Adaptive roles of cytokinins in enhancing plant resilience and yield against environmental stressors

Identification of a Specific Role of Dihydrozeatin in the Regulation of the Cell Differentiation Activity in Arabidopsis Roots

The plant hormones cytokinins are a class of heterogeneous active compounds that control multiple aspects of development and physiology. Among cytokinins, trans-zeatin (tZ), the most abundant cytokinin, has been extensively studied in relation to its effects on development, and it plays a key role in promoting cell differentiation. In analogy with tZ, here we demonstrate that dihydrozeatin (DHZ) controls (root) development by promoting cell differentiation. By means of pharmacological and genetic analysis, we demonstrate that DHZ is specifically and uniquely perceived by the histidine kinase (HK) receptor AHK3, and that this interaction is sufficient to promote cell differentiation in the root meristem via activation of the transcription factors ARABIDOPSIS RESPONSE REGULATOR 1, 12, and 11. We also show that DHZ and tZ activity might be conserved among plants. Our results support the idea that different types of cytokinins act via specific receptors to exert their roles and suggest new approaches to study their activity in differentiation.

Trans-zeatin modulates shade stress adaptation in soybean through transcription associated metabolic network

This study explores the molecular mechanisms by which trans-zeatin (tZ), a cytokinin, influences shade stress responses in shade-sensitive and shade-tolerant recombinant inbred lines (RILs) 160 and 165 of soybean (Glycine max) under varied light conditions. Using an integrative multi-omics approach combining metabolomics and transcriptomics, we elucidate the regulatory networks underlying soybean adaptation to shade stress. Using an integrative multi-omics approach that combines metabolomics and transcriptomics, we dissect the complex regulatory networks that enable soybean plants to adapt to shade stress. Our results demonstrate that tZ significantly affects growth, biomass accumulation, photosynthetic efficiency, and yield in soybean plants. Metabolomic analysis revealed that shade stress impacts key metabolic pathways, including phenylpropanoids, flavonoids, flavone and flavonol, anthocyanin, and brassinosteroid biosynthesis, with tZ treatment enhances the adaptive responses of soybean plants. Transcriptomic data further identified differential gene expression in these pathways, alongside those related to hormone-mediated signaling pathway, cell wall biogenesis, and defence response pathways underlining the molecular adjustments to tZ and shade stress. Importantly, the integration of metabolomics and transcriptomics data revealed key KEGG pathways and genes regulated by tZ treatment in RIL 160 under shade stress, including significant alterations in phenylpropanoids, flavonoids, hormone-mediated signaling pathway, cell wall biogenesis and defence response, anthocyanin biosynthesis, and fatty acid degradation pathways as well key responsive transcription factors. This study provides insights into the role of tZ in mediating soybean responses to shade stress at the molecular level, offering insights into improving soybean resilience to low light conditions and informing future agricultural practices for optimizing crop yield.

Exploring the Interplay of Explant Origin and Culture Density on Olive Micropropagation Efficiency

Apical dominance and culture heterogeneity significantly limit the efficiency of olive micropropagation, hindering the rapid production of plantlets. This study explores how manipulating the explant origin (topophysis) and density can mitigate these challenges. Explants originating from apical and middle sections were cultivated at densities of 18, 24, and 30 explants per vessel. After 12 weeks, significant differences in the growth parameters were observed based on the explant origin and density. The middle-section explants exhibited superior shoot proliferation and node production, especially at higher densities. The callus weight also increased with the density, while the internode length remained relatively stable. Hormone analysis demonstrated the density-dependent spatial distribution pattern of aromatic and isoprenoid cytokinins. Notably, at higher densities, the aromatic free bases in the apical-section leaves showed migration toward the shoot apices, while this migration was less pronounced in the middle-section leaves. Isoprenoid cytokinins displayed complex distribution patterns, with free bases and O-glucosides often increasing toward the basal nodes. These findings demonstrate that optimizing the explant origin and density can effectively reduce apical dominance and enhance culture homogeneity in olive micropropagation. This approach offers a promising strategy for improving the micropropagation protocols for olive and potentially other woody plants, leading to more efficient and cost-effective production of high-quality plantlets for commercial use.

