Gibberellin disturbs the balance of endogenesis hormones and inhibits adventitious root development of Pseudostellaria heterophylla through regulating gene expression related to hormone synthesis

The Targeted Metabolomic Signatures of Phytohormones in Leaves of Mulberry (Morus alba L.) Are Crucial for Regrowth and Specifically Modulated by the Differential Stubble Lengths

Vegetative propagation of mulberry (Morus alba L.) via sapling methods, due to the ability to exponentially multiply lateral buds on stem cuttings to enhance rapid shoot formation, is crucial for sericulture industries. The sprouting of mulberry using stubbles is an emerging method for rapid and mass production of mulberry leaves, but the growth mechanisms associated with its use remain obscure. This study is the first to report how the differential stubble lengths from mulberry plants alter and modulate phytohormones and the associated mechanisms. This study seeks to evaluate the growth mechanisms by elucidating the phytohormone signature modulation in response to differential stubble lengths of 0 cm, 5 cm, 10 cm, 20 cm, and a control via targeted metabolomics analysis in mulberry leaves. The results consistently show that the use of differential stubble lengths of mulberry promoted growth, the number of buds, aboveground biomass, and branch and leaf weights by improving the net photosynthesis, transpiration rate, stomatal conductance, and intercellular CO2 relative to the control. The differential stubble lengths not only caused contrasting responses in the contents of plant hormones, including salicylic acid (SA), abscisic acid (ABA), indole-3-acetic acid (IAA), jasmonic acid (JA), and gibberellin (GA), but also modulated higher elemental contents relative to the control. The results further reveal significant and positive correlations between the phytohormones and all growth, biomass, and photosynthetic parameters, highlighting the role of phytohormones in the sprouting and rejuvenation of mulberry stubbles. Meanwhile, the targeted metabolomics analysis identified a total of 11 differentially accumulated phytohormones in response to the differential stubble lengths, which were significantly implicated and enriched in three major pathways, including the biosynthesis of plant hormones (ko01070), metabolic pathways (ko01100), and the plant hormone signal transduction pathway (ko04575). The use of stubbles for rapid leaf production in mulberry plants is of great importance to improve early sprouting and cutting survival, as well as shortening growth and rooting time, and is highly recommended for the sericulture industries.

Tetramycin ameliorates tebuconazole·azoxystrobin to control leaf spot and viral diseases of Taizishen

Leaf spot and viral diseases are the most frequently occurring leaf problems in Taizishen production. In this study, we examined the controlling role played by the co-application of tetramycin and low dose tebuconazole·azoxystrobin against leaf spot and viral diseases in Taizishen, investigating its resistance, electrophysiological information, growth and quality. Among them, electrophysiological information indicators include electrical signals [intrinsic capacitance (IC), resistance (IR), impedance (IZ), capacitive reactance (IXc), and inductive reactance (IXL)], intracellular water metabolism, nutrient transport, and plant metabolic activity. The results indicate that 0.3% tetramycin 1000-time + 75% tebuconazole·azoxystrobin 2000-time diluent controlled leaf spot and viral diseases the best, with protection effects of 90.03%~90.46% and 71.67%~73.08% at 15~30 days after the last fungicide application, respectively. These values are obviously higher than those treated with high doses of tetramycin or tebuconazole·azoxystrobin alone. Concurrently, their combined application could notably enhance total soluble flavonoids, total soluble phenols, protective enzyme activity, IC, intracellular water metabolism, nutrient transport, and metabolic activity, while reducing its MDA, IR, IZ, IXc, and IXL. Moreover, their co-application also could obviously ameliorate photosynthesis, biomass, agronomic trait, and root growth and quality, as well as actually reduce tebuconazole·azoxystrobin input. Additionally, the control effects of leaf spot and viral diseases in Taizishen treated by their combined application exhibited significant correlations with its disease resistance, electrophysiology, photosynthesis, growth, and quality parameters. This study highlights the combined application of low-dosage tebuconazole·azoxystrobin and tetramycin as a practicable measure for controlling leaf spot and viral diseases in Taizishen, promoting its resistance, growth, and quality, as well as reducing chemical pesticide application.

