Cytokinin Research Articles (Page 1)

The Dual Role of Ethylene in Plant Growth and Abiotic Stress: Mechanisms, Regulation, and Mitigation through ACC Deaminase.

From roots to resilience: Strigolactones for boosting crop resilience and productivity under stressful environments.

The effects of foliar applications of zinc oxide nanoparticles and various biostimulants were studied to alleviate water stress in sugar beet. The experiment used a split-split-plot layout based on a Randomized Complete Block Design (RCBD) with three replications over two growing seasons (2022–2024). The main plot consisted of two irrigation levels: Irrigation after 60 and 120 mm of evaporation was considered normal irrigation (WW) and water deficit stress (WD). Zinc nanoparticle (ZnO-NPs) levels (control, 0.2, and 0.4 mg L−1) were assigned to subplots, and biostimulants (control, chitosan, proline, and chitosan + proline) were assigned to sub-subplots. The results shoewd under WD conditions foliar spraying of 4 mg L−1 of ZnO-NPs increased the chlorophyll b content (22.85%), carotenoid (9.58%), proline content (18.42%), beta-glycine (13.20%), stomatal conductance (33.53%), gibberellin (GA) (9.09%), cytokinin (CK) (13.07%), catalase enzyme activity (CAT) (7.86%), superoxide dismutase (SOD) (25.56%), ascorbate peroxidase (APX) (5.34%), and root yield (RY) (10.48%) and decreased abscisic acid (ABA) (11.24%), malondialdehyde (MAD) (17.33%), and hydrogen peroxide (17.18%) compared to the control. Among biostimulants treatments, application of chitosan + proline under WD conditions increased the content of chlorophyll a (37.44%), chlorophyll b (16.23%), proline (4.87%), beta-glycine (18.09%), GA (7.00%), auxin (IAA) (35.40%), CK (18.03%), CAT (11.42%), APX (19.6%), and RY (11.46%) compared to control, and decreased the content of ABA (24.16%), MAD (9.03%), and hydrogen peroxide (11.50%). In this experiment, the combination of 2 mg L-1 ZnO-NPs with chitosan and proline exhibited a synergistic effect, increasing the content of chlorophyll a and b, relative water content (RWC), SOD, and RY, while reducing ABA. The lowest IBRv2 values were recorded for control + proline, control + chitosan, 2 mg L−1 ZnO-NPs + Control, 4 mg L−1 ZnO-NPs + Control, and 4 mg L−1 ZnO-NPs + Proline treatments. 4 mg L−1 ZnO-NPs + chitosan + proline (I = 0.803) and 4 mg L−1 ZnO-NPs + proline (I = 0.809) showed the smallest increases in MAD content. In terms of RY, the least decrease was observed in the treatments of 4 mg L−1 ZnO-NPs + Chitosan and Proline (I = − 0.492) and 4 mg L−1 ZnO-NPs + Proline (I = − 1.014).

Melatonin (MT), an antioxidant and growth regulator, interacts with almost all phytohormones, but the molecular mechanisms of these interactions are poorly understood. Using mRNA sequencing (mRNA-seq) technology, we analysed the global regulation of MT-induced expression of genes involved in metabolism, signalling and responses to major phytohormones under prolonged high-intensity light (HL) stress. Plants respond to MT through the activation of auxin and brassinosteroid (BS) response genes, which were identified among the enriched categories of differentially expressed genes (DEGs) with increased expression, and the suppression of abscisic acid and ethylene signalling and response genes, which were among the enriched downregulated categories. MT also suppressed growth-inhibiting genes involved in jasmonic acid (JA) and salicylic acid (SA) signalling and response and activated genes encoding the growth-promoting hormones gibberellins and cytokinins (CKs), which is consistent with the role of MT in stress alleviation. However, the expression of some unique genes, which are positively or negatively modulated by stress, was reinforced by MT treatment, illustrating the extraordinary type of regulation that enhances the action of specific hormone-mediated mechanisms. The study of signal integration between MT and hormones with the involvement of signalling mutants revealed that some interactions are regulated at the transcriptional level and require the activity of relevant signalling pathways. Disruption of CAND2 completely abolished melatonin-dependent activation of the mitogen-activated protein kinases MAP3K17 and MKK7, suggesting that the MAP3K17-MKK7 module is an important player in the MT-triggered MAPK pathway, acting downstream of CAND2.

