IAA Content Research Articles

Root physiological and morphology processes co-regulate the growth of Chinese-fir saplings in response to warming and precipitation reduction in the sub-tropical regions

Subtropical China is projected to experience elevated temperature greater than the mean global temperature increase and is accompanied by reduced precipitation. The plasticity of roots to changing environment strongly influences ecosystem feedbacks to climate change. However, knowledge gaps on the individual and combined effects of warming and precipitation reduction on root systems hinder our ability to accurately predict the growth and adaptability of forests under future climate change. To examine the effects of warming (W) and precipitation reduction (P) on roots physiology and morphology of Chinese-fir saplings, we used a randomized complete block design with factorial soil warming (ambient, ambient + 5℃) and precipitation reduction (ambient, ambient-50%) treatments. A full excavation method was adopted to obtain roots, then we measured the root physiology (osmoregulatory substances, oxidant substances, protective enzymes, endogenous hormones), morphology (specific root length, SRL; surface root area, SRA; root tissue density, RTD). The content of carbon and nitrogen, isotopes (δ13C and δ15N); soil temperature, soil moisture and sapling growth were also measured. We found that compared with the control, W decreased the abscisic acid (IAA) content; P increased the contents of hydrogen peroxide (H2O2) and proline (Pro), and decreased the contents of IAA and cytokinin (CTK); warming plus precipitation reduction (WP) increased the Pro content, and decreased the contents of IAA and CTK. In addition, the effects of W and P on root morphology varied with soil depth and root diameter class. W, P, and WP all increased fine root SRL and SRA in deep soil. Warming and precipitation reduction could affect physiological traits (e.g. non-enzymatic substances and antioxidant enzymes) and subsequently morphological traits via influencing soil environment and root tissue chemistry. Collectively, the results indicated that Chinese-fir saplings responded to warming and precipitation reduction by comprehensive regulation of the non-enzymatic substances (e.g., osmotic substances and endogenous hormones) of fine roots and changing root morphological characteristics in deep soil.

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.

Indole-3-Acetic Acid (IAA) and Sugar Mediate Endosperm Development in Rice (Oryza sativa L.)

The yield potential of large-panicle rice is often limited by grain-filling barriers caused by the development of inferior spikelets (IS). Photoassimilates, which are the main source of rice grain filling, mainly enter the caryopsis through the dorsal vascular bundle. The distribution of assimilates between superior spikelets (SS) and IS is influenced by auxin-mediated apical dominance; however, the mechanism involved is still unclear. In this study, the effect of auxin signaling on the grain filling of SS and IS was investigated in two large-panicle japonica rice varieties, W1844 and CJ03. Compared to SS, IS displayed delayed initiation of filling and a significantly lower grain weight. Furthermore, the endosperm development in IS remained stagnant at the coenocytic stage. The development of the dorsal vascular bundle in the IS was also slow, and poor sucrose-unloading was observed during the initial grain filling stage. However, the endosperm development in IS immediately started after the improvement of dorsal vascular bundle development. GUS activity staining further revealed that indole-3-acetic (IAA) was localized in the dorsal vascular bundle and surrounding areas, suggesting that the low IAA content observed in the IS during the initial grain filling stage may have delayed the development of the dorsal vascular bundle. Therefore, these results demonstrate that IAA may control sugar transport and unloading by regulating dorsal vascular bundle development, consequently affecting endosperm development in IS.

Single-Base Methylome Analysis of Sweet Cherry (Prunus avium L.) on Dwarfing Rootstocks Reveals Epigenomic Differences Associated with Scion Dwarfing Conferred by Grafting

