Search Results (62)

Since the onset of industrialization, the safety of arable land has become a pressing global concern, with soil salinization emerging as a critical threat to agricultural productivity and food security. To address this challenge, the cultivation of economically valuable salt-tolerant plants has been proposed as a viable strategy. In the study, we investigated the physiological and molecular responses of Lycium ruthenicum Murr. to varying NaCl concentrations. Results revealed a concentration-dependent dual effect: low NaCl levels significantly promoted seed germination, while high concentrations exerted strong inhibitory effects. To elucidate the mechanisms underlying these divergent responses, a combined analysis of metabolomics and transcriptomics was applied to identify key metabolic pathways and genes. Notably, salt stress enhanced photosynthetic efficiency through coordinated modulation of ribulose 5-phosphate and erythrose-4-phosphate levels, coupled with the upregulation of critical genes encoding RPIA (Ribose 5-phosphate isomerase A) and RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase). Under low salt stress, L. ruthenicum maintained intact cellular membrane structures and minimized oxidative damage, thereby supporting germination and early growth. In contrast, high salinity severely disrupted PS I (Photosynthesis system I) functionality, blocking energy flow into this pathway while simultaneously inducing membrane lipid peroxidation and triggering pronounced cellular degradation. This ultimately suppressed seed germination rates and impaired root elongation. These findings suggested a mechanistic framework for understanding L. ruthenicum adaptation under salt stress and pointed out a new way for breeding salt-tolerant crops and understanding the mechanism. Full article

High temperature has an adverse effect on apple production worldwide. Photosynthesis is a process especially vulnerable to heat stress, which can reduce photosynthetic efficiency, plant growth, development, and ultimately yield. Although the effects of heat stress on apples have been partially examined, the photochemical reactions and heat tolerance of specific rootstocks have still not been sufficiently investigated. Identification of rootstocks with better photosynthetic performance and adaptation to heat stress enables the selection of rootstocks, which could contribute to stable yields and good fruit quality even at elevated temperatures. In this study, chlorophyll a fluorescence (ChlF) induction kinetics was used to investigate the heat tolerance between two apple rootstocks (M.9 and G.210). In addition, we employed lipid peroxidation measurements, hydrogen peroxide quantification, proline content, and total phenolic and flavonoid assessments. Analysis of chlorophyll fluorescence parameters and OJIP curves (different steps of the polyphasic fluorescence transient; O–J–I–P phases) revealed significant differences in their responses, with higher values of the PI_ABS parameter indicating better PS II stability and overall photosynthetic efficiency in M.9 rootstock. The higher contents of chlorophyll, carotenoids, proline, and significant increase in the accumulation of phenolics, and flavonoids in this rootstock also contributed to its better adaptation to heat stress. Oxidative stress was more pronounced in G.210 through higher H₂O₂ and MDA levels, which could point to its lower capacity to adjust to heat stress conditions. This research can provide a scientific basis for further breeding programs and growing plans due to climate change and the occurrence of extremely high temperatures. Full article

Saccharides critically influence tobacco quality. To elucidate the effects of postharvest shading (PS) pre-curing on saccharide metabolic flux, a targeted glycomics analysis was conducted. Compared to light exposure (CK), PS delayed chlorophyll degradation during pre-curing but accelerated yellowing, ultimately resulting in similar pigment levels. Additionally, PS inhibited photosynthesis, leading to reduced starch content and increased soluble sugar content before curing. Furthermore, PS altered the starch-to-sugar conversion, ultimately resulting in significantly higher soluble sugar content and lower starch content. Targeted glycomics analysis identified 21 saccharides, with glucose, D-fructose, and sucrose being dominant. Notably, PS ultimately increased glucose, D-fructose, and sucrose levels by 74.09%, 66.49%, and 17.36%, respectively. Pairwise comparisons revealed 6, 12, 5, 13, 10, and 11 differentially expressed metabolites before curing and at 38, 40, 42, 54, and 68 °C during curing, respectively, between PS and CK. Conjoint analysis identified methylgalactoside and three oligosaccharides (sucrose, raffinose, and maltose) as the central metabolites of saccharide metabolism during curing. D-mannose, D-sorbitol, and D-glucuronic acid were identified as biomarkers for assessing storage-induced metabolic perturbations using random forest algorithms. Collectively, these findings suggest that PS might enhance tobacco quality via carbohydrate metabolism modulation, providing a scientific basis for pre-curing protocol optimization and industrial application. Full article