Nanocarriers can improve pesticide delivery efficiency and reduce phytotoxicity, thereby supporting sustainable strategies for crop protection. Given this potential, it is essential to investigate their effects on crop physiology and development. The effects of porphyrin-containing covalent organic framework (COF) carriers on the delivery and biological performance of the fungicide Fludioxonil (FLU) were evaluated in Nicotiana tabacum. The COF exhibited a highly ordered crystalline architecture with an encapsulation efficiency of 60.9%. Treatments included FLU@COF, free FLU, untreated controls and additional reference groups, applied at concentrations of 5 and 50 mg L-1. Compared with free FLU, the FLU@COF formulation enhanced antifungal activity against Fusarium oxysporum by 35.3%. Furthermore, it exhibited high soil mobility, facilitating effective dissemination. The COF penetrated root tissues and was systemically distributed throughout the plant. As a result, treated plants exhibited a 37.4% increase in leaf area, a 25.2% increase in plant height and more than 25.2% increases in chlorophyll a and b contents. Phytohormone profiling revealed that levels of indole-3-acetic acid (IAA), cytokinin (CK) and gibberellin (GA) each increased by more than 20.0%, accompanied by higher accumulation of carbon, nitrogen and soluble sugars. Multi-omics analyses, supported by virus-induced gene silencing (VIGS), demonstrated that the UV RESISTANCE LOCUS 8 (UVR8)-mediated CONSTITUTIVELY PHOTOMORPHOGENIC 1-ELONGATED HYPOCOTYL 5 (COP1-HY5) signalling pathway regulates COF-induced growth promotion. Moreover, the COF delivery system exhibited high biocompatibility and reduced the ecological toxicity of FLU. Collectively, these findings establish a robust, low-toxicity nanocarrier platform with strong potential for safe and effective application in sustainable agriculture.

Myogenesis is a tightly regulated process essential for embryonic development, postnatal growth, and muscle regeneration. We recently identified that cytokinins (CTKs), a class of adenine-derived signaling molecules originally characterized in plants, are present in cultured skeletal muscle cells. The most abundant type of cytokinins detected within cultured muscle cells was isopentenyladenine (iP) in its nucleotide, riboside, and free base derivatives. The purpose of this study was to determine whether CTKs are also present in regenerating muscle tissue in vivo and to characterize the effects of iP and its riboside form, isopentenyladenosine (iPR), on muscle cell proliferation and differentiation. These effects were observed relative to adenine and adenosine, and to a second class of cytokinins with a large aromatic side chain, kinetin (the free base), and kinetin riboside. Cardiotoxin was used to induce muscle injury and repair processes in the gastrocnemius of 3- and 12-month-old mice. Samples were collected 3- and 7 days post-injury for ultra high-performance liquid chromatography tandem mass spectrometry with electrospray ionization (UHPLC-(ESI+)-HRMS/MS). Four CTKs (N6-benzyladenine (BA), dihydrozeatin-9-N-glucoside (DZ9G), isopentenyladenosine (iPR), and 2-methylthio-isopentenyladenosine (2-MeSiPR) were detected. 2-MeSiPR levels were significantly influenced by aging, as this CTK was increased in response to injury only in the younger mice. Treatment of C2C12 myoblasts with 10 µM of isopentenyladenosine (iPR) or kinetin riboside reduced cell proliferation, whereas iP (the free base) increased proliferation in a biphasic response. During differentiation, both iPR and kinetin riboside impaired myotube formation, while the free-base forms of iP and kinetin had no effect. Our data establishes that CTKs are present within muscle tissue and highly responsive to injury and aging. Furthermore, the biological activities of CTKs in muscle cells are influenced by structural modifications, including riboside conjugation and side chain composition. Understanding these differences provides insight into the distinct roles of CTKs in muscle cell metabolism and differentiation, offering potential implications for the use of exogenous CTKs in muscle biology and regenerative medicine.

