Plant Stress Resistance Research Articles

Sage leaf rock rose water extract: a bio-solution for enhancing the growth and salt stress resistance of sorghum plants.

Sorghum bicolor, a versatile cereal grain, holds significant agronomic importance globally and plays a crucial role in addressing food insecurity. However, salinity, a major abiotic stress, poses a threat to food production by reducing soil fertility and hindering plant growth and yield. In this study, we investigated the potential of Cistus salviifolius water extract (CSE) in mitigating salt stress in sorghum plants. Salt stress severely impacted plant growth, biomass, and chlorophyll production, and reduced indole-3-acetic acid (IAA) levels, which negatively affected plant development. Salt stress also led to the buildup of reactive oxygen species (ROS), hence, resulting in oxidative harm to sorghum plants and also affecting their carbon and nitrogen metabolism. On the other hand, CSE treatments increased IAA and chlorophyll content which promoted growth under stress. Furthermore, this extract exhibited strong ROS scavenging capacity and safeguarded plants against oxidative stress by enhancing the activities of antioxidant enzymes (superoxide dismutase, glutathione peroxidase, glutathione-S-transferase, and glutathione reductase) and increasing the production of osmolytes. Additionally, CSE treatments enhanced the activities of carbon/nitrogen enzymes (phosphoenolpyruvate carboxylase, malate dehydrogenase, glutamate dehydrogenase, aspartate aminotransferase, and glutamine synthase), promoting energy synthesis and crop growth. This led to a significant increase in sorghum growth in salted soil with the highest rise recorded for 5mg/L of CSE (an increase of 48.23% and 158.36% in length and weight compared to the salt control), which highlights this extract's potential as a biostimulant to enhance crop tolerance to salinity and contribute to sustainable agriculture.

Exogenous Selenium Endows Salt-Tolerant and Salt-Sensitive Soybeans with Salt Tolerance through Plant-Microbial Coactions

Soil salinization is a common abiotic stress that seriously affects soybean growth and yield, underscoring the need to enhance plant salt tolerance for sustainable agriculture development. Selenium is a beneficial element that has been shown to promote plant growth, development and stress resistance. This study employed pot experiments to investigate the effects of different salt levels (0, 50, 100 and 150 mM NaCl) on salt-tolerant (Zhonghuang 13) and salt-sensitive soybean (Dongnong 63) varieties. Additionally, the critical salt concentration (100 mM NaCl) was selected to explore the effects of exogenous selenium (0, 0.5, 1 and 3 mg·kg−1) on improving salt tolerance in salt-tolerant and salt-sensitive soybeans under salt stress. Results showed that as salt concentration increased, plant height, shoot and root fresh weight, SPAD value and enzyme activity of both salt-tolerant and salt-sensitive soybeans significantly decreased. The increasing concentration of exogenous selenium significantly decreased the proline content of salt-sensitive and salt-tolerant soybeans by 40.65–58.87% and 38.51–50.46%, respectively, and the MDA content by 19.33–30.36% and 16.94–37.48%, respectively. Selenium supplementation also reduced the content of Na+ in salt-sensitive and salt-tolerant soybeans and improved K+ absorption in soybeans, which increased the K+/Na+ ratio. Moreover, high-throughput sequencing of the 16S ribosomal RNA gene demonstrated that selenium application optimized the rhizosphere microecology structure of salt-tolerant and salt-sensitive soybean varieties and enhanced functional genes related to lipid metabolism, energy metabolism and cell motility of rhizosphere microorganisms. In summary, selenium application improved the salt tolerance of the two soybean varieties by enhancing the physiological resistance to salt stress and optimizing the structure and function of the rhizosphere microbial community.