Chlorine (Cl) is an essential nutrient for higher plants, playing a critical role in their growth and development. However, excessive Cl application can be detrimental, leading to its limited use in controlled-environment agriculture. Recently, Cl has been recognized as a beneficial macronutrient, yet studies investigating its impact on plant growth and fruit quality remain scarce. In this study, we determined the optimal Cl concentration in nutrient solutions through a series of cultivation experiments. A comparative analysis of Cl treatments at 1, 2, and 3 mM revealed that 3 mM Cl⁻ significantly enhanced chlorophyll content, biomass accumulation, and yield. Furthermore, we examined the effects of 3 mM Cl⁻ (supplied as 1.5 mM CaCl₂ and 3 mM KCl) on leaf photosynthesis, chlorophyll fluorescence, and fruit sugar metabolism. The results demonstrated that Cl⁻ treatments enhanced the activity of Photosystem I (PS I) and Photosystem II (PS II), leading to a 25.53% and 28.37% increase in the net photosynthetic rate, respectively. Additionally, Cl⁻ application resulted in a 12.3% to 16.5% increase in soluble sugar content in mature tomato fruits. During fruit development, Cl⁻ treatments promoted the accumulation of glucose, fructose, and sucrose, thereby enhancing fruit sweetness and overall quality. The observed increase in glucose and fructose levels was attributed to the stimulation of invertase activity. Specifically, acidic invertase (AI) activity increased by 61.6% and 62.6% at the green ripening stage, while neutral invertase (NI) activity was elevated by 56.2% and 32.8% in the CaCl₂ and KCl treatments, respectively, at fruit maturity. Furthermore, sucrose synthase (SS-I) activity was significantly upregulated by 1.5- and 1.4-fold at fruit maturity, while sucrose phosphate synthase (SPS) activity increased by 76.4% to 77.8% during the green ripening stage. These findings provide novel insights into the role of Cl⁻ in tomato growth and metabolism, offering potential strategies for optimizing fertilization practices in protected horticulture. Full article

Nanoplastics (NPs), an emerging pollutant distributed in different sizes in the aquatic environment, adversely affect aquatic ecosystems. However, knowledge of the effects of NPs of various sizes on phytoplankton, especially freshwater microalgae, is still limited. In this study, we explore the effects of three polystyrene NPs (PS-NPs) with different particle sizes (20, 50, and 80 nm) on the chronic toxicity of a widely distributed freshwater microalga, Chlorella pyrenoidosa. The results showed that PS-NPs-20, PS-NPs-50, and PS-NPs-80 promoted the growth of C. pyrenoidosa at the early stage of exposure, with the highest promotion rates of 46.1%, 56%, and 86.2%, respectively. PS-NPs-20 and PS-NPs-50 inhibited the photosynthesis and growth of C. pyrenoidosa during the mid- and late-exposure periods and also induced an increase in the secretion of reactive oxygen species and extracellular polymers. The highest inhibition rates were 33.2% and 13.6%, respectively. By contrast, the growth-promoting effect of PS-NPs-80 continued until the middle stage, and it was only at the late stage of exposure that some growth-inhibitory effects occurred, with the highest inhibition rate of only 7.8%. The results of transmission electron microscopy showed that PS-NPs-20 damaged algal cells more severely than PS-NPs-50 and PS-NPs-80 on day 21. Notably, a size-dependent effect of PS-NPs was observed on the toxicity of C. pyrenoidosa, but no dose-dependent effect was found. These results will improve our understanding of the toxicity of PS-NPs to microalgae and may provide a basis for evaluating the ecological risk of PS-NPs in freshwater environments. Full article

