Application of Chlorophyll Fluorescence Analysis Technique in Studying the Response of Lettuce (Lactuca sativa L.) to Cadmium Stress.

To reveal the impact of cadmium stress on the physiological mechanism of lettuce, simultaneous determination and correlation analyses of chlorophyll content and photosynthetic function were conducted using lettuce seedlings as the research subject. The changes in relative chlorophyll content, rapid chlorophyll fluorescence induction kinetics curve, and related chlorophyll fluorescence parameters of lettuce seedling leaves under cadmium stress were detected and analyzed. Furthermore, a model for estimating relative chlorophyll content was established. The results showed that cadmium stress at 1 mg/kg and 5 mg/kg had a promoting effect on the relative chlorophyll content, while cadmium stress at 10 mg/kg and 20 mg/kg had an inhibitory effect on the relative chlorophyll content. Moreover, with the extension of time, the inhibitory effect became more pronounced. Cadmium stress affects both the donor and acceptor sides of photosystem II in lettuce seedling leaves, damaging the electron transfer chain and reducing energy transfer in the photosynthetic system. It also inhibits water photolysis and decreases electron transfer efficiency, leading to a decline in photosynthesis. However, lettuce seedling leaves can mitigate photosystem II damage caused by cadmium stress through increased thermal dissipation. The model established based on the energy captured by a reaction center for electron transfer can effectively estimate the relative chlorophyll content of leaves. This study demonstrates that chlorophyll fluorescence techniques have great potential in elucidating the physiological mechanism of cadmium stress in lettuce, as well as in achieving synchronized determination and correlation analyses of chlorophyll content and photosynthetic function.

Engineering High-Tortuosity 3D Gradient Structure and CFD-Assisted Multifield Analysis for Solar Interfacial Evaporation.

Solar interfacial evaporation is a promising method for solving the global shortage of fresh water. While 2D evaporators can efficiently localize solar-converted heat at the thin layer of the water-air interface, 3D solar evaporators can maximize energy reutilization while maintaining effective mass transport ability, few studies are conducted to explore the effect of gradient porosity on evaporation performance. In this study, a multifield assisted strategy based on a gradient 3D structure with high tortuosity is proposed, which creates a thermal field environment for efficient evaporation through high absorption of sunlight and excellent photothermal conversion and uses the gradient structure to optimize the internal pressure field to enhance water evaporation and transport. This hierarchically nanostructured solar absorber, with porosity inhomogeneity-induced pressure gradient and optimized temperature management, is a valuable design idea for manufacturing a more efficient 3D solar evaporator in the field of seawater desalination. Owing to the understanding of optimizing the dimension by various simulation parameters, the evaporation efficiencies of such structures are found to be 165.7%, suppressing the most evaporator. Moreover, it can provide new ideas and references for the fields of mass transfer and thermal management.

UGT89AC1-mediated quercetin glucosylation is induced upon herbivore damage and enhances Camellia sinensis resistance to insect feeding.

Quercetin is a key flavonol in tea plants (Camellia sinensis (L.) O. Kuntze) with various health benefits, and it often occurs in the form of glucosides. The roles of quercetin and its glucosylated forms in plant defense are generally not well-studied, and remain unknown in the defense of tea. Here, we found higher contents of quercetin glucosides and a decline of the aglucone upon Ectropis grisescens (E. grisescens) infestation of tea. Nine UGTs were strongly induced, among which UGT89AC1 exhibited the highest activity toward quercetin in vitro and in vivo. The mass of E. grisescens larvae that fed on plants with repressed UGT89AC1 or varieties with lower levels of UGT89AC1 was significantly lower than that of larvae fed on controls. Artificial diet supplemented with quercetin glucoside also reduced the larval growth rate, whereas artificial diet supplemented with free quercetin had no significant effect on larval growth. UGT89AC1 was located in both the cytoplasm and nucleus, and its expression was modulated by JA, JA-ILE, and MeJA. These findings demonstrate that quercetin glucosylation serves a defensive role in tea against herbivory. Our results also provide novel insights into the ecological relevance of flavonoid glycosides under biotic stress in plants.