Depletion of Gibberellin Signaling Up-Regulates LBD16 Transcription and Promotes Adventitious Root Formation in Arabidopsis Leaf Explants

Adventitious root (AR) formation in plants originates from non-root organs such as leaves and hypocotyls. Auxin signaling is essential for AR formation, but the roles of other phytohormones are less clear. In Arabidopsis, at least two distinct mechanisms can produce ARs, either from hypocotyls as part of the general root architecture or from wounded organs during de novo root regeneration (DNRR). In previous reports, gibberellin acid (GA) appeared to play reverse roles in both types of ARs, since GA treatment blocks etiolation-induced AR formation from hypocotyls, whereas GA synthesis and signaling mutants apparently displayed reduced DNRR from detached leaves. In order to clarify this contradiction, we employed the GA biosynthesis inhibitor paclobutrazol (PBZ) and found that PBZ had positive effects on both types of AR formation in Arabidopsis. Consistently, GA treatment had negative effects on both AR formation mechanisms, while loss of GA synthesis and signaling promoted DNRR under our conditions. Our results show that PBZ treatment can rescue declined AR formation in difficult-to-root leaf explants such as erecta receptor mutants. Furthermore, transcriptional profiling revealed that PBZ treatment altered GA, brassinosteroids, and auxin responses, which included the up-regulation of LBD16 that is well known for its pivotal role in AR initiation.

Synergistic Effects of Oligochitosan and Pyraclostrobin in Controlling Leaf Spot Disease in Pseudostellaria heterophylla

Pseudostellaria heterophylla (or Taizishen in Chinese), a medicinal, edible, and ornamental Chinese herb, is seriously affected by leaf spot disease (LSD). Oligochitosan is a natural agricultural antibiotic that is produced via the degradation of chitosan, which is deacetylated from chitin; pyraclostrobin is a broad-spectrum and efficient strobilurin fungicide. In this work, the ability of pyraclostrobin, oligochitosan, and their formula to manage P. heterophylla leaf spot disease and their role in its resistance, leaf photosynthesis, agronomic plant traits, root growth, and root quality were studied. The results show that the joint application of oligochitosan and low-dosage pyraclostrobin could control LSD more efficiently, with control effects of 85.75-87.49% compared to high-dosage pyraclostrobin or oligochitosan alone. Concurrently, the application of this formula could more effectively improve the resistance, leaf photosynthesis, agronomic plant traits, root yield, and medicinal quality of P. heterophylla, as well as reduce the application of pyraclostrobin. This finding suggests that 30% pyraclostrobin suspension concentrate (SC) 1500-time + 5% oligosaccharin aqueous solutions (AS) 500-time diluent can be recommended for use as a feasible formula to manage LSD and reduce the application of chemical pesticides.

Insights into the Hormone-Regulating Mechanism of Adventitious Root Formation in Softwood Cuttings of Cyclocarya paliurus and Optimization of the Hormone-Based Formula for Promoting Rooting

Adventitious root (AR) formation is vital for successful cutting propagation in plants, while the dynamic regulation of phytohormones is viewed as one of the most important factors affecting AR formation. Cyclocarya paliurus, a hard-to-root plant, is faced with the bottleneck of cloning its superior varieties in practice. In this study, ten treatments were designed to figure out the best hormone-based formula for promoting AR formation in softwood cuttings and explore their hormone-regulating mechanisms. Both the rooting process and the rooting parameters of the softwood cuttings were significantly affected by different hormone-based formulas (p < 0.05), while the greatest rooting rate (93%) and root quality index were achieved in the H3 formula (SR3:IR3 = 1:1). Significant differences in the measured phytohormone concentrations, as well as in their ratios, were detected among the cuttings sampled at various AR formation stages (p < 0.05), whereas the dynamics for each phytohormone varied greatly during AR formation. The transcriptome analysis showed 12,028 differentially expressed genes (DEGs) identified during the rooting process of C. paliurus cuttings, while the KEGG enrichment analysis indicated that a total of 20 KEGG terms were significantly enriched in all the comparison samples, with 253 DEGs detected in signal transduction. Furthermore, 19 genes with vital functions in regulating the hormone signaling pathway were identified by means of a WGCNA analysis. Our results not only optimize a hormone-based formula for improving the rooting of C. paliurus cuttings but also provide an insight into the hormonal regulatory network during AR formation in softwood C. paliurus cuttings.

