Plant Physiology and Biochemistry最新文献

Flavonol glycosides are secondary metabolites important for plant development and stress defense such as UV-B irradiation. UDP-glycosyltransferase (UGT) catalyzes the last step in the biosynthesis of flavonol glycosides. Eriobotrya japonica is abundant in flavonol glycosides, but UGTs responsible for accumulation of flavonol glycosides remain unknown. Here, 13 flavonol glycosides including monoglycosides and diglycosides were characterized in different tissues of loquat by LC-MS/MS. UV-B irradiation significantly increased the accumulation of four quercetin glycosides and two kaempferol glycosides in loquat fruit. Based on UGT gene family analysis, transcriptome analysis, enzyme assays of recombinant proteins as well as transient overexpression assays in Nicotiana benthamiana, three UGTs were identified, i.e. EjUGT78T4 as flavonol 3-O-galactosyltransferase, EjUGT78S3 as flavonol 3-O-glucosyltransferase, and EjUGT91AK7 as flavonol 1 → 6 rhamnosyltransferase. This work elucidates the formation of flavonol glycosides in loquat through UGT-mediated glycosylation.

Alfalfa (Medicago sativa L.) is a prominent and distinct species within the pasture germplasm innovation industry. However, drought poses a substantial constraint on the yield and distribution of alfalfa by adversely affecting its growth. Although lineage-specific genes are instrumental in modulating plant responses to stress, their role in mediating alfalfa's tolerance to drought stress has yet to be elucidated. In this study, a total of 199 alfalfa-specific genes (ASGs) and 3054 legume-specific genes (LSGs) were identified in alfalfa. Compared with evolutionarily conserved genes, ASGs have shorter sequence length and fewer or no intron. Many alfalfa ASGs can be induced by various abiotic stresses, and the capability of MsASG166 to enhance drought resistance has been substantiated through transgenic research in both yeast and Arabidopsis thaliana. The RNA-Seq and WGCNA analyses revealed that DREB2A and MADS are pivotal genes in the molecular mechanisms through which MsASG166 positively modulates plant drought resistance. This study marks the first identification of lineage-specific genes in alfalfa and an examination of the molecular roles of the MsASG166 gene in drought stress responses. The findings offer valuable genetic resources for the development of novel, genetically engineered alfalfa germplasm with enhanced drought tolerance.

A deep understanding of ammonia (NH₃) emissions from cropland can promote efficient crop production. To date, little is known about leaf NH₃ emissions because of the lack of rapid detection methods. We developed a method for detecting leaf NH₃ emissions based on portable NH₃ sensors. The study aimed to (i) determine the performance of the method in detecting leaf NH₃ emissions; (ii) analyze the variation of leaf NH₃ emissions with foliar rank; and (iii) elucidate the relationships between leaf NH₃ emissions and other leaf parameters. Maize (Zea mays L.) was used as the tested plant. The results showed that the NH₃ sensors had good repeatability, accuracy, and selectivity in detecting NH₃. The response time of the method ranged 7-22 s and the NH₃ reading ranged 0.078-0.463 μmol mol^-1. Leaf NH₃ emissions were observed mainly in daytime (negligible at night). Daytime leaf NH₃ emission rates ranged 0.347-1.725 μg N cm^-2 d^-1. The middle leaves (near the ear) were the major contributor to plant NH₃-N loss. There were significant linear relationships between leaf NH₃ emission rates and other nondestructively-measured leaf parameters [e.g., SPAD (soil and plant analyzer development, which reflects the relative concentration of leaf chlorophyll), stomatal conductance, transpiration rate, and net photosynthetic rate] (p < 0.01), as well as with leaf apoplastic ammonium (NH₄⁺) concentration and leaf total N concentration (p < 0.01). Nitrogen application increased leaf apoplastic NH₄⁺ concentration, leaf total N concentration, and leaf NH₃ emission rate. Overall, nondestructively-measured leaf NH₃ emission rates can partly reflect maize growth status and provide information for N management in maize production.

