Stress Treatment Research Articles

Physiological and Transcriptomic Characterization of Rice Genotypes under Drought Stress

Drought is a primary abiotic stress that inhibits rice (Oryza sativa L.) growth and development, and during the reproductive stage it has a negative impact on the rice seed-setting rate. This research study examined two rice lines, La-96 (drought sensitive) and La-163 (drought resistant), for drought stress treatment (with soil moisture at 20% for 7 days) and control (normal irrigation and kept soil moisture ≥40%). To elucidate the photosynthesis and molecular mechanisms underlying drought tolerance in rice, leaf photosynthetic traits and transcriptome sequencing were used to compare differences between two contrasting recombinant inbred lines (RIL) during drought and subsequent recovery at the booting stage. The rice line La-96 showed a significant decrease in seed-setting rate after being treated for seven days’ drought stress (from 86.64% to 22.75%), while La-163 was slightly affected (from 89.04% to 79.33%). The photosynthetic activities of both lines significantly decreased under the drought treatment, and these traits of La-163 recovered to a comparable level with the control after three days of rewatering. The transcriptome of both lines in three treatments (the control, drought stress, and subsequent recovery) were tested, and a total of 16,051 genes were identified, among which 10,566 genes were differentially expressed in various treatments and rice lines. Comprehensive gene expression profiles revealed that the specifically identified DEGs were involved in the ribosome synthesis and the metabolic pathway of photosynthesis, starch, and sucrose metabolism. The DEGs that are activated and respond quickly, as seen during recovery in the tolerant rice line, may play essential roles in regulating subsequent growth and development. This study uncovered the molecular genetic pathways of drought tolerance and extended our understanding of the drought tolerance mechanisms and subsequent recovery regulation in rice.

Hyperspectral Prediction Models of Chlorophyll Content in Paulownia Leaves under Drought Stress.

This study explored the quantitative inversion of the chlorophyll content in Paulownia seedling leaves under drought stress and analyzed the factors influencing the chlorophyll content from multiple perspectives to obtain the optimal model. Paulownia seedlings were selected as the experimental materials for the potted water control experiments. Four drought stress treatments were set up to obtain four types of Paulownia seedlings: one pair of top leaves (T1), two pairs of leaves (T2), three pairs of leaves (T3), and four pairs of leaves (T4). In total, 23 spectral transformations were selected, and the following four methods were adopted to construct the prediction model, select the best spectral preprocessing method, and explore the influence of water bands: partial least squares modeling with all spectral bands (all-band partial least squares, AB-PLS), principal component analysis partial least squares (PCA-PLS), correlation analysis partial least squares (CA-PLS), correlation analysis (water band) partial least squares, ([CA(W)-PLS]), and vegetation index modeling. Based on the prediction accuracy and the uniformity of different leaf positions, the optimal model was systematically explored. The results of the analysis of spectral reflectance showed significant differences at different leaf positions. The sensitive bands of chlorophyll were located near 550 nm, whereas the sensitive bands of water were located near 1440 and 1920 nm. The results of the vegetation index models indicate that the multiple-index models outperformed the single-index models. Accuracy decreased as the number of indicators decreased. We found that different model construction methods matched different optimal spectral preprocessing methods. First derivative spectra (R') was the best preprocessing method for the AB-PLS, PCA-PLS, and CA-PLS models, whereas the inverse log spectra (log(1/R)) was the best preprocessing method for the CA(W)-PLS model. Among the 14 indices, the green normalized difference vegetation index (GNDVI) was most correlated with the chlorophyll content sensitivity indices, and the water index (WI) was most correlated with the water sensitive indices. At the same time, the water band affected the cross validation accuracy. When characteristic bands were used for modeling, the cross validation accuracy was significantly increased. In contrast, when vegetation indices were used for modeling, the accuracy of the cross validation increased slightly but its predictive ability was reduced; thus, these changes could be ignored. We found that leaf position also affected the prediction accuracy, with the first pair of top leaves exhibiting the worst predictive ability. This was a bottleneck that limited predictive capability. Finally, we found that the CA(W)-PLS model was optimal. The model was based on 23 spectral transformations, four PLS construction methods, water bands, and different leaf positions to ensure systematicity, stability, and applicability.

