Gibberellin Content Research Articles

CsPHYB–CsPIF3/4 Regulates Hypocotyl Elongation by Coordinating the Auxin and Gibberellin Biosynthetic Pathways in Cucumber (Cucumis sativus L.)

Hypocotyl length is closely related to quality in seedlings and is an important component of plant height vital for plant-type breeding in cucumber. However, the underlying molecular mechanisms of hypocotyl elongation are poorly understood. In this study, the endogenous hormone content of indole acetic acid (IAA) and gibberellin (GA3) showed an increase in the long hypocotyl Csphyb (phytochrome B) mutant AM274M compared with its wild-type AM274W. An RNA-sequencing analysis identified 1130 differentially expressed genes (DEGs), of which 476 and 654 were up- and downregulated in the mutant AM274M, respectively. A KEGG enrichment analysis exhibited that these DEGs were mainly enriched in the plant hormone signal transduction pathway. The expression levels of the pivotal genes CsGA20ox-2, in the gibberellin biosynthesis pathway, and CsYUCCA8, in the auxin biosynthesis pathway, were notably elevated in the hypocotyl of the mutant AM274M, in contrast to the wild-type AM274W. Additionally, GUS staining and a dual-luciferase reporter assay corroborated that the phytochrome-interacting factors CsPIF3/4 can bind to the E(G)-box motifs present in the promoters of the CsGA20ox-2 and CsYUCCA8 genes, thereby modulating their expression and subsequently influencing hypocotyl elongation. Consequently, this research offers profound insights into the regulation of hypocotyl elongation by auxin and gibberellin in response to light signals and establishes a crucial theoretical groundwork for cultivating robust cucumber seedlings in agricultural practice.

Phytohormonal homeostasis, chloroplast stability, and heat shock transcription pathways related to the adaptability of creeping bentgrass species to heat stress.

Creeping bentgrass (Agrostis stolonifera) is a cool-season perennial turfgrass and is frequently utilized in high-quality turf areas. However, a poor to moderate resistance to heat stress limits its promotion and utilization in transitional and worm climate zones. The objectives of the study were to assess the heat tolerance of 18 creeping bentgrass genotypes in the field and to further uncover differential mechanisms of heat tolerance between heat-tolerant and heat-sensitive genotypes. The results showed that 18 different genotypes had different heat tolerance during summer months of 2021 and 2022. Among them, 13M was identified as the best heat-tolerant cultivar based on the subordinate function values analysis of five physiological indicators. Under controlled growth conditions, heat stress significantly inhibited photosynthetic capacity and also accelerated oxidative damage and chlorophyll (Chl) degradation in both heat-tolerant 13M and heat-sensitive PA4. However, as compared with heat-sensitive PA4, 13M maintained significantly higher net photosynthetic rate, water use efficiency, and total antioxidant capacity as well as less Chl degradation and damage to chloroplast ultrastructure. Significantly higher contents of abscisic acid, cytokinin, gibberellin, and polyamines (spermine, spermidine, and putrescine) were also detected in 13M than that in PA4 in the later stage of heat stress, but 13M exhibited significantly lower indoleacetic acid content than PA4 during heat stress. In addition, heat-upregulated genes involved in heat shock transcriptional pathways were more pronounced in 13M than in PA4. These findings indicated that better heat tolerance of 13M could be related to more stable Chl metabolism, better photosynthetic and antioxidant capacities, endogenous hormonal homeostasis, and more effective heat shock transcriptional pathway. 13M is more appropriate for planting in transitional and subtropical zones instead of widely used PA4.

Estratégias para a fixação e desenvolvimento de frutos da mangueira ‘Keitt’ cultivada no semiárido

ABSTRACT: The mango tree presents a high level of fruit abscission, which is increased in semiarid regions due to environmental stress. The use of biostimulants and phytoregulators has shown to be a promising strategy to improve fruit setting. Thus, the present study defined the best strategy for setting and development of the fruit, with the application of phytoregulators and biostimulants on the ‘Keitt’ mango tree, cultivated in the São Francisco Valley. Two experiments were performed. In experiment 1, a randomized block design was used, with four treatments T1: control, T2: gibberellic acid (AG3) + 2,4-dichlorophenoxyacetic acid (2,4-D), T3: AG3 + 2,4-D+Benzyladenine, T4: Biostimulant + CoMo® (sources of cobalt and molybdenum). In experiment 2, the factorial scheme (2 ×3 + 1) distributed in randomized blocks was established, corresponding to two forms of potassium fertilization (recommended and adjusted), three gibberellin concentrations (0, 10 and 20 mg L-1) and additional treatment (control - recommended potassium fertilization and no setting strategy). The variables analyzed include the relative number of fruits, the number of fruits for domestic and foreign markets, productive potential, production, productivity, fruit volume, fruit mass, and the yield of peel, pulp and stone. The application of 10 mg L-1 AG3 + 10 mg L-1 2,4-D + 10 mg L-1 Benzyladenine in full flowering of the ‘Keitt’ mango tree, increased the setting and the production of the fruit. Regardless of fertilization, sequential applications at 10 or 20 mg L-1 of AG3 proved to be an effective strategy to produce ‘Keitt’ mango tree. Adjusted potassium fertilization and the application at 10 mg L-1 of AG3 promotes the production of fruits with greater mass and volume.