The native Hotan Red grape germplasm from Xinjiang has strong saline–alkali tolerance. To clarify the physiological mechanisms of Hotan Red grapes in response to saline–alkali stress, Hotan Red hydroponic seedlings were used as the research material in this study and were subjected to the combined saline–alkali stress treatments of 0, 40, 80, 120 and 160 mmol·L⁻¹. After the 15th day of stress, plant height, shoot thickness, saline–alkali injury index, photosynthetic parameters, chlorophyll fluorescence parameters, osmoregulatory substance content, oxidation products and antioxidant enzymes of Hotan Red were determined. The results showed that the growth of plant height and shoot thickness of Hotan Red was inhibited, chlorophyll content decreased and the salinity damage index increased with increasing saline–alkali stress. Saline–alkali stress resulted in a non-stomatal limitation of photosynthesis in Hotan Red, which was manifested by a decrease in net photosynthetic rate, transpiration rate and stomatal conductance, and an increase in the concentration of intercellular carbon dioxide, in which the net photosynthetic rate reached a minimum value of 3.56 μmol·m⁻²·s⁻¹ under 120 mmol·L⁻¹ saline–alkali stress; the actual photochemical efficiency of PSII in the light and maximal quantum yield of PSⅡ decreased, with minimum values of 0.16 and 0.60, respectively. Accumulation of superoxide anion, hydrogen peroxide, malondialdehyde, proline, soluble sugars and soluble proteins, and enhancement of superoxide dismutase, catalase and peroxidase activities were observed in Hotan Red under saline–alkali stress. Partial least squares path model analysis showed that photosynthesis was the main driver of saline–alkali injury in Hotan Red, followed by oxidation products and antioxidant enzymes, with osmoregulators playing an indirect role. This study revealed the physiological mechanism by which Hotan Red tolerates saline–alkali stress, providing a basis for further research into the mechanism of saline–alkali tolerance in grapes. Full article

The rising concentration of microplastics (MPs) in aquatic environments poses increasing ecological risks, yet their impacts on biological communities remain largely unrevealed. This study investigated how aminopolystyrene microplastics (PS-NH₂) affect physiology and gene expression using the freshwater alga Navicula sp. as the test species. After exposing Navicula sp. to high PS-NH₂ concentrations for 24 h, growth was inhibited, with the most significant effect seen after 48 h. Increasing PS-NH₂ concentrations reduced chlorophyll content, maximum photochemical quantum yield (Fv/Fm), and the photochemical quenching coefficient (Qp), while the non-photochemical quenching coefficient (NPQ) increased, indicating a substantial impact on photosynthesis. PS-NH₂ exposure, damaged cell membrane microstructures, activated antioxidant enzymes, and significantly increased malondialdehyde (MDA), glutathione peroxidase (GPX), and superoxide dismutase (SOD) activities. Transcriptomic analysis revealed that PS-NH₂ also affected the gene expression of Navicula sp. The differentially expressed genes (DEGs) are mainly related to porphyrin and chlorophyll metabolism, carbon fixation in photosynthesis, endocytosis, and glycolysis/gluconeogenesis. Protein–protein interaction (PPI) analysis revealed significant interactions among DEGs, particularly within photosystem II. These findings shed insights into the toxic mechanisms and environmental implications of microplastic interactions with phytoplankton, deepening our understanding of the potential adverse effects of microplastics in aquatic ecosystems. Full article

Siberian apricot (Prunus sibirica) is an important ecological and commercial woody plant that is negatively affected by spring frosts. However, the mechanisms that control gene expression in adaptation to freezing remain largely unknown. In this work, we investigated the physiological, molecular, and phenotypic characteristics of pistils of two P. sibirica clones that differ in their ability to withstand freezing stress. A total of 14,717 unigenes categorized into 38 functional groups were identified. Additionally, the two P. sibirica clones included 3931 up-regulated and 2070 down-regulated differentially expressed genes (DEGs). Many DEGs are related to Ca²⁺ and MAPK signaling, carbohydrate biosynthesis and metabolism, plant hormone signal transduction, biosynthesis of amino acids, and photosynthesis. The metabolism of carbohydrates, amino acids, lipids, secondary metabolites, plant hormone signal transduction, and terpenoid metabolism were the transcriptome modifications most significantly altered by freezing stress. Real-time quantitative PCR (RT-qPCR) was used to verify the precision of the RNA-seq data. PsbHLH18, PsMYB4, PsMYB44, PsPOD1, and PsCDPK5 may play important roles in the freezing tolerance of the P. sibirica floral organ. This study provides a foundation for further studies on the complex mechanisms of freezing stress response in P. sibirica. Full article