Background‘Tuershao’ is a new chayote (Sechium edule) variety whose tuberous roots and tender shoots are edible. These parts are rich in beneficial substances, including amino acids, proteins, phenolic compounds, flavonoids, cucurbitacin, and selenium, demonstrating their unique value. However, its ovary cannot develop into a mature fruit, and cutting techniques help to achieve the breeding of ‘Tuershao’.ResultsThis study found that using peat soil as the substrate and treating semi-hard branches with 1.0 g·L⁻¹ indole-3-butyric acid (IBA) achieved the highest rooting rate of 94.33%, with the maximum values in root length, root surface area, root volume, and root diameter. Additionally, exogenous hormone treatment led to greater fluctuations in the contents of soluble sugar, starch, and soluble protein in ‘Tuershao’. The activities of catalase (CAT), polyphenol oxidase (PPO), peroxidase (POD), and superoxide dismutase (SOD) were also enhanced. The contents of endogenous hormones such as auxin (IAA), cytokinin (CTK), and gibberellin A3 (GA3) increased, while abscisic acid (ABA) decreased.ConclusionsTreating semi-hard branches with 1.0 g·L⁻¹ IBA on peat soil shows the best effect in promoting rooting of ‘Tuershao’ cuttings. Exogenous IBA can promote nutrient metabolism, enhance antioxidant enzyme activities, and regulate endogenous hormone levels in ‘Tuershao’ cuttings, thereby further promoting rooting.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07455-0.

Seed number per silique (SNPS) is an important determinant for seed yield in rapeseed (Brassica napus). Here, the molecular mechanism of BnaC9.APT5 (Adenine phosphoribosyltransferase 5) regulating SNPS was identified by combining gene function with biochemical analyses. Overexpression (OE) of Arabidopsis Adenine Phosphoribosyltransferase 5 (AtAPT5) and ectopic expression of BnaC9.APT5 in Arabidopsis thaliana increased SNPS by c. 9%. By contrast, the Arabidopsis knockout mutant had 18% fewer seeds per silique. OE of BnaC9.APT5 in rapeseed increased SNPS by c. 11% through upregulating cytokinin (CK) biosynthesis genes. The enzyme activity analysis showed that BnaC9.APT5 converts adenine to adenosine monophosphate. Spraying the Arabidopsis knockout mutant with 6-benzylaminopurine increased SNPS by 34%. The treatment of the Arabidopsis AtAPT5 and rapeseed BnaC9.APT5 OE lines with the CK biosynthesis inhibitor lovastatin reduced SNPS by c. 7% and 9%, respectively. Thus, BnaC9.APT5 controls SNPS via the CK metabolism in rapeseed. A 48-bp InDel in the BnaC9.APT5 promoter was significantly associated with gene expression and SNPS and has been selected during rapeseed 'double-low' quality breeding. Our data provide clear evidence of the role of the BnaC9.APT5 gene for the genetic improvement of modern rapeseed.