Regulatory Mechanism of Exogenous ABA on Gibberellin Signaling and Antioxidant Responses in Rhododendron chrysanthum Pall. Under UV-B Stress.

In the present work, we examined the effects of exogenous abscisic acid (ABA) under ultraviolet B (UV-B) exposure on gibberellin (GA) production, signaling, and antioxidant-related genes in Rhododendron chrysanthum Pall (R. chrysanthum). Using transcriptomics, acetylated proteomics, and widely targeted metabolomics, the effects of UV-B stress on R. chrysanthum and the regulatory effects of exogenous ABA on it were revealed from multiple perspectives. The findings revealed that R. chrysanthum's antioxidant enzyme genes were differentially expressed by UV-B radiation and were substantially enriched in the glutathione metabolic pathway. Exogenous ABA supplementation boosted plant resistance to UV-B damage and further enhanced the expression of antioxidant enzyme genes. Furthermore, under UV-B stress, glutathione reductase, glutathione peroxidase, and L-ascorbate peroxidase were found to be the primary antioxidant enzymes controlled by exogenous ABA. In addition, gibberellin content was altered due to UV-B and exogenous ABA treatments, with greater effects on GA3 and GA53. The acetylation proteomics study's outcomes disclosed that the three main oxidative enzymes' acetylation modifications were dramatically changed during UV-B exposure, which may have an impact on the antioxidant enzymes' functions and activities. The protective impact of exogenous ABA and gibberellin on R. chrysanthum's photosynthetic system was further established by measuring the parameters of chlorophyll fluorescence. This research offers a theoretical foundation for the development of breeding highly resistant plant varieties as well as fresh insights into how hormone levels and antioxidant systems are regulated by plants in response to UV-B damage.

Exploring the mechanism of seed shattering in Psathyrostachys juncea through histological analysis and comparative transcriptomics

BackgroundSeed shattering (SS) negatively impacts seed yield in Psathyrostachys juncea. Understanding and improving the SS trait requires elucidating the regulatory mechanisms of SS and identifying the key genes involved.ResultsThis study presents a comprehensive analysis of the abscission zone (AZ) structures at four developmental stages in two P. juncea genotypes. High-SS P. juncea (H) exhibited a significantly higher SS rate than low-SS P. juncea (L) at all four developmental stages. Anatomical analysis revealed that the degree of lignification in the AZ cell walls is related to the integrity of the abscission structure. The degradation of the AZ in H occurred earlier and was more severe compared to L. At different developmental stages of the AZ, H exhibited higher cellulase and polygalacturonase activities and higher abscisic acid contents compared to L. Conversely, L showed higher lignin, cytokinin, auxin, and gibberellin contents than H. Transcriptomic analysis identified key metabolic pathways related to SS in P. juncea, such as phenylpropanoid biosynthesis, fructose and mannose metabolism, galactose metabolism, and pentose and glucuronate interconversions. The integration of morphological, histological, physiochemical, and metabolic data led to the identification of critical genes, including AUX1, CKX, ABF, GH3, 4CL, CCoAOMT, BGAL, Gal, and PG. The roles of these genes were involved in the regulation of plant hormones and in the synthesis and degradation of cell walls within the AZ.ConclusionsThis study provides an in-depth understanding of the regulatory mechanisms of SS in P. juncea through comparative transcriptomic analysis. The SS in P. juncea may result from the degradation of the cell wall regulated by cell wall hydrolases genes. The genes identified in this study provide a basis for the genetic improvement of SS traits and serve as a reference for research on other grass species.

Gibberellin Treatment Accelerates Starch Decomposition and Seed Germination in Sticky Nightshade (Solanum sisymbriifolium Lam.)

