IAA Content Research Articles

Construction and analysis of the tapping panel dryness-related lncRNA/circRNA-miRNA-mRNA ceRNA network in latex of Hevea brasiliensis

Tapping panel dryness (TPD) results in a severe reduction in latex yield in Hevea brasiliensis. However, the molecular regulatory mechanisms of TPD occurrence are still largely unclear. In this study, whole-transcriptome sequencing was carried out on latex from TPD and healthy trees. In total, 7078 long noncoding RNAs (lncRNAs), 3077 circular RNAs (circRNAs), 4956 miRNAs, and 25041 mRNAs were identified in latex, among which 435 lncRNAs, 68 circRNAs, 320 miRNAs, and 1574 mRNAs were differentially expressed in the latex of TPD trees. GO and KEGG analyses indicated that plant hormone signal transduction, MAPK signaling pathway, and ubiquitin-mediated proteolysis were the key pathways associated with TPD onset. Phytohormone profiling revealed significant changes in the contents of 28 hormonal compounds, among which ACC, ABA, IAA, GA, and JA contents were increased, while SA content was reduced in TPD latex, suggesting that hormone homeostasis is disrupted in TPD trees. Furthermore, we constructed a TPD-related competitive endogenous RNA (ceRNA) regulatory network of lncRNA/circRNA-miRNA-mRNA with 561 edges and 434 nodes (188 lncRNAs, 5 circRNAs, 191 miRNAs, and 50 mRNAs) and identified two hub lncRNAs (MSTRG.11908.1 and MSTRG.8791.1) and four hub miRNAs (hbr-miR156, miR156-x, miRf10477-y, and novel-m0452-3p). Notably, the lncRNA-miR156/157-SPL module containing three hubs probably plays a crucial role in TPD onset. The expression of network hubs and the lncRNA-miR156/157-SPL module were further validated by qRT-PCR. Our results reveal the TPD-associated ceRNA regulatory network of lncRNA/circRNA-miRNA-mRNA in latex and lay a foundation for further investigation of molecular regulatory mechanisms for TPD onset in H. brasiliensis.

Trehalose alleviates the inhibition of adventitious root formation caused by drought stress in cucumber through regulating ROS metabolism and activating trehalose and plant hormone biosynthesis

Trehalose (Tre) plays a vital role in response to drought stress in plants but its regulatory mechanism remains unclear. Here, this study explores the mechanism of re-regulated drought tolerance during cucumber adventitious root formation. Our results indicate that 2 mM Tre displays remarkable drought alleviation in the aspect of root number, root length, fresh weight, and dry weight. Under drought stress, Tre could inhibit greatly the MDA, H2O2, and O2− accumulation, enhance obviously the activities of SOD, POD, and CAT enzymes and up-regulate significantly the transcript levels of SOD, POD, and CAT genes. Furthermore, Tre treatment also promotes Tre metabolism during drought stress: significantly increases starch and Tre contents and decreases glucose content, the biosynthesis enzymatic activity of the Tre metabolic pathway including TPS and TPP are enhanced and the activity of degradation enzyme THL is decreased, and corresponding genes TPS1, TPS2, TPPA, and TPPB are up-regulated. Tre significantly reversed the decrease caused by PEG in IAA, ethylene, ABA, and BR contents and the increase caused by PEG in GA3 and KT contents. Collectively, Tre appears to be the effective treatment in counteracting the negative effects of drought stress during adventitious root formation by regulating ROS, Tre metabolisms and plant hormones.

Effect of spermidine, glutamine, and proline on somatic embryogenesis and silver nanoparticles supplied culture improved rhizome formation of Panax vietnamensis var. langbianensis