Mechanistic insights into Suanzaoren Decoction's improvement of cardiac contractile function in anxiety-induced cardiac insufficiency

Ethnopharmacological relevanceAccording to traditional Chinese medicine, Anxiety-induced cardiac blood insufficiency leads to palpitations and restlessness. Suanzaoren Decoction (SD) is effective in replenishing blood and promoting blood circulation. Clinical practice has shown that it has a better therapeutic effect on cardiac insufficiency. However, its mechanism of action is still unclear. Aim of the studyThe study aims to determine the mechanism by which SD treats chronic restraint stress (CRS)-induced anxiety-induced cardiac insufficiency (ACI). Materials and methodsSD was orally administered to mice with CRS-induced ACI. Firstly, we constructed an anxiety model in mice by CRS. Subsequently, SD was investigated to assess cardiac function and pathological changes through echocardiography, H&E staining, and Masson staining. Thirdly, the function of sympathetic and parasympathetic nerves was evaluated using enzyme-linked immunosorbent assay (ELISA) and enzyme activity assays. Network pharmacology and molecular docking were employed to predict potential targets for SD treatment of cardiac insufficiency. CaMKII expression was scrutinized utilizing publicly accessible databases. CaMKII was identified as a target through immunohistochemistry and Western Blot analysis in mouse hearts. Finally, the therapeutic mechanism of SD was confirmed in injured cardiomyocytes via Western Blot and quantitative PCR. ResultsSD exerted anxiolytic effects by increasing the frequency of entries into and the duration spent in open arms while reducing the time spent in the light chamber and increasing the number of transitions between light and dark chambers. Additionally, it mitigated cardiac insufficiency, as evidenced by the enhancement of left ventricular ejection fraction (LVEF) and attenuation of cardiomyocyte damage and inflammatory infiltration.However, SD did not alleviate the elevated norepinephrine (NE) and decreased Acetylcholine (Ach) in anxiety states. To investigate the mechanism of action of SD, we constructed a Drug-Component-Target-Disease network, identifying 13 potential active compounds. Additionally, leveraging bioinformatics analysis and molecular docking targeting heart diseases characterized by clinical left ventricular ejection fraction (LVEF), we focused on the CaMKII target. The ability of SD to modulate CaMKII expression and phosphorylation in the mouse heart was investigated using immunohistochemistry and Western blotting. SD was found to alleviate NE-injured cardiomyocytes by modulating the Ca2+/CaMKII/MEF2 and GATA4 pathways. ConclusionSD is a potential formula for the treatment of chronic restraint stress (CRS)-induced ACI that ameliorates cardiomyocyte injury and improves cardiac function. Its efficacy is associated with the inhibition of the Ca2+/CaMKII/MEF2 and GATA4 signaling pathways.

Whole-Genome Bisulfite Sequencing (WGBS) Analysis of Gossypium hirsutum under High-Temperature Stress Conditions

Background: DNA methylation is an important part of epigenetic regulation and plays an important role in the response of plants to adverse stress. Methods: In this study, whole-genome bisulfite sequencing (WGBS) was performed on the high-temperature-resistant material Xinluzao 36 and the high-temperature-sensitive material Che 61–72 at 0 h and 12 h under high-temperature stress conditions. Results: The results revealed that the Gossypium hirsutum methylation levels of CG and CHG (H = A, C, or T) decreased after the high-temperature stress treatment, and the methylation level of the A subgenome was significantly greater than that of the D subgenome. The methylation level of CHH increased, and the methylation level of CHH in the D subgenome was significantly greater than that in the A subgenome after high-temperature stress treatment. The methylation density of CG is lower than that of CHG and CHH, and the methylation density of the middle region of chromosomes is greater than that of both ends, which is opposite to the distribution density of genes. There were 124 common differentially methylated genes in the CG, CHG, and CHH groups, and 5130 common DEGs and differentially methylated genes were found via joint analysis with RNA-seq; these genes were significantly enriched in the biosynthesis of plant hormones, thiamine metabolism, glutathione metabolism, and tyrosine metabolism pathways. DNA methylation did not affect the expression of many genes (accounting for 85.68% of the differentially methylated genes), DNA methylation-promoted gene expression was located mainly in the downstream region of the gene or gene body, and the expression of inhibitory genes was located mainly in the upstream region of the gene. Conclusions: This study provides a theoretical basis for further exploration of the gene expression and functional regulatory mechanism of G. hirsutum DNA methylation under high-temperature stress conditions.