Physio-biochemical evaluation of Si-rich biochar amendment to improve the salt stress tolerance of Grand Nain and Williams banana genotypes

Banana is one of the plants with low salt tolerance and raising its ability to withstand salt stress contributes to increasing its production. Silicon (Si) is one of the important elements in increasing the salt stress resistance in plants. Therefore, Si-rich biochar has been suggested to improve the salt resistance of Williams (WL) and Grand Nain (GN) banana cultivars. Water salinity (tap water, 2, 4, and 6 dS m−1) and Si-rich biochar with low (LSiB) or high rate (HSiB) in a pot experiment were studied. Si-rich biochar significantly mitigated the salt stress and improved the growth of WL and GN banana cultivars. Si-rich biochar was effective in enhancing chlorophyll, carotenoids, calcium (Ca++) and potassium (K+) in banana leaves. HSiB was more effective than LSiB in mitigating the accumulation of sodium (Na+) in the plant leaves. HSiB raised the phenolic, carbohydrate, and proline in WL leaf tissues by 35, 49, and 14%, while these increases were 20%, 44%, and 21% in the case of GN cultivar. Banana leaves exposed to salt stress had higher levels of malondialdehyde (MDA), while Si-rich biochar reduced those levels. Antioxidant enzymes activity were raised by salt stress, and HSiB performed better than LSiB at boosting antioxidant enzyme activity. The production of osmo-protectants such as phenols, carbohydras, and proline were higher in the banana plants treated with HSiB compared to LSiB ones. Si-rich biochar mitigated the salt stress by increasing the uptake of Ca and K, improving the antioxidant defense, and enhancing the production of combatable solutes.

Fenoxycarb, a carbamate insect growth regulator, inhibits brassinosteroid action.

Brassinosteroids (BRs) are steroid hormones that regulate plant growth, development, and stress resistance. In this study, we evaluated the effect of agrochemicals on dark-induced hypocotyl elongation, which is regulated by BRs, to identify novel chemicals that regulate BR action. We found that the juvenile hormone agonist fenoxycarb inhibited dark-induced hypocotyl elongation in Arabidopsis. Treatment with the same class of juvenile hormone agonist, pyriproxyfen, did not affect hypocotyl elongation. Co-treatment with fenoxycarb and BR partly canceled the fenoxycarb-induced hypocotyl suppression. In addition, gene expression analysis revealed that fenoxycarb altered the BR-responsive gene expression. These results indicate that fenoxycarb is a BR action inhibitor.

Melatonin enhances drought tolerance by affecting jasmonic acid and lignin biosynthesis in wheat (Triticum aestivum L.)

Drought severely affects the yield of wheat (Triticum aestivum L.), which is mainly grown in arid and semi-arid regions. Melatonin plays an important role in various types of stress resistance in plants, including drought resistance. However, the molecular mechanism through which melatonin affects drought tolerance remains largely unknown. In this study, we revealed that melatonin (100 μM) significantly improved drought resistance during the maturation stage of Chinese Spring, Shi4185, and Hanxuan10 varieties, but not Chang6878. Further physiological, transcriptomic, and proteomic data analysis at the wheat seedling stage revealed that melatonin increased jasmonic acid (JA) content, upregulating the expression of JA genes (LOX1.5 and LOX2.1) and two transcription factors (HY5 and MYB86) under drought conditions. It also upregulated genes related to lignin biosynthesis (4CL2, P5CS1, and CCR2) as well as starch and sucrose metabolism (PME53 and SUS4). Additionally, melatonin alleviated photosynthetic and cell membrane damage caused by drought stress through maintaining low levels of hydrogen peroxide. The current results elucidate melatonin-regulated pathways in wheat and provide evidence for using melatonin as a potential biostimulant to improve wheat drought resistance under field conditions in the future.

Potential regulatory genes of light induced anthocyanin accumulation in sweet cherry identified by combining transcriptome and metabolome analysis.

Anthocyanins exist widely in various plant tissues and organs, and they play an important role in plant reproduction, disease resistance, stress resistance, and protection of human vision. Most fruit anthocyanins can be induced to accumulate by light. Here, we shaded the "Hong Deng" sweet cherry and performed an integrated analysis of its transcriptome and metabolome to explore the role of light in anthocyanin accumulation. The total anthocyanin content of the fruit and two of its anthocyanin components were significantly reduced after the shading. Transcriptome and metabolomics analysis revealed that PAL, 4CL, HCT, ANS and other structural genes of the anthocyanin pathway and cyanidin 3-O-glucoside, cyanidin 3-O-rutinoside, and other metabolites were significantly affected by shading. Weighted total gene network analysis and correlation analysis showed that the upstream and middle structural genes 4CL2, 4CL3, and HCT2 of anthocyanin biosynthesis may be the key genes affecting the anthocyanin content variations in fruits after light shading. Their expression levels may be regulated by transcription factors such as LBD, ERF4, NAC2, NAC3, FKF1, LHY, RVE1, and RVE2. This study revealed for the first time the possible role of LBD, FKF1, and other transcription factors in the light-induced anthocyanin accumulation of sweet cherry, thereby laying a preliminary foundation for further research on the role of light in anthocyanin accumulation of deep red fruit varieties and the genetic breeding of sweet cherry.