Lang Bian ginseng (Panax vietnamensis var. langbianensis) is a rare and traditional herbal medicine with many pharmacological activities. It was first discovered by Duy et al. (2016) in Lam Dong province, Vietnam. Until now, there has been only one publication on Lang Bian ginseng micropropagation via somatic embryogenesis (Anh et al., 2022). However, this study still had limitations, including the small number of somatic embryos and the time-consuming. This study investigated the effect of spermidine, glutamine, and proline on the enhancement of somatic embryogenesis (SE) of Lang Bian ginseng using thin cell layer culture technology. The results showed that the optimal SE rate and the number of somatic embryos per explant were achieved on MS medium supplemented with 0.01 mM spermidine in leaf explants (93.32 % and 54.20 embryos, respectively) and petiole explants (96.66 % and 68.80 embryos, respectively) and higher compared to these in other treatments, including control, glutamine, and proline treatments. Besides, adding 0.01 mM spermidine to the culture medium also improved the quality of somatic embryos, mainly cotyledonary stage, through an enhanced synthesis of antioxidant enzymes [catalase (CAT) and superoxide dismutase (SOD), and ascorbate peroxidase (APX)]. In addition, the fluctuations of endogenous hormones during initiation and maturation of SE derived from 0.01 mM spermidine treatment were recorded. Endogenous CKs (ZEA, 2iP, KIN, mT), IAA, and GA3 concentrations were the highest during the induction stage in both explants. Meanwhile, the remaining endogenous hormones (MEL, ABA, and SA) exhibited no inevitable fluctuation trends. In addition, IAA was only detected at the induction stage of SE in both explants. Moreover, cotyledonary somatic embryos derived from 0.01 mM spermidine treatment grew well in MS medium supplemented with 1.2 mg/L AgNPs.

Low-concentration exogenous 3-indoleacetic acid improves fruit-setting rate of Marsdenia tenacissima by inhibiting the expression of embryo abortion-related genes

Marsdenia tenacissima is a medicinal plant characterized by many flowers, few fruits, and a low fruit-setting rate. Exogenous auxins can improve the fruit-setting rate of plants; however, their impacts on M. tenacissima and regulatory mechanisms remain unclear. In this study, we conducted a field experiment to determine the fruit-setting rate, seed-setting rate, fruit size, and changes in transcriptional expression of related genes by spraying 10 and 50 mg·L-1 of 3-indoleacetic acid (IAA). The control plants were sprayed with distilled water. Our results indicated that the fruit-setting rate was 0.15 when treated with 10 mg·L-1 of IAA, which was 2.76-fold higher than that of the control. Compared with that of the control, the number of differentially expressed genes (DEGs) regulated by 10 mg·L-1 of IAA was 28.6-fold higher than that regulated by 50 mg·L-1 of IAA. These DEGs were closely related to hormone metabolism and fruit development. By transcriptome analysis, spraying 10 mg·L-1 of IAA increased the expressions of STP6, MYB17, and LAX3 and reduced those of CXE18, ILR1-like 3, and SAUR50; this possibly affected the ovule, embryo, and fruit development, thereby elevating the fruit-setting rate of M. tenacissima. Our results indicated that low IAA concentration increased the fruit-setting rate of M. tenacissima, providing theoretical and practical support for promoting the seed yield of M. tenacissima.

Molecular characterization of vermicompost-derived IAA-releasing bacterial isolates and assessment of their impact on the root improvement of banana during primary hardening.

The hardening step of micropropagation is crucial to make the in vitro raised plants mature and further enhancing their survivability in the external environment. Auxin regulates various root physiological parameters in plant systems. Therefore, the present study aimed to assess the impact of three vermicompost-derived IAA-releasing microbial strains, designated S1, S2, and S3, as biofertilizers on in vitro raised banana plantlets during primary hardening. The High-Performance Thin-Layer Chromatography (HPTLC) analysis of these strains revealed a higher IAA content for S1 and S2 than that of S3 after 144h of incubation. In total, seven different treatments were applied to banana plantlets, and significant variations were observed in all plant growth parameters for all treatments except autoclaved cocopeat (100%) mixed with autoclaved vermicompost (100%) at a 1:1 ratio. Among these treatments, the application of S3 biofertilizer: autoclaved cocopeat (1:1), followed by S2 biofertlizer: autoclaved cocopeat (1:1), was found to be better than other treatments for root numbers per plant, root length per plant, root volume, and chlorophyll content. These findings have confirmed the beneficial effects of microbial strains on plant systems and propose a link between root improvement and bacterial auxin. Further, these strains were identified at the molecular level as Bacillus sp. As per our knowledge, this is the first report of Bacillus strains isolated from vermicompost and applied as biofertilizer along with cocopeat for the primary hardening of banana. This unique approach may be adopted to improve the quality of plants during hardening, which increases their survival under abiotic stresses.

