline metabolism were the key traits that were assessed under different treatments. The P deficiency distinctly declined growth of barley seedlings, which was due to enhancement in oxidative stress leading to inhibition of photosynthesis. These results were also in parallel with an enhancement in antioxidant activity, particularly SOD and CAT, and endogenous proline level and its biosynthetic enzyme (P5CS). The addition of Si exhibited beneficial effects on barley plants grown in Pi-deficient medium as reflected in increased growth, photosynthetic activity, and redox balance through the regulation of antioxidant machinery particularly ascorbate-glutathione cycle. We noticed that auxin and NO were also found to be independently participating in Si-mediated improvement of growth and other parameters in barley roots under Pi deficiency. Data of gene expression analysis for PHOSPHATE TRANSPORTER1 (HvPHT1) indicate that Si helps in increasing Pi uptake as per the need of Pi-deficient barley seedlings, and also auxin and NO both appear to help Si in accomplishing this task probably by inducing lateral root formation. These results are suggestive of possible application of Si as a fertilizer to correct the negative effects of nutritional stresses in plants. Further research at genetic level to understand Si-induced mechanisms for mitigating Pi deficiency can be helpful in the development of new varieties with improved tolerance against Pi deficiency, especially for cultivation in areas with Pi-deficient soils.

Redox regulation by priming agents towards a sustainable agriculture.

Plant are sessile organisms that are often subjected to a multitude of environmental stresses, with the occurrence of these events being further intensified by global climate change. Crop species therefore require specific adaptations to tolerate climatic variability for sustainable food production. Plant stress results in excess accumulation of reactive oxygen species (ROS) leading to oxidative stress, and loss of cellular redox balance in the plant cells. Moreover, enhancement of cellular oxidation as well as oxidative signals have recently been recognized as crucial players in plant growth regulation under stress conditions. Multiple roles of redox regulation in crop production have been well documented, and major emphasis has focused on key redox-regulated proteins and non-protein molecules, such as NAD(P)H, thioredoxins, glutathione, glutaredoxins, peroxiredoxins, ascorbate, and reduced ferredoxin. These have been widely implicated in the regulation of (epi)genetic factors modulating growth and vigor of crop plants, particularly within an agricultural context. In this regard, priming with the employment of chemical and biological agents has emerged as a fascinating approach to improve plant tolerance against various abiotic and biotic stressors. Priming in plants is a physiological process, where prior exposure to specific stressors induces a state of heightened alertness, enabling a more rapid and effective defense response upon subsequent encounters with similar challenges. Priming is reported to play an important role in the regulation of cellular redox homeostasis, maximizing crop productivity under stress conditions and thus achieving yield security. By taking this into consideration, the present review is an up-to-date critical evaluation of promising plant priming technologies and their role in the regulation of redox components towards enhanced plant adaptations to extreme unfavorable environmental conditions. The challenges and opportunities of plant priming are addressed, with the aim to encourage future research in this field towards effective application in crop stress management including horticultural species.

Nitric oxide acts upstream of indole-3-acetic acid in ameliorating arsenate stress in tomato seedlings.

After their discovery, nitric oxide (NO) and indole-3-acetic acid (IAA) have been reported as game-changing cellular messengers for reducing abiotic stresses in plants. But, information regarding their shared signaling in regulating metal stress is still unclear. Herein, we have investigated about the joint role of NO and IAA in mitigation of arsenate [As(V)] toxicity in tomato seedlings. Arsenate being a toxic metalloid increases the NPQ level and cell death while decreasing the biomass accumulation, photosynthetic pigments, chlorophyll a fluorescence, endogenous NO content in tomato seedlings. However, application of IAA or SNP to the As(V) stressed seedlings improved growth together with less accumulation of arsenic and thus, preventing cell death. Interestingly, addition of c-PTIO, {2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide, a scavenger of NO} and 2, 3, 5-triidobenzoic acid (TIBA, an inhibitor of polar auxin transport) further increased cell death and inhibited activity of GST, leading to As(V) toxicity. However, addition of IAA to SNP and TIBA treated seedlings reversed the effect of TIBA resulting into decreased As(V) toxicity. These findings demonstrate that IAA plays a crucial and advantageous function in NO-mediated reduction of As(V) toxicity in seedlings of tomato. Overall, this study concluded that IAA might be acting as a downstream signal for NO-mediated reduction of As(V) toxicity in tomato seedlings.