Leaf color mutants serve as ideal materials for studying photosynthesis, chlorophyll metabolism, and other physiological processes. Here, we identified a spontaneous yellow-leaf mutant (yl1) with chlorophyll-reduced leaves from G. hirsutum L. cv ZM24. Compare to wild type ZM24 with green leaves, yl1 exhibited patchy yellow leaves and reduced chlorophyll content. To further explore the mechanisms of the patchy yellow phenotype of the mutant plant, the transcriptomics and proteomics profiles were conducted for the mutant and wild types. A total of 9247 differentially expressed genes (DEGs) and 1368 differentially accumulated proteins (DAPs) were identified. Following gene ontology (GO) annotation and KEGG enrichment, the DEGs/DAPs were found to be significantly involved in multiple important pathways, including the obsolete oxidation-reduction process, photosynthesis, light-harvesting, the microtubule-based process, cell redox homeostasis, and the carbohydrate metabolic process. In photosynthesis and the light-harvesting pathway, a total of 39 DAPs/DEGs were identified, including 9 genes in the PSI, 7 genes in the PS II, 9 genes in the light-harvesting chlorophyll protein complex (LHC), 10 genes in the PsbP family, and 4 genes in the cytochrome b6/f complex. To validate the reliability of the omics data, GhPPD1, a DAPs in the PsbP family, was knocked down in cotton using the TRV-based VIGS system, and it was observed that the GhPPD1-silenced plants exhibited patchy yellow color, accompanied by a significant decrease in chlorophyll content. In conclusion, this study integrated transcriptomic and proteomic approaches to gain a deeper understanding of the mechanisms underlying the chlorophyll-reduced leaf phenotype. Full article

Nitrogen (N) is the most important nutrient in coffee, with a direct impact on productivity, quality, and sustainability. N uptake by the roots is dominated by ammonium (NH₄⁺) and nitrates (NO₃⁻), along with some organic forms at a lower proportion. From the perspective of mineral fertilizer, the most common N sources are urea, ammonium (AM), ammonium nitrates (AN), and nitrates; an appropriate understanding of the right balance between N forms in coffee nutrition would contribute to more sustainable coffee production through the better N management of this important crop. The aim of this research was to evaluate the influences of different NH₄-N/NO₃-N ratios in coffee from a physiological and agronomical perspective, and their interaction with soil water levels. Over a period of 5 years, three trials were conducted under controlled conditions in a greenhouse with different growing media (quartz sand) and organic soil, with and without water stress, while one trial was conducted under field conditions. N forms and water levels directly influence physiological responses in coffee, including photosynthesis (Ps), chlorophyll content, dry biomass accumulation (DW), nutrient uptake, and productivity. In all of the trials, the plants group in soils with N ratios of 50% NH₄-N/50% NO₃-N, and 25% NH₄-N/75% NO₃-N showed better responses to water stress, as well as a higher Ps, a higher chlorophyll content, a higher N and cation uptake, higher DW accumulation, and higher productivity. The soil pH was significantly influenced by the N forms: the higher the NO₃⁻-N share, the lower the acidification level. The results allow us to conclude that the combination of 50% NH₄-N/50% NO₃-N and 25% NH₄-N/75% NO₃-N N forms in coffee improves the resistance capacity of the coffee to water stress, improves productivity, reduces the soil acidification level, and improves ion balance and nutrient uptake. Full article