Exogenous auxin regulates the growth and development of peach fruit at the expansion stage by mediating multiple-hormone signaling

BackgroundFruit expansion stage is crucial to fruit yield and quality formation, and auxin plays a significant role by mediating multi-hormone signals during fruit expansion. However, till now, it is still unclear of the molecular regulatory network during auxin-mediated peach fruit expansion.ResultsHere, exogenous NAA application markedly increased IAA content and drastically decreased ABA content at the fruit expansion stage. Correspondingly, NAA mainly induced the auxin biosynthesis gene (1 PpYUCCA) and early auxin-responsive genes (7PpIAA, 3 PpGH3, and 14 PpSAUR); while NAA down-regulated ABA biosynthesis genes (2 PpNCED, 1 PpABA3, and 1 PpAAO3). In addition, many DEGs involved in other plant hormone biosynthesis and signal transduction were significantly enriched after NAA treatment, including 7 JA, 7 CTK, 6 ETH, and 3 GA. Furthermore, we also found that NAA treatment down-regulated most of genes involved in the growth and development of peach fruit, including the cell wall metabolism-related genes (PpEG), sucrose metabolism-related genes (PpSPS), phenylalanine metabolism-related genes (PpPAL, Pp4CL, and PpHCT), and transcription factors (PpNAC, PpMADS-box, PpDof, PpSBP, and PpHB).ConclusionOverall, NAA treatment at the fruit expansion stage could inhibit some metabolism processes involved in the related genes in the growth and development of peach fruit by regulating multiple-hormone signaling networks. These results help reveal the short-term regulatory mechanism of auxin at the fruit expansion stage and provide new insights into the multi-hormone cascade regulatory network of fruit growth and development.

Effects of thidiazuron on the quality and storage properties of mango fruit during postharvest

Abstract Thidiazuron (TDZ) is used for the expansion of fruits, but excessive levels of TDZ lead to a decline in fruit quality. The appropriate concentration of TDZ for mango expansion without a decline in quality is not clear. In the present study, four different concentrations (5, 10, 15, and 20 mg/L) of TDZ were applied via spraying on mango plants, and several physiological and biochemical indicators were measured. The results showed that TDZ treatment significantly increased mango fruit size and single-fruit weight. In mango fruit, TDZ treatment decreased the disease index, delayed the increase in the malondialdehyde and H2O2 content, and maintained firmness and antioxidant capacities at a relatively high level during postharvest storage. At the same time, TDZ treatment delayed the decrease in the giberellin, indoleacetic acid and jasmonic acid content in mango, and reduced the accumulation of abscisic acid and ethylene. These trends are consistent with TDZ treatment leading to extension of the shelf life of mango. Furthermore, ethylene biosynthesis, signal transduction, and cell wall dismantling-related genes were investigated. The results indicated that the expression of the MiACS, MiETR2, MiERF113, MiERF010, MiERF054, MiEXP, MiPG14, MiPG21, MiCEL, and MiPEL genes in mango was inhibited under TDZ treatment compared with the control. In summary, TDZ treatment can significantly increase the size and weight of mango fruit and can extend its shelf life. The most suitable concentration is 10–15 mg/L TDZ, which will not affect the quality of mango fruit.

A sustainable electrochemical analytical platform for rapid detection of indole-3-acetic acid in Marchantia polymorpha