Plant grafting using dwarfing rootstocks is one of the important cultivation measures in the sweet cherry (Prunus avium) industry. In this work, we aimed to explore the effects of the dwarfing rootstock “Pd1” (Prunus tomentosa) on sweet cherry ‘Shuguang2’ scions by performing morphological observations using the paraffin slice technique, detecting GA (gibberellin) and IAA (auxin) contents using UPLC-QTRAP-MS (ultra-performance liquid chromatography coupled with a hybrid triple quadrupole-linear ion trap mass spectrometer), and implementing integration analyses of the epigenome and transcriptome using whole-genome bisulfite sequencing and transcriptome sequencing. Anatomical analysis indicated that the cell division ability of the SAM (shoot apical meristem) in dwarfing plants was reduced. Pd1 rootstock significantly decreased the levels of GAs and IAA in sweet cherry scions. Methylome analysis showed that the sweet cherry genome presented 15.2~18.6%, 59.88~61.55%, 28.09~33.78%, and 2.99~5.28% methylation at total C, CG, CHG, and CHH sites, respectively. Shoot tips from dwarfing plants exhibited a hypermethylated pattern mostly due to increased CHH methylation, while leaves exhibited a hypomethylated pattern. According to GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis, DMGs (differentially methylated genes) and DEGs (differentially expressed genes) were enriched in hormone-related GO terms and KEGG pathways. Global correlation analysis between methylation and transcription revealed that mCpG in the gene body region enhanced gene expression and mCHH in the region near the TSS (transcription start site) was positively correlated with gene expression. Next, we found some hormone-related genes and TFs with significant changes in methylation and transcription, including SAURs, ARF, GA2ox, ABS1, bZIP, MYB, and NAC. This study presents a methylome map of the sweet cherry genome, revealed widespread DNA methylation alterations in scions caused by dwarfing rootstock, and obtained abundant genes with methylation and transcription alterations that are potentially involved in rootstock-induced growth changes in sweet cherry scions. Our findings can lay a good basis for further epigenetic studies on sweet cherry dwarfing and provide valuable new insight into understanding rootstock–scion interactions.

Optimization of fermentation conditions for Bacillus velezensis TCS001 and evaluation of its growth promotion and disease prevention effects on strawberries

Bacillus velezensis TCS001 is a novel biocontrol bacterium with broad-spectrum antifungal activity and plant growth-promoting effects, holding great potential for development in agricultural production. This study optimized the fermentation conditions for B. velezensis TCS001 through single-factor experiments combined with response surface methodology, and developed a formulation for TCS001 suspension concentrate (TCS001-SC). The efficacy of TCS001-SC to promote the growth of strawberries and to prevent and control strawberry anthracnose was evaluated. The optimal liquid fermentation condition for TCS001 was determined to be 2.89 % soluble peanut cake powder, 3.0 % glucose, 3.0 % soluble starch, 0.002 % FePO4, 0.006 % KCl, 0.6 % NaCl, 0.05 % MgCl2·6H2O, 0.3 % K2HPO4, 0.15 % KH2PO4, 0.05 % CaCO3, 0.005 % MnSO4, a working volume of 31 % (77.5 mL/250 mL), a rotation speed of 173 r/min, a cultivation temperature of 28°C, an inoculum volume of 1.0 %, and a pH of 7.0. The 15 L fermenter upscale culture achieved a spore count of 9.46 × 109 CFU/mL, which was 2.01 times the spore count of 4.7 × 109 CFU/mL before optimization, and a preliminary TCS001-SC was developed with the fermented broth as the main component. Agar plate confrontation tests showed that TCS001 had antifungal activity against five types of anthracnose fungi, with inhibition rates ranging from 70.3 % to 87.2 %. TCS001-SC could promote the growth of strawberries and induce a rapid defense enzyme response in their leaves, enhancing the plant's resistance to pathogens. After treatment, individual strawberry plants showed significant increases in the number of leaves, fresh weight of stems and leaves, root fresh weight, leaf area, plant height, and the content of POD, SOD, CAT enzymes, GA, IAA, and ABA compared to the control.Additionally, it shows good prevention and control effects against strawberry anthracnose, with a control efficacy of 60.45% after five spray treatments at a concentration of 2 × 107 CFU/mL, which is not significantly different from the efficacy of commercial microbial agents such as Bacillus subtilis wettable powder, subsequent field trials will be conducted to determine its potential as a microbial pesticide. This study provides important support for the future industrial production and application of the strain TCS001.

Use of plant growth regulators and their combined application to enhance lipid productivity in the filamentous microalga Tribonema sp.