Silicon, a quasi-essential element: Availability in soil, fertilizer regime, optimum dosage, and uptake in plants.

The essentiality of silicon (Si) has always been a matter of debate as it is not considered crucial for the lifecycles of most plants. But beneficial effects of endogenous Si and its supplementation have been observed in many plants. Silicon plays a pivotal role in alleviating the biotic and abiotic stress in plants by acting as a physical barrier as well as affecting molecular pathways involved in stress tolerance, thus widely considered as "quasi-essential". In soil, most of Si is found in complex forms as mineral silicates which is not available for plant uptake. Monosilicic acid [Si(OH)4] is the only plant-available form of silicon (PAS) present in the soil. The ability of a plant to uptake Si is positively correlated with the PAS concentration of the soil. Since many cultivated soils often lack a sufficient amount of PAS, it has become common practice to supplement Si through the use of Si-based fertilizers in various crop cultivation systems. This review outlines the use of natural and chemical sources of Si as fertilizer, different regimes of Si fertilization, and conclude by identifying the optimum concentration of Si required to observe the beneficial effects in plants. Also, the different mathematical models defining the mineral dynamics for Si uptake at whole plant scale considering various natural factors like plant morphology, mineral distribution, and transporter expression have been discussed. Information provided here will further help in increasing understanding of Si role and thereby facilitate efficient exploration of the element as a fertilizer in crop production.

Evolution of reactive oxygen species cellular targets for plant development.

Reactive oxygen species (ROS) are the key players in regulating developmental processes of plants. Plants have evolved a large array of gene families to facilitate the ROS-regulated developmental process in roots and leaves. However, the cellular targets of ROS during plant evolutionary development are still elusive. Here, we found early evolution and large expansions of protein families such as mitogen-activated protein kinases (MAPK) in the evolutionarily important plant lineages. We review the recent advances in interactions among ROS, phytohormones, gasotransmitters, and protein kinases. We propose that these signaling molecules act in concert to maintain cellular ROS homeostasis in developmental processes of root and leaf to ensure the fine-tuning of plant growth for better adaptation to the changing climate.

Transcriptome analysis of waterlogging-induced adventitious root and control taproot of Mentha arvensis.

KEY MESSAGE: The present study reports differentially expressed transcripts in the waterlogging-induced adventitious root (AR) of Mentha arvensis; the identified transcripts will help to understand AR development and improve waterlogging stress response. Waterlogging notably hampers plant growth in areas facing waterlogged soil conditions. In our previous findings, Mentha arvensis was shown to adapt better in waterlogging conditions by initiating the early onset of adventitious root development. In the present study, we compared the transcriptome analysis of adventitious root induced after the waterlogging treatment with the control taproot. The biochemical parameters of total carbohydrate, total protein content, nitric oxide (NO) scavenging activity and antioxidant enzymes, such as catalase activity (CAT) and superoxide dismutase (SOD) activity, were enhanced in the adventitious root compared with control taproot. Analysis of differentially expressed genes (DEGs) in adventitious root compared with the control taproot were grouped into four functional categories, i.e., carbohydrate metabolism, antioxidant activity, hormonal regulation, and transcription factors that could be majorly involved in the development of adventitious roots. Differential expression of the upregulated and uniquely expressing thirty-five transcripts in adventitious roots was validated using qRT-PCR. This study has generated the resource of differentially and uniquely expressing transcripts in the waterlogging-induced adventitious roots. Further functional characterization of these transcripts will be helpful to understand the development of adventitious roots, leading to the resistance towards waterlogging stress in Mentha arvensis.