A Genome-Wide Identification and Expression Analysis of the Xyloglucan Endotransglucosylase/Hydrolase Gene Family in Melon (Cucumis melo L.)

The xyloglucan endotransglucosylase/hydrolase (XTH) family is an important multigene family in plants that plays a key role in cell wall reconstruction and stress tolerance. However, the specific traits of XTH genes and their expression patterns under different stresses have not been systematically studied in melon. In this study, based on the genomic data of Cucumis melon, 29 XTH genes were identified; most of these genes contain two conserved domains (Glyco_hydro_16 and XET_C domains). Based on neighbor-joining phylogenetic analysis, the CmXTHs were divided into four subfamilies, I/II, IIIA, and IIIB, which are distributed across nine chromosomes of melon. Collinearity analysis showed that the melon XTH genes have an evolutionary history consistent with three species: Arabidopsis, tomato, and cucumber. The promoter regions of the CmXTH genes contain numerous cis-acting elements, which are associated with plant growth, hormonal response, and stress responses. RNA-Seq analysis indicated that CmXTH genes exhibit different expression patterns under drought and salt stress treatments, suggesting that this gene family plays an important role under abiotic stress. This study provides a theoretical basis for further studies on the molecular function of XTH genes in melon.

Functional Identification and Regulatory Active Site Screening of the DfDXS Gene of Dryopteris fragrans.

Dryopteris fragrans (L.) Schott has anti-inflammatory and antioxidant properties, and terpenoids are important components of its active constituents. The methyl-D-erythritol 4-phosphate (MEP) pathway is one of the major pathways for the synthesis of terpene precursors in plants, and 1-deoxy-D-xylulose-5-phosphate synthase (DXS) is the first rate-limiting enzyme in this pathway. DXS has been shown to be associated with increased stress tolerance in plants. In this experiment, two DXS genes were extracted from the D. fragrans transcriptome and named DfDXS1 and DfDXS2. Based on phylogenetic tree and conserved motif analyses, DXS was shown to be highly conserved evolutionarily and its localization to chloroplasts was determined by subcellular localization. Prokaryotic expression results showed that the number and growth status of recombinant colonies were better than the control under 400 mM NaCl salt stress and 800 mM mannitol-simulated drought stress. In addition, the DfDXS1 and DfDXS2 transgenic tobacco plants showed improved resistance to drought and salt stress. DfDXS1 and DfDXS2 responded strongly to methyl jasmonate (MeJA) and PEG-mimicked drought stress following exogenous hormone and abiotic stress treatments of D. fragrans. The transcriptional active sites were investigated by dual luciferase and GUS staining assays, and the results showed that the STRE element (AGGGG), the ABRE element (ACGTGGC), and the MYC element (CATTTG) were the important transcriptional active sites in the promoters of the two DXS genes, which were closely associated with hormone response and abiotic stress. These results suggest that the DfDXS gene of D. fragrans plays an important role in hormone signaling and response to stress. This study provides a reference for analyzing the molecular mechanisms of stress tolerance in D. fragrans.

Involvement of the Metallothionein gene OsMT2b in Drought and Cadmium Ions Stress in Rice

Abiotic stress is one of the major factors restricting the production of rice (Oryza sativa L.). Developing rice varieties with dual abiotic stress tolerance is essential to ensure sustained rice production, which is necessary to illustrate the regulation mechanisms underlying dual stress tolerance. At present, only a few genes that regulate dual abiotic stress tolerance have been reported. In this study, we determined that the expression of OsMT2b was induced by both drought and Cd2+ stress. After stress treatment, OsMT2b-overexpression lines exhibited enhanced drought tolerance and better physiological performance in terms of relative water content and electrolyte leakage compared with wild-type (WT). Further analysis indicated that ROS levels were lower in OsMT2b-overexpression lines than in WT following stress treatment, suggesting that OsMT2b-overexpression lines had a stronger ability to scavenge ROS under stress. Reverse transcription-quantitative PCR (RT-qPCR) results demonstrated that under drought stress, OsMT2b influenced the expression of genes involved in ROS scavenging to enhance drought tolerance in rice. In addition, OsMT2b-overexpression plants displayed increased tolerance to Cd2+ stress, and physiological assessment results were consistent with the observed phenotypic improvements. Thus, enhancing ROS scavenging ability through OsMT2b overexpression is a novel strategy to boost rice tolerance to both drought and Cd2+ stress, offering a promising approach for developing rice germplasm with enhanced resistance to the abiotic stressors.