A Type I reaction center (RC) (Fe-S type, ferredoxin reducing) is found in several phyla containing anoxygenic phototrophic bacteria. These include the heliobacteria (HB), the green sulfur bacteria (GSB), and the chloracidobacteria (CB), for which high-resolution homodimeric RC-photosystem (PS) structures have recently appeared. The 2.2-Å X-ray structure of the RC-PS of Heliomicrobium modesticaldum revealed that the core PshA apoprotein (PshA-1 and PshA-2 homodimeric pair) exhibits a structurally conserved PSI arrangement comprising five C-terminal transmembrane α-helices (TMHs) forming the RC domain and six N-terminal TMHs coordinating the light-harvesting (LH) pigments. The Hmi. modesticaldum structure lacked quinone molecules, indicating that electrons were transferred directly from the A₀ (8¹-OH-chlorophyll (Chl) a) acceptor to the F_X [4Fe-4S] component, serving as the terminal RC acceptor. A pair of additional TMHs designated as Psh X were also found that function as a low-energy antenna. The 2.5-Å resolution cryo-electron microscopy (cryo-EM) structure for the RC-PS of the green sulfur bacterium Chlorobaculum tepidum included a pair of Fenna–Matthews–Olson protein (FMO) antennae, which transfer excitations from the chlorosomes to the RC-PS (PscA-1 and PscA-2) core. A pair of cytochromes c_Z (PscC) molecules was also revealed, acting as electron donors to the RC bacteriochlorophyll (BChl) a’ special pair, as well as PscB, housing the [4Fe-4S] cluster F_A and F_B, and the associated PscD protein. While the FMO components were missing from the 2.6-Å cryo-EM structure of the Zn- (BChl) a’ special pair containing RC-PS of Chloracidobacterium thermophilum, a unique architecture was revealed that besides the (PscA)₂ core, consisted of seven additional subunits including PscZ in place of PscD, the PscX and PscY cytochrome c serial electron donors and four low mol. wt. subunits of unknown function. Overall, these diverse structures have revealed that (i) the HB RC-PS is the simplest light–energy transducing complex yet isolated and represents the closest known homolog to a common homodimeric RC-PS ancestor; (ii) the symmetrically localized Ca²⁺-binding sites found in each of the Type I homodimeric RC-PS structures likely gave rise to the analogously positioned Mn₄CaO₅ cluster of the PSII RC and the Tyr_Z RC donor site; (iii) a close relationship between the GSB RC-PS and the PSII Chl proteins (CP)43 and CP47 was demonstrated by their strongly conserved LH-(B)Chl localizations; (iv) LH-BChls of the GSB-RC-PS are also localized in the conserved RC-associated positions of the PSII Chl_Z-D1 and Chl_Z-D2 sites; (v) glycosylated carotenoids of the GSB RC-PS are located in the homologous carotenoid-containing positions of PSII, reflecting an O₂-tolerance mechanism capable of sustaining early stages in the evolution of oxygenic photosynthesis. In addition to the close relationships found between the homodimeric RC-PS and PSII, duplication of the gene encoding the ancestral Type I RC apoprotein, followed by genetic divergence, may well account for the appearance of the heterodimeric Type I and Type II RCs of the extant oxygenic phototrophs. Accordingly, the long-held view that PSII arose from the anoxygenic Type II RC is now found to be contrary to the new evidence provided by Type I RC-PS homodimer structures, indicating that the evolutionary origins of anoxygenic Type II RCs, along with their distinct antenna rings are likely to have been preceded by the events that gave rise to their oxygenic counterparts. Full article