Analyses of Multilocus Sequences and Morphological Features Reveal Ilyonectria Species Associated with Black Rot Disease of Gastrodia elata.

Black rot is a common disease of Gastrodia elata, causing serious threats to G. elata production. In this study, a total of 17 Cylindrocarpon-like strains were isolated from G. elata black rot tissues. Multilocus sequence analyses based on ITS, HIS, TEF, and TUB combined with morphological characterizations were performed to identify six Ilyonectria species, including four new species, Ilyonectria longispora, I. sinensis, I. xiaocaobaensis, and I. yunnanensis, and two known species, I. changbaiensis and I. robusta. The pathogenicity of 11 isolates comprising type strains of the four new species and representative isolates from each of the six species was tested on healthy tissues of G. elata. All isolates were pathogenic to G. elata tissues, and symptoms were identical to black rot disease, confirming that our isolates were the causal agents of black rot disease of G. elata.

Multi-genome comprehensive identification of SSR/SV and development of molecular markers database to serve Sorghum bicolor (L.) breeding.

BACKGROUND: As an important food and cash crop, identification of DNA molecular markers is of great significance for molecular marker-assisted breeding of Sorghum (Sorghum bicolor (L.) moench). Although some sorghum-related mutation databases have been published, the special SSR and SV databases still need to be constructed and updated. RESULTS: In this study, the quality of 18 different sorghum genomes was evaluated, and two genomes were assembled at chromosome level. Through the identification and comparative analysis of SSR loci in these genomes, the distribution characteristics of SSR in the above sorghum genomes were initially revealed. At the same time, five representative reference genomes were selected to identify the structural variation of sorghum. Finally, a convenient SSR/SV database of sorghum was constructed by integrating the above results ( http://www.sorghum.top:8079/ ; http://43.154.129.150:8079/ ; http://47.106.184.91:8079/ ). Users can query the information of related sites and primer pairs. CONCLUSIONS: Anyway, our research provides convenience for sorghum researchers and will play an active role in sorghum molecular marker-assisted breeding.

A geraniol synthase regulates plant defense via alternative splicing in tea plants.

Geraniol is an important contributor to the pleasant floral scent of tea products and one of the most abundant aroma compounds in tea plants; however, its biosynthesis and physiological function in response to stress in tea plants remain unclear. The proteins encoded by the full-length terpene synthase (CsTPS1) and its alternative splicing isoform (CsTPS1-AS) could catalyze the formation of geraniol when GPP was used as a substrate in vitro, whereas the expression of CsTPS1-AS was only significantly induced by Colletotrichum gloeosporioides and Neopestalotiopsis sp. infection. Silencing of CsTPS1 and CsTPS1-AS resulted in a significant decrease of geraniol content in tea plants. The geraniol content and disease resistance of tea plants were compared when CsTPS1 and CsTPS1-AS were silenced. Down-regulation of the expression of CsTPS1-AS reduced the accumulation of geraniol, and the silenced tea plants exhibited greater susceptibility to pathogen infection than control plants. However, there was no significant difference observed in the geraniol content and pathogen resistance between CsTPS1-silenced plants and control plants in the tea plants infected with two pathogens. Further analysis showed that silencing of CsTPS1-AS led to a decrease in the expression of the defense-related genes PR1 and PR2 and SA pathway-related genes in tea plants, which increased the susceptibility of tea plants to pathogens infections. Both in vitro and in vivo results indicated that CsTPS1 is involved in the regulation of geraniol formation and plant defense via alternative splicing in tea plants. The results of this study provide new insights into geraniol biosynthesis and highlight the role of monoterpene synthases in modulating plant disease resistance via alternative splicing.

Two new Trichoderma species (Hypocreales, Hypocreaceae) isolated from decaying tubers of Gastrodiaelate.

Species of Trichoderma are widely distributed around the world. In this study, two new species in Trichoderma, named as T.albidum and T.variegatum, were introduced and illustrated. These species were isolated from diseased tubers of Gastrodiaelata in China and identified based on morphological characteristics and multi-gene sequence analyses of three loci that is the internal transcribed spacer regions of the ribosomal DNA (ITS), the translation elongation factor 1-α encoding gene (tef1-α) and the gene encoding the second largest nuclear RNA polymerase subunit (rpb2). Distinctions between the new species and their close relatives were discussed. According to results of the phylogenetic analyses, T.albidum belonged to the Harzianum clade and T.variegatum are grouped with species of the Spirale clade. The expansion of two clades provided research foundations for the prevention and control of tuber diseases in G.elata.