Sticky nightshade (Solanum sisymbriifolium Lam.) is a spiny species with a variety of disease resistance characteristics found worldwide within the Solanum genus. However, its low germination rate and long germination period pose obstacles to the effective use of this species. Here, we treated Sticky nightshade with different concentrations of gibberellin (GA3) and observed paraffin sections of Sticky nightshade seeds treated with different GA3 concentrations over different time ranges. The results showed that a 400 mg/L exogenous GA3 concentration at room temperature could improve the germination rate of Sticky nightshade the most effectively. Exogenous GA3 treatment can significantly accelerate the hydrolysis of starch granules and increase the germination rate of seeds. Subsequently, we also measured the MDA content of Sticky nightshade seeds treated with different GA3 concentrations over different time ranges. The result reveals that GA3 treatment can steadily decrease Sticky nightshade seeds’ MDA content during germination, indicating that exogenous GA3 treatment also reduces membrane peroxidation and maintains the stability of the plasma membrane. In this paper, we identified an optimal GA3-treated concentration of Sticky nightshade to improve seed germination at room temperature and explored the reason why the exogenous GA3 treatment of Sticky nightshade seed increased the germination rate.

Pre-sowing treatment of acorns with gibberellic acid and N-hexanoyl-L-homoserine lactone induced changes in growth and hormonal balance of Quercus robur L. seedlings

Abstract This study aimed to assess and compare the impact of priming with gibberellic acid (GA3) and N-hexanoyl-L-homoserine lactone (C6-HSL) on acorn germination, seedling growth, and the balance of endogenous phytohormones in 47-day-old seedlings of pedunculated oak (Quercus robur L.). We hypothesized that exogenous GA3 and C6-HSL induce changes in hormonal homeostasis, which activate the germination of acorns and growth of seedlings. Acorns were soaked for 24 hours in water (control) and solutions of gibberellic acid (50 mg/L) and C6-HSL (300 ng/ml). The dynamics and distribution of endogenous cytokinins, abscisic (ABA), indole-3-acetic (IAA), gibberellic (GA3 and GA4) and salicylic (SA) acid in 47-day-old seedlings' organs of Q. robur were analysed using HPLC-MS. Priming with GA3 solution resulted in 85.8% of acorn germination, surpassing the control by 24.6%, whereas priming with C6-HSL solution led to 93.4% germination, surpassing the control by 32.2%. GA3-primed plants (GA3+plants) showed enhanced shoot growth, while C6-HSL-primed (C6-HSL+plants) plants had intensive root development. GA3 also caused epicotyl shoot thickening. Both regulators increased cytokinins, mainly active zeatin forms, with pronounced changes in shoots under C6-HSL and in roots under GA3. ABA content increased in both GA3+ and C6-HSL+plants, with a more significant effect in the roots of C6-HSL+plants. Both regulators negatively impacted IAA accumulation, with GA3 exhibiting a more pronounced effect, causing IAA accumulation to shift from shoots to roots post priming, whereas IAA dominance occurred in the shoots of non-primed acorns (C-plants) and C6-HSL+plants. The total gibberellin content increased in primed seedlings, with GA4 accumulating in GA3+plants and GA3 in C6-HSL+plants, surpassing GA3+plants by 40.7%. GA3+plants exhibited decreased SA in roots, contrasting with increased SA in the roots of C6-HSL+plants. In conclusion, both growth regulators optimized acorn germination, induced changes in hormonal homeostasis and enhanced seedling growth, with increased root growth in C6-HSL plants and shoot growth in GA3 plants.

Argonaute 1 negatively regulates cadmium tolerance via modulating jasmonic acid and gibberellin contents, antioxidant enzymes, and chlorophyll level in tobacco

Cadmium (Cd) is one of the most toxic heavy metal pollutants that limits plant productivity and poses a threat to human health. In this study, we identified argonaute 1 (AGO1), a key factor in the RNA interference pathway, which is suppressed by Cd stress in Nicotiana tabacum L. Overexpression of NtAGO1 (AGO1-OE), knockout of NtAGO1 (ago1-KO), and wild-type (WT) plants were employed to investigate the mechanism of NtAGO1-mediated Cd tolerance in tobacco. The results showed that AGO1-OE plants exhibited higher levels of reactive oxygen species (ROS) and lower chlorophyll content, and their seedlings accumulated lower Cd levels than WT plants. Cd stress affected the content of endogenous plant hormones differently, with jasmonic acid (JA) increasing by 57.42 % and gibberellins (GA) decreasing by 24.51 %, both of which were negatively regulated by NtAGO1. Application of exogenous GA3 and methyl jasmonate confirmed that plant hormones up-regulate antioxidant enzyme activity. Furthermore, the foliar application of GA3 inhibited the expression of chlorophyll degradation-related genes, impeded Cd-induced chlorophyll degradation and promoted plant growth. Our results demonstrate that NtAGO1 negatively regulates the response of tobacco to Cd stress by decreasing JA and GA levels, providing a foundation for the use of genetic engineering methods to enhance the efficiency of phytoremediation.