Oleaginous Tribonema sp. has shown great potential in biodiesel production. However, effective strategies are still needed to increase overall lipid productivity for cost-effectiveness. Although the effects of plant growth regulators (PGRs) on enhancing microalgal growth and lipid content have been widely demonstrated, the synergistic effects of their combinations on improving lipid productivity in Tribonema sp. remain unclear. In this study, we investigated the comparative effects of five PGRs (e.g., fulvic acid, melatonin, gibberellin, γ-aminobutyric acid [GABA], and indoleacetic-3-acid [IAA]) at different concentrations (0.1–10 mg/L) on the growth, nitrogen uptake, and lipid content of Tribonema sp. The results showed that 10 mg/L GABA and 0.1 mg/L IAA were optimal conditions, contributing to an approximately 33.00 % increase in lipid productivity compared with the control (without PGRs). Based on these findings, the combination of optimized concentrations of GABA and IAA, especially in equal proportions, resulted in a more desirable fatty acid profile and produced the highest biomass, lipid content, and lipid productivity, with increases of 23.55 %, 25.62 %, and 54.95 %, respectively, over the control. This combination also significantly increased nitrogen removal efficiency in the medium, which was 46.24 % higher that of the control. These results were attributed to the significant upregulation of genes associated with nitrogen metabolism mediated by the synergy of IAA and GABA, promoting nitrate uptake by algal cells in the medium. Genes involved in photosynthesis and lipid synthesis were also upregulated, facilitating simultaneous biomass and lipid accumulation to maximize lipid productivity. Overall, this study is the first to report the combined application of GABA and IAA as an effective strategy to enhance lipid productivity in Tribonema sp., providing insights into the underlying mechanisms. These findings offer a promising solution for economically improving microalgal lipid production.

Effect of postharvest cold storage and subsequent shelf-life on fruit quality and endogenous phytohormones in nectarine fruit

Cold storage is the main approach to extend the postharvest storage period of nectarines. The objective of this study was to investigate fruit quality (flavor and nutrition) and endogenous phytohormone changes and their related transcriptional changes in nectarine fruit after cold storage and subsequent shelf-life, which was performed metabolome, transcriptome and physiological analysis. Cold storage led to irreversible flavor loss due to the inhibition of aroma biosynthesis genes at low temperature. Sugar and organic acid content was affected, with an increase in glucose, fructose and malic acid, and a decrease in sorbitol and citric acid after cold storage or shelf-life. For fruit nutritional quality, total flavonoids or total carotenoids was not significantly affected by cold storage, whereas shelf-life process enhanced their accumulation. The activities of key enzymes for flavonoid biosynthesis, PAL and C4H, were enhanced during the shelf-life process, resulting in a significant increase in flavonoids and enhanced free radicals scavenging capacity. Meanwhile, shelf-life process increased carotenoids content by improving the expression of carotenoid biosynthesis genes PSY, ZDS and ZISO. Additionally, cold storage significantly increased the IAA content and ethylene production, thereby inducing the up-regulation of related signaling transduction genes. The shelf-life process further increased ethylene production, as well as salicylic acid and jasmonic acid content. This study unravels these crucial physiological and associated transcriptional changes of nectarines after cold storage, and may provide a theoretical foundation for improving fruit quality of peaches after cold storage.

Nitrate Starvation Induces Lateral Root Organogenesis in Triticum aestivum via Auxin Signaling.

The lateral root (LR) is an essential component of the plant root system, performing important functions for nutrient and water uptake in plants and playing a pivotal role in cereal crop productivity. Nitrate (NO3-) is an essential nutrient for plants. In this study, wheat plants were grown in 1/2 strength Hoagland's solution containing 5 mM NO3- (check; CK), 0.1 mM NO3- (low NO3-; LN), or 0.1 mM NO3- plus 60 mg/L 2,3,5-triiodobenzoic acid (TIBA) (LNT). The results showed that LN increased the LR number significantly at 48 h after treatment compared with CK, while not increasing the root biomass, and LNT significantly decreased the LR number and root biomass. The transcriptomic analysis showed that LN induced the expression of genes related to root IAA synthesis and transport and cell wall remodeling, and it was suppressed in the LNT conditions. A physiological assay revealed that the LN conditions increased the activity of IAA biosynthesis-related enzymes, the concentrations of tryptophan and IAA, and the activity of cell wall remodeling enzymes in the roots, whereas the content of polysaccharides in the LRP cell wall was significantly decreased compared with the control. Fourier-transform infrared spectroscopy and atomic microscopy revealed that the content of cell wall polysaccharides decreased and the cell wall elasticity of LR primordia (LRP) increased under the LN conditions. The effects of LN on IAA synthesis and polar transport, cell wall remodeling, and LR development were abolished when TIBA was applied. Our findings indicate that NO3- starvation may improve auxin homeostasis and the biological properties of the LRP cell wall and thus promote LR initiation, while TIBA addition dampens the effects of LN on auxin signaling, gene expression, physiological processes, and the root architecture.

