ABA Content Research Articles

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.

γ-Aminobutyric Acid Alleviates Salinity-Induced Impairments in Rice Plants by Improving Photosynthesis and Upregulating Osmoprotectants and Antioxidants

Salt stress is a significant abiotic stress that hinders the growth of rice (Oryza sativa L.) and reduces their yield. Previous research has examined the synthesis of γ-aminobutyric acid (GABA) and its role in plant resistance under various abiotic stresses. However, the synthesis of GABA and its ability to mitigate damage caused by salt stress—particularly its effects on osmotic adjustment, antioxidant defense, photosynthesis, and overall plant growth throughout the entire rice lifecycle—remains unclear. Therefore, we conducted two experiments using salt-tolerant rice cultivar Lianjian 5 (J-5) and salt-susceptible cultivar Lianjing 7 (L-7). In Experiment I, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. In Experiment II, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. Therefore, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. Subsequently, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. We measured the activities of superoxide dismutase, peroxidase, and catalase, as well as photosynthetic characteristics such as photosynthesis, transpiration, chlorophyll content, stomatal density and size, and leaf anatomical features. The RNA-seq analysis revealed that GABA production is enhanced via the glutamate decarboxylase (GAD) gene (LOC4333932) in the salt-resistant rice cultivar. Exogenous GABA application improves salt-stress tolerance by increasing endogenous ABA and GABA contents, which enhance osmotic adjustment, boost antioxidant defenses, and regulate ion balance. These combined effects help maintain photosynthetic efficiency and support overall plant growth under salt-stressed environments. Additionally, the increased proportion of mesophyll cell periphery covered by chloroplasts (Sc/Sm) indicated enhanced mesophyll conductance. These helped maintain photosynthesis under saline conditions while reducing water consumption.

Integration of mRNA-miRNA Reveals the Possible Role of PyCYCD3 in Increasing Branches Through Bud-Notching in Pear (Pyrus bretschneideri Rehd.).

Bud-notching in pear varieties with weak-branches enhances branch development, hormone distribution, and germination, promoting healthier growth and improving early yield. To examine the regulatory mechanisms of endogenous hormones on lateral bud germination in Pyrus spp. (cv. 'Huangguan') (Pyrus bretschneideri Rehd.), juvenile buds were collected from 2-year-old pear trees. Then, a comprehensive study, including assessments of endogenous hormones, germination and branching rates, RNA-seq analysis, and gene function analysis in these lateral buds was conducted. The results showed that there was no significant difference in germination rate between the control and bud-notching pear trees, but the long branch rate was significantly increased in bud-notching pear trees compared to the control (p < 0.05). After bud-notching, there was a remarkable increase in IAA and BR levels in the pruned section of shoots, specifically by 141% and 93%, respectively. However, the content of ABA in the lateral buds after bud-notching was not significantly different from the control. Based on RNA-seq analysis, a notable proportion of the differentially expressed genes (DEGs) were linked to the plant hormone signal transduction pathway. Notably, the brassinosteroid signaling pathway seemed to have the closest connection with the branching ability of pear with the related genes encoding BRI1 and CYCD3, which showed significant differences between lateral buds. Finally, the heterologous expression of PyCYCD3 has a positive regulatory effect on the increased Arabidopsis growth and branching numbers. Therefore, the PyCYCD3 was identified as an up-regulated gene that is induced via brassinosteroid (BR) and could act as a conduit, transforming bud-notching cues into proliferative signals, thereby governing lateral branching mechanisms in pear trees.

Combination of maleic hydrazide and coumarin inhibits rice seed germination involving reactive oxygen species accumulation, ABA metabolism and starch degradation