ChIFNα regulates adventitious root development in Lotus japonicus via an auxin-mediated pathway

Adventitious roots (ARs), developing from non-root tissue, play an important role in some plants. Here, the molecular mechanism of AR differentiation in Lotus japonicus L. (L. japonicus) with the transformed chicken interferon alpha gene (ChIFNα) encoding cytokine was studied. ChIFNα transgenic plants (TP) were identified by GUS staining, PCR, RT-PCR, and ELISA. Up to 0.175 μg/kg rChIFNα was detected in TP2 lines. Expressing rChIFNα promotes AR development by producing longer roots than controls. We found that the effect was enhanced with the auxin precursor IBA treatment in TP. IAA contents, POD, and PPO activities associated with auxin regulation were higher than wild type (WT) in TP and exogenous ChIFNα treatment plants. Transcriptome analysis revealed 48 auxin-related differentially expressed genes (DEGs) (FDR < 0.05), which expression levels were verified by RT-qPCR analysis. GO enrichment analysis of DEGs also highlighted the auxin pathway. Further analysis found that ChIFNα significantly enhanced auxin synthesis and signaling mainly with up-regulated genes of ALDH, and GH3. Our study reveals that ChIFNα can promote plant AR development by mediating auxin regulation. The findings help explore the role of ChIFNα cytokines and expand animal gene sources for the molecular breeding of growth regulation of forage plants.

Integrated Transcriptomic and Metabolomic Analysis Reveals the Mechanism of Gibberellic acid Regulates the Growth and Flavonoid Synthesis in Phellodendron chinense Schneid Seedlings

The phytohormone gibberellic acids (GAs) play a crucial role in the processes of growth, organ development, and secondary metabolism. However, the mechanism of exogenous GA3 regulating the growth and flavonoid synthesis in Phellodendron chinense Schneid (P. chinense Schneid) seedlings remains unclear. In this study, the physicochemical properties, gene expression level, and secondary metabolite of P. chinense Schneid seedlings under GA3 treatment were investigated. The results showed that GA3 significantly improved the plant height, ground diameter, fresh weight, chlorophyll content, soluble substance content, superoxide dismutase, and peroxidase activities. This was accompanied by elevated relative expression levels of Pc(S)-GA2ox, Pc(S)-DELLA, Pc(S)-SAUR50, Pc(S)-PsaD, Pc(S)-Psb 27, Pc(S)-PGK, Pc(S)-CER3, and Pc(S)-FBA unigenes. Conversely, a notable reduction was observed in the carotenoid content, catalase activity and the relative expression abundances of Pc(S)-KAO, Pc(S)-GID1/2, and Pc(S)-GH 3.6 unigenes in leaves of P. chinense Schneid seedlings (p < 0.05). Furthermore, GA3 evidently decreased the contents of pinocembrin, pinobanksin, isosakuranetin, naringin, naringenin, (-)-epicatechin, tricetin, luteolin, and vitexin belonged to flavonoid in stem bark of P. chinense Schneid seedlings (p < 0.05). These results indicated that exogenous GA3 promoted growth through improving chlorophyll content and gene expression in photosynthesis and phytohormone signal pathway and inhibited flavonoid synthesis in P. chinense Schneid seedlings.