Microbial diversity and interactions: Synergistic effects and potential applications of Pseudomonas and Bacillus consortia

Microbial diversity and interactions in the rhizosphere play a crucial role in plant health and ecosystem functioning. Among the myriads of rhizosphere microbes, Pseudomonas and Bacillus are prominent players known for their multifaceted functionalities and beneficial effects on plant growth. The molecular mechanism of interspecies interactions between natural isolates of Bacillus and Pseudomonas in medium conditions is well understood, but the interaction between the two in vivo remains unclear. This paper focuses on the possible synergies between Pseudomonas and Bacillus associated in practical applications (such as recruiting beneficial microbes, cross-feeding and niche complementarity), and looks forward to the application prospects of the consortium in agriculture, human health and bioremediation. Through in-depth understanding of the interactions between Pseudomonas and Bacillus as well as their application prospects in various fields, this study is expected to provide a new theoretical basis and practical guidance for promoting the research and application of rhizosphere microbes.

A Comparative Analysis of the Effect of 24-Epibrassinolide on the Tolerance of Wheat Cultivars with Different Drought Adaptation Strategies Under Water Deficit Conditions

Drought is a serious environmental challenge that reduces the productivity of valuable crops, including wheat. Brassinosteroids (BRs) is a group of phytohormones that have been used to enhance wheat drought tolerance. Wheat cultivars with different adaptation strategies could have their own specific drought tolerance mechanisms, and could react differently to treatment with growth regulators. In this work, the effect of seed pretreatment with 0.4 µM 24-epibrassinolide (EBR) was investigated in two wheat (Triticum aestivum L.) cultivars contrasting in drought behavior, tolerant Ekada 70 (cv. E70) and sensitive Zauralskaya Zhemchuzhina (cv. ZZh), in early ontogenesis under dehydration (PEG-6000) or soil drought conditions. EBR pretreatment mitigated the stress-induced inhibition of seedling emergence and growth, as well as membrane damage in cv.E70 but not in ZZh. An enzyme-linked immunosorbent assay (ELISA) revealed substantial changes in hormonal balance associated with ABA accumulation and a drop in the levels of IAA and cytokinins (CKs) in drought-subjected seedlings of both cultivars, especially ZZh. EBR-pretreatment reduced drought-induced hormone imbalance in cv. E70, while it did not have the same effect on ZZh. EBR-induced changes in the content of wheat germ agglutinin (WGA) belonging to the protective proteins in E70 seedlings suggest its contribution to EBR-dependent adaptive responses. The absence of a detectable protective effect of EBR on the ZZh cultivar may be associated with its insensitivity to pre-sowing EBR treatment.

6-Benzylaminopurine-dependent starch accumulation is key to drought tolerance in tall fescue subjected to water deficiency

Drought is a natural disaster that exerts considerable adverse impacts on the agricultural sector. This study aimed to investigate the cytokinin-mediated carbohydrate accumulation in the aerial parts of the plant and the roots in four-month-old drought-stressed tall fescue (Festuca arundinacea Schreb.) plants. To achieve this, exogenous treatments containing 50 mM of the synthetic cytokinin 6-Benzylaminopurine (6-BA) were applied prior to the onset of drought stress and every seven days during the 14-day drought stress period. These plants were subjected to varying levels of soil water holding capacity (WHC): 25 ± 5% (severe stress), 50 ± 5% (moderate stress), and 100 ± 5% (control). A range of morpho-physiological, biochemical, and molecular responses were evaluated. Our data suggest that the reduction of starch and the accumulation of water-soluble carbohydrates (WSCs) induced by severe drought stress were mitigated (reduced by half) in the roots and shoots of plants treated with 6-BA under similar drought conditions. This treatment may support plants by promoting the normal storage of energy reserves, thereby enhancing their resilience during subsequent periods of water scarcity. Furthermore, the application of 6-BA facilitates the regulation of carbohydrate accumulation, proline content, and enzymatic activity. 6-BA functions by downregulating the expression of cytokinin oxidase/dehydrogenase genes, particularly FaCKX1 and FaCKX3, and by upregulating the FaIPT8 gene. This mechanism inhibits the degradation of cytokinins and promotes root growth under conditions of severe drought stress. 6-BA reduced FaPIN1 expression during moderate drought stress compared to the corresponding control, indicating that cytokinins can alter auxin transport mechanisms and help plants prioritize growth processes under water scarcity. The application of 6-BA not only serves as an effective sink for enhancing starch accumulation in leaves but also inhibits the expression of the chlorophyll degradation gene (FaSGR), thereby preventing chlorophyll degradation. This dual action aids plants in sustaining their growth and development during episodes of short-term drought stress.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-025-01559-5.