Cytokinins (CKs) are central regulators of leaf senescence, yet their cultivar-specific functions in cereals remain insufficiently understood. Here, we examined dark-induced senescence (DIS) in three barley (Hordeum vulgare L.) cultivars: Carina, Lomerit, and Bursztyn, focusing on responses to exogenous benzyladenine (BA) and inhibition of endogenous CK biosynthesis via the mevalonate (MVA) pathway using lovastatin (LOV). Bursztyn, a winter cultivar, displayed a previously uncharacterized stay-green phenotype, characterized by delayed chlorophyll and protein degradation and reduced sensitivity to BA with respect to chlorophyll retention. In contrast, Carina (spring) senesced rapidly but exhibited strong responsiveness to BA. Lomerit (winter) showed an intermediate phenotype, combining moderate natural resistance to senescence with clear responsiveness to BA. CK application suppressed SAG12 cysteine protease accumulation in all cultivars, serving as a marker of senescence and N remobilization, stabilized photosystem II efficiency, preserved photosynthetic proteins, and alleviated oxidative stress without promoting excessive energy dissipation. Although BA only partially mitigated the decline in net CO2 assimilation, it sustained ribulose-1,5-bisphosphate regeneration, supported electron transport, and stabilized Rubisco and Rubisco activase. Moreover, LOV-based inhibition of the MVA pathway of CK biosynthesis revealed that endogenous CK contributions to senescence delay were most pronounced in Lomerit, moderate in Bursztyn, and negligible in Carina, indicating genotype-specific reliance on MVA-versus methylerythritol phosphate (MEP) pathway-derived CK pools. Collectively, these findings identify Bursztyn as a novel genetic resource for stay-green traits and demonstrate that BA delays DIS primarily by maintaining photosynthetic integrity and redox balance. The results highlight distinct regulatory networks shaping CK-mediated senescence responses in cereals, with implications for improving stress resilience and yield stability.

trans-Zeatin N-glucosides can delay salt accelerated leaf senescence in Arabidopsis thaliana.

Fluctuations in nitrate availability impact cytokinin biosynthesis through histone modifications of IPT3 in Arabidopsis roots for growth acclimation.

Cinnamomum burmanni serves as a principal arboreal species utilized for the extraction of essential oils, and its foliage and branches contain a wide array of terpenoid compounds. These compounds are extensively utilized in the cosmetic and pharmaceutical sectors. However, the organ-specific distribution of phytohormones and the underlying molecular regulatory mechanisms in C. burmanni have not been fully elucidated. Consequently, this study presents the first comprehensive metabolomic, transcriptomic, and full-length transcriptomic analyses aimed at systematically elucidating the organ-specific hormone distribution and molecular regulatory networks within the leaves, stems, and roots of borneol-type C. burmanni. The research identified 70 significantly differential hormones, including 32 cytokinin (CTK)-related hormones, 19 auxin-related hormones, and seven gibberellin (GA)-related hormones, uncovering distinct organ-specific patterns: indole-3-acetic acid (IAA) predominantly accumulated in leaves, while GA and CTK were highly expressed in stems. Additionally, 812 differentially expressed genes (DEGs) were identified among different organs, including 50 hormone signaling-related DEGs pinpointed via weighted gene co-expression network analysis (WGCNA). Further investigations indicated that several putative transcription factors (TFs), including ARF, bHLH (PIF3/4), GRAS (DELLA), G2-like (GLK/KAN1/2/HH2O/APL/FT), and ARR-B, may constitute a core regulatory module that mediates hormone-dependent growth, development, and terpenoid biosynthesis. This study establishes the first multi-omics-driven hormonal interaction network framework for the molecular breeding of C. burmanni while developing a gene editing target atlas to elucidate synergistic regulatory mechanisms underlying medicinal secondary metabolite biosynthesis.

The Target of Rapamycin (TOR) is an evolutionarily conserved protein kinase that serves as a crucial signaling hub, seamlessly integrating a wide range of internal and external signals to meticulously regulate cellular and organismal physiology. TOR is crucial in regulating the different phases of lifecycle in plants including embryogenesis, seed germination, meristem activation, root and leaf development, flowering and senescence. Beyond its central role in growth and development, emerging research has revealed its significant involvement in the response to environmental stresses. Even though plant growth regulators such as auxin, cytokinin (CK), brassinosteroid (BR), gibberellin (GA), abscisic acid (ABA), ethylene (ET), salicylic acid (SA), jasmonic acid (JA) and nitric oxide (NO) function as pivotal signaling molecules in modulating plant development and stress responses, how they coordinate with the energy status still remains obscure. Here we summarize the current findings on the dynamic interconnection between TOR and these discrete phytoregulators and their potential role in executing diverse biological processes in plants.