Cytokinin and indole-3-acetic acid crosstalk is indispensable for silicon mediated chromium stress tolerance in roots of wheat seedlings.

The rising heavy metal contamination of soils imposes toxic impacts on plants as well as other life forms. One such highly toxic and carcinogenic heavy metal is hexavalent chromium [Cr(VI)] that has been reported to prominently retard the plant growth. The present study investigated the potential of silicon (Si, 10 µM) to alleviate the toxicity of Cr(VI) (25 µM) on roots of wheat (Triticum aestivum L.) seedlings. Application of Si to Cr(VI)-stressed wheat seedlings improved their overall growth parameters. This study also reveals the involvement of two phytohormones, namely auxin and cytokinin and their crosstalk in Si-mediated mitigation of the toxic impacts of Cr(VI) in wheat seedlings. The application of cytokinin alone to wheat seedlings under Cr(VI) stress reduced the intensity of toxic effects of Cr(VI). In combination with Si, cytokinin application to Cr(VI)-stressed wheat seedlings significantly minimized the decrease induced by Cr(VI) in different parameters such as root-shoot length (10.8% and 13%, respectively), root-shoot fresh mass (11.3% and 10.1%, respectively), and total chlorophyll and carotenoids content (13.4% and 6.8%, respectively) with respect to the control. This treatment also maintained the regulation of proline metabolism (proline content, and P5CS and PDH activities), ascorbate-glutathione (AsA-GSH) cycle and nutrient homeostasis. The protective effect of Si and cytokinin against Cr(VI) stress was minimized upon supplementation of an inhibitor of polar auxin transport- 2,3,5-triiodobenzoic acid (TIBA) which suggested a potential involvement of auxin in Si and cytokinin-mediated mitigation of Cr(VI) toxicity. The exogenous addition of a natural auxin - indole-3-acetic acid (IAA) confirmed auxin is an active member of a signaling cascade along with cytokinin that aids in Si-mediated Cr(VI) toxicity alleviation as IAA application reversed the negative impacts of TIBA on wheat roots treated with Cr(VI), cytokinin and Si. The results of this research are also confirmed by the gene expression analysis conducted for nutrient transporters (Lsi1, CCaMK, MHX, SULT1 and ZIP1) and enzymes involved in the AsA-GSH cycle (APX, GR, DHAR and MDHAR). The overall results of this research indicate towards possible induction of a crosstalk between cytokinin and IAA upon Si supplementation which in turn stimulates physiological, biochemical and molecular changes to exhibit protective effects against Cr(VI) stress. Further, the information obtained suggests probable employment of Si, cytokinin and IAA alone or combined in agriculture to maintain plant productivity under Cr(VI) stress and data regarding expression of key genes can be used to develop new crop varieties with enhanced resistance against Cr(VI) stress together with its reduced load in seedlings.

Methyl-salicylate: A surveillance system for triggering immunity in neighboring plants.

After being infested by aphids, plants trigger a signaling pathway that involves methyl salicylate as an airborne signaling molecule. Thus, the regulation of communication for systemically acquired resistance produced via methyl salicylate is helpful in generating stress resistance among plants against aphid infestation.

Boldine: a narrative review of the bioactive compound with versatile biological and pharmacological potential.