Auxin (mainly indole-3-acetic acid, IAA) is one of the most essential phytohormones with various roles for land plants at different evolution stages and its polar transportation in plants suggested the importance of obtaining its amounts in different plant tissues. Because Marchantia polymorpha is at the entry evolution level, the IAA contents in its tissues would be useful for the study of IAA evolution. Although electrochemical detection offers a possible method for the measurement of IAA amounts, the cost for fabrication of electrochemical sensors is still high given the amounts of IAA tests in the future. Herein a low-cost disposable electrochemical analytical platform was constructed for analysis of IAA in tiny plant samples. Specifically, disposable carbon electrodes were prepared by modifying stainless steel wire mesh with inexpensive carbon ink because of less amounts of materials. The electrode was then integrated with a paper-based analytical device to form a disposable and low-cost platform for rapid electrochemical detection of IAA. For the modified electrode, the highest electrochemical responses for IAA could be obtained when the carbon ink was diluted for 3.5 times. The optimized pH value of the buffer solution for testing was 7.0, which is close to the physiological condition. Coupled with sample treatment using zirconium beads, this approach could successfully differentiate IAA in different tissues of Marchantia polymorpha. The obtained results agreed well with previous reports. This study suggested a sustainable electrochemical analytical detection platform for the study of IAA in practical applications.

The Sink–Source Relationship Regulated Camellia oleifera Flower Bud Differentiation by Influencing Endogenous Hormones and Photosynthetic Characteristics

To explore the reasons for the differences in flower bud differentiation in Camellia oleifera under different sink–source relationships, different types of new shoots (T1 and T2) were selected to represent different sink–source relationships (new shoots with one fruit borne alongside at the bottom of the new shoots-T1; new shoots without one fruit borne alongside at the bottom of the new shoots-T2), and the flower bud differentiation rate, endogenous hormones and photosynthetic characteristics were determined. With the increase in the sink, the flower differentiation rate decreased significantly and the IAA and GA3 content in the leaves and ABA content in the buds increased significantly, while the GA3 and ZT content in the buds decreased significantly, which were significantly and positively correlated with the flower differentiation rate, with correlation coefficients of 0.777 and 0.817, respectively. Furthermore, an increase in the number of sinks contributed significantly to the increase in soluble sugar and starch content in leaves, while the soluble sugar and starch content in flower buds decreased significantly with the increase in sinks, with maximum differences of 3.45 mg·g−1 (soluble sugar in leaves), 4.09 mg·g−1 (soluble sugar in flower buds), 7.08 mg·g−1 (starch in leaves) and 4.87 mg·g−1 (starch in flower buds), and the high soluble sugar and starch content in flower buds at preflower bud differentiation with correlation coefficients of 0.854 and 0.837, respectively. The chlorophyll content and net photosynthetic rate increased with increasing sinks. In the presence of fruit at the base of the new shoot, more 13C assimilates were allocated to fruit and less to flower buds, resulting in a decrease in the rate of flower bud differentiation. The 13C assimilate allocated to the flower buds of T1 (6.71 mg·g−1) was significantly lower than the 13C assimilate allocated to the flower buds of T2 (10.26 mg·g−1) during late bud differentiation, and the difference between T1 and T2 was greatest during this period. Our work demonstrated that the sink–source relationship regulated Camellia oleifera flower bud differentiation by influencing endogenous hormones and photosynthetic characteristics. To achieve stable production of Camellia oleifera in successive years in the future, the ratio of the number of new shoots of the two types in relation to the different sink–source relationships should be reasonable.

Plant Growth Stimulatory Effect of Terrein and Its Mechanism of Action in Crops under Drought Stress

Drought is one of the most important factors that limit crop yield. In this study, the growth promotive activity of terrein, a microbial metabolite, on four selected agricultural plants (Vigna radiata, Brassica chinensis, Triticum aestivum and Sorghum bicolor) under drought conditions was assessed via pot experiment. Terrein effectively stimulated the seedling growth of tested species and increased their fresh and dry weight at low concentrations (2 and 10 μg/mL), either applied as a seed soaking agent or a spray solution, especially on root growth. The maximum stimulatory effect on root growth was observed on B. chinensis seedlings (99.20%), on fresh weight was found on T. aestivum seedlings (97.23%), and on dry weight was discovered on V. radiata seedlings (58.33%), implying that this stimulatory effect was species-specific. Further study revealed that the application of terrein significantly raised the contents of GA3, IAA and CTK; meanwhile, MDA content declined significantly, whereas the activity of POD, CAT and SOD was boosted significantly, suggesting that terrein can stimulate plant growth by reducing the production of ROS. Our work is the first study focusing on terrein’s plant growth promotive activity, indicating terrein has the potential to be further explored as an environment-friendly growth regulator.