Chitosan Enhances Low-Dosage Difenoconazole to Efficiently Control Leaf Spot Disease in Pseudostellaria heterophylla (Miq.) Pax

Pseudostellaria heterophylla (Miq.) Pax is a popular clinical herb and nutritious health food. However, leaf spot disease caused by fungal pathogens frequently occurs and seriously influences the growth, quality, and yield of P. heterophylla. In this work, the field control roles of difenoconazole, chitosan, and their combination in the leaf spot disease in P. heterophylla and their effects on the disease resistance, photosynthetic capacity, medicinal quality, and root yield of P. heterophylla are investigated. The results manifest that 37% difenoconazole water-dispersible granule (WDG) with 5000-time + chitosan 500-time dilution liquid had a superior control capacity on leaf spot disease with the control effects of 91.17%~88.19% at 15~30 days after the last spraying, which significantly (p < 0.05) exceeded that of 37% difenoconazole WDG 3000-time dilution liquid and was significantly (p < 0.01) higher than that of 37% difenoconazole WDG 5000-time dilution liquid, chitosan 500-time dilution liquid, or chitosan 1000-time dilution liquid. Simultaneously, this combination could more effectively enhance the disease resistance, photosynthetic capacity, medicinal quality, and tuberous root yield of P. heterophylla compared to when these elements were applied alone, as well as effectively reduce difenoconazole application. This study emphasizes that chitosan combined with a low dosage of difenoconazole can be proposed as a green, efficient, and alternative formula for controlling leaf spot disease in P. heterophylla and enhancing its resistance, photosynthesis, quality, and yield.

The Roles of Gibberellins in Regulating Leaf Development

Plant growth and development are correlated with many aspects, including phytohormones, which have specific functions. However, the mechanism underlying the process has not been well elucidated. Gibberellins (GAs) play fundamental roles in almost every aspect of plant growth and development, including cell elongation, leaf expansion, leaf senescence, seed germination, and leafy head formation. The central genes involved in GA biosynthesis include GA20 oxidase genes (GA20oxs), GA3oxs, and GA2oxs, which correlate with bioactive GAs. The GA content and GA biosynthesis genes are affected by light, carbon availability, stresses, phytohormone crosstalk, and transcription factors (TFs) as well. However, GA is the main hormone associated with BR, ABA, SA, JA, cytokinin, and auxin, regulating a wide range of growth and developmental processes. DELLA proteins act as plant growth suppressors by inhibiting the elongation and proliferation of cells. GAs induce DELLA repressor protein degradation during the GA biosynthesis process to control several critical developmental processes by interacting with F-box, PIFS, ROS, SCLl3, and other proteins. Bioactive GA levels are inversely related to DELLA proteins, and a lack of DELLA function consequently activates GA responses. In this review, we summarized the diverse roles of GAs in plant development stages, with a focus on GA biosynthesis and signal transduction, to develop new insight and an understanding of the mechanisms underlying plant development.

Plant Development and Crop Yield: The Role of Gibberellins

Gibberellins have been classically related to a few key developmental processes, thus being essential for the accurate unfolding of plant genetic programs. After more than a century of research, over one hundred different gibberellins have been described. There is a continuously increasing interest in gibberellins research because of their relevant role in the so-called "Green Revolution", as well as their current and possible applications in crop improvement. The functions attributed to gibberellins have been traditionally restricted to the regulation of plant stature, seed germination, and flowering. Nonetheless, research in the last years has shown that these functions extend to many other relevant processes. In this review, the current knowledge on gibberellins homeostasis and mode of action is briefly outlined, while specific attention is focused on the many different responses in which gibberellins take part. Thus, those genes and proteins identified as being involved in the regulation of gibberellin responses in model and non-model species are highlighted. The present review aims to provide a comprehensive picture of the state-of-the-art perception of gibberellins molecular biology and its effects on plant development. This picture might be helpful to enhance our current understanding of gibberellins biology and provide the know-how for the development of more accurate research and breeding programs.

Identification and characterization of miRNAome and target genes in Pseudostellaria heterophylla

miRNAs play a crucial role in the development and growth of plants by inhibiting the function of targeted genes at the post-transcription level. However, no miRNAs in Pseudostellaria heterophylla have been reported and their function in the morphogenesis of organs is still unclear. In this study, a total of 159 conserved miRNAs (belonging to 64 families) and 303 level miRNAs were identified from P. heterophylla. Some of them showed specifically up or down-regulated expression in different tissues and numbers of unigenes involved in Plant-pathogen interaction and MAPK signaling pathway-plant were targeted. The significant negative correlation of expression profiles between 30 miRNAs and their target genes (37 unigenes) was observed, respectively. Further, a large number of genes involved with signal transduction of auxin, zeatin, abscisic acid and, jasmonic acid were targeted. Predicated targets of two miRNAs were validated by 5'RLM-RACE, respectively. A large number of mRNAs from four pathogens were targeted by miRNAs from P. heterophylla and some of them were targeted by miR414. In summary, we reported a population of miRNAs from four different vegetative tissues of P. heterophylla by high throughput sequencing, which was analyzed by combining with the constructed transcriptome. These results may help to explain the function of miRNAs in the morphogenesis of organs and defense of pathogens, and may provide theoretical basis for breeding and genetic improvement of P. heterophylla.