Effects of Cytokinins on Morphogenesis, Total (Poly)Phenolic Content and Antioxidant Capacity of In Vitro-Cultured Hop Plantlets, cvs. Cascade and Columbus

(1) Background: Humulus lupulus L. plants constitute a rich source of bioactive compounds. The synthesis of bioactive compounds in plants is often triggered by the activation of secondary metabolism, which can be induced by biotic or abiotic elicitors. In vitro, the effect of the elicitors can be studied in a controlled environment and in a small space, independently of seasonal variations. Cytokinins are frequently used in plant tissue culture for bud regeneration, branching and shoot elongation due to their role in cell division enhancement. This study aimed to investigate the effects of different cytokinins on the growth parameters, total (poly)phenolic content and antioxidant capacity of in vitro-grown hop plants to evaluate hop vitro-derived biomass as a potential source of bioactive compounds. (2) Methods: unimodal hop (cvs. Cascade and Columbus) explants were cultured on media enriched with four cytokinins (kinetin, 6-benzylaminopurine, meta-topolin and 6-(γ,γ-dimethylallylamino)-purine) at four concentrations. (3) Results: A genotype-dependent response to different cytokinins was encountered. (4) Conclusions Columbus explants could root in culture media auxin-free, providing valuable opportunities for commercial nurseries. Moreover, cytokinins were confirmed to be valuable elicitors to stimulate the bioactive compound biosynthesis in micropropagated hop plants, making them a precious source for various industries.

Interplay Between Phytohormones and Sugar Metabolism in Dendrocalamus latiflorus

Dendrocalamus latiflorus, a species of giant bamboo, holds significant ecological and economic value. This review delves into the intricate interplay between phytohormones and sugar metabolism in Dendrocalamus latiflorus, emphasizing species-specific mechanisms that enhance its ecological adaptability and rapid growth. By synthesizing recent research, this work highlights how phytohormones, including auxins, cytokinins, and abscisic acid, regulate sugar metabolism pathways such as glycolysis and starch degradation in response to environmental stimuli. These hormones influence crucial plant processes, including cell division, elongation, stress responses, and sugar metabolism pathways such as glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation. Geographic variations in these processes are examined, demonstrating their role in environmental adaptation and ecological resilience. For instance, populations in nutrient-rich soils exhibit enhanced cytokinin activity and sugar transport efficiency, while those in water-limited areas display elevated abscisic acid levels, aiding drought tolerance. This targeted focus on D. latiflorus provides novel insights into its potential applications in sustainable forestry and agroforestry systems. By integrating recent advances, this review highlights the critical role of phytohormone-sugar interplay in improving the productivity and stress resilience of D. latiflorus, with implications for agroforestry systems and climate change adaptation.

Mechanisms and Impact of Rhizosphere Microbial Metabolites on Crop Health, Traits, Functional Components: A Comprehensive Review

Current agricultural practices face numerous challenges, including declining soil fertility and heavy reliance on chemical inputs. Rhizosphere microbial metabolites have emerged as promising agents for enhancing crop health and yield in a sustainable manner. These metabolites, including phytohormones, antibiotics, and volatile organic compounds, play critical roles in promoting plant growth, boosting resistance to pathogens, and improving resilience to environmental stresses. This review comprehensively outlines the mechanisms through which rhizosphere microbial metabolites influence crop health, traits, functional components, and yield. It also discusses the potential applications of microbial secondary metabolites in biofertilizers and highlights the challenges associated with their production and practical use. Measures to overcome these challenges are proposed, alongside an exploration of the future development of the functional fertilizer industry. The findings presented here provide a scientific basis for utilizing rhizosphere microbial metabolites to enhance agricultural sustainability, offering new strategies for future crop management. Integrating these microbial strategies could lead to increased crop productivity, improved quality, and reduced dependence on synthetic chemical inputs, thereby supporting a more environmentally friendly and resilient agricultural system.