Sucrose nonfermenting-1-related protein kinase 2 (SnRK2) intricately modulates plant responses to abiotic stresses and abscisic acid (ABA) signaling. In pepper genome, five SnRK2 genes with sequence homology to CaSnRK2.6 showed distinct expression patterns across various pepper organs and in response to treatments with ABA, drought, mannitol, and salt. This study elucidated the roles of two pepper (Capsicum annuum) subclass II SnRK2s-CaDSK2-1 and CaDSK2-2-in ABA signaling and stress responses. ABA specifically induced CaDSK2-1 activity, whereas CaDSK2-2 did not respond to ABA. Both kinases displayed stress-induced kinase activity, with CaDSK2-2 showing faster and stronger activation in response to drought and mannitol than that of CaDSK2-1. Unlike CaDSK2-2, CaDSK2-1 overexpression in pepper plants led to increased leaf temperatures and enhanced ABA-responsive gene expression in response to ABA treatment compared with those of the control. However, both kinases contributed to enhanced drought resistance. During seed germination in Arabidopsis, the overexpression of CaDSK2-2, but not CaDSK2-1, led to ABA hypersensitivity. Among the key regulators of the ABA signaling pathway, CaDSK2-1 specifically interacts with clade A protein phosphatase 2C (PP2C) CaADIP1, whereas CaDSK2-2 interacts with various PP2Cs, including CaADIP1. CaADIP1 negatively regulated the kinase activity of both CaDSK2-1 and CaDSK2-2 and mitigated ABA hypersensitivity mediated by CaDSK2-2 during Arabidopsis seed germination. These findings suggest distinct roles for pepper subclass II SnRK2s in drought stress responses and ABA signaling.

The enzymatic hydrolysis of cell wall polysaccharides results in the production of oligosaccharides with nature of damage-associated molecular patterns (DAMPs) that are perceived by plants as danger signals. The in vitro oxidation of oligogalacturonides and cellodextrins by plant FAD-dependent oligosaccharide-oxidases (OSOXs) suppresses their elicitor activity in vivo, suggesting a protective role of OSOXs against a prolonged activation of defense responses potentially deleterious for plant health. However, OSOXs are also produced by phytopathogens and saprotrophs, complicating the understanding of their role in plant-microbe interactions. Here, we demonstrate the oxidation catalyzed by specific fungal OSOXs also converts the elicitor-active cello-tetraose and xylo-tetraose into elicitor-inactive forms, indicating that the oxidation state of cell wall oligosaccharides is crucial for their DAMP function, irrespective of whether the OSOX originates from fungi or plants. In addition, we also found that certain OSOXs can transfer the electrons from the reducing end of these oligosaccharides to oxidized phenolics (bi-phenoquinones) instead of molecular O₂, highlighting an unexpected sub-functionalization of these enzymes. The activity of OSOXs may be crucial for a thorough understanding of cell wall metabolism since these enzymes can redirect the reducing power from sugars to phenolic components of the plant cell wall, an insight with relevant implications for plant physiology and biotechnology.

The plant UDP-glycosyltransferases (UGTs) regulate several metabolic processes during root growth and development by conjugating sugar moieties to various small molecules. RsUGT71B5 is a novel UDP-glycosyltransferase in Raphanus sativus L., but its biological function is not well established. In this study, we generated RsUGT71B5-overexpressing transgenic Arabidopsis lines to determine the mechanisms by which RsUGT71B5 regulated root growth and development. Ectopic overexpression of RsUGT71B5 significantly enhanced root growth and seedling development. In culture medium supplemented with 1-3% exogenous sucrose, RsUGT71B5 overexpression increased the root length and surface area in the transgenic Arabidopsis lines compared with the wild type. Furthermore, transgenic RsUGT71B5 overexpression partially suppressed the inhibitory effects of 12% sucrose on root growth and development. RNA sequencing data analysis identified 102 differential expressed genes (DEGs), including 56 upregulated and 46 downregulated genes, in the transgenic RsUGT71B5 overexpression lines (OE). QRT-PCR analyses confirmed significant upregulation of glutathione S-transferases such as AT1G02930 (GSTF6) and AT1G02920 (GSTF7) in the transgenic RsUGT71B5 overexpression lines. KEGG pathway analyses of the DEGs showed that RsUGT71B5 overexpression regulated glutathione and sugar metabolism. In summary, this study demonstrated that RsUGT71B5 regulated root growth and development by modulating glutathione and sugar metabolism.

The accumulation of disposable face masks (DFMs) has become a significant threat to the environment due to extensive use during the COVID-19 pandemic. In this research, we investigated the degradation of DFMs after their disposal in landfills. We replicated the potential degradation process of DFMs, including exposure to sunlight before subjecting them to synthetic landfill leachate (LL). After exposure to UV radiation, all three layers of the DFMs displayed surface abrasions and fractures, becoming less stable with increased UV exposure duration, indicating an aging process. Changes in the surface morphology of the DFMs and carbonyl index after UV exposure confirmed this aging process. DFM aging in LL accelerated by 11% compared to deionized (DI) water after 28 days. Different analytical techniques, including microscopy, FT-IR, Raman spectroscopy, and ICP-MS were used to detect microplastics and metals in the leachates. The microfibers collected from the leachates were primarily made of polypropylene, and the abundance of smaller microfibers (<40 μm) increased with the aging time of DFMs in leachate. Additionally, this study examines the toxicity of UV-weathered DFM leachates collected at different periods on Allium cepa, a model terrestrial plant. Leachates from DFM aged in landfill caused 15% more harm to A. cepa root cells due to increased oxidative stress (66%) compared to leachates aged in DI water. Additionally, DFM leachates aged in landfills showed a 29% increase in heavy metal content over time compared to those aged in DI water, potentially leading to significant phytotoxicity. In summary, this report highlights the impact of disposing DFMs in landfills and their biological effects on a model plant.