Pre-harvest sprouting (PHS) in cereal crops is a prevalent phenomenon that impacts grain yield and quality. Several PHS inhibitory compounds were screened and identified in previous studies, such as eugenol (EUG), maleic hydrazide (MH), coumarin (COU), etc. However, few studies have focused on the combination of PHS inhibitors, and the inhibitory mechanism remains unclear. Here, through combination tests of EUG, MH, and COU, the optimal combination of PHS inhibitors was selected as MH 20 mg L−1 + COU 100 mg L−1, which presented the lowest germination percentages. The optimal combination treatment significantly decreased the germination rate, α-amylase activity, content of soluble sugar and soluble protein, enhanced ABA content and the activity of superoxide dismutase (SOD) and peroxidase (POD), inhibited the production of superoxide anion (O2−) and hydrogen peroxide, and reduced the content of malondialdehyde (MDA); conversely, this trend is precisely the opposite in normal germination. Furthermore, gene expression analysis revealed that the optimal combination of MH and COU significantly decreased the expression level of OsAmy1A and OsAmy3D at 12 and 48 h after imbibition (HAI); and promoted the expression of OsRbohs (OsRbohA, OsRbohC, OsRbohD, OsRbohE, OsRbohH) and ABA biosynthetic genes OsNCED1, OsNCED2, and OsNCED5, especially OsNCED2 at 12 HAI, but down-regulated expression of OsRbohs and ABA catabolic genes OsABA8ox1-3 at 48 HAI. These results demonstrated that the delay in seed germination induced by MH and COU involved in ROS, ABA, and sugars; the optimal combination of MH and COU inhibited the germination process by promoting ABA biosynthesis and reducing ABA catabolism, and restraining the α-amylase activity to lower soluble sugar content. Intriguingly, although the expression of OsRbohs, which play a crucial role in generating ROS, increased in early imbibition (12h), the activity of the antioxidant enzymes SOD and POD also increased with the optimal combination treatment of MH and COU, which lead to the delay in ROS accumulation and inhibition of germination. These results have deepened our understanding of the regulatory mechanism of PHS inhibitors and provided theoretical support for the application of MH and COU in preventing sprouting before crop harvesting.

PdbCRF5 Overexpression Negatively Regulates Salt Tolerance by Downregulating PdbbZIP61 to Mediate Reactive Oxygen Species Scavenging and ABA Synthesis in Populus davidiana × P. bolleana.

Salt stress is the main factor limiting the large-scale cultivation of Shanxin poplar; therefore, improving its salt tolerance is crucial. In this study, we identified and characterized a CRF gene (PdbCRF5) in Shanxin poplar. Compared with the wild-type poplar, the Shanxin poplar overexpressing PdbCRF5 were more sensitive to salt stress. The PdbCRF5-silenced plants exhibited improved salt tolerance. ChIP‒PCR, EMSA, and Y1H confirmed that PdbCRF5 can regulate the expression of the PdbbZIP61 by binding to ABRE element. Further analysis revealed that the overexpression of PdbbZIP61 can reduce cell damage by increasing ROS scavenging, and on the other hand, overexpression of PdbbZIP61 can improve the salt tolerance of Shanxin poplar by regulating the expression of the PdbNCED genes to increase the ABA content. In addition, we also demonstrated that PdbCRF5 can inhibit the expression of the PdbbZIP61 in combination with PdbCRF6. The overexpression of PdbCRF6 also reduced the salt tolerance of Shanxin poplar. Therefore, we found that PdbCRF5 negatively regulates the salt tolerance of Shanxin poplar by inhibiting the PdbbZIP61, indicating that PdbCRF5 plays an important role in the tolerance of Shanxin poplar to salt stress and is an important candidate gene for gene editing and breeding in forest trees.

Effects of foliar spraying with melatonin and chitosan Nano-encapsulated melatonin on tomato (Lycopersicon esculentum L. cv. Falcato) plants under salinity stress

Melatonin has been found to be crucial in the growth and development of plants under stress conditions. In this study, the effects of melatonin and nano melatonin regarding the growth and development of tomato plants, along with their photosynthetic pigment, phenol, and antioxidant activity, were investigated under saline conditions. The study was conducted using a completely randomized design with three replications, and the applied treatments were salt stress and foliar spraying of melatonin at a concentration of 0 (control), melatonin (Mel), and nano capsule-melatonin (Nano-Mel) at 500 µM. Salinity treatments included application of sodium chloride with two concentration of 0 mM NaCl (S1) and 50 mM NaCl (S2). Under saline conditions, Mel and Nano-Mel increased both shoot and root fresh and dry weights, improved relative water content (RWC), and enhanced antioxidant activity and phenolic content. Salinity elevated leaf ABA content, unaffected by Mel or Nano-Mel. Chlorophyll fluorescence and SPAD values demonstrated resilience to salinity with Mel and Nano-Mel applications. Nano-Mel notably mitigated Na + accumulation in leaves under salinity, helping maintain K + homeostasis. Proline levels rise due to salinity but decreased with Mel and Nano-Mel treatments. Electrolyte leakage (EL) increased under salinity but is significantly reduced by Mel, indicating enhanced membrane stability. The findings reveal that salinity stress significantly reduced plasma membrane intrinsic protein (PIP) expression in roots and leaves, whereas Mel and Nano-Mel treatments enhance PIP expression, particularly in roots. The study concludes that Mel and Nano-Mel effectively alleviate salinity-induced stress, promoting growth and maintaining physiological homeostasis in tomato plants.