ABSTRACTAmyloidosis, a self‐assembly of proteins or peptides, is associated with numerous degenerative diseases, such as gelsolin amyloidosis, which remain without a cure. Gelsolin protein is an actin‐binding protein, but when aggregated in a diseased state, it is a potential drug target. Specifically, gelsolin mutations, N184K and D187Y, have been linked to renal amyloidosis and systemic progressive deposition of amyloids, respectively. Understanding how such mutations mitigate gelsolin aggregation and how this process can be prevented through small molecule inhibitors is of interest. Herein, we explored the efficacies of plant‐based naturally occurring cytokinin (CK) molecules as aggregation modulators in vitro. Using various biophysical methods, such as spectroscopy and microscopy, the aggregation of wild‐type gelsolin peptide 184NNGDCFILDL193 and its mutants (N184K, D187Y) was investigated. The mutations significantly promoted aggregation, which is of biological significance. The CK trans‐zeatin (tZ) was a more effective disaggregation promoter compared with kinetin (Kin). The experimentally determined IC50 values were in the 9–20 μM range. The mode of inhibition was identified as direct non‐covalent complexation between the CK and the peptides by using mass spectrometry and molecular docking studies. Data show that CKs are promising amyloid modulators, which can be easily translatable to other amyloid systems.

Somatic embryogenesis (SE) is a crucial strategy for in vitro regeneration in woody plants, yet its efficiency is affected by multiple factors, and the underlying regulatory mechanisms remain insufficiently understood. In this study, callus tissues from two Liriodendron sino-americanum genotypes involving different hybrid combinations, ON-LoS and TN-LoS, were treated with varying concentrations (0, 0.005, 0.01, 0.05 mg/L) of exogenous zeatin (ZT) to evaluate its regulatory effect on SE. Treatment with 0.01 mg/L ZT significantly promoted SE in ON-LoS but suppressed it in TN-LoS, indicating that ZT elicited divergent regulatory effects on SE between the two genotypes. To explore the molecular basis of this divergence, transcriptome analysis was conducted at the early stage of SE. Differentially expressed genes (DEGs) were significantly enriched in hormone signaling, particularly in the cytokinin (CK) and brassinosteroid (BR) signaling pathways, as well as biosynthetic and redox-related pathways. In particular, given the established role of cell cycle-related gene CYCD3 (Lchi20922) in promoting cell division, CYCD3 was markedly upregulated by ZT in ON-LoS but downregulated in TN-LoS. These results indicate that ZT regulates SE efficiency through differential modulation of CYCD3 expression in distinct genotypes. This study enhances our understanding of the molecular basis of SE regulation in Liriodendron sino-americanum and offers a theoretical framework for improving regeneration efficiency in woody plants.

GA participates in FR light-induced internode elongation of cucumber by regulating the expression of genes/proteins related to aquaporins, expansins, cell wall biosynthesis, hormone metabolism, and signal transduction. This study investigated the effects of the interaction between far-red (FR) light and gibberellin (GA) on the internode elongation of cucumber (Cucumis sativus L. 'Zhongnong No. 26') seedlings through combined physiological, biochemical, transcriptomic, and proteomic analyses. The results revealed that FR light and GA significantly promoted internode elongation in cucumber seedlings, whereas a GA biosynthesis inhibitor (PAC) inhibited the promoting effect of FR light. Hormone content determination revealed that FR light and GA decreased the contents of abscisic acid (ABA), indole-3-acetic acid (IAA), cytokinin (CTK), and jasmonate (JA) in cucumber seedling internodes. Bioinformatics analysis revealed that the expression patterns of the Co-DEGs and Co-DEPs were consistent in the FR (WL combined with FR light) and WLG (WL, in which plants were sprayed GA) groups, as well as in the FRP (FR, in which plants were sprayed PAC) and WL (full-spectrum LED white light) groups, suggesting that the mechanisms of FR and GA were similar in these Co-DEGs and Co-DEPs. Further analysis of these Co-DEGs and Co-DEPs revealed that they were involved mainly in cell wall biosynthesis and modification, lignin synthesis, hormone metabolism, and signal transduction pathways. In conclusion, this study revealed the important role of GA in FR light-induced internode elongation in cucumber seedlings, and this promoting effect was achieved mainly through the regulation of aquaporins, expansins, hormone metabolism, and signal transduction-related genes/proteins. This study provides new insights into the molecular mechanism of FR light-induced internode elongation in cucumber seedlings.