The Physiological Mechanism of Melatonin Enhancing the Tolerance of Oat Seedlings under Saline–Alkali Stress

Exogenous melatonin (MT) regulates plant growth and mitigates stress in response to stress. To analyze the machinery of exogenous melatonin, which improves salt and alkaline tolerance in oats, MT’s function was identified in the oat seed germination stage in our previous study. In this study, morphogenesis, photosynthetic physiology, hormone levels, and ion homeostasis were evaluated using the same MT treatment concentration. The results revealed that compared to the S45 treatment, the 100 μmol·L−1 MT treatment efficiently increased the seedling height and main root length of oat seedlings; promoted secondary root development; enhanced the root volume and root surface area; maintained a higher photosynthetic pigment content (carotenoids; chlorophyll a; chlorophyll b); raised the leaf photosynthetic rate (Pn), intercellular CO2 concentration (Ci), conductance to H2O (Gs), and transpiration rate (Tr); enhanced the light energy absorption and conversion of leaves; increased the leaf GA3, Tryptamine (TAM), and IAA contents; and decreased ABA levels. Hierarchical cluster analysis revealed that MT treatment also increased the contents of P, K, Ca, Mn, Cu, Mg, Fe, Zn, Mo, Cd, Al, Se, Ni, Co, and Ti; decreased the Na/K ratio; and maintained cellular ionic homeostasis in oat seedlings under saline–alkali stress, as compared with the untreated group. These findings showed that MT treatment enhanced the adaptation of oat to saline–alkali stress through regulating the physiological process of seedling growth. This suggests that MT plays a different role in improving saline–alkali tolerance in the germination and seedling stages of oat.

Characterization of rhizosphere fungi of the ebony plant (Diospyros celebica Bakh.) which has the potential to produce Indole-3-Acetic Acid and Gibberelic Acid Phytohormones

Ebony (Diospyros celebica Bakh.) is a slow-growing species that is an impacting factor in the extinction of this species. Efforts to reduce the ebony population can be performed by employing microbes to stimulate ebony growth. This study aimed to obtain bacterial isolates with the potential of producing IAA and GA3 that can be further utilized as biofertilizer agents. Research stages encompassed soil sample isolation, isolation of bacteria, and analysis of IAA and GA3. The research was in complete randomized design (CRD). Thirteen isolates were successfully purified and analyzed with their IAA and GA3 hormones. The highest IAA concentrations were observed in EP1b at 48 incubation hours (44.39 ppm), EP3d at 72 incubation hours (34.93 ppm), and EP3c at 72 incubation hours (34.48 ppm). EP2c, EP2e, and EP2a produced the highest GA3 concentration at 24 incubation hours which were 3.88 ppm, 3.88 ppm, and 3.81 ppm, respectively.

Rhizobacteria Increases Growth and Development of Blackberry Saplings

In this study, the effects of rhizobacteria on vegetative growth of Chester Thornless blackberry cultivars saplings were investigated. In this context, plant height, shoot number, stem diameter, average shoot length, root length, plant fresh and dry weight, root fresh and dry weight, IAA, ABA, GA, cytokinin, zeatin hormones and N, P, K, Ca, Mg, S, Mn, Fe, Zn, Cu, Na nutrients were investigated. According to the evaluations, the highest plant fresh and dry weights and root fresh and dry weights were obtained from the SK50 bacteria strain. It was determined that plant height, stem diameter, average shoot length and root length maximum increased with SK-39 strain. Bacteria applications increased the IAA, GA, cytokinin and zeatin contents and decreased the ABA content in the leaves. With bacteria applications, leaf N, P, K, Ca, S, Zn, Cu and Na contents increased compared to control. According to the results of the research, it can be recommended to use Herbaspirillum huttiense SK-39, Achromobacter xylosoxidans denitrificans SK-50, Pantoea agglomerans GC subgroup SY-43 and Microbacterium ester aromaticum SY-48 bacteria strains in order to promote growth and development in the cultivation of blackberry cultivars.

Optimization and reactor-scale production of plant growth regulators by Pleurotus eryngii.