OBJECTIVE: Boldine is a plant-derived bioactive compound that has a beneficial impact on human health. Boldine is an aporphine alkaloid mainly obtained from the leaves and bark of the Chilean Boldo tree (Peumus boldus, Family: Monimiaceae). There are plenty of preclinical evidence supports that boldine exerts its beneficial effects against various diseases. Lumiskin™, a patented and marketed formulation by Revitol Skincare for skin brightening, contains Dicetyl boldine, a boldine derivative. CONTENT: All the available information on the Chilean boldo tree (P. boldus Molina) species was actualized by systematically searching the scientific databases (PubMed, SciFinder, Web of Science, Google Scholar, Scopus and others) and scientific literature. This article covers the recent advances in pharmacokinetic, toxicological, pharmacological/biological activities, and molecular mechanisms of the bioactive compound to understand health benefits of boldine better. SUMMARY: Boldine exerts antioxidant, hepatoprotective, anti-atherosclerotic, anti-diabetic, analgesic, antipyretic, anti-inflammatory, anti-epileptic, neuroprotective, nephroprotective, anti-arthritis, anticancer and nootropic effects. Moreover, boldine exhibits its various pharmacological activities by altering antioxidant parameters (MDA, superoxide dismutase, glutathione), peroxynitrite, inflammatory markers apoptotic index, caspase-3, acetyl-cholinesterase, myeloperoxidase, TNF-α (Tumor necrosis factor-α), iNOS, Bcl-2-associated X protein (BAX), ACE-1(Angiotensin-converting enzyme-1), dopamine D2 receptors and nicotinic acetylcholine receptor. Boldine has the potential to modulate a variety of biological networks. OUTLOOK: Due to its versatile pharmacological effects reported in various experimental animals as well as in randomized clinical trials for the treatment of facial melasma and for treatment of urinary stone lithotripsy in children as a complementary phytotherapy; in the future, this compound might be developed as a novel drug for a different indication.

Epigenetics governs senescence.

Petal is one of the most esthetic and essential parts of a flower that fascinates the pollinators to enhance pollination. Petal senescence is a highly controlled and organized natural phenomenon assisted by phytohormones and gene regulation. It is an inelastically programmed event preceding to which petals give rise to color and scent that captivate pollinators, representing a flower's maturity for sexual reproduction. Till today, many genes involved in the petal senescence through genetic as well as epigenetic changes in response to hormones have been identified. In most of the species, petal senescence is controlled by ethylene, whereas others are independent of this hormone. It has also been proved that the increase in the carbohydrate contents like mannitol, inositol and trehalose delayed the senescence in tulips and Gladiolus. An increased sugar content prevents the biosynthesis of EIN3-like mRNA and further upregulates several senescence correlated genes. A wide range of different transcription factors as well as regulators are disparately expressed in ethylene insensitive and ethylene sensitive petal senescence. DcHB30, a downregulating factor, which upon linking physically to DcWRKY75 leads to the upregulation of ethylene promoting petal senescence. Here we describe the role of ethylene in petal senescence through epigenetic changes. Studies show that ethylene causes petal senescence through epigenetic changes. Feng et al. (Plant Physiol 192:546-564, 2023) observed that ARABIDOPSIS HOMOLOG OF TRITHORAX1 (DcATX1) promotes trimethylation of histone 3 (H3) at 4th lysine (H3K4me3) in Carnation. H3K4me3 further stimulates the expression of genes of ethylene biosynthesis and senescence, leading to senescence in Carnation.

Encapsulated nanopesticides application in plant protection: Quo vadis?

The increased global food insecurity due to the growing population can be addressed with precision and sustainable agricultural practices. To tackle the issues regarding food insecurity, farmers used different agrochemicals that improved plant growth and protection. Among these agrochemicals, synthetic pesticides used for plant protection in the agricultural field have various disadvantages. Conventional applications of synthetic pesticides have drawbacks such as rapid degradation, poor solubility, and non-target effects, as well as increased pesticide runoff that pollutes the environment. Nanotechnology has evolved as a potential solution to increase agricultural productivity through the development of different nanoforms of agrochemicals such as nanopesticides, nano-fabricated fertilizers, nanocapsules, nanospheres, nanogels, nanofibers, nanomicelles, and nano-based growth promoters. Encapsulation of these pesticides inside the nanomaterials has provided good biocompatibility over conventional application by inhibiting the early degradation of active ingredients (AI), increasing the uptake and adhesion of pesticides, improving the stability, solubility, and permeability of the pesticides, and decreasing the environmental impacts due to the pesticide runoff. In this review, different nanoforms of encapsulated pesticides and their smart delivery systems; nanocarriers in RNA interference (RNAi) based pesticides; environmental fate, practical implications, management of nanopesticides; and future perspectives are discussed.