Unraveling the role of chrysin in mitigating cadmium toxicity in pepper by improving antioxidant defense, phytohormone biosynthesis and photosystem II and aquaporins related transcripts.

Phytohormones revisited: what makes a compound a hormone in plants.

Ribosylated forms of plant hormones cytokinins (CKs) are the dominant CK species translocated at long distances. The irreplaceable role of root-to-shoot translocated trans-zeatin riboside (tZR) in the mediation of shoot development implies the existence of a yet uncharacterized CK riboside-specific membrane transport system. In this work, we report significant differences in the kinetics of the membrane transport of CK nucleobases and ribosides and the overall affinity of membrane-bound carriers towards the two CK forms. We further characterize the membrane transport of CK nucleobases and ribosides mediated by AtENT3 (EQULIBRATIVE NUCLEOSIDE TRANSPORTER 3) in tobacco BY-2 cells. Combining experimental data with computational modelling, we show that residues Tyr61 and Asp129, which are conserved among plant ENTs but not among ENTs from other species, are necessary for CK binding and that their mutation abolishes the ability of AtENT3 to transport CKs. Lastly, we show that changes in AtENT3 have different effects on the concentrations of tZR throughout Arabidopsis thaliana plants and on the overall CK concentrations in roots, implying that AtENT3 participates both on the long- and short-distance transport of CKs.

Sprouting ability is an important indicator for evaluating the production performance of sweetpotato. However, the storage roots sprouting ability varies among different varieties. Currently, research on the sweetpotato storage roots sprouting (SPSRS) mainly focuses on physiology, rarely studies on the key metabolism and regulatory genes during the sprouting process. In this study, we compared transcriptomes and hormone metabolites in sprout buds of two sweetpotato varieties with contrasting sprouting abilities (strong-sprouting vs. late-sprouting) at 0 and 3 days post-harvest. In the SPSRS process of strong-sprouting variety (0d_vs_3d), a total of 2902 differentially expressed genes (DEGs), including 2411 up-regulated and 491 down-regulated genes were identified. But they were detected only, 45 up-regulated genes and 126 down-regulated genes between 0d and 3d of late-sprouting variety. Gene Ontology (GO) analysis showed that the DEGs between 0d and 3d in strong-sprouting variety and late-sprouting variety were mainly related to photosynthesis, light harvesting (GO:0009765), photosystem II (GO:0009523), and chlorophyll-binding (GO:0016168). In the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, DEGs in strong-sprouting variety were mainly associated with photosynthesis-antenna proteins. Both GO analysis and KEGG analysis indicated that DEGs in strong-sprouting variety (0d_vs_3d) were primarily related to photosynthesis. Hormone metabolites detection results showed that low abscisic acid (ABA) concentrations are crucial for SPSRS, while high indole-3-acetic acid (IAA) concentrations play a promoting role. Gibberellins (GAs) and cytokinins (CKs) are not key hormones for SPSRS. During the SPSRS process, IbGA2ox, IbGA20ox, and IbGA3ox were involved in regulation of GAs, while IbAMI1 was involved in regulation of IAA, and IbCYP707A1 and IbUGT73B2 were involved in regulation of ABA. Our study results also suggest that IbCYP707A1 is a key gene for SPSRS.