Multi-Omics analysis reveals the important role of indole-3-acetic acid homeostasis in male fertility of cotton

Auxin (Indole-3-acetic acid, IAA) is essential for anther development and male fertility, but little is known about its homeostasis in developing anthers due to its complex and diverse synthesis pathways. Here, we employed transcriptomic, targeted metabolomic, and amino acid analyses on a wild type (WT) cotton (Gossypium hirsutum) line SD98–6 and its nearly-isogenic male sterile (MS) line SD98–6A, to delve into the relationship between IAA and anther fertility. In WT anthers, IAA homeostasis was achieved mainly through self-synthesis, conjugate hydrolysis, and polar transport, and accumulation of IAA exhibited an inverted "U" pattern with the highest content observed at the tetrad stage. In MS anthers, no IAA accumulation was observed after the meiosis stage and the IAA content remained constantly low, mainly due to reduction of the substrates (phenylalanine and tryptophan) for IAA synthesis, and significantly decreased expression of the genes involved in IAA synthesis. Meanwhile, carbohydrate metabolism pathways directly contributing to IAA synthesis and synthesis of amino acids were malfunctional in MS anthers based on the expression profile of the metabolic genes and content measurement. These results provide valuable insights into the IAA homeostasis in cotton anthers and imply that genes related to IAA homeostasis are potential targets for development of IAA-sensitive male sterile cotton lines.

Postponed Application of Phosphorus and Potassium Fertilizers Mitigates the Damage of Late Spring Coldness by Improving Winter Wheat Root Physiology.

Late spring coldness (LSC) is the main limiting factor threatening wheat yield and quality stability. Optimal nutrient management is beneficial in mitigating the harms of LSC by improving wheat root physiology. This study proposed a nutrient management strategy that postponed the application of phosphorus (P) and potassium (K), effectively strengthening wheat's defense against LSC. This experiment used the winter cultivar "Yannong19" (YN 19) as plant material for two consecutive years (2021-2022 and 2022-2023). Two fertilizer treatments were used: traditional P and K fertilizers application (R1: base fertilizer: jointing fertilizer = 10:0) and postponed P and K fertilizers application (R2: base fertilizer: jointing fertilizer = 5:5); wheat plants at the anther connective formation stage shifted to temperature-controlled phytotrons for normal (T0, 11 °C/4 h) and low temperatures (T1, 4 °C/4 h; T2, -4 °C/4 h) as treatments of LSC. The results showed that under low temperature (LT) treatment, compared with R1, the R2 treatment increased the concentrations of osmotic adjustment substances (soluble sugars and soluble protein contents by 6.2-8.7% and 3.0-8.9%), enhanced activities of antioxidant enzymes (superoxide dismutase, peroxidase and catalase activities by 2.2-9.1%, 6.2-9.7% and 4.2-8.4%), balanced the hormone concentrations (increased IAA and GA3 contents by 2.8-17.5% and 10.4-14.1% and decreased ABA contents by 7.2-14.3%), and reduced the toxicity (malondialdehyde, hydrogen peroxide content and O2·- production rate by 5.7-12.4%, 17.7-22.8% and 19.1-19.1%) of the cellular membranes. Furthermore, the wheat root physiology in R2 significantly improved as the root surface area and dry weight increased by 5.0-6.6% and 4.7-6.6%, and P and K accumulation increased by 7.4-11.3% and 12.2-15.4% compared to R1, respectively. Overall, the postponed application of P and K fertilizers enhanced the physiological function of the root system, maintained root morphology, and promoted the accumulation of wheat nutrients under the stress of LSC.