Comparative transcriptomics analysis reveals MdGRAS53 contributes to disease resistance against Alternaria blotch of apple

Alternaria blotch disease, caused by Alternaria alternata apple pathotype (AAAP), is one of the most prevalent diseases in apple production. To identify AAAP resistance-related genes and provide a theoretical basis for Alternaria blotch disease resistance breeding, we used two apple cultivars, 'Jonathan', a variety resistant to AAAP infection, and 'Starking Delicious', a variety susceptible to AAAP infection, as materials to perform transcriptome sequencing of apple leaves 72 h after AAAP infection. A Venn diagram showed that a total of 5229 DEGs of 'Jonathan' and 4326 DEGs of 'Starking Delicious' were identified. GO analysis showed that these DEGs were clustered into 25 GO terms, primarily "metabolic process" and "catalytic activity." Functional classification analyses of the DEGs indicated that "MAPK signaling pathway-plant pathway" is the most significant metabolic pathway among the top 15 KEGG pathways, followed by the "plant hormone signal transduction" pathway. There are more DEGs in 'Jonathan' that are significantly classified GO terms and KEGG pathways than in 'Starking Delicious'. Specifically, 13 DEGs were identified as involved in the GA-GID1-DELLA module, and the expression of MdGRAS53, a homologous gene of DELLA, was significantly upregulated in 'Jonathan' compared with 'Starking Delicious'. Phenotype analysis revealed that exogenous hormone GA3 suppressed apple resistance to AAAP infection and reduced the expression of MdGRAS53. The opposite result was observed for exogenous spraying of paclobutrazol (PAC), an inhibitor of gibberellin synthesis. Overexpression of MdGRAS53 in apple leaves by transient transformation decreased lesion area and the number of spores in leaves infected with AAAP, while silencing MdGRAS53 showed the opposite result. Meanwhile, SA/JA signaling pathway-related genes were upregulated significantly in MdGRAS53-overexpressed leaves and downregulated significantly in MdGRAS53-silenced leaves. The findings suggest that the GA-GID1-DELLA module is involved in apple resistance to AAAP, and MdGRAS53, a DELLA homologous gene, may play a positive role in this resistance by modulating cooperative JA- and SA-dependent pathways.

Study on the Regulatory Effects of GA3 on Soybean Internode Elongation

Excessive plant height is an important factor that can lead to lodging, which is closely related to soybean yield. Gibberellins are widely used as plant growth regulators in agricultural production. Gibberellic acid (GA₃), one of the most effective active gibberellins, has been used to regulate plant height and increase yields. The mechanism through which GA₃ regulates internode elongation has been extensively investigated. In 2019 and 2020, we applied GA₃ to the stems, leaves, and roots of two soybean cultivars, Heinong 48 (a high-stalk cultivar) and Henong 60 (a dwarf cultivar), and GA₃ was also applied to plants whose apical meristem was removed or to girded plants to compare the internode length and stem GA₃ content of soybean plants under different treatments. These results suggested that the application of GA₃ to the stems, leaves, and roots of soybean increased the internode length and GA₃ content in the stems. Application of GA₃ decreased the proportion of the pith in the soybean stems and primary xylem while increasing the proportion of secondary xylem. The apical meristem is an important site of GA₃ synthesis in soybean stems and is involved in the regulation of stem elongation. GA₃ was shown to be transported acropetally through the xylem and laterally between the xylem and phloem in soybean stems. We conclude that the GA₃ level in stems is an important factor affecting internode elongation.