Unlocking a 'lock-key' mechanism governing pollen-pistil interactions.

Pollen-pistil interactions ensure genetic diversity and shape the reproductive success of plants. Lan et al. recently revealed that the interaction among various receptor-like kinases, cell-wall proteins, and stigmatic RALF peptides (sRALFs) or pollen RALF peptides (pRALFs) on the stigma surface govern the penetration of pollen tubes in members of the Brassicaceae.

Sustainable agriculture.

Developing sustainable agricultural practices is currently becoming an increasingly relevant challenge. As the worldwide population rises and climate change affects agriculture globally, new and sustainable approaches must be adopted to ensure food security. In this editorial, we invite contributions to a BMC Plant Biology collection on 'Sustainable agriculture,' covering research on the environmental and socioeconomic factors that affect sustainable agricultural practices and their management.

Whole chloroplast genome-specific non-synonymous SNPs reveal the presence of substantial diversity in the pigeonpea mini-core collection.

To unravel the plastid genome diversity among the cultivated groups of the pigeonpea germplasm, we characterized the SNP occurrence and distribution of 142 pigeonpea mini-core collections based on their reference-based assembly of the chloroplast genome. A total of 8921 SNPs were found, which were again filtered and finally 3871 non-synonymous SNPs were detected and used for diversity estimates. These 3871 SNPs were classified into 12 groups and were present in only 44 of the 125 genes, demonstrating the presence of a precise mechanism for maintaining the whole chloroplast genome throughout evolution. The Acetyl-CoA carboxylase D gene possesses the maximum number of SNPs (12.29%), but the Adenosine Tri-Phosphate synthatase cluster genes (atpA, atpB, atpE, atpF, atpH, and atpI) altogether bear 43.34% of the SNPs making them most diverse. Various diversity estimates, such as the number of effective alleles (1.013), Watterson's estimate (0.19), Tajima's D ( - 3.15), Shannon's information index (0.036), suggest the presence of less diversity in the cultivated gene pool of chloroplast genomes. The genetic relatedness estimates based on pairwise correlations were also in congruence with these diversity descriptors and indicate the prevalence of rare alleles in the accessions. Interestingly, no stratification was observed either through STRUCTURE, PCoA, or phylogenetic analysis, indicating the common origin of the chloroplast in all the accessions used, irrespective of their geographical distribution. Further 6194 Cleaved Amplified Polymorphic Sequences (CAPS) markers for 531 SNPs were developed and validated in a selected set of germplasm. Based on these results, we inferred that all of the cultivated gene pools of pigeonpea have a common origin for the chloroplast genome and they possess less diversity in protein-coding regions, indicating a stable and evolved plastid genome. At the same time, all diversity analysis indicates the occurrence of rare alleles, suggesting the suitability of the mini-core collection in future pigeonpea improvement programs. In addition, the development of chloroplast genome-based CAPS markers would have utility in pigeonpea breeding programs. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03785-8.

Does MPK4/12-HT1 function as a CO2/bicarbonate sensor to regulate the stomatal conductance under high CO2 levels?

KEY MESSAGE: Recently, a HT1 protein has been identified which causes continuous opening of stomata because of its kinase activity. However, reversible interaction between MAP4/12 and HT1 protein acts as a CO2/bicarbonate sensor and causes the closing of stomata by inhibiting HT1 kinase activity.

Simultaneous intervention against oxidative stress and inflammation by targeting Nrf2/ARE and NLRP3 inflammasome pathway mitigates thioacetamide-induced liver fibrosis in rat.