Cultivable Endophyte Resources in Medicinal Plants and Effects on Hosts.

With the increasing demand for medicinal plants and the increasing shortage of resources, improving the quality and yield of medicinal plants and making more effective use of medicinal plants has become an urgent problem to be solved. During the growth of medicinal plants, various adversities can lead to nutrient loss and yield decline. Using traditional chemical pesticides to control the stress resistance of plants will cause serious pollution to the environment and even endanger human health. Therefore, it is necessary to find suitable pesticide substitutes from natural ingredients. As an important part of the microecology of medicinal plants, endophytes can promote the growth of medicinal plants, improve the stress tolerance of hosts, and promote the accumulation of active components of hosts. Endophytes have a more positive and direct impact on the host and can metabolize rich medicinal ingredients, so researchers pay attention to them. This paper reviews the research in the past five years, aiming to provide ideas for improving the quality of medicinal plants, developing more microbial resources, exploring more medicinal natural products, and providing help for the development of research on medicinal plants and endophytes.

Deciphering the synergistic effect of Jasmonic acid and Spermine in mitigating root-knot nematode stress in tomato plants through enhancing growth and activity of antioxidant enzymes

Root-Knot nematodes (RKNs) are one of the major plant pathogens that can substantially reduce plant growth and development. Management of RKNs is one of the major concerns as chemical pesticides pose a potential risk to humans and other life forms and also have toxic effects to environment. There is a need to find out some alternative eco-friendly strategies for management of these parasites. Jasmonic acid (JA) and Spermine (Spm) are those plant growth regulators (PGRs) that have positive effects on plant growth and alleviates toxic effects caused by various stresses including RKNs. Keeping this in mind,present study accessed the potential of these (PGRs), JA and Spm on morphological and biochemical attributes in 45 days old Solanum lycopersicum plants under nematode stress. It was observed that nematode infection resulted in reduced plant growth and photosynthetic pigments. Application of JA and Spm improved growth parameters and photosynthetic pigments. Moreover, tomato plants after JA and Spm supplementation lowered the activities of H2O2, DPPH and MDA thus decreasing nuclear and membrane damage caused by nematode stress. Additionally, enzymatic CAT (Catalase), SOD (Superoxide dismutase), GuPOX (Guaiacol peroxidase), APOX (Ascorbate peroxidase), PPO (Polyphenol oxidase), GST (Glutathione-S-transferase) and non-enzymatic (ascorbic acid, glutathione, and tocopherol) antioxidant levels increased markedly under nematode stress, but application of JA and Spm further improved these attributes. Taken together, the current study demonstrated that JA and Spm are suitable agents for managing nematode stress resistance in tomato plants.

Response of exogenous melatonin on transcription and metabolism of soybean under drought stress.

Amino acid metabolism is an important factor in regulating nitrogen source assimilation and source/sink transport in soybean. Melatonin can improve plant stress resistance, but whether it affects amino acid metabolism is not known. Therefore, this study investigated whether exogenous melatonin had an effect on amino acid metabolism of soybean under drought conditions and explored its relationship with yield. The treatments were normal water supply treatment (WW), drought stress treatment (D), drought stress and melatonin treatment group (D + M), sprayed with 100 μmol/L melatonin. The effects of melatonin on amino acid metabolism and grain filling were studied by physiological and omics experiments using Kangxian 9 (drought-sensitive variety) and Suinong 26 (drought-resistant variety) soybean cultivars. The results showed that drought stress decreased the activity of carbon and nitrogen metabolizing enzymes, which inhibited the accumulation of dry matter and protein, and decreased the yield. In the drought-sensitive soybean variety, glycoenzymes and amino acid synthetases synthetic genes were upregulated in melatonin-treated soybeans, hence carbon and nitrogen metabolism enzyme activity increased, increasing the carbohydrate and amino acid contents simultaneously. This resulted in higher dry matter and yield than drought-stressed soybean not treated with melatonin. In the drought-resistant variety, the grain weight per plant increased by 7.98% and 6.57% in 2020 and 2021, respectively, while it increased by 23.20% and 14.07% in the drought-sensitive variety during the respective years. In conclusion, melatonin treatment can enhance the activity of nitrogen and carbon metabolism and amino acid content by upregulating the expression of soybean metabolic pathway and related genes, thus increasing the yield of soybean under drought stress.