The aims of the this study are to select the best cultivation type for plant growth regulator (PGR) production, to optimize PGR production with statistical experimental design, and to calculate bioprocess parameters and yield factors during PGR production by P. eryngii in flask and reactor scales. Submerged fermentation was the best cultivation type with 4438.67 ± 37.14, 436.95 ± 27.31, and 54.32 ± 3.21mg/L of GA3, ABA, and IAA production values, respectively. The Plackett-Burman and Box-Behnken designs were used to determine effective culture parameters and interactive effects of the selected culture parameters on PGR production by Pleurotus eryngii under submerged fermentation. The statistical model is valid for predicting PGR production by P. eryngii. After these studies, maximum PGR production (7926.17 ± 334.09, 634.92 ± 12.15, and 55.41 ± 4.38mg/L for GA3, ABA, and IAA, respectively) was reached on the 18th day of fermentation under optimized conditions. The optimum formula was 50g/L fructose, 3g/L NaNO3, and 1.5g/L KH2PO4, 1mg/L thiamine, incubation temperature 25°C, initial medium pH 7.0, and an agitation speed of 150rpm. The kinetics of PGR production was investigated in batch cultivation under 3-L stirred tank reactor conditions. Concentrations of GA3, ABA, and IAA of 10,545.00 ± 527.25, 872.32 ± 21.81, and 60.48 ± 3.48mg/L were obtained at the reactor scale which were 4.1, 3.4, and 2.3 times higher than the initial screening values. The specific growth rate (µ), the volumetric (rp) and specific (Qp) PGR production rates, 486.11mg/L/day and 107.43mg/g biomass/day for GA3, confirmed the successful transfer of optimized conditions to the reactor scale. In the presented study, PGR production of P. eryngii is reported for the first time.

Influence of a Hydrocarbon Biodestructor on the Growth and Content of Phytohormones in Secale cereale L. Plants under Petroleum Pollution of the Soil

The phytoremediation of soil contaminated with petroleum depends on the association of plants with rhizosphere bacteria capable of promoting plant growth and destroying petroleum hydrocarbonates. In the present work, we studied the effects of “Lenoil” biological product containing bacteria Pseudomonas turukhanskensis IB 1.1, capable of destroying petroleum hydrocarbons on Secale cereale L plants, which previously proved to be resistant to the weak oil pollution of gray forest soil and to the composition of microorganisms in their rhizosphere. The composition of microorganisms in the rhizosphere of rye roots was studied, morphometric parameters of shoots and roots of rye plants were estimated, and hormone concentration was immunoassayed under conditions of 4% petroleum pollution of the soil. Addition of petroleum to the soil increased the content of oligonitrophilic (by 24%) and hydrocarbon-oxidizing (by 33%) microorganisms; however, the content of cellulolytic (by 12.5 times) microorganisms in the rhizosphere decreased. The use of Lenoil led to a further increase in the number of cellulolytic (by 5.6 times) and hydrocarbon-oxidizing (by 3.8 times) microorganisms and a decrease in the number of oligonitrophilic (by 22.7%) microorganisms in the rhizosphere. Under petroleum pollution, the content of auxins (IAA), zeatin riboside, zeatin nucleotide, and zeatin decreased, while the content of abscisic acid (ABA) increased in the shoots of rye plants. Lenoil treatment led to an eight-fold increase in the IAA content in the roots and a decrease in the ABA content in the aerial part and in the roots. It was shown for the first time that the treatment of petroleum-contaminated soil with “Lenoil” increased root mass due to the development of lateral roots, concurrent with high root IAA content. Petroleum pollution increased the deposition of lignin and suberin in the roots, which strengthened the apoplastic barrier and, thus, reduced the infiltration of toxic components. The deposition of suberin and lignin decreased under ”Lenoil” treatment, indicating a decrease in the concentration of toxic petroleum components in the soil degraded by the bacteria. Thus, the biological preparation reduced the growth-inhibiting effect of petroleum on rye plants by increasing the content of growth-stimulating phytohormones (IAA and cytokinins) and reducing the content of ABA, justifying the importance of further study of relevant hormones for the improvement of phytoremediation.