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.

An Enhanced Interaction of Graft and Exogenous SA on Photosynthesis, Phytohormone, and Transcriptome Analysis in Tomato under Salinity Stress.

Salt stress can adversely affect global agricultural productivity, necessitating innovative strategies to mitigate its adverse effects on plant growth and yield. This study investigated the effects of exogenous salicylic acid (SA), grafting (G), and their combined application (GSA) on various parameters in tomato plants subjected to salt stress. The analysis focused on growth characteristics, photosynthesis, osmotic stress substances, antioxidant enzyme activity, plant hormones, ion content, and transcriptome profiles. Salt stress severely inhibits the growth of tomato seedlings. However, SA, G, and GSA improved the plant height by 22.5%, 26.5%, and 40.2%; the stem diameter by 11.0%, 26.0%, and 23.7%; the shoot fresh weight by 76.3%, 113.2%, and 247.4%; the root fresh weight by 150.9%, 238.6%, and 286.0%; the shoot dry weight by 53.5%, 65.1%, and 162.8%; the root dry weight by 150.0%, 150.0%, and 166.7%, and photosynthesis by 4.0%, 16.3%, and 32.7%, with GSA presenting the most pronounced positive effect. Regarding the osmotic stress substances, the proline content increased significantly by more than 259.2% in all treatments, with the highest levels in GSA. Under salt stress, the tomato seedlings accumulated high Na+ levels; the SA, G, and GSA treatments enhanced the K+ and Ca2+ absorption while reducing the Na+ and Al3+ levels, thereby alleviating the ion toxicity. The transcriptome analysis indicated that SA, G, and GSA influenced tomato growth under salt stress by regulating specific signaling pathways, including the phytohormone and MAPK pathways, which were characterized by increased endogenous SA and decreased ABA content. The combined application of grafting and exogenous SA could be a promising strategy for enhancing plant tolerance to salt stress, offering potential solutions for sustainable agriculture in saline environments.

ABA-regulated MAPK signaling pathway promotes hormesis in sugar beet under cadmium exposure

Sugar beet (Beta vulgaris L.) shows potential as an energy crop for cadmium (Cd) phytoremediation. To elucidate its in vivo response strategy to Cd exposure, seedlings were treated with 1, 3, and 5 mmol/L CdCl2 (Cd-1, Cd-3, and Cd-5) for 6 h, using 0 mmol/L CdCl2 (Cd-0) as the control. The results showed that Cd-3 promoted a unique “hormesis” effect, leading to superior growth performance, increased levels of chlorophyll, soluble protein, and SOD activity, and reduced MDA content in sugar beet, compared to Cd-1, Cd-5, and even Cd-0. GO and KEGG enrichments and PPI networks of transcriptomic analysis revealed that the differentially expressed genes (DEGs) were primarily involved in lipid metabolism, cellular protein catabolism, and photosynthesis. Notably, the MAPK signaling pathway was significantly enriched only under Cd-3, with the up-regulation of ABA-related core gene BvPYL9 and an increase in ABA content after 6 h of Cd exposure. Furthermore, overexpression of BvPYL9 in Arabidopsis thaliana (OE-1 and OE-2) resulted in enhanced growth (fresh weight, dry weight, and root length), as well as higher ABA and soluble protein contents under different Cd treatments. Cd-induced transcriptional responses of BvPYL9 were also evident in OE-1 and OE-2, especially at 10 µmol/L, indicated by qRT-PCR. These findings suggest that ABA-mediated MAPK signaling pathway is activated in response to Cd toxicity, with BvPYL9 being a key factor in the cascade effects for the Cd-induced hormesis in sugar beet.

Exogenous melatonin promoted seed hypocotyl germination of Paeonia ostia 'Fengdan' characterized by regulating hormones and starches.