Liver fibrosis is a typical pathological state/stage involved in most chronic liver diseases and its persistence results in cirrhosis. Inflammasomes are cytoplasmic sensors that induce inflammation in response to stress. Glibenclamide (GLB) is an USFDA-approved drug for type 2 diabetes and is reported to possess anti-inflammatory activity by inhibiting inflammatory cytokines. Dimethyl fumarate (DMF) is an USFDA-approved drug for multiple sclerosis and has been reported to activate the Nrf2/ARE pathway to maintain the cellular antioxidant balance. A total of 36 rats were randomized into six groups (n = 6 each). The rats were injected with thioacetamide (TAA) 200 mg/kg, intraperitoneally every third day for eight consecutive weeks to induce liver fibrosis and oral treatment of GLB 0.5 mg/kg/day and DMF 25 mg/kg/day, and their combinations were provided for the last four consecutive weeks. Treatment with GLB, DMF, and GLB+DMF significantly protected against TAA-mediated oxidative stress and inflammatory conditions by improving hepatic function test, triglycerides, hydroxyproline, and histopathological alterations, by inhibiting the NLRP3 inflammasome signaling and fibrogenic markers, and by activating Nrf2/ARE pathway in Wistar rats. The present results suggest that simultaneous Nrf2/ARE activation and NLRP3 inflammasome inhibition could significantly contribute to developing a novel therapy for patients with liver fibrosis.

Zinc induced regulation of PCR1 gene for cadmium stress resistance in rice roots.

In this study, the interaction between zinc (Zn) and cadmium (Cd) was investigated in rice roots to evaluate how Zn can protect the plants from Cd stress. Rice seedlings were treated with Cd (100 µM) and Zn (100 µM) in different combinations (Cd alone, Zn alone, Zn+ Cd, Zn+ Cd+ L-NAME, Zn+ Cd+ L-NAME+ SNP). Rice roots treated with only Zn also displayed similar toxic effects, however when combined with Cd exhibited improved growth. Treating the plant with Zn along with Cd distinctly reduced Cd concentration in roots while increasing its own accumulation due to modulation in expression of Zinc-Regulated Transporter (ZRT)-/IRT-Like Protein (OsZIP1) and Plant Cadmium Resistance1 (OsPCR1). Cd reduced plant biomass, cell viability, pigments, photosynthesis and causing oxidative stress due to inhibition in ascorbate-glutathione cycle. L-NAME (NG-nitro L-arginine methyl ester), prominently suppressed the beneficial impacts of Zn against Cd stress, whereas the presence of a NO donor, sodium nitroprusside (SNP), significantly reversed this effect of L-NAME. Collectively, results point that NO signalling is essential for Zn- mediated cross-tolerance against Cd stress via by modulating uptake of Cd and Zn and expression of OsZIP1 and OsPCR1, and ROS homeostasis due to fine tuning of ascorbate-glutathione cycle which finally lessened oxidative stress in rice roots. The results of this study can be utilized to develop new varieties of rice through genetic modifications which will be of great significance for maintaining crop productivity in Cd-contaminated areas throughout the world.

Ameliorative effects of Si-SNP synergy to mitigate chromium induced stress in Brassica juncea.

Hyperaccumulation of heavy metal in agricultural land has hampered yield of important crops globally. It has consequently deepened concerns regarding the burning issue of food security in the world. Among heavy metals, Chromium (Cr) is not needed for plant growth and found to pose detrimental effects on plants. Present study highlights the role of exogenous application of sodium nitroprusside (SNP, exogenous donor of NO) and silicon (Si) in alleviating detrimental ramification of Cr toxicity in Brassica juncea. The exposure of B. juncea to Cr (100 µM) under hydroponic system hampered the morphological parameters of plant growth like length and biomass and physiological parameters like carotenoid and chlorophyll contents. It also resulted in oxidative stress by disrupting the equilibrium between ROS production and antioxidant quenching leading to accumulation of ROS such as hydrogen peroxide (H2O2) and superoxide (O2•‾) radicle which causes lipid peroxidation. However, application of Si and SNP both individually and in combination counteracted oxidative stress due to Cr by regulating ROS accumulation and enhancing antioxidant metabolism by upregulation of antioxidant genes of DHAR, MDHAR, APX and GR. As the alleviatory effects were more pronounced in plants treated with combined application of Si and SNP; therefore, our findings suggest that dual application of these two alleviators can be used to mitigate Cr stress.