Chitosan nanoparticles upregulate C and N metabolism in soybean plants grown under elevated levels of atmospheric carbon dioxide

Despite the wide utilization of chitosan nanoparticles (CSNPs) as a promising approach for sustainable agriculture, their efficiency under elevated CO2 (eCO2), has not been evaluated. The interactive effects of CSNPs and eCO2 were evaluated on the growth and C and N metabolism of soybean plants. Plants were treated with CSNPs and grown under ambient CO2 (410 ppm, aCO2) or eCO2 (645 ppm). Regardless of CO2 level, CSNPs improved the net photosynthetic rate. CSNPs aggravated the effect of eCO2 treatment on the levels of non-structural carbohydrates (i.e., glucose, fructose, sucrose, and starch), especially in shoots, which was inconsistence with the upregulation of carbohydrates metabolizing enzymes. Being the most pivotal energetic and signaling organic compounds in higher plants, the synergistic action of CSNPs and eCO2 on the accumulation of soluble sugars upregulated the N metabolism as indicated by induced activities of nitrate reductase, arginase, glutamate dehydrogenase, glutamine synthetase, and glutamine oxoglutarate aminotransferase which was manifested finally as increased shoot and root total nitrogen content as well as proline and aspartate in roots. At the hormonal level, the coexistence of eCO2 with CSNPs further supports their positive impact on the contents of IAA and, to a lesser extent, GAs. The present data prove that the biofertilization capacity of CSNPs is even more potent under futuristic eCO2 levels and could even further improve the growth and resilience of plants.

Herbicide 2,4-dichlorophenoxyacetic acid interferes with MAP kinase signaling in Fusarium graminearum and is inhibitory to fungal growth and pathogenesis

Plant hormones are important for regulating growth, development, and plant-pathogen interactions. Some of them are inhibitory to growth of fungal pathogens but the underlying mechanism is not clear. In this study, we found that hyphal growth of Fusarium graminearum was significantly reduced by high concentrations of IAA and its metabolically stable analogue 2,4-dichlorophenoxyacetic acid (2,4-D). Besides inhibitory effects on growth rate, treatments with 2,4-D also caused significant reduction in conidiation, conidium germination, and germ tube growth. Treatments with 2,4-D had no obvious effect on sexual reproduction but significantly reduced TRI gene expression, toxisome formation, and DON production. More importantly, treatments with 2,4-D were inhibitory to infection structure formation and pathogenesis at concentrations higher than 100 µM. The presence of 1000 µM 2,4-D almost completely inhibited plant infection and invasive growth. In F. graminearum, 2,4-D induced ROS accumulation and FgHog1 activation but reduced the phosphorylation level of Gpmk1 MAP kinase. Metabolomics analysis showed that the accumulation of a number of metabolites such as glycerol and arabitol was increased by 2,4-D treatment in the wild type but not in the Fghog1 mutant. Transformants expressing the dominant active FgPBS2S451D T455D allele were less sensitive to 2,4-D and had elevated levels of intracellular glycerol and arabitol induced by 2,4-D in PH-1. Taken together, our results showed that treatments with 2,4-D interfere with two important MAP kinase pathways and are inhibitory to hyphal growth, DON biosynthesis, and plant infection in F. graminearum.

Ring Stripping, Ring Cutting, and Growth Regulators Promote Phase Change and Early Flowering in Pear Seedlings.