Short-Term Warming Induces Cyanobacterial Blooms and Antibiotic Resistance in Freshwater Lake, as Revealed by Metagenomics Analysis

Climate change threatens freshwater ecosystems, potentially intensifying cyanobacterial blooms and antibiotic resistance. We investigated these risks in Cosseys Reservoir, New Zealand, using short-term warming simulations (22 °C, 24 °C, and 27 °C) with additional oxidative stress treatments. A metagenomic analysis revealed significant community shifts under warming. The cyanobacterial abundance increased from 6.11% to 20.53% at 24 °C, with Microcystaceae and Nostocaceae proliferating considerably. The microcystin synthesis gene (mcy) cluster showed a strong association with cyanobacterial abundance. Cyanobacteria exhibited enhanced nutrient acquisition (pstS gene) and an upregulated nitrogen metabolism under warming. Concurrently, antibiotic resistance genes (ARGs) increased, particularly multidrug resistance genes (50.82% of total ARGs). A co-association network analysis identified the key antibiotic-resistant bacteria (e.g., Streptococcus pneumoniae and Acinetobacter baylyi) and ARGs (e.g., acrB, MexK, rpoB2, and bacA) central to resistance dissemination under warming conditions. Oxidative stress exacerbated both cyanobacterial growth and ARGs’ proliferation, especially efflux pump genes (e.g., acrB, adeJ, ceoB, emrB, MexK, and muxB). This study demonstrated that even modest warming (2–5 °C) could promote both toxic cyanobacteria and antibiotic resistance. These findings underscore the synergistic effects of temperature and oxidative stress posed by climate change on water quality and public health, emphasizing the need for targeted management strategies in freshwater ecosystems. Future research should focus on long-term impacts and potential mitigation measures.

Exploring the influence of saline-alkaline stress on germination and seedling growth traits of Arta (Calligonum comosum L. Herit) as influenced by saline-alkaline stresses

This research was conducted to study the effects of saline stress (9:1 M ratio of NaCl: Na2SO4, pH 6.27–6.49), alkaline stress (9:1 M ratio of NaHCO3: Na2CO3, pH 9.11–9.25) and saline/alkaline combined stress (NaCl: Na2SO4:NaHCO3: Na2CO3 9:1:9:1, pH 8.94–9.17) using concentrations 25, 50, 75 and 100 mmol/L on seed germination and seedling growth traits of Calligonum comosum L’Her. The experiments were carried out in the laboratories of the Botany and Microbiology Department in the female university dormitory of the Science College, King Saud University. The results of seed germination included the percentage of seed germination, the lengths of both radicle and plumule, and both fresh and dry weights of the seedlings after 14 days of growth under stress treatments. Germination results indicated a significant gradual decrease in seed germination rates with an increase in the concentration of stress treatments, and seed germination was inhibited at concentrations higher than 100 mmol/L in all stress treatments. Also, there was a differential decrease in the parameters of seedling growth represented by the radicle and plumule lengths and both fresh and dry seedling weights with the increase in the concentrations and the greatest effect was the alkaline stress.

The influence of tensile stress on the strength and residual stress of C19400 alloy under ultrasonic vibration treatment

The C19400 alloy strip used for etching lead frames was studied, and the evolution law of its mechanical properties, residual stress, and microstructure under the ultrasonic vibration and tensile stress treatment was studied. The influence mechanism of ultrasonic vibration and tensile stress on the strength and residual stress of C19400 alloy was determined. The results show that high strength, high conductivity and low residual stress of C19400 alloy can be obtained under the coupling effect of ultrasonic vibration and tensile stress. The tensile strength is 430.57 MPa, the electrical conductivity is 57.73 % IACS, the transverse direction residual stress is −1 MPa, and the rolling direction residual stress is −21 MPa, and the residual stress relief rates are 97 % and 68 %, respectively. Under the coupling effect of alternating load and tensile stress, dislocations are annihilated and reorganized, the dislocation configuration tends to be uniformly arranged, and the dislocation density decreases. Compared with the original cold rolled state, the proportion of high angle grain boundaries of the alloy is slightly increased, and the texture strength is significantly reduced. These results have guiding significance for producing high strength, high conductivity and low residual stress of C19400 alloy.