Alternative Splicing for Leucanthemella linearis NST1 Contributes to Variable Abiotic Stress Resistance in Transgenic Tobacco.

Leucanthemella linearis is a marsh plant in the family Compositae. It has good water and moisture resistance and ornamental properties, which makes it one of the important materials for chrysanthemum breeding and genetic improvement. The NST1 (NAC secondary wall enhancement factor 1) gene is associated with the thickening of the secondary walls of fiber cells in the plant ducts and the secondary xylem and plays an important role in plant stress resistance. In this study, two variable spliceosomes of the NST1 gene were identified from a chrysanthemum plant by using bioinformatics, qRT-PCR, transgene, and paraffin section methods to explore the molecular mechanism of the variable splicing of NST1 under abiotic stress. The results show that only three amino acids were found to be different between the two LlNST1 variants. After being treated with salt, drought, and low temperatures, analysis of the expression levels of the LlNST1 and LlNST1.1 genes in Ll showed that LlNST1.1 could respond to low temperatures and salt stress and had a weak response to drought stress. However, the expression level of LlNST1 under the three treatments was lower than that of LlNST1.1. LlNST1 transgenic tobacco showed increased saline-alkali resistance and low-temperature resistance at the seedling stage. LlNST1.1 transgenic tobacco also showed enhanced saline-alkali resistance and drought resistance at the seedling stage. In conclusion, the functions of the two variable spliceosomes of the NST1 gene are very different under abiotic stress. Therefore, this study verified the function of the variable spliceosome of NST1 and improved the stress resistance of the chrysanthemum plant under examination by regulating the expression of the NST protein, which lays a material foundation for the improvement of plant stress resistance materials and has important significance for the study of the resistance of chrysanthemum plants to abiotic stress.

Antioxidant and drought-acclimation responses in UV-B-exposed transgenic Nicotiana tabacum displaying constitutive overproduction of H2O2.

Hydrogen peroxide (H2O2) is an important molecule that regulates antioxidant responses that are crucial for plant stress resistance. Exposure to low levels of ultraviolet-B radiation (UV-B, 280-315nm) can also activate antioxidant defenses and acclimation responses. However, how H2O2 and UV-B interact to promote stress acclimation remains poorly understood. In this work, a transgenic model of Nicotiana tabacum cv Xanthi nc, with elevated Mn-superoxide dismutase (Mn-SOD) activity, was used to study the interaction between the constitutive overproduction of H2O2 and a 14-day UV-B treatment (1.75kJm-2 d-1 biologically effective UV-B). Subsequently, these plants were subjected to a 7-day moderate drought treatment to evaluate the impact on drought resistance of H2O2- and UV-dependent stimulation of the plants' antioxidant system. The UV-B treatment enhanced H2O2 levels and altered the antioxidant status by increasing the epidermal flavonol index, Trolox Equivalent Antioxidant Capacity, and catalase, peroxidase and phenylalanine ammonia lyase activities in the leaves. UV-B also retarded growth and suppressed acclimation responses in highly H2O2-overproducing transgenic plants. Plants not exposed to UV-B had a higher drought resistance in the form of higher relative water content of leaves. Our data associate the interaction between Mn-SOD transgene overexpression and the UV-B treatment with a stress response. Finally, we propose a hormetic biphasic drought resistance response curve as a function of leaf H2O2 content in N. tabacum cv Xanthi.

Effects of stress-induced ABA on root architecture development: Positive and negative actions

Root architecture development, an agronomic trait that influences crop yield, is regulated by multiple plant hormones. Abscisic acid (ABA) is a stress hormone that responds to multiple stresses, including salt, drought, and cold stress, and modulates various aspects of plant growth and development. In recent years, it has been found that ABA synthesized under mild stress or well-watered conditions can support plant growth and stress resistance by positively regulating root architecture development. In this review, we summarize the molecular, cellular, and organismal basis of ABA homeostasis in the root and how ABA signaling affects root architecture development both as an inhibitor and as an activator. We discuss the implications of these studies and the potential for exploiting the components of ABA signaling in designing crop plants with improved root system development and stress resistance.