An integrated physiological indicator and transcriptomic analysis reveals the response of soybean buds to high-temperature stress.

Under global warming, high temperature (HT) has become a major meteorological factor affecting soybean production. To explore the candidate genes and regulatory mechanism of the soybean bud response to HT stress, previously identified as HT-tolerant ('Handou14'; HD14) and HT-sensitive ('Jiadou36'; JD36) were treated for 5 days in an artificial climate incubator either with HT (43°C (day)/ 33°C (night), 16h light/8h darkness) or the non-stress growth condition (25°C, 16h light/8h darkness) as the control at the bud stage were used as experimental materials in this study. After HT treatment, changes in physiological indicators including hypocotyl length, enzyme activity and hormone content were detected; at the same time, the cotyledons, hypocotyls, and main roots were collected for transcriptome sequencing analysis. Analyzing the mechanisms of HT stress response in the bud stage of HD14 and JD36 at physiological and transcription levels. Analysis of physiological indicator showed that the activities of superoxide dismutase (SOD) were significantly increased 47.4% and 41.2% in the cotyledon of HD14 and the main root of JD36, and the contents of peroxidase (POD) were significantly increased 61.5% and 125% in the hypocotyl of HD14 and JD36; the contents of malonaldehyde (MDA) were significantly increased 44.8% and 22.2% in the main root of HD14 and JD36 after HT treatment. The content of abscisic acid (ABA) were significantly increased 1.9 fold and 1.2 fold in the root of HD14 and JD36 in response to HT treatment, whereas the content of gibberellin (GA) were decreased 2.2 fold and 1.3 fold in the cotyledon and root, and increased 1.6 fold in the hypocotyl in HD14 (P < 0.05). Thus, higher SOD and POD activities, higher ABA content, and a smaller increase in MDA content may improve tolerance to HT stress. The HT-tolerant cultivar may have stronger GA signal transduction in the hypocotyl to combat the negative effects of HT. RNA-sequencing was performed to analyze the differential expression of genes in buds of the two cultivars under the HT treatment and control condition. In total, 3,633, 1,964, 9,934, and 3,036 differentially expressed genes (DEGs) were identified in the CH (control group of HD14) vs. TH (HT-treatment group of HD14), CJ (control group of JD36) vs. TJ (HT-treatment group of JD36), TJ vs. TH, and CJ vs. CH comparison groups, respectively. Bioinformatic analysis revealed that most DEGs were mainly involved in metabolic processes, catalytic activity, carbohydrate, energy transduction, and signaling pathways. The results of qRT-PCR validation (86.67%) and changes in physiological indicators were consistent with the RNA-sequencing data. Five DEGs were selected as candidate genes in the response to HT stress at the bud stage. In summary, soybean cells are protected from oxidative damage by an increase in antioxidant enzyme activities and accumulation of hormone content under HT stress. Concomitantly, changes in the expression of crucial genes and signal transmission processes are induced, thus initiating adaptive and protective mechanisms. This study provides a theoretical basis for clarification of the physiological and molecular mechanisms in the response to HT stress of soybean bud.

Physiological characteristics during the formation of aromatic components in xylem of Aquilaria sinensis induced by exogenous substances.

An inductive combination of plant growth regulators, inorganic salts, and fungi is essential for the formation of aromatic components in the xylem of Aquilaria sinensis. However, the dynamics of xylem physiology and the relationships between physiological properties and aromatic components after artificial induction remain unclear. In this study, the changes in physiological properties of A. sinensis xylem during induction were determined and analyzed under four induction treatments and a control group. The defense hormone contents of jasmonic acid, salicylic acid, aminocyclopropane-1-carboxylic acid, and abscisic acid obtained from the four induction treatments increased significantly. However, the concentrations of gibberellin and indoleacetic acid were decreased compared to the control group. An initially upward and then downward trend was observed in the main antioxidant enzyme activities. Additionally, malonaldehyde content decreased obviously, while proline content tended to increase and then decrease as induction continued. The total and soluble sugar content was evidently reduced after treatment, and the soluble sugar content recovered more rapidly with time. Thirty-three aromatic components were identified in all treatments, and the primary aromatic components were terpenes, aromatics and chromones, the relative contents of which varied among treatments. These results provide new insights for optimization and innovation of agarwood induction techniques by exploring the formation of aromatics in the xylem of A. sinensis and its physiological responses following induction with exogenous substances (ethephon, NaCl, CaCl2 and fungal mixed solution).