Volatile compound-mediated plant-plant interactions under stress with the tea plant as a model.

Plants respond to environmental stimuli via the release of volatile organic compounds (VOCs), and neighboring plants constantly monitor and respond to these VOCs with great sensitivity and discrimination. This sensing can trigger increased plant fitness and reduce future plant damage through the priming of their own defenses. The defense mechanism in neighboring plants can either be induced by activation of the regulatory or transcriptional machinery, or it can be delayed by the absorption and storage of VOCs for the generation of an appropriate response later. Despite much research, many key questions remain on the role of VOCs in interplant communication and plant fitness. Here we review recent research on the VOCs induced by biotic (i.e. insects and pathogens) and abiotic (i.e. cold, drought, and salt) stresses, and elucidate the biosynthesis of stress-induced VOCs in tea plants. Our focus is on the role of stress-induced VOCs in complex ecological environments. Particularly, the roles of VOCs under abiotic stress are highlighted. Finally, we discuss pertinent questions and future research directions for advancing our understanding of plant interactions via VOCs.

(Z)-3-Hexenol integrates drought and cold stress signaling by activating abscisic acid glucosylation in tea plants.

Cold and drought stresses severely limit crop production and can occur simultaneously. Although some transcription factors and hormones have been characterized in plants subjected each stress, the role of metabolites, especially volatiles, in response to cold and drought stress exposure is rarely studied due to lack of suitable models. Here, we established a model for studying the role of volatiles in tea (Camellia sinensis) plants experiencing cold and drought stresses simultaneously. Using this model, we showed that volatiles induced by cold stress promote drought tolerance in tea plants by mediating reactive oxygen species and stomatal conductance. Needle trap microextraction combined with GC-MS identified the volatiles involved in the crosstalk and showed that cold-induced (Z)-3-hexenol improved the drought tolerance of tea plants. In addition, silencing C. sinensis alcohol dehydrogenase 2 (CsADH2) led to reduced (Z)-3-hexenol production and significantly reduced drought tolerance in response to simultaneous cold and drought stress. Transcriptome and metabolite analyses, together with plant hormone comparison and abscisic acid (ABA) biosynthesis pathway inhibition experiments, further confirmed the roles of ABA in (Z)-3-hexenol-induced drought tolerance of tea plants. (Z)-3-Hexenol application and gene silencing results supported the hypothesis that (Z)-3-hexenol plays a role in the integration of cold and drought tolerance by stimulating the dual-function glucosyltransferase UGT85A53, thereby altering ABA homeostasis in tea plants. Overall, we present a model for studying the roles of metabolites in plants under multiple stresses and reveal the roles of volatiles in integrating cold and drought stresses in plants.

Genome-wide identification of the PYL gene family of tea plants (Camellia sinensis) revealed its expression profiles under different stress and tissues.

BACKGROUND: PYL (Pyrabactin resistance 1-like) protein is a receptor of abscisic acid (ABA), which plays an important role in ABA signaling and influences plant growth and development and stress response. However, studies on PYL gene family in tea plants have not been reported. RESULTS: In this study, we identified 20 PYL genes from the reference genome of tea plant ('Shuchazao'). Phylogeny analysis indicated that PYLs from tea and other plant species were clustered into seven groups. The promoter region of PYL genes contains a large number of cis-elements related to hormones and stresses. A large number of PYL genes responding to stress were found by analyzing the expression levels of abiotic stress and biotic stress transcriptome data. For example, CSS0047272.1 were up-regulated by drought stress, and CSS0027597.1 could respond to both anthracnose disease and geometrid feeding treatments. In addition, 10 PYL genes related to growth and development were verified by RT-qPCR and their tissue expression characteristics were revealed. CONCLUSIONS: Our results provided a comprehensive characteristic of the PYL gene family in tea plants and provided an important clue for further exploring its functions in the growth and development, and resistance to stress of tea plants.