THE SIGNIFICANCE OF CHLOROPHYLLS AND CAROTENOIDS IN ENHANCING SEED TOLERANCE TO ABIOTIC STRESS

the degradation of chlorophylls during seed ripening, residual levels are detectable in mature seeds, affecting their stress tolerance. Carotenoids, predominantly lutein and β-carotene, accumulate in seeds under accelerated aging conditions and high-temperature germination, influencing stress response. The ratio of carotenoid to chlorophyll content (Car/Chl) emerges as a potential indicator of seed stress tolerance, with higher ratios correlating with enhanced resilience to stressors. Objective: This study aims to elucidate the significance of chlorophylls and carotenoids in enhancing seed tolerance to abiotic stressors by investigating their roles and interactions within seeds under stress conditions. Methods: Physiologically mature seeds containing residual chlorophylls were subjected to stress treatments, and carotenoid levels were assessed during seed aging and germination experiments. The Car/Chl ratio was calculated to evaluate its relationship with seed stress tolerance. Results: Seeds with elevated Car/Chl ratios exhibited higher tolerance to stress treatments, suggesting a protective role of carotenoids against oxidative stress induced by chlorophylls under abiotic stress conditions. Carotenoid accumulation during aging and germination further underscored their role in stress response, influencing seed resilience. Conclusion: although residual in mature seeds, chlorophylls contribute to oxidative stress under abiotic stressors. Conversely, carotenoids act as antioxidants, mitigating stress-induced damage and enhancing seed tolerance. The Car/Chl ratio is valuable for assessing seed stress resilience, providing insights into seed physiology under adverse environmental conditions.

Stress-Induced Autophagy Is Essential for Microspore Cell Fate Transition to the Initial Cell of Androgenesis.

The isolated microspores can be reprogrammed towards embryogenesis via stress treatment during in vitro culture, and produce (doubled) haploid plants as a breeding source of new genetic variability. However, the mechanism underlying the cell fate transition from gametogenesis to embryogenesis remains largely unknown. Here, we report that autophagy plays a key role in cell fate transition for microspore embryogenesis (referred to as androgenesis) in Nicotiana tabacum. Immunofluorescence and transmission electronic microscopy detection unveiled that autophagy was triggered in microspores following exposure to inductive stress, and a transient wave of the numerous autophagy-related genes (ATGs) expression occurred before the initiation of microspore embryogenesis. Suppression or promotion of the original autophagy levels could inhibit microspore embryogenesis, indicating that stress-induced autophagic homeostasis is essential for cell fate transition. Furthermore, quantitative proteomics analysis revealed that autophagy might be involved in lignin biosynthesis and chromatin decondensation for promoting reprogramming for androgenesis initiation. Altogether, we reveal an essential role of autophagy in the microspore cell fate transition and androgenesis initiation, providing novel insight for understanding this critical developmental process.

McWRKY43 Confers Cold Stress Tolerance in Michelia crassipes via Regulation of Flavonoid Biosynthesis.

WRKY transcription factor (TF) plays a crucial role in plant abiotic stress response, but it is rarely reported in Michelia crassipes. Our studies have found that the transcription factor McWRKY43, a member of the IIc subgroup, is strongly upregulated under cold stress. In this study, we cloned the full length of McWRKY43 to further investigate the function of McWRKY43 in resistance to cold stress and its possible regulatory pathways in M. crassipes. Under cold stress, the seed-germination rate of transgenic tobacco was significantly higher than that of the wild type, and the flavonoid content, antioxidant enzyme activities, and proline content of transgenic tobacco seedlings were significantly increased, which promoted the expression of flavonoid pathway structural genes. In addition, the transient transformation of McWRKY43 in the M. crassipes leaves also found the accumulation of flavonoid content and the transcription level of flavonoid structural genes, especially McLDOX, were significantly increased under cold stress. Yeast one-hybrid (Y1H) assay showed that McWRKY43 could bind to McLDOX promoter, and the transcription expression of McLDOX was promoted by McWRKY43 during cold stress treatment. Overall, our results indicated that McWRKY43 is involved in flavonoid biosynthetic pathway to regulate cold stress tolerance of M. crassipes, providing a basis for molecular mechanism of stress resistance in Michelia.