Comparative transcriptomic and hormonal analyses reveal potential regulation networks of adventitious root formation in Metasequoia glyptostroboides Hu et Cheng

BackgroundThe extract from Metasequoia glyptostroboides Hu et Cheng, a rare and endangered species native to China, exhibits numerous biological and pharmacological activities. The species is recalcitrant to rooting during micropropagation, a challenge that has yet to be resolved. In this study, transcriptomic and hormonal analyses were conducted to appreciate the molecular mechanism of adventitious root (AR) formation in optimized rooting conditions.ResultsThe use of 2/5-strength Woody Plant Medium (WPM) significantly promoted AR formation of M. glyptostroboides shoots while the content of endogenous auxin, cytokinins and gibberellins (GAs) varied at different stages of AR formation. Transcriptomic analysis showed the significant up- or down-regulation of differentially expressed genes (DEGs) associated with plant hormone signal transduction and the phenylpropanoid biosynthesis pathway in response to 2/5-strength WPM. DEGs related to the biosynthesis of indole-3-acetic acid, cytokinins and GAs were identified. Transcript factors involved in 13 families were also revealed. A weighted gene co-expression network analysis indicated a strong correlation between hormones and genes involved in plant hormone signal transduction and the phenylpropanoid biosynthetic pathway.ConclusionsThese results indicate that the AR-promoting potential of 2/5-strength WPM in M. glyptostroboides was due to complex interactions between hormones and the expression of genes related to plant hormone signal transduction and the phenylpropanoid biosynthetic pathway.

Gibberellin action‐based strategies show promise in the control of Striga—A major threat to global agriculture

Societal Impact StatementThe root‐parasitic plant Striga hermonthica can cause severe crop failure, leading to significant agricultural and economic losses in Africa. Despite the promising target offered by the Striga seed germination mechanism for developing control methods, effective control methods have yet to be established. For seed germination, Striga must undergo an incubation under warm and humid conditions, a process termed conditioning, which allows it to germinate. Here, we report that the plant hormone gibberellin stimulates the conditioning process in Striga seeds. Our findings suggest that the quantitative control of gibberellin in plants is a promising approach for controlling Striga infestations and may help alleviate substantial threats to food security.Summary The root‐parasitic plant S. hermonthica is a serious agricultural threat in Africa. Although a number of control methods have been employed to combat Striga, there is still a need to develop more effective control methods. Striga seeds germinate only in the presence of host plants, owing to the need for host‐released stimulants, primarily strigolactone. To detect signals from the host, Striga seeds must be exposed to a specific warm, dark, and moist environment, which is known as conditioning. Gibberellin directly promotes germination in many nonparasitic plants, but Striga seeds are insensitive to exogenous gibberellin. Consequently, the role of gibberellin in the germination of Striga seeds is unclear. We demonstrated that the effect of the gibberellin biosynthesis inhibitor paclobutrazol was higher in seeds during the conditioning, compared with those already conditioned, suggesting that gibberellin primarily regulates conditioning rather than germination. The content of an active form gibberellin, gibberellin A4 (GA4) exhibited an increase throughout the conditioning period, and we quantified the elevated expression levels of some gibberellin biosynthesis genes. The GA4 treatment shortened the conditioning period required for strigolactone‐induced seed germination. We also discovered that gibberellin upregulated ShACO1, the gene responsible for ethylene synthesis, during conditioning, and that the inhibition of GR24‐induced germination by the ethylene biosynthesis inhibitor α‐aminoisobutyric acid was gradually alleviated by GA4. Our findings demonstrate that gibberellin is critical for conditioning and germination processes but acts as a minor stimulant in Striga seeds. This study demonstrates the potential of quantitative endogenous gibberellin control for Striga management, providing valuable insights for alleviating food security issues.

Synergistic effects of SAP and PGPR on physiological characteristics of leaves and soil enzyme activities in the rhizosphere of poplar seedlings under drought stress.