Hybrid breeding is the most important means of selecting pear (Pyrus) varieties, but a long juvenile period severely restricts the selection of new varieties. In this study, we used 'Yuluxiang' × 'Akituki' 4-year-old seedling trees to study the effects of plant growth regulators, ring stripping, and ring cutting on the promotion of phase change and flowering to assist in shortening the breeding cycle. A single application of 100 mg/kg 6-BA + 1000 mg/kg PP333 was most effective in promoting phase change and flowering. This treatment effectively inhibited the growth and thickening of annual shoots, significantly increased soluble sugar and protein contents in buds, increased the ABA content by 45.41%, decreased the IAA content by 7.35%, increased the expression of the flower-promoting genes FT and LFY by 2273.41% and 1153.71%, respectively, and decreased the expression of the flower-suppressing gene TFL1 by 74.92%. The flowering plant rate increased by 23.34% compared to the control. Both ring stripping and ring cutting were effective in promoting phase change and flowering, significantly increasing the flowering rate, inflorescence number, and the number of flowering plants. For improving the flowering rate, the ring-stripping treatment had the strongest effect and effectively inhibited the growth and thickening of annual shoots, while also significantly increasing the soluble sugar and protein contents in buds, reducing the contents of IAA and GA3 by 8.73% and 50.12%, respectively, increasing the expression of FT and LFY by 80.01% and 821.14%, respectively, and reducing the expression of the flower-suppressing gene TFL1 by 59.22%. In conclusion, ring stripping, ring cutting, and spraying of 100 mg/kg 6-BA + 1000 mg/kg PP333 were effective in promoting phase change and early flowering in seedling trees.

Characterization of the Molecular Events Underlying the Establishment of Axillary Meristem Region in Pepper.

Plant architecture is a major motif of plant diversity, and shoot branching patterns primarily determine the aerial architecture of plants. In this study, we identified an inbred pepper line with fewer lateral branches, 20C1734, which was free of lateral branches at the middle and upper nodes of the main stem with smooth and flat leaf axils. Successive leaf axil sections confirmed that in normal pepper plants, for either node n, Pn (Primordium n) < 1 cm and Pn+1 < 1 cm were the critical periods between the identification of axillary meristems and the establishment of the region, whereas Pn+3 < 1 cm was fully developed and formed a completely new organ. In 20C1734, the normal axillary meristematic tissue region establishment and meristematic cell identity confirmation could not be performed on the axils without axillary buds. Comparative transcriptome analysis revealed that "auxin-activated signaling pathway", "response to auxin", "response to abscisic acid", "auxin biosynthetic process", and the biosynthesis of the terms/pathways, such as "secondary metabolites", were differentially enriched in different types of leaf axils at critical periods of axillary meristem development. The accuracy of RNA-seq was verified using RT-PCR for some genes in the pathway. Several differentially expressed genes (DEGs) related to endogenous phytohormones were targeted, including several genes of the PINs family. The endogenous hormone assay showed extremely high levels of IAA and ABA in leaf axils without axillary buds. ABA content in particular was unusually high. At the same time, there is no regular change in IAA level in this type of leaf axils (normal leaf axils will be accompanied by AM formation and IAA content will be low). Based on this, we speculated that the contents of endogenous hormones IAA and ABA in 20C1734 plant increased sharply, which led to the abnormal expression of genes in related pathways, which affected the formation of Ams in leaf axils in the middle and late vegetative growth period, and finally, nodes without axillary buds and side branches appeared.

The deteriorating effects of cadmium accumulation on the yield and quality of maize crops

Food security is critical for survival but increasing heavy metal particularly cadmium concentration in the environment due to human activity poses a threat to both plants and animals. The experiment was designed to investigate the potential impact of varying concentrations of cadmium on the growth, metabolites, and accumulation of cadmium in the edible portion of maize. The objective was to gain scientific insights into the relationship between cadmium exposure and maize physiology, biochemistry, and accumulation of the heavy metal. Significant reduction was recorded in the agronomic attributes including root shoot length, fresh and dry weight and chlorophyll contents of the maize (p < 0.05). Higher level of cadmium imposes destruction of the antioxidant defense system of the host indicated by the lower catalases activity (92% reduction). Along with this, growth and stress related metabolites like IAA, salicylic acid, proteins, lipid and sugar contents decreased approximately by 50% at the lowest concentration while reaching 70 to 77% at the highest concentration of cadmium. Interestingly, plants exposed to cadmium for 60-days duration approximately 20 to 25 mg/kg of cadmium was accumulated in plants parts of which most of the cadmium (50% or higher) were translocated to the shoot of the host plants. This data also showed that the maximum concentration of cadmium is accumulated in the stem, followed by the leaf, and then the seed. The concentration of cadmium in seeds varies from 2 to 4 mg/kg, which is a highly prohibited amount of cadmium in food for human consumption.