Sexual dimorphism in physiological responses of turbot (Scophthalmus maximus L) under acute hypoxia and reoxygenation

Dissolved oxygen (DO) is a crucial factor throughout fish life cycle. In this study, the hematology, hepatic antioxidant levels, histomorphology of the liver and gill were determined in both female and male turbot under acute hypoxia to evaluated the underlying mechanisms and potential sexual dimorphism difference. Results showed that acute hypoxia stress treatment for 3 h significantly increased plasma cortisol, glucose, hemoglobin (HGB), cholesterol (CHO), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and hepatic malondialdehyde (MDA) contents, red blood cell count (RBC) number, hepatic superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), alanine-aminotransferase (ALT) and aspartate-aminotransferase (AST) activity in both male and female turbot. Male obtained higher plasma CHO, TG and LDL contents, GSH-Px and SOD activity than female under hypoxia. Meanwhile, hypoxia increased gill respiratory frequency, secondary lamellar length, secondary lamellar width, perimeter, lamellar surface area and gill surface area and decreased interlamellar distance. Acute hypoxia induced clubbing, hyperplasia, hypertrophy of gill filaments and hepatic vacuolization in both male and female turbot. The aforementioned parameters were recovered to normal levels after reoxygenation for 12 h. In conclusion, sex dimorphism difference of turbot hematological (RBC, HGB) and biochemical (glucose, CAT, GSH-Px, MDA) parameters were observed under hypoxia stress, while male demonstrated more hypoxia tolerance than female. These results help understand turbot hypoxia tolerance mechanisms and provide more data for management in captivity.

Genome-Wide Characterization and Expression Analysis of CsPALs in Cucumber (Cucumis sativus L.) Reveal Their Potential Roles in Abiotic Stress and Aphid Stress Tolerance.

Phenylalanine ammonia lyase (PAL) is a pivotal enzyme in the phenylalanine metabolic pathway in plants and has a crucial role in the plant's response to environmental stress. Although the PAL family has been widely studied in many plant species, limited is known about its particular role in cucumbers under stress. We investigated the physicochemical properties, gene structure, gene duplication events, conserved motifs, cis-acting elements, protein interaction networks, stress-related transcriptome data, and quantitatively validated key stress-related genes. The main results indicated that 15 PAL genes were grouped into four clades: I, II, and III when arranged in a phylogenetic tree of PAL genes in angiosperms. The analysis of the promoter sequence revealed the presence of multiple cis-acting elements related to hormones and stress responses in the cucumber PAL genes (CsPALs). The analysis of protein interaction networks suggested that CsPAL1 interacts with eight other members of the PAL family through CsELI5 and CsHISNA, and directly interacts with multiple proteins in the 4CL family. Further investigation into the expression patterns of CsPAL genes in different tissues and under various stress treatments (NaCl, Cu2+, Zn2+, PEG6000, aphids) demonstrated significant differential expression of CsPALs across cucumber tissues. In summary, our characterization of the CsPAL family offers valuable insights and provides important clues regarding the molecular mechanisms of CsPALs in managing abiotic and biotic stress interactions in cucumbers.