Super absorbent polymers (SAP) provide moisture conditions that allow plant growth-promoting rhizobacteria (PGPR) to enter the soil for acclimatization and strain propagation. However, the effects of SAP co-applied with PGPR on the physiological characteristics of leaves and rhizosphere soil enzyme activities of poplar seedlings are not well understood. Here, a pot experiment using one-year-old poplar seedlings with five treatments, normal watering, drought stress (DR), drought stress + SAP (DR+SAP), drought stress + Priestia megaterium (DR +PGPR) and drought stress + SAP + P. megaterium (DR+S+P), was performed to analyze the contents of non-enzymatic antioxidants, osmotic regulators and hormones in leaves, as well as rhizosphere soil enzyme activities. Compared with normal watering, the DR treatment significantly decreased the contents of dehydroascorbate (DHA; 19.08%), reduced glutathione (GSH; 14.18%), oxidized glutathione, soluble protein (26.84%), indoleacetic acid (IAA; 9.47%), gibberellin (GA) and zeatin (ZT), the IAA/abscisic acid (ABA), GA/ABA, ZT/ABA and (IAA+GA+ZT)/ABA (34.67%) ratios in leaves, and the urease and sucrase activities in the rhizosphere soil. Additionally, it significantly increased the soluble sugar, proline and ABA contents in leaves. However, in comparison with the DR treatment, the DR+S+P treatment significantly increased the DHA (29.63%), GSH (15.13%), oxidized glutathione, soluble protein (29.15%), IAA (12.55%) and GA contents, the IAA/ABA, GA/ABA, ZT/ABA and (IAA+GA+ZT)/ABA (46.85%) ratios in leaves, and the urease, sucrose and catalase activities in rhizosphere soil to different degrees. The soluble sugar, proline and ABA contents markedly reduced in comparison to the DR treatment. The effects of the DR+SAP and DR+PGPR treatments were generally weaker than those of the DR+S+P treatment. Thus, under drought-stress conditions, the simultaneous addition of SAP and P. megaterium enhanced the drought adaptive capacities of poplar seedlings by regulating the non-enzymatic antioxidants, osmotic regulators, and endogenous hormone content and balance in poplar seedling leaves, as well as by improving the rhizosphere soil enzyme activities.

Allelochemicals Released from Rice Straw Inhibit Wheat Seed Germination and Seedling Growth

Recently, returning rice straw to soil has become a common problem in wheat production because it causes decreased wheat seedling emergence. Allelopathy is an important factor affecting seed germination. However, the effects of rice straw extracts on wheat seed germination and seedling growth remain unclear. Wheat seeds and seedlings were treated with 30 g L−1 of rice leaf extracts (L1), 60 g L−1 of rice leaf extracts (L2), 30 g L−1 of rice stem extracts (S1), 60 g L−1 of rice stem extracts (S2) and sterile water (CK) to study the allelopathic effects of rice straw extracts on wheat seed germination and seedling growth. The α-amylase and antioxidant enzyme activities in wheat seeds; the agronomic traits, photosynthetic indicators, and nutrient contents of wheat seedlings; and the phenolic acids in rice stem extracts were determined. Common allelochemicals, including 4-hydroxybenzoic acid, hydrocinnamic acid, trans-cinnamic acid, vanillic acid, benzoic acid, protocatechualdehyde, caffeic acid, syringic acid, sinapic acid, and salicylic acid, were detected in rice stem extracts. Low-concentration rice leaf and stem extracts (30 g L−1) had no effect on the germination rate of wheat seeds. High-concentration (60 g L−1) rice stem and leaf extracts decreased the seed germination rate by 11.00% and 12.02%. Rice stem extract (60 g L−1) decreased the α-amylase activity, and gibberellin content of wheat seeds but increased superoxide dismutase, peroxidase, and catalase activities and malondialdehyde content in wheat seeds. Allelochemicals entered the internal tissues of wheat seeds, where they decreased the gibberellin content and α-amylase activity and increased the antioxidant enzyme activity, ultimately leading to an inhibitory effect on seed germination. Rice stem and leaf extracts decreased the SPAD value and photosynthetic indicators of wheat seedlings. Rice stem extract (60 g L−1) decreased the fresh weight and root length of wheat seedlings by 31.37% and 45.46%. Low-concentration rice leaf and stem extract (30 g L−1) had no effect on the nutrient contents of wheat seedlings. Rice leaf and stem extracts (60 g L−1) decreased the nitrogen and potassium contents of wheat seedlings. These results indicated that low-concentration rice leaf and stem extract (30 g L−1) had no effect on wheat seed germination and the high-concentration rice stem extract (60 g L−1) released allelochemicals and inhibited wheat seed germination and seedling growth. These findings provide a basis for the improvement of straw return techniques.

Polyacrylamide Regulated Phytohormone Balance and Starch Degradation to Promote Seed-Potato Sprouting and Emergence

Potatoes are typically seeded as tubers, and their slow sprouting significantly impacts production. Therefore, the effects of polyacrylamide (20 g·L−1, 30 g·L−1, and 40 g·L−1) as a seed potato dressing on sprouting, seedling growth, and biomass were investigated. The phytohormone content, respiratory intensity, and starch metabolism enzyme activity were analyzed to elucidate the physiological mechanisms involved. The sprouting rate significantly increased after 20 g·L−1 and 30 g·L−1 treatments by 40.63% and 15.63%, respectively. The sprouting energy was the highest (52.0%) at 20 g·L−1, 7.67 times higher than the control. The 20 g·L−1 and 30 g·L−1 treatments also promoted emergence and growth, with the emergence rate increasing by 18.18% and 27.27% and growth increasing by over 8.1% and 11.9%, respectively. These effects were related to changes in phytohormone content and accelerated starch conversion. After treatment, the auxin and cytokinin contents in the apical buds increased significantly at the germination initiation stage, and during the germination and vigorous growth phases, the auxin, cytokinin, and gibberellin contents increased. Polyacrylamide treatment activated α-amylase and promoted starch degradation, increasing soluble sugar content to provide nutrients and energy for sprouting. This study provides a promising approach for promoting potato tuber sprouting and seedling growth.