Piriformospora indica modifies cucumber’s tolerance to Meloidogyne incognita by regulating various agro-physiological traits, antioxidant enzymes, and abscisic acid pathway genes

Root knot nematode (RKN), Meloidogyne incognita, is considered a major soil-borne pathogen that can cause severe yield losses for vegetables and diverse crops. Usually, reducing of M. incognita damage is mainly relies on the application of nematicides and good agricultural practices. However, the use of synthetic nematicides is restricted due to concerns about their impact on the environment and human health. As a result, the use of alternative strategies is becoming necessary to combat RKN resistance. This study evaluates the antagonistic impact of the root mutualistic fungus Pirforomospora indica on M. incognita. It also assesses its influence on the nutritional status, photo-synthesis, antioxidant enzyme activity, endogenous abscisic acid (ABA) levels, and selected ABA related-responsive genes in cucumber plants. Roots of cucumber seedlings were inoculated with P. indica and the second-stage juveniles (1000 J2 per plant). The results demonstrated that P. indica significantly reduced M. incognita invasion in roots, resulting in a 24% reduction in root galling and 42.6% decline in final population. Inoculating plants with both P. indica and RKN increased performance of root fresh and dry weight, as well as improved photochemical efficiency of PSII (Fv/Fm), photosystem II efficiency (PSII), catalase (CAT), peroxidase (POD), and superoxide dis-mutase (SOD). Furthermore, P. indica colonization, either alone or in combination with M. incognita, significantly improved number of fruits per plant, average fruit weight, the plant's marketable yield, and leaf nutrient content (N, P, K and Mg), Moreover, there was an increase in IAA content combined with a decrease in ABA content in roots of dual inoculation plants, if compared to M. incognita infested plants. The highest ABA content was recorded in the root of RKN-cucumber plants. The decline in ABA content due to P. indica treatment was consistent with the modulation of ABA pathway genes, specifically PP2C, PYL1, RK2,1, and RK2,2. The mixed of P. indica and M. incognita led to a decrease in the expression of PP2C, PLY1, RK2,1, and RK2,2 in comparison to the control group. These results indicate that P. indica application could help reduce the negative effects of RKN on important crops.

Allele-Specific Hormone Dynamics in Highly Transgressive F2 Biomass Segregants in Sugarcane (Saccharum spp.).

Sugarcane holds global promise as a biofuel feedstock, necessitating a deep understanding of factors that influence biomass yield. This study unravels the intricate dynamics of plant hormones that govern growth and development in sugarcane. Transcriptome analysis of F2 introgression hybrids, derived from the cross of Saccharum officinarum "LA Purple" and wild Saccharum robustum "MOL5829", was conducted, utilizing the recently sequenced allele-specific genome of "LA Purple" as a reference. A total of 8059 differentially expressed genes were categorized into gene models (21.5%), alleles (68%), paralogs (10%), and tandemly duplicated genes (0.14%). KEGG analysis highlighted enrichment in auxin (IAA), jasmonic acid (JA), and abscisic acid (ABA) pathways, revealing regulatory roles of hormone repressor gene families (Aux/IAA, PP2C, and JAZ). Signaling pathways indicated that downregulation of AUX/IAA and PP2C and upregulation of JAZ repressor genes in high biomass segregants act as key players in influencing downstream growth regulatory genes. Endogenous hormone levels revealed higher concentrations of IAA and ABA in high biomass, which contrasted with lower levels of JA. Weighted co-expression network analysis demonstrated strong connectivity between hormone-related key genes and cell wall structural genes in high biomass genotypes. Expression analysis confirmed the upregulation of genes involved in the synthesis of structural carbohydrates and the downregulation of inflorescence and senescence-related genes in high biomass, which suggested an extended vegetative growth phase. The study underscores the importance of cumulative gene expression, including gene models, dominant alleles, paralogs, and tandemly duplicated genes and activators and repressors of disparate hormone (IAA, JA, and ABA) signaling pathways are the points of hormone crosstalk in contrasting biomass F2 segregants and could be applied for engineering high biomass acquiring varieties.