Effects of cadmium stress on the growth and physiological characteristics of sweet potato

This study evaluated the responses of sweet potatoes to Cadmium (Cd) stress through pot experiments to theoretically substantiate their comprehensive applications in Cd-polluted agricultural land. The experiments included a CK treatment and three Cd stress treatments with 3, 30, and 150 mg/kg concentrations, respectively. We analyzed specified indicators of sweet potato at different growth periods, such as the individual plant growth, photosynthesis, antioxidant capacity, and carbohydrate Cd accumulation distribution. On this basis, the characteristics of the plant carbon metabolism in response to Cd stress throughout the growth cycle were explored. The results showed that T2 and T3 treatments inhibited the vine growth, leaf area expansion, stem diameter elongation, and tuberous root growth of sweet potato; notably, T3 treatment significantly increased the number of sweet potato branches. Under Cd stress, the synthesis of chlorophyll in sweet potato was significantly suppressed, and the Rubisco activity experienced significant reductions. With the increasing Cd concentration, the function of PS II was also affected. The soluble sugar content underwent no significant change in low Cd concentration treatments. In contrast, it decreased significantly under high Cd concentrations. Additionally, the tuberous root starch content decreased significantly with the increase in Cd concentration. Throughout the plant growth, the activity levels of catalase, peroxidase, and superoxide dismutase increased significantly in T2 and T3 treatments. By comparison, the superoxide dismutase activity in T1 treatment was significantly lower than that of CK. With the increasing application of Cd, its accumulation accordingly increased in various sweet potato organs. The the highest bioconcentration factor was detected in absorbing roots, while the tuberous roots had a lower bioconcentration factor and Cd accumulation. Moreover, the transfer factor from stem to petiole was the highest of the potato organs. These results demonstrated that sweet potatoes had a high Cd tolerance and a restoration potential for Cd-contaminated farmland.

Chromosome doubling increases PECTIN METHYLESTERASE 2 expression, biomass, and osmotic stress tolerance in kiwifruit

Abstract Chromosome doubling-induced polyploidization is a popular tool for crop breeding. Polyploidy crops commonly have multiple advantages, including increased biomass and stress tolerance. However, little is known about the genes responsible for these advantages. We found kiwifruit (Actinidia chinensis cv. Hongyang) PECTIN METHYLESTERASE 2 (AcPME2)is substantially upregulated in artificially created tetraploid plants that show increased biomass and enhanced tolerance to osmotic stress. Overexpression (OE) of AcPME2 led to increased biomass and enhanced stress tolerance in Arabidopsis (Arabidopsis thaliana), tomato (Solanum lycopersicum), and kiwifruit. Upon short-term osmotic stress treatment, AcPME2-OE plants showed higher levels of demethylesterified pectins and more Ca2+ accumulation in the cell wall than Col-0 plants, which led to increased cell wall stiffness. The stress-induced plasmolysis assays indicated that AcPME2 dynamically mediated the cell wall stiffness in response to osmotic stress, which is dependent on Ca2+ accumulation. Transcriptomic analysis discovered that dozens of stress-responsive genes were significantly upregulated in the AcPME2-OE plants under osmotic stress. Besides, AcPME2-mediated cell wall reinforcement prevented cell wall collapse and deformation under osmotic stress. Our results revealed a single gene contributes to two advantages of polyploidization (increased biomass and osmotic stress tolerance) and that AcPME2 dynamically regulates cell wall stiffness in response to osmotic stress.

Adaptation to Environmental Stressors Conferred by Gene Copy Number Variation in Herbicide Resistant Amaranthus palmeri

Many rampant agricultural weeds have been found to contain gene copy number variation, a genetic adaptation that can facilitate the evolution of stress resistance. Amaranthus palmeri is a highly competitive and problematic agricultural weed in the United States which continues to naturalize, spreading northward to Canada. A.palmeri has gained attention due to its rapid evolution of herbicide resistance— a mechanism conferred by gene copy number variation of EPSPS. Researchers hypothesize that this gene is contained within an amplicon alongside other stress tolerance related genes. This raises the question of whether increased EPSPS gene copy number is associated with higher tolerance to environmental stressors, beyond herbicide stress. To prepare for addressing this hypothesis, I conducted a pilot project testing the ideal conditions for germination of A.palmeri. I planted 200 seeds divided between greenhouse and growth chamber environments. Many seeds benefit from a period of cold as a signal to break dormancy, thus, each category was further divided into two treatments: control and cold stratified (seeds were incubated in a –23 cold room for a week). I was interested in whether the increased consistency of temperature, light intensity, and photoperiod provided by a growth chamber, relative to a greenhouse, would increase germination rates. Results indicate that greenhouse grown seedlings had a 71% germination rate and within each treatment, 86% of cold stratified plants germinated while only 56% of the control group germinated. Whereas in the growth chamber, surprisingly only 26% of plants germinated with a breakdown of 22% cold stratified and 30% control. Thus, to germinate enough plants for a large-scale experiment, I chose to cold stratify seeds and grow them in the greenhouse for my undergraduate thesis. In this common garden experiment, I am currently growing 500 plants which will be divided into four stress treatment categories: control, salinity, drought, and salinity x drought. Using phenotypic measurements and digital droplet PCR (ddPCR) to quantify EPSPS gene copy number, I will test for a possible association between plants with a higher tolerance to these simulated environmental stressors and the presence of increased EPSPS gene copy number.