Seed hypocotyl germination signifies the initiation of the life cycle for plants and represents a critical stage that heavily influences subsequent plant growth and development. While previous studies have established the melatonin (MEL; N-acetyl-5-methoxytrytamine) effect to stimulate seed germination of some plants, its specific role in peony germination and underlying physiological mechanism have yet to be determined. This study aims to evaluate the MEL effect for the hypocotyl germination of peony seeds, further ascertain its physiological regulation factors. In this work, seeds of Paeonia ostia 'Fengdan' were soaked into MEL solution at concentrations of 50, 100, 200, and 400 µM for 48 h and then germinated in darkness in incubators. Seeds immersed in distilled water without MEL for the same time were served as the control group. At concentrations of 100 and 200 µM, MEL treatments improved the rooting rate of peony seeds, while 400 µM inhibited the process. During seed germination, the 100 and 200 µM MEL treatments significantly reduced the starch concentration, and α-amylase was the primary amylase involved in the action of melatonin. Additionally, compared to the control group, 100 µM MEL treatment significantly increased the GA3 concentration and radicle thickness of seeds, but decreased ABA concentration. The promotion effect of 200 µM MEL pretreatment on GA1 and GA7 was the most pronounced, while GA4 concentration was most significantly impacted by 50 µM and 100 µM MEL. Correlation analysis established that 100 µM MEL pretreatment most effectively improved the rooting rate characterized by increasing α-amylase activity to facilitate starch decomposition, boosting GA3 levels, inhibiting ABA production to increase the relative ratio of GA3 to ABA. Moreover, MEL increased radicle thickness of peony seeds correlating with promoting starch decomposition and enhancing the synthesis of GA1 and GA7.

Effect of CO2 Elevation on Tomato Gas Exchange, Root Morphology and Water Use Efficiency under Two N-Fertigation Levels.

Atmospheric elevated CO2 concentration (e[CO2]) decreases plant nitrogen (N) concentration while increasing water use efficiency (WUE), fertigation increases crop nutrition and WUE in crop; yet the interactive effects of e[CO2] coupled with two N-fertigation levels during deficit irrigation on plant gas exchange, root morphology and WUE remain largely elusive. The objective of this study was to explore the physiological and growth responses of ambient [CO2] (a[CO2], 400 ppm) and e[CO2] (800 ppm) tomato plant exposed to two N-fertigation regimes: (1) full irrigation during N-fertigation (FIN); (2) deficit irrigation during N-fertigation (DIN) under two N fertilizer levels (reduced N (N1, 0.5 g pot-1) and adequate N (N2, 1.0 g pot-1). The results indicated that e[CO2] associated with DIN regime induced the lower N2 plant water use (7.28 L plant-1), maintained leaf water potential (-5.07 MPa) and hydraulic conductivity (0.49 mol m-2 s-1 MPa-1), greater tomato growth in terms of leaf area (7152.75 cm2), specific leaf area (223.61 cm2 g-1), stem and total dry matter (19.54 g and 55.48 g). Specific root length and specific root surface area were increased under N1 fertilization, and root tissue density was promoted in both e[CO2] and DIN environments. Moreover, a smaller and denser leaf stomata (4.96 µm2 and 5.37 mm-2) of N1 plant was obtained at e[CO2] integrated with DIN strategy. Meanwhile, this combination would simultaneously reduce stomatal conductance (0.13 mol m-2 s-1) and transpiration rate (1.91 mmol m-2 s-1), enhance leaf ABA concentration (133.05 ng g-1 FW), contributing to an improvement in WUE from stomatal to whole-plant scale under each N level, especially for applying N1 fertilization (125.95 µmol mol-1, 8.41 µmol mmol-1 and 7.15 g L-1). These findings provide valuable information to optimize water and nitrogen fertilizer management and improve plant water use efficiency, responding to the potential resource-limited and CO2-enriched scenario.

WRKY transcription factor 40 from eggplant (Solanum melongena L.) regulates ABA and salt stress responses

Plants are affected by many environmental factors during their various stages of growth, among which salt stress is a key factor. WRKY transcription factors play important roles in the response to stress in plants. In this study, SmWRKY40 from eggplant (Solanum melongena L.) was found to belong to the subfamily of WRKY transcription factor group II, closely related to the evolution of wild tomato ScWRKY40 (Solanum chilense). The expression of SmWRKY40 could be induced by several abiotic stresses (drought, salt, and high temperature) and ABA to different degrees, with salt stress being the most significant. In Arabidopsis thaliana, the seed germination rate of SmWRKY40 overexpression seedlings was significantly higher than those of the wild type under high concentrations of NaCl and ABA, and root elongation of overexpression lines was also longer than wild type under NaCl treatments. SmWRKY40 overexpression lines were found to enhance Arabidopsis tolerance to salt with lower ROS, MDA, higher soluble protein, proline accumulation, and more active antioxidant enzymes. The expression level of genes related to stress and ABA signaling displayed significant differences in SmWRKY40 overexpression line than that of WT. These results indicate that SmWRKY40 regulates ABA and salt stress responses in Arabidopsis.