Response of seed vigor to experimental warming in a double rice cropping system

Climate warming affects rice seed vigor during ripening, which plays a crucial role in seed quality. However, the actual response of rice seed vigor to warming is still unclear. In this study, seeds after warming treatment in a double rice cropping system were used to determine seed vigor and related physiological traits during germination. Warming treatment significantly improved the germination index (GI), seed vigor index (VI), and seedling dry weight (SDW) for the late-season rice seeds but had no effect on hull thickness, grain weight, and starch and protein contents for both early- and late-season rice seeds, and these parameters were highly associated with germination rate, GI, VI, and SDW. Warming treatment increased gibberellin (GA) content and α-amylase and β-amylase activities in endosperm and coleoptile in both seasons during the later stage of germination, reaching a significant level on the 7th d. Moreover, indole-3-acetic acid (IAA) content was consistently increased in the coleoptile but decreased in the endosperm in response to warming, and warming did not affect zeatin content. These results suggest that future global warming will improve rice seed vigor by regulating the synthesis of endogenous hormones and amylases, especially in the late-season rice.

The monokaryotic filamentous fungus Ustilago sp. HFJ311 promotes plant growth and reduces Cd accumulation by enhancing Fe transportation and auxin biosynthesis

Infection with smut fungus like Ustilago maydis decreases crop yield via inducing gall formation. However, the in vitro impact of Ustilago spp. on plant growth and stress tolerance remains elusive. This study investigated the plant growth promotion and cadmium stress mitigation mechanisms of a filamentous fungus discovered on a cultural medium containing 25 μM CdCl2. ITS sequence alignment revealed 98.7 % similarity with Ustilago bromivora, naming the strain Ustilago sp. HFJ311 (HFJ311). Co-cultivation with HFJ311 significantly enhanced the growth of various plants, including Arabidopsis, tobacco, cabbage, carrot, rice, and maize, and improved Arabidopsis tolerance to abiotic stresses like salt and metal ions. HFJ311 increased chlorophyll and Fe contents in Arabidopsis shoots and enhanced root-to-shoot Fe translocation while decreasing root Fe concentration by approximately 70 %. Concurrently, HFJ311 reduced Cd accumulation in Arabidopsis by about 60 %, indicating its potential for bioremediation in Cd-contaminated soils. Additionally, HFJ311 stimulated IAA concentration by upregulating auxin biosynthesis genes. Overexpression of the Fe transporter IRT1 negated HFJ311's growth-promotion effects under Cd stress. These results suggest that HFJ311 stimulates plant growth and inhibits Cd uptake by enhancing Fe translocation and auxin biosynthesis while disrupting Fe absorption. Our findings offer a promising bioremediation strategy for sustainable agriculture and food security.

Hormones metabolism as affected by LED blue light in citrus fruit

The LED Blue Light (LBL) (450 nm) effect on hormones levels and on jasmonates (JAs) metabolism in oranges was investigated. The quantum flux (2 days, 60 μmol m−2. s−1) was chosen for its efficacy in reducing postharvest rot caused by this crop's main postharvest phytopathogenic fungus (Penicillium digitatum). The analysis of abscisic (ABA), salicylic (SA) and indole-3-acetic (IAA) acids, and of JAs-related metabolites, revealed that LBL modifies all studied metabolites and had major effects on JAs levels, mainly on jasmonic acid (JA) and its precursor cis-(+)-12-oxo-phytodienoic acid (OPDA). This agrees with the up-regulation of the genes participating in their synthesis. Results highlight the relevance of CsLOX1 and CsLOX5, and the contribution of CsAOC3, in the LBL-induced OPDA biosynthesis, whereas CsOPR2, CsACX1 and CsACX3 would play a part in the synthesis of JA from OPDA. Data also suggest that the applied LBL quantum flux favors fruit JA perception by increasing the expression of the coronatine insensitive 1 (COI1) receptor; and signaling by down-regulating abundant CsJAZ negative regulators. Differences in OPDA and JA between the LBL-treated oranges and their control fruit left in the dark disappeared after shifting the LBL-treated oranges to darkness for 3 more days. However, the LBL and darkness combination slightly increased IAA and SA contents.