The Biosynthesis and Functions of Polyamines in the Interaction of Plant Growth-Promoting Rhizobacteria with Plants.

Plant growth-promoting rhizobacteria (PGPR) are members of the plant rhizomicrobiome that enhance plant growth and stress resistance by increasing nutrient availability to the plant, producing phytohormones or other secondary metabolites, stimulating plant defense responses against abiotic stresses and pathogens, or fixing nitrogen. The use of PGPR to increase crop yield with minimal environmental impact is a sustainable and readily applicable replacement for a portion of chemical fertilizer and pesticides required for the growth of high-yielding varieties. Increased plant health and productivity have long been gained by applying PGPR as commercial inoculants to crops, although with uneven results. The establishment of plant-PGPR relationships requires the exchange of chemical signals and nutrients between the partners, and polyamines (PAs) are an important class of compounds that act as physiological effectors and signal molecules in plant-microbe interactions. In this review, we focus on the role of PAs in interactions between PGPR and plants. We describe the basic ecology of PGPR and the production and function of PAs in them and the plants with which they interact. We examine the metabolism and the roles of PAs in PGPR and plants individually and during their interaction with one another. Lastly, we describe some directions for future research.

The Fragile culm19 (FC19) mutation largely improves plant lodging resistance, biomass saccharification, and cadmium resistance by remodeling cell walls in rice

Cell wall is essential for plant upright growth, biomass saccharification, and stress resistance. Although cell wall modification is suggested as an effective means to increase biomass saccharification, it is a challenge to maintain normal plant growth with improved mechanical strength and stress resistance. Here, we reported two independent fragile culm mutants, fc19–1 and fc19–2, resulting from novel mutations of OsIRX10, produced by the CRISPR/Cas9 system. Compared to wild-type, the two mutants exhibited reduced contents of xylose, hemicellulose, and cellulose, and increased arabinose and lignin without significant alteration in levels of pectin and uronic acids. Despite brittleness, the mutants displayed increased breaking force, leading to improved lodging resistance. Furthermore, the altered cell wall and increased biomass porosity in fc19 largely increased biomass saccharification. Notably, the mutants showed enhanced cadmium (Cd) resistance with lower Cd accumulation in roots and shoots. The FC19 mutation impacts transcriptional levels of key genes contributing to Cd uptake, sequestration, and translocation. Moreover, transcriptome analysis revealed that the FC19 mutation resulted in alterations of genes mainly involved in carbohydrate and phenylpropanoid metabolism. Therefore, a hypothetic model was proposed to elucidate that the FC19 mutation-mediated cell wall remodeling leads to improvements in lodging resistance, biomass saccharification, and Cd resistance.

Foliar Spraying of Glycine Betaine Alleviated Growth Inhibition, Photoinhibition, and Oxidative Stress in Pepper (Capsicum annuum L.) Seedlings under Low Temperatures Combined with Low Light.

Low temperature combined with low light (LL stress) is a typical environmental stress that limits peppers' productivity, yield, and quality in northwestern China. Glycine betaine (GB), an osmoregulatory substance, has increasingly valuable effects on plant stress resistance. In this study, pepper seedlings were treated with different concentrations of GB under LL stress, and 20 mM of GB was the best treatment. To further explore the mechanism of GB in response to LL stress, four treatments, including CK (normal temperature and light, 28/18 °C, 300 μmol m-2 s-1), CB (normal temperature and light + 20 mM GB), LL (10/5 °C, 100 μmol m-2 s-1), and LB (10/5 °C, 100 μmol m-2 s-1 + 20 mM GB), were investigated in terms of pepper growth, biomass accumulation, photosynthetic capacity, expression levels of encoded proteins Capsb, cell membrane permeability, antioxidant enzyme gene expression and activity, and subcellular localization. The results showed that the pre-spraying of GB under LL stress significantly alleviated the growth inhibition of pepper seedlings; increased plant height by 4.64%; increased root activity by 63.53%; and decreased photoinhibition by increasing the chlorophyll content; upregulating the expression levels of encoded proteins Capsb A, Capsb B, Capsb C, Capsb D, Capsb S, Capsb P1, and Capsb P2 by 30.29%, 36.69%, 18.81%, 30.05%, 9.01%, 6.21%, and 16.45%, respectively; enhancing the fluorescence intensity (OJIP curves), the photochemical efficiency (Fv/Fm, Fv'/Fm'), qP, and NPQ; improving the light energy distribution of PSΠ (Y(II), Y(NPQ), and Y(NO)); and increasing the photochemical reaction fraction and reduced heat dissipation, thereby increasing plant height by 4.64% and shoot bioaccumulation by 13.55%. The pre-spraying of GB under LL stress also upregulated the gene expression of CaSOD, CaPOD, and CaCAT; increased the activity of the ROS-scavenging ability in the pepper leaves; and coordinately increased the SOD activity in the mitochondria, the POD activity in the mitochondria, chloroplasts, and cytosol, and the CAT activity in the cytosol, which improved the LL resistance of the pepper plants by reducing excess H2O2, O2-, MDA, and soluble protein levels in the leaf cells, leading to reduced biological membrane damage. Overall, pre-spraying with GB effectively alleviated the negative effects of LL stress in pepper seedlings.