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.

Transcriptome Analysis Reveals Genes and Pathways Associated with Drought Tolerance of Early Stages in Sweet Potato (Ipomoea batatas (L.) Lam.).

The yield of sweet potato [Ipomoea batatas (L.) Lam] can be easily threatened by drought stress. Typically, early stages like the seedling stage and tuber-root expansion stage are more vulnerable to drought stress. In this study, a highly drought-tolerant sweet potato cultivar "WanSu 63" was subjected to drought stress at both the seedling stage (15 days after transplanting, 15 DAT) and the tuber-root expansion stage (45 DAT). Twenty-four cDNA libraries were constructed from leaf segments and root tissues at 15 and 45 DAT for Next-Generation Sequencing. A total of 663, 063, and 218 clean reads were obtained and then aligned to the reference genome with a total mapped ratio greater than 82.73%. A sum of 7119, 8811, 5463, and 930 differentially expressed genes were identified from leaves in 15 days (L15), roots in 15 days (R15), leaves in 45 days (L45), and roots in 45 days (R45), respectively, in drought stress versus control. It was found that genes encoding heat shock proteins, sporamin, LEA protein dehydrin, ABA signaling pathway protein gene NCED1, as well as a group of receptor-like protein kinases genes were enriched in differentially expressed genes. ABA content was significantly higher in drought-treated tissues than in the control. The sweet potato biomass declined sharply to nearly one-quarter after drought stress. In conclusion, this study is the first to identify the differentially expressed drought-responsive genes and signaling pathways in the leaves and roots of sweet potato at the seedling and root expansion stages. The results provide potential resources for drought resistance breeding of sweet potato.

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 gene CmPYL6 strongly contributes to cold tolerance in oriental melon.

The current simple and crude facilities make melon production more susceptible to cold stress during off-season cultivation in China. The ABA signalling pathway is an important target for breeding cold-tolerant melon. Cold-tolerant No. 330 and cold-sensitive No. 410 oriental melon genotypes were used to analyse the relationship between ABA and cold tolerance. 12 CmPYLs, ABA receptors, were identified from the melon genome database according to sequence alignment and phylogenetic analysis. Gene function of CmPYL6 in cold tolerance was analysed using VIGS in No. 330 and overexpression in Arabidopsis WT. A total of 12 CmPYL members contain the representative domain and conserved sites. Under cold treatment, No.330 seedlings had lower electrolyte leakage and MDA content, higher ABA content and CmPYL6 expression than seedlings of No. 410. Exogenous application of ABA upregulated expression of CmPYL6 and enhanced cold tolerance of both genotypes, while inhibiting ABA accumulation reduced expression of CmPYL6 and cold tolerance of both genotypes. CmPYL6-silenced No. 330 seedlings had reduced cold tolerance, increased electrolyte leakage and MDA content as well as limited proline and soluble sugar content, while CmPYL6 overexpressed transgenic Arabidopsis plants had enhanced cold tolerance, with limited electrolyte leakage and MDA content, as well as increased proline and soluble sugar content. The CmPYL6 gene is probably an important ABA receptor in regulating cold tolerance of oriental melon. Our study provides a direction for improving breeding of cold tolerance of oriental melon.

Artemisia annua ZFP8L regulates glandular trichome development.

Trichomes are known to be important biofactories that contribute to the production of secondary metabolites, such as terpenoids. C2H2-zinc finger proteins (C2H2-ZFPs) are vital transcription factors of plants' trichome development. However, little is known about the function of Artemisia annua C2H2-ZFPs in trichome development. To explore the roles of this gene family in trichome development, two C2H2-ZFP transcription factors, named AaZFP8L and AaGIS3, were identified; both are hormonally regulated in A. annua. Overexpression of AaZFP8L in tobacco led to a significant increase in the density and length of glandular trichomes, and improved terpenoid content. In contrast, AaGIS3 was found to positively regulate non-glandular trichome initiation and elongation, which reduces terpenoid accumulation. In addition, ABA contents significantly increased in AaZFP8L-overexpressing tobacco lines and AaZFP8L also can directly bind the promoter of the ABA biosynthesis genes. This study lays the foundation for further investigating A. annua C2H2-ZFPs in trichome development and terpenoid accumulation.