Morphological characterization and transcriptome analysis of rolled and narrow leaf mutant in soybean

BackgroundIn plants, the leaf functions as a solar panel, where photosynthesis converts carbon dioxide and water into carbohydrates and oxygen. In soybean, leaf type traits, including leaf shape, leaf area, leaf width, and leaf width so on, are considered to be associated with yield. In this study, we performed morphological characterization, transcriptome analysis, and endogenous hormone analysis of a rolled and narrow leaf mutant line (rl) in soybean.ResultsCompared with wild type HX3, mutant line rl showed rolled and narrower leaflet, and smaller leaf, meanwhile rl also performed narrower pod and narrower seed. Anatomical analysis of leaflet demonstrated that cell area of upper epidermis was bigger than the cell area of lower epidermis in rl, which may lead rolled and narrow leaf. Transcriptome analysis revealed that several cytokinin oxidase/dehydrogenase (CKX) genes (Glyma.06G028900, Glyma.09G225400, Glyma.13G104700, Glyma.14G099000, and Glyma.17G054500) were up-regulation dramatically, which may cause lower cytokinin level in rl. Endogenous hormone analysis verified that cytokinin content of rl was lower. Hormone treatment results indicated that 6-BA rescued rolled leaf enough, rescued partly narrow leaf. And after 6-BA treatment, the cell area was similar between upper epidermis and lower epidermis in rl. Although IAA content and ABA content were reduced in rl, but exogenous IAA and ABA didn’t affect leaf type of HX3 and rl.ConclusionsOur results suggest abnormal cytokinin metabolism caused rolled and narrow leaf in rl, and provide valuable clues for further understanding the mechanisms underlying leaf development in soybean.

The tomato WRKY-B transcription factor modulates lateral branching by targeting BLIND, PIN4, and IAA15.

Lateral branching is a crucial agronomic trait that impacts crop yield. In tomato ( Solanum lycopersicum ), excessive lateral branching is unfavorable and results in substantial labor and management costs. Therefore, optimizing lateral branching is a primary objective in tomato breeding. Although many genes related to lateral branching have been reported in tomato, the molecular mechanism underlying their network remains elusive. In this study, we found that the expression profile of a WRKY gene, WRKY-B (for WRKY-BRANCING), was associated with the auxin-dependent axillary bud development process. Wrky-b mutants generated by the CRISPR/Cas9 editing system presented fewer lateral branches, while WRKY-B overexpression lines presented more lateral branches than did wild-type plants. Furthermore, WRKY-B can directly target the well-known branching gene BLIND (BL) and the auxin efflux carrier gene PIN4 to activate their expression. Both the bl and pin4 mutants exhibited reduced lateral branching, similar to the wrky-b mutant. The IAA contents in the axillary buds of the wrky-b, bl, and pin4 mutant plants were significantly higher than those in the wild-type plants. In addition, WRKY-B can also directly target the AUX/IAA gene IAA15 and repress its expression. In summary, WRKY-B works upstream of BL, PIN4, and IAA15 to regulate the development of lateral branches in tomato.

Exploring hormonal regulation and candidate genes in leaflet nyctinasty of Averrhoa carambola

Averrhoa carambola, a commonly cultivated tree, exhibits leaflet nyctinastic movement. However, the underlying mechanism remains unclear. The pulvinus, as a motor organ, coordinates the motion of its attached leaflet. During the leaflet expansion, flexor cells shift from contraction to expansion, with concurrent expansion and fusion of vacuole. In contrast, the extensor cells move from expansion to contraction, causing vacuole contraction and increased vacuole numbers. During the process of leaflet expansion and closure, the contents of IAA and IPA in flexor muscles increased significantly, but did not show significant changes in extensor muscles, BR content showed an opposite trend in extensor and flexor muscles, and the content of ZR increased significantly in extensor muscles but decreased significantly in flexor muscles, and ZR content only decreased in extensor muscles, but did not show significant changes in flexor muscles. Exogenous IAA (50–100 μM) significantly aids in leaflet unfolding during night time. Transcriptome analysis reveals gene enrichment in circadian rhythms, hormone signaling, ion channels, and other pathways during leaflet opening and closure. The expression of AcaCRY3, AcaPHOT1–1, AcaAPRR2, AcaLHY, and AcaAKT1–1 is prominent during expansion, while AcaAUX22–1 stands out during closure. These findings suggest a potential regulatory pathway in A. carambola 'Daguo Tianyangtao 2′ leaflets, involving light, circadian rhythm, hormone signaling, and ion channels. Findings of this study can do a great deal to broaden the plant nyctinastic movement research.