Metabolic Profiling of Endophytic Bacteria in Relation to Their Potential Application as Components of Multi-Task Biopreparations

Agricultural crops are exposed to various abiotic and biotic stresses that can constrain crop productivity. Focusing on a limited subset of key groups of organisms has the potential to facilitate the monitoring of the functions of human-managed ecosystems. Endophytic bacteria can enhance plant stress resistance and can help plants to cope with the negative impacts of stress factors through the induction of different mechanisms, influencing plant biochemistry and physiology. In this study, we characterise endophytic bacteria isolated from different plants based on their metabolic activity and ability to synthesise 1-aminocyclopropane-1-carboxylic acid deaminase (ACCD), the activity of hydrolytic exoenzymes, the total phenolic compounds (TPC) and iron-complexing compounds (ICC). Test GEN III MicroPlate indicated that the evaluated endophytes are highly metabolically active, and the best used substrates were amino acids, which may be important in selecting potential carrier components for bacteria in biopreparations. The ACCD activity of strain ES2 (Stenotrophomonas maltophilia) was the highest, whereas that of strain ZR5 (Delftia acidovorans) was the lowest. Overall, the obtained results indicated that ∼91.3% of the isolates were capable of producing at least one of the four hydrolytic enzymes. In addition, most of the tested strains produced ICC and TPC, which play a significant role in reducing stress in plants. The results of this study suggest that the tested endophytic bacterial strains can potentially be used to mitigate climate change-associated stresses in plants and to inhibit plant pathogens.Graphical

Nonlinear model prediction of needle chlorophyll content of Picea koraiensis Nakai at different needle ages based on hyperspectral features

Pigment content is a critical assessment indicator in the study of plant physiological metabolism, stress resistance, ornamental characteristics, and forest health. Spectral imaging technology is widely used for rapid and non-destructive determination of plant physicochemical parameters. To address the shortcomings of previous models of spectral reflectance prediction of chlorophyll content of needles only from the perspective of traditional algorithms and ignoring physical models, this research integrates variable complexity and refined classification of physical models to validate the increased accuracy of both the conventional partial least squares (PLS) method and the traditional neural network algorithm. The results of the conifer chlorophyll models of Picea koraiensis Nakai with different needle ages based on spectral reflectance and vegetation index parameters showed that the improved nonlinear state transition algorithm-backpropagation (STA-BP) neural network model approach (R2 of 0.73–0.89) and the nonlinear Stacking partial least squares (Stacking-PLS) model approach (R2 of 0. 67–0.85) is slightly more robust than the traditional algorithms nonlinear BP model (R2 of 0.63–0.82) and linear PLS model (R2 of 0.60–0.76). This finding suggests that the nonlinear fitting of chlorophyll content in needles of different needle ages in P. koraiensis Nakai surpasses the traditional linear model fitting methodology. Furthermore, the model fitting of chlorophyll content in conifers of different needle ages outperforms the mixed P. koraiensis Nakai model, suggesting that chlorophyll models using needle refinement classification help to improve model robustness. This study provides data and theoretical support for rapid and non-invasive characterization of physiological and biochemical properties of needles of different needle ages using spectral imaging techniques to predict growth and community structure productivity of forest trees in the coming years.