Nanoparticles play a significant role in enhancing crop yield and reducing nutrient loss through precise nutrient delivery mechanisms. However, it is imperative to ascertain the specific plant physiology altered by these nanoparticles. This study investigates the effects of green-synthesized nanoparticles, specifically boron nitride and sulphur, on sunflower yield, seed quality, and physiological activities. Conducted over two field experiments in 2019 and 2020, the research assesses the efficacy of these nanoparticles compared to traditional fertilizers. The first experiment revealed that a foliar application of green-synthesized nano boron nitride at 1500 ppm significantly enhanced seed yield (65.45 g in 2019 and 63.27 g in 2020), increased filled seed count, and reduced chaffiness. Additionally, this treatment improved pollen fertility, germination rates, and pollen tube growth compared to higher concentrations and borax treatments. These findings indicate that nano boron nitride enhances esterase activity, contributing to improved reproductive performance in sunflower. The second experiment focused on green-synthesized nano sulphur, comparing foliar application and seed treatment. Results showed that a foliar application at 600 ppm led to increased head diameter, head weight, and 100-seed weight outperforming both seed treatment and chemically synthesized alternatives. Overall, this research demonstrates the potential of green-synthesized nanoparticles to enhance sunflower crop characteristics and oil production, offering valuable insights for sustainable agricultural practices.

SnRK1 (SNF1-related kinase 1), a member of the SNF1 protein kinase superfamily, has been demonstrated to play a role in plant growth and development, as well as in stress responses. In this experiment, the leaf senescence of 'Xintaimici' cucumber was simulated by dark treatment and studied using SnRK1 activator/inhibitor and transient transformation technology. The effects of SnRK1 on cucumber leaf senescence, reactive oxygen species (ROS) metabolism, chloroplast structure, and photosynthetic characteristics were studied. The results demonstrated that the CsSnRK1 gene in cucumber leaves responded to dark-induced senescence. Furthermore, alterations in SnRK1 activity/expression affected the dark-induced leaf senescence process. Specifically, the activation of SnRK1 activity/expression can inhibit membrane lipid peroxidation by reducing the accumulation of ROS in leaves, slowing the decomposition of chloroplasts, repairing damage to photosystem II in leaves, delaying the senescence of leaves, and improving the photosynthetic capacity of leaves. Conversely, the inhibition of SnRK1 activity/expression had the opposite effect. These findings underscore the inhibitory role of SnRK1 in dark-induced cucumber leaf senescence. Our findings clarified the role of SnRK1 in regulating cucumber leaf senescence as well as its underlying physiological mechanisms, and will aid future studies of the molecular mechanism by which SnRK1 regulates cucumber leaf senescence.

Soil heavy metal pollution is a major abiotic stressor frequently encountered by plants in conjunction with other biotic stresses like insect herbivory. Yet, it remains largely unexplored how soil metal pollution and insect herbivory act together to influence emissions of plant volatile organic compounds (VOCs), which mediate multiple ecological functions and play crucial roles in atmospheric processes. Here, we assessed the individual and combined effects of soil cadium (Cd) pollution and insect herbivory by Clostera anachoreta on VOC emissions from the seedlings of eastern cottonwood Populus deltoides, and whether these effects depend on plant sex. We found that plant sex notably influenced VOC emission and altered blend compositions, with male seedlings emitting higher amounts of monoterpenes, sesquiterpenes, homoterpenes and green leaf volatiles (GLVs) than females. Soil Cd exposure significantly increased emissions of monoterpenes, GLVs, and nitrogenous VOCs in males but not in females. Comparatively, larval feeding exerted the strongest effects on VOC emissions and their composition, albeit to varying extent between males and females, and among different VOC classes. Importantly, Cd exposure amplified herbivore-induced VOC emissions in males. For instance, under both Cd and herbivory conditions, male seedlings showed a 68.1-fold increase in nitrogenous VOC emissions, almost twice the combined effects of Cd (8.7-fold) and herbivory (26.3-fold). Taken together, these results suggest that soil metal pollution can boost herbivore-induced VOC emissions in a sex-specific manner, with potential implications for ecological interactions and atmospheric processes.