Genomic Organization and Expression Profiling of GOLDEN2-like Transcription Factor Genes in Eggplant and Their Role in Heat Stresses

GOLDEN2-like (GLK) transcription factor genes are involved in chloroplast biogenesis during all stages of plant growth and development, as well as in the response to biotic and abiotic stresses. However, little is known about this transcription factor family in eggplant. In this study, we identified 54 GLK genes in the eggplant genome (S. melongena L.) and classified them into seven groups (G1–G7). Structural analysis illustrated that the SmGLK proteins of specific groups are relatively conserved. Cis-acting elements indicated that these genes are likely to be involved in multiple responses stimulated by light, phytohormones, and abiotic stress. Collinear analysis indicated that expansion of the SmGLK gene family primarily occurred through segmental duplication. Tissue-specific expression analysis revealed that SmGLKs were preferentially expressed in leaves, fruits, and seeds. Further screening of SmGLK genes revealed their differential expression under various treatments. Notably, SmGLK18 was significantly responsive to multiple phytohormones and stress treatments, whereas SmGLK3 and SmGLK12 were highly induced by ABA, IAA, SA, and drought treatments. Our study provides new information on the eggplant GLK family systematically and comprehensively. For the first time, we propose that SmGLK18 may play a key role in improving heat resistance. This study provides valuable candidate gene resources for further functional research and will benefit eggplant molecular breeding.

Genome-wide identification and expression analysis of CmoADHs in Cucurbita moschata—Critical role of CmoADH9 in drought tolerance

In plants, alcohol dehydrogenases (ADHs) are involved in stress response, organ development, fruit ripening, and metabolite synthesis. However, little is known regarding ADH-encoding genes (ADHs) in Cucurbita moschata which is usually used as a rootstock for cucumber, melon, watermelon, and other cucurbit crops to resist soil-borne diseases and abiotic stresses. We identified 11 CmoADHs in the C. moschata genome that were unevenly distributed across seven chromosomes. These genes were predicted to encode stable cytoplasmic acidic proteins, sharing a low degree of identity with each other. The genes exhibited different intron–exon structures. Analysis of cis-acting regulatory elements showed that CmoADHs contain environmental stress-, hormone response-, light response-, and development/tissue specificity-related elements in their promoters. Expression pattern analysis revealed that CmoADH2, CmoADH3, CmoADH4, CmoADH9, CmoADH10, and CmoADH11 had the highest expression levels in the roots, which were significantly higher than those in the other tested tissues. These six genes may play important roles in the growth and development of roots, and in related abiotic stress responses. CmoADH1, CmoADH5, CmoADH6, CmoADH7, CmoADH8 had the highest expression in the apical region and could be involved in the differentiation of newly formed tissues. To study the role of CmoADHs in abiotic stress, salt, drought, low temperature, and ethephon treatments were performed. Under drought conditions, CmoADHs showed different expression trends. The expression levels of CmoADH1, CmoADH2, CmoADH3, and CmoADH9 increased significantly and peaked after 1 h of drought treatment, indicating that these four genes are more sensitive to drought stress. Under salt treatment, all CmoADHs showed a significant increase or decrease in expression within 6 h, except for CmoADH5 and CmoADH10, which were insensitive to salt treatment. The expression of most of the CmoADHs was significantly downregulated by low-temperature treatment. Ethephon treatment significantly induced the expression of all the CmoADHs, except CmoADH2, to different degrees within 12 h. CmoADH9 was found to be involved in root growth and drought stress resistance. Identification of these ADH genes can provide useful resources for conferring stress resistance in other economically important crops.