Role of selective autophagy receptors in tomato response to cold stress

Selective autophagy transports damaged organelles or proteins to the autophagosome for degradation through specific cargo receptors. In recent years, an increasing number of selective autophagy receptors in plants have been identified, and they are known to play critical roles in plant development, growth, and stress resistance. However, the exact functions of selective autophagy receptors in crop response to environmental stimuli, particularly cold stress, are largely unknown. In this study, twelve potential selective autophagy receptors were identified in tomato and revealed that cold stress induced the expression of selective autophagy receptor genes, secretory protein 62 (SEC62), next to BRCA1 gene 1a (NBR1a),and NBR1b, but not the expression of ATG8 Interacting Protein 2 (ATI2) and other selective autophagy receptors in tomato plants. Silencing these cold-induced selective autophagy receptor genes via virus-induced gene silencing reduced tomato cold tolerance, as indicated by visual phenotype, maximum photochemical efficiency, membrane integrity and autophagy production. Furthermore, the accumulation of cold-induced oxidized proteins and reactive oxygen species (ROS) increased in SEC62-, NBR1a-, or NBR1b-silenced plants, whereas no notable changes were observed between TRV control and ATI2-silenced plants. Additionally, the activities and expression of antioxidant enzymes, the ratio of reduced glutathione to oxidized glutathione, and the expression level of cold response genes decreased in SEC62-, NBR1a-, or NBR1b-silenced plants compared with TRV control plants under cold stress. These results suggest that several selective autophagy receptors of tomato plants confer cold tolerance by inducing autophagy for the degradation of denatured proteins and activation of antioxidant and CBF pathways.

In vitro regeneration of Haloxylon ammodendron

Haloxylon ammodendron (C.A.Mey) Bunge is one of the important species of arid desert vegetation in China, and it is also an ideal material for studying plant stress resistance, which plays an extremely important role in protecting desert ecosystems and preventing land desertification. However, there are relatively few studies on the regeneration of the fusiform, and the genetic transformation system has not been successfully reported, which restricts the in-depth study of the molecular mechanism of shuttle propagation and stress resistance. In the present study, the seeds, hypocotyls, cotyledons, cotyledon nodes, terminal buds and fixed buds were used as explants, and a set of tissue culture and plant regeneration system was established by inducing adventitious buds, adventitious bud rooting and transplanting. The results showed that amongst different H. ammodendron explants, i.e., seeds, hypocotyls, cotyledons and cotyledon nodes, the last induced budding effect was better. The optimal medium for inducing clandine buds by cotyledon segment differentiation is 0.5 mg·L-1 NAA+0.5 mg·L-1 6-BA induced budding rate was high, reaching 61.90%, rooting medium was 1/2 MS+1 mg·L-1 NAA +1 mg·L-1 IBA + 1 mg·L-1 IAA with a rooting rate of 50%. The results of this study will provide a theoretical basis for the genetic transformation of H. ammodendron.

Effects of attapulgite on the growth status of submerged macrophytes Vallisneria spiralis and sediment microenvironment

The effects of raw attapulgite clay and thermally modified attapulgite clay on the growth status of submerged plant Vallisneria Spiralis (V. spiralis) and the microenvironment of sediment were first explored. The results demonstrated that the attapulgite could effectively promote the development of V. spiralis and improve plant stress resistance by enhancing the activity of antioxidant enzymes. The 10% addition of attapulgite clay increased the biomass of V. spiralis by 27%∼174%, and the promoted rate of raw attapulgite clay was 2∼5 times of modified attapulgite clay. The attapulgite increased redox potential in sediment (P < 0.05) and provided proper niches for organism propagation, further promoting the degradation of organic matter and nutrient metabolism in sediment. The value of Shannon, Chao, and Ace was 9.98, 4865.15, 5029.08 in the 10% modified attapulgite group, and 10.12, 4856.85, 4947.78 in the 20% raw attapulgite group, respectively, indicating that the attapulgite could increase the microbial diversity and abundance in sediment. Additionally, the nutrient elements, such as Ca, Na, S, Mg, K, Zn, and Mo, that dissolved from attapulgite may also promote the V. spiralis growth. This study provided an environment-friendly approach to facilitating submerged macrophyte restoration in the eutrophic lake ecosystem.