Functional Characterization of the Gibberellin (GA) Receptor ScGID1 in Sugarcane.

Sugarcane smut caused by Sporisorium scitamineum represents the most destructive disease in the sugarcane industry, causing host hormone disruption and producing a black whip-like sorus in the apex of the stalk. In this study, the gibberellin metabolic pathway was found to respond to S. scitamineum infection, and the contents of bioactive gibberellins were significantly reduced in the leaves of diseased plants. The gibberellin receptor gene ScGID1 was identified and significantly downregulated. ScGID1 localized in both the nucleus and cytoplasm and had the highest expression level in the leaves. Eight proteins that interact with ScGID1 were screened out using a yeast two-hybrid assay. Novel DELLA proteins named ScGAI1a and ScGA20ox2, key enzymes in GA biosynthesis, were both found to interact with ScGID1 in a gibberellin-independent manner. Transcription factor trapping with a yeast one-hybrid system identified 50 proteins that interacted with the promoter of ScGID1, among which ScS1FA and ScPLATZ inhibited ScGID1 transcription, while ScGDSL promoted transcription. Overexpression of ScGID1 in transgenic Nicotiana benthamiana plants could increase plant height and promote flowering. These results not only contribute to improving our understanding of the metabolic regulatory network of sugarcane gibberellin but also expand our knowledge of the interaction between sugarcane and pathogens.

Comparative Analysis of Phytohormone Biosynthesis Genes Responses to Long-Term High Light in Tolerant and Sensitive Wheat Cultivars.

Phytohormones are vital for developmental processes, from organ initiation to senescence, and are key regulators of growth, development, and photosynthesis. In natural environments, plants often experience high light (HL) intensities coupled with elevated temperatures, which pose significant threats to agricultural production. However, the response of phytohormone-related genes to long-term HL exposure remains unclear. Here, we examined the expression levels of genes involved in the biosynthesis of ten phytohormones, including gibberellins, cytokinins, salicylic acid, jasmonic acid, abscisic acid, brassinosteroids, indole-3-acetic acid, strigolactones, nitric oxide, and ethylene, in two winter wheat cultivars, Xiaoyan 54 (XY54, HL tolerant) and Jing 411 (J411, HL sensitive), when transferred from low light to HL for 2-8 days. Under HL, most genes were markedly inhibited, while a few, such as TaGA2ox, TaAAO3, TaLOG1, and TaPAL2, were induced in both varieties. Interestingly, TaGA2ox2 and TaAAO3 expression positively correlated with sugar content but negatively with chlorophyll content and TaAGP expression. In addition, we observed that both varieties experienced a sharp decline in chlorophyll content and photosynthesis performance after prolonged HL exposure, with J411 showing significantly more sensitivity than XY54. Hierarchical clustering analysis classified the phytohormone genes into the following three groups: Group 1 included six genes highly expressed in J411; Group 2 contained 25 genes drastically suppressed by HL in both varieties; and Group 3 contained three genes highly expressed in XY54. Notably, abscisic acid (ABA), and jasmonic acid (JA) biosynthesis genes and their content were significantly higher, while gibberellins (GA) content was lower in XY54 than J411. Together, these results suggest that the differential expression and content of GA, ABA, and JA play crucial roles in the contrasting responses of tolerant and sensitive wheat cultivars to leaf senescence induced by long-term HL. This study enhances our understanding of the mechanisms underlying HL tolerance in wheat and can guide the development of more resilient wheat varieties.

Exogenous putrescine application imparts salt stress-induced oxidative stress tolerance via regulating antioxidant activity, potassium uptake, and abscisic acid to gibberellin ratio in Zinnia flowers