Intercropping is a traditional and sustainable planting method that can make rational use of natural resources such as light, temperature, fertilizer, water, and CO₂. Due to its efficient resource utilization, intercropping, in particular, maize and legume intercropping, is widespread around the world. However, the molecular details of these pathways remain largely unknown. In this study, physiological, transcriptome, and proteome analyses were compared between maize monocropping and maize–peanut intercropping. The results show that an intercropping system enhanced the ability of carbon fixation and carboxylation of maize leaves. Apparent quantum yield (AQY), the light-saturated net photosynthetic rate (LSPn), the light saturation point (LSP), and the light compensation point (LCP) were increased by 11.6%, 9.4%, 8.9%, and 32.1% in the intercropping system, respectively; carboxylation efficiency (CE), the CO₂ saturation point (Cisat), the Rubisco maximum carboxylation rate (Vcmax), the maximum electron transfer rate (Jmax), and the triose phosphate utilization rate (TPU) were increased by 28.5%, 7.3%, 18.7%, 29.2%, and 17.0%, respectively; meanwhile, the CO₂ compensation point (Γ) decreased by 22.6%. Moreover, the transcriptome analysis confirmed the presence of 588 differentially expressed genes (DEGs), and the numbers of up-regulated and down-regulated genes were 383 and 205, respectively. The DEGs were primarily concerned with ribosomes, plant hormone signal transduction, and photosynthesis. Furthermore, 549 differentially expressed proteins (DEPs) were identified in the maize leaves in both the maize monocropping and maize–peanut intercropping systems. Bioinformatics analysis revealed that 186 DEPs were related to 37 specific KEGG pathways in each of the two treatment groups. Based on the physiological, transcriptome, and proteome analyses, it was demonstrated that the photosynthetic characteristics in maize leaves can be improved by maize–peanut intercropping. This may be related to PS I, PS II, cytochrome b6f complex, ATP synthase, and photosynthetic CO₂ fixation, which is caused by the improved CO₂ carboxylation efficiency. Our results provide a more in-depth understanding of the high yield and high-efficiency mechanism in maize and peanut intercropping. Full article

The Chinese plum (Prunus salicina L.) is a fruit tree belonging to the Rosaceae family, native to south-eastern China and widely cultivated throughout the world. Fruit sugar metabolism and color change is an important physiological behavior that directly determines flavor and aroma. Our study analyzed six stages of fruit growth and development using RNA-seq, yielding a total of 14,973 DEGs, and further evaluation of key DEGs revealed a focus on sugar metabolism, flavonoid biosynthesis, carotenoid biosynthesis, and photosynthesis. Using GO and KEGG to enrich differential genes in the pathway, we selected 107 differential genes and obtained 49 significant differential genes related to glucose metabolism. The results of the correlation analyses indicated that two genes of the SWEET family, evm.TU.Chr1.3663 (PsSWEET9) and evm.TU.Chr4.676 (PsSWEET2), could be closely related to the composition of soluble sugars, which was also confirmed in the ethylene treatment experiments. In addition, analysis of the TOP 20 pathways between different growth stages and the green stage, as well as transient overexpression in chili, suggested that capsanthin/capsorubin synthase (PsCCS) of the carotenoid biosynthetic pathway contributed to the color change of plum fruit. These findings provide an insight into the molecular mechanisms involved in the ripening and color change of plum fruit. Full article

Iron is an essential micronutrient for citrus, playing an important role in photosynthesis and yield. The aim of this paper was to evaluate the tolerance to Fe deficiency of five citrus rootstocks: sour orange (S), Carrizo citrange (C), Citrus macrophylla (M), Troyer citrange (T), and Volkamer lemon (V). Plants were grown for 5 weeks in nutrient solution that contained the following Fe concentrations (in µM): 0, 5, 10, 15, and 20. At the end of the experiment, biomass (dry weight—DW), leaf area, total leaf chlorophyll (CHL), and the activity of root chelate reductase (FCR) were recorded. Additionally, the mineral composition of roots (R) and shoots (S) was evaluated. Principal component analysis was used to study the relationships between all parameters and, subsequently, the relations between rootstocks. In the first component, N-S, P-S, Ca-S, Cu-S, Zn-S, Mn-S, Zn-R, and Mn-R concentrations were related to leaf CHL and FCR. Increases in leaf CHL, Mg-R, and DW (shoots and roots) were inversely related to Cu-R, which was shown in the second component. The values obtained were consistent for V10, C15, and C20, but in contrast for S0 and S5. In conclusion, micronutrient homeostasis in roots and shoots of all rootstocks were affected by Fe stress conditions. The Fe/Cu ratio was significantly related to CHL, which may be used to assist rootstock performance. Full article