OPTIMIZATION OF THE MODE OF DEPOSITION OF ASEPTIC CULTURES IN VITRO OF A RARE AND ENDEMIC SPECIES ALLIUM IVASCZENKOAE

Optimization of the method of medium-term storage of the rare and endangered plant species Allium ivasczenkoae under in vitro conditions using modern approaches of biotechnology is an urgent task. Aseptic microplants Allium ivasczenkoae were used as starting material. The cultivation of microplants was carried out on nutrient media supplemented in various combinations with an increased concentration of sucrose, mannitol, chlorocholine chloride, ABA and BAP at various temperature and light conditions of deposition. The survival dynamics of A. ivasczenkoae varied depending on cultivation regimes. After 9 months of deposition, the survival of test-tube plants in mode 1 (control) was 20%, mode 2 - 60-80%, mode 3 - 30-50%. Under experimental conditions, the best results were obtained by depositing aseptic cultures for 9 months at a low positive temperature and low light intensity (mode 2) on nutrient media with the addition of CCC 120 mg/l and a sucrose concentration of 60 g/l and (B-1) and MS medium containing 0.5 mg/l BAP and 3 g/l mannitol (MSВМ). This mode of deposition made it possible to lengthen the period between transplants, as well as to maintain the viability of A. ivasczenkoae microplants from 60 to 80%. The data obtained make it possible to optimize the mode of medium-term storage of Allium ivasczenkoae under in vitro conditions for the mass production of rare species of bulbous plants in order to restore, reproduce and preserve the number of valuable gene pool and natural populations, create gene banks in vitro, reintroduce and green building.

Exogenous Calcium Alleviates the Photosynthetic Inhibition and Oxidative Damage of the Tea Plant under Cold Stress

Calcium (Ca2+), a second messenger, plays a crucial role in plant growth and development as well as in responding to biotic and abiotic stresses. In this work, we explored the role of exogenous calcium in alleviating cold stress and examined the relationship between calcium chloride (CaCl2) and calcium channel blockers, lanthanum chloride (LaCl3), in tea plants under cold stress at the physiological and transcriptional levels. Exogenous Ca2+ partially offsets the negative impacts of cold stress which increased the tolerance of tea plants by significantly raising the photochemical efficiency of PSII, protective enzyme activities, and the ABA content, which reduced the relative electrical conductivity (REC) level and the malondialdehyde (MDA) concentration. At the transcriptome level, exogenous Ca2+ significantly enhanced the expression of key genes involved in cold response pathways. Nevertheless, LaCl3 treatment not only significantly inhibited the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), but also increased cold damage. This study aims to provide essential insight into the role of exogenous Ca2+ in tea plants responding to cold stress, and to better understand the molecular mechanisms that facilitate Ca-mediated cold tolerance.

BcSRC2 interacts with BcAPX4 to increase ascorbic acid content for responding ABA signaling and drought stress in pak choi

Abstract As a reducing substance, ascorbic acid functioned well in abiotic and biotic stress. However, the regulatory mechanism of drought resistance is rarely known in pak choi. Here we found a gene BcSRC2 containing a C2 domain that responds to ABA signal and drought regulation in pak choi. Silencing of BcSRC2 reduces ascorbic acid content and drought resistance of pak choi. In Arabidopsis, BcSRC2 overexpression promotes ascorbic acid accumulation and increases drought tolerance. Meanwhile, transcriptome analysis between WT and BcSRC2-overexpressing pak choi suggests that ascorbic acid-related genes are regulated. BcSRC2 interacts with BcAPX4 and inhibit APX activity in vitro and in vivo, increasing the ascorbic acid content. We also found that drought stress increases ABA content, which reduces the expression of BcMYB30. BcMYB30 bound to the promoter of BcSRC2 and reduced its expression. Overall, our results suggest that a regulatory module, BcMYB30-BcSRC2-BcAPX4, plays a central role in increasing ascorbic acid content for responding ABA-mediated drought regulation in pak choi.