This research was conducted to investigate the efficacy of putrescine (PUT) treatment (0, 1, 2, and 4 mM) on improving morphophysiological and biochemical characteristics of Zinnia elegans “State Fair” flowers under salt stress (0, 50, and 100 mM NaCl). The experiment was designed in a factorial setting under completely randomized design with 4 replications. The results showed that by increasing the salt stress intensity, the stress index (SSI) increased while morphological traits such as plant height decreased. PUT treatments effectively recovered the decrease in plant height and flower quality compared to the not-treated plants. Treatment by PUT 2 mM under 50 and 100 mM salt stress levels reduced the SSI by 28 and 35%, respectively, and increased plant height by 20 and 27% compared to untreated plants (PUT 0 mM). 2 mM PUT treatment also had the greatest effect on increasing fresh and dry biomass, number and surface area of leaves, flower diameter, internodal length, leaf relative water content, protein contents, total chlorophyll contents, carotenoids, leaf potassium (K+) content, and K+/Na+ ratio in treated plants compared to untreated control plants. The treatment of 2 mM PUT decreased the electrolyte leakage, leaf sodium (Na+) content, H2O2, malondialdehyde, and proline content. Furthermore, PUT treatments increased the activity of defense-related enzymes including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonium lyase (PAL), and reduced the abscisic acid (ABA) content while increased the level of gibberellin (GA) content compared to untreated samples under all different levels of salinity stress. In this research, enhancing the plant’s antioxidant system, increasing K+ absorption, K+/Na+ ratio, and reducing the ABA/GA ratio are likely the most important mechanisms of PUT treatment, which improved growth, and maintained the visual quality of zinnia flowers under salt stress conditions.

Determination and Analysis of Endogenous Hormones and Cell Wall Composition between the Straight and Twisted Trunk Types of Pinus yunnanensis Franch

Pinus yunnanensis Franch., one of the pioneer species of wild mountain afforestation in southwest China, plays an essential role in the economy, society and environment of Yunnan Province. Nonetheless, P. yunnanensis’ trunk twisting and bending phenomenon has become more common, which significantly restricts its use and economic benefits. In order to clarify the compositional differences between the straight and twisted trunk types of P. yunnanensis and to investigate the reasons for the formation of twisted stems, the present study was carried out to dissect the macroscopic and microscopic structure of the straight and twisted trunk types of P. yunnanensis, to determine the content of cell wall components (lignin, cellulose, hemicellulose), determine the content of endogenous hormones, and the expression validation of phytohormone-related differential genes (GA2OX, COI1, COI2) and cell wall-related genes (XTH16, TCH4). The results showed that the annual rings of twisted trunk types were unevenly distributed, eccentric growth, insignificant decomposition of early and late wood, rounding and widening of the tracheid cells, thickening of the cell wall, and reduction of the cavity diameter; the lignin and hemicellulose contents of twisted trunk types were higher; in twisted trunk types, the contents of gibberellin (GA) and jasmonic acid (JA) increased, and the content of auxin (IAA) was reduced; the GA2OX were significantly down-regulated in twisted trunk types, and the expressions of the genes associated with the cell wall, COI1, COI2, TCH4 and XTH16, were significantly up-regulated. In conclusion, the present study found that the uneven distribution of endogenous hormones may be an important factor leading to the formation of twisted trunk type of P. yunnanensis, which adds new discoveries to reveal the mechanism of the genesis of different trunk types in plants, and provides a theoretical basis for the genetic improvement of forest trees.

Deciphering physiological and transcriptional mechanisms of maize seed germination.

Maize is a valuable raw material for feed and food production. Healthy seed germination is important for improving the yield and quality of maize. Seed aging occurs relatively fast in crops and it is a process that delays germination as well as reduces its rate and even causes total loss of seed viability. However, the physiological and transcriptional mechanisms that regulate maize seeds, especially aging seed germination remain unclear. Coronatine (COR) which is a phytotoxin produced by Pseudomonas syringae and a new type of plant growth regulator can effectively regulate plant growth and development, and regulate seed germination. In this study, the physiological and transcriptomic mechanisms of COR-induced maize seed germination under different aging degrees were analyzed. The results showed that 0.001-0.01μmol/L COR could promote the germination of aging maize seed and the growth of primary roots and shoots. COR treatment increased the content of gibberellins (GA3) and decreased the content of abscisic acid (ABA) in B73 seeds before germination. The result of RNA-seq analysis showed 497 differentially expressed genes in COR treatment compared with the control. Three genes associated with GA biosynthesis (ZmCPPS2, ZmD3, and ZmGA2ox2), and two genes associated with GA signaling transduction (ZmGID1 and ZmBHLH158) were up-regulated. Three genes negatively regulating GA signaling transduction (ZmGRAS48, ZmGRAS54, and Zm00001d033369) and two genes involved in ABA biosynthesis (ZmVP14 and ZmPCO14472) were down-regulated. The physiological test results also showed that the effects of GA and ABA on seed germination were similar to those of high and low-concentration COR, respectively, which indicated that the effect of COR on seed germination may be carried out through GA and ABA pathways. In addition, GO and KEGG analysis suggested that COR is also highly involved in antioxidant enzyme systems and secondary metabolite synthesis to regulate maize seed germination processes. These findings provide a valuable reference for further research on the mechanisms of maize seed germination.