Drought stimulus enhanced stress tolerance in winter wheat (Triticum aestivum L.) by improving physiological characteristics, growth, and water productivity

The impact of drought events on the growth and yield of wheat plants has been extensively reported; however, limited information is available on the changes in physiological characteristics and their effects on the growth and water productivity of wheat after repeated drought stimuli. Moreover, whether appropriate drought stimulus can improve stress resistance in plants by improving physiological traits remains to be explored. Thus, in this study, a pot experiment was conducted to investigate the effects of intermittent and persistent mild [65%–75% soil water-holding capacity (SWHC)], moderate (55%–65% SWHC), and severe drought (45%–55% SWHC) stress on the growth, physiological characteristics, yield, and water-use efficiency (WUE) of winter wheat. After the second stress stimulus, persistent severe drought stress resulted in 30.98%, 234.62%, 53.80%, and 31.00% reduction in leaf relative water content, leaf water potential, photosynthetic rate (Pn), and indole-3-acetic acid content (IAA), respectively, compared to the control plants. However, abscisic acid content, antioxidant enzyme activities, and osmoregulatory substance contents increased significantly under drought stress, especially under persistent drought stress. After the second rehydration stimulus (ASRR), the actual and maximum efficiency of PSII and leaf water status in the plants exposed to intermittent moderate drought (IS2) stress were restored to the control levels, resulting in Pn being 102.56% of the control values; instantaneous WUE of the plants exposed to persistent severe drought stress was 1.79 times that of the control plants. In addition, the activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase, as well as the content of proline, under persistent mild drought stress increased by 52.98%, 33.47%, 51.95%, 52.35%, and 17.07% at ASRR, respectively, compared to the control plants, which provided continuous antioxidant protection to wheat plants. This was also demonstrated by the lower H2O2 and MDA contents after rehydration. At ASRR, the IAA content in the IS2 and persistent moderate drought treatments increased by 36.23% and 19.61%, respectively, compared to the control plants, which favored increased aboveground dry mass and plant height. Compared to the control plants, IS2 significantly increased wheat yield, WUE for grain yield, and WUE for biomass, by 10.15%, 32.94%, and 33.16%, respectively. Collectively, IS2 increased grain growth, yield, and WUE, which could be mainly attributed to improved physiological characteristics after drought-stimulated rehydration.

Integrating GWAS, RNA-Seq and functional analysis revealed that BnaA02.SE mediates silique elongation by affecting cell proliferation and expansion in Brassica napus.

Rapeseed (Brassica napus) silique is the major carbohydrate source for seed development, and the final silique length has attracted great attention from breeders. However, no studies had focused on the dynamic character of silique elongation length (SEL). Here, the dynamic SEL investigation in a natural population including 588 lines over two years indicate that dynamic SEL during 0-20 days after flowering was the most essential stage associated with seed number per silique (SPS) and thousand seed weight (TSW). Then, nine loci were identified to be associated with SEL based on GWAS analysis, among which five SNPs (over 50%) distributed on the A02 chromosome within 6.08 to 6.48 Mb. Subsequently, we screened 5078 differentially expressed genes between two extreme materials. An unknown protein, BnaA02.SE, was identified combining with GWAS and RNA-Seq analysis. Subcellular localization and expression profiles analysis demonstrated that BnaA02.SE is a chloroplast- and nucleus-localized protein mainly expressed in pericarps and leaves. Furthermore, transgenic verification and dynamic cytological observation reveal that overexpressed BnaA02.SE can promote silique elongation by regulating JA and IAA contents, affecting cell proliferation and expansion, respectively, and finally enhance seed yield by influencing SPS and TSW. Haplotype analysis reveal that the homologs of BnaA02.SE may also be involved in silique elongation regulation. Our findings provided comprehensive insights into a newly SEL trait, and cloned the first gene (BnaA02.SE) controlling silique elongation in B. napus. The identified BnaA02.SE and its homologs can offer a valuable target for improving B. napus yield.