Apocarotenoids are allosteric effectors of a dimeric plant glycosyltransferase involved in defense and lignin formation.

Glycosyltransferases are nature's versatile tools to tailor the functionalities of proteins, carbohydrates, lipids, and small molecules by transferring sugars. Prominent substrates are hydroxycoumarins such as scopoletin, which serve as natural plant protection agents. Similarly, C13-apocarotenoids, which are oxidative degradation products of carotenoids/xanthophylls, protect plants by repelling pests and attracting pest predators. We show that C13-apocarotenoids interact with the plant glycosyltransferase NbUGT72AY1 and induce conformational changes in the enzyme catalytic center ultimately reducing its inherent UDP-α-d-glucose glucohydrolase activity and increasing its catalytic activity for productive hydroxycoumarin substrates. By contrast, C13-apocarotenoids show no effect on the catalytic activity toward monolignol lignin precursors, which are competitive substrates. In vivo studies in tobacco plants (Nicotiana benthamiana) confirmed increased glycosylation activity upon apocarotenoid supplementation. Thus, hydroxycoumarins and apocarotenoids represent specialized damage-associated molecular patterns, as they each provide precise information about the plant compartments damaged by pathogen attack. The molecular basis for the C13-apocarotenoid-mediated interplay of two plant protective mechanisms and their function as allosteric enhancers opens up potential applications of the natural products in agriculture and pharmaceutical industry.

Application of Carbon Fiber-Reinforced Ceramic Composites in Active Thermal Protection of Advanced Propulsion Systems: A Review.

Thermal protection is one of the crucial issues for the advanced propulsion systems of Reusable Launch Vehicles. New service requirements for materials, such as high strength, low density, low thermal expansion, high thermal stability, etc., are raised for the thermal structure with the increasing demand of flight Mach numbers and thrust-to-weight ratio. Carbon fiber-reinforced ceramic composites, which generally meet the aforementioned requirements, show great potential for various applications and they have been widely applied in the thermal protection for hypersonic vehicles. This paper gives a comprehensive and systematic review of current research status for carbon fiber-reinforced ceramic composites applied in the thermal structure of advanced propulsion systems. Three aspects are presented and discussed: the ceramic composites fabrication and the property characterization, the thermal performance of composite thermal structure used in practical engines, and the numerical methods for predicting mechanical and thermal properties of composites as well as the physicochemical phenomenon in the cooling channels. Firstly, the main manufacturing processes for the carbon-reinforced ceramic composites are presented and the corresponding advantages and disadvantages are analyzed. The high-temperature oxidation and ablation behaviors of composites are demonstrated and the improvement of oxidation and ablation resistance by introducing the ultra-high-temperature ceramics into C/C composites is discussed in detail. Then, several typical applications of carbon fiber-reinforced ceramic composites (mainly C/SiC), including the work of RCI, JAXA and NASA, have been reviewed and analyzed. After that, the current research status of macroscale equivalent and multiscale numerical methods for predicting the mechanical and thermal properties of composites as well as the complex physicochemical phenomenon occurring in hydrocarbon fuels are sorted out. Finally, several potential prospects are pointed out for the future research on the thermal protection of advanced propulsion systems based on the carbon fiber-reinforced ceramic composites.

Identification of gene family members and a key structural variation reveal important roles of OVATE genes in regulating tea (Camellia sinensis) leaf development.

OVATE genes are a new class of transcriptional repressors with important regulatory roles in plant growth and development. Through genome-wide analysis of the OVATE gene family of tea plants, 26 and 13 family members were identified in cultivated and ancient tea plants, respectively. Syntenic results showed that OVATE gene family in cultivated tea plants may have experienced a special expansion event. Based on phylogenetic tree analysis, all OVATE genes were divided into four groups, and the third group had the largest number, reaching 16. Transcriptome data from different organs and populations indicated that many OVATE family members were highly expressed in young shoots and leaves, and their expression levels gradually decreased as tea leaves developed. Finally, the expression trends of the six key candidate genes were verified by RT-qPCR, which were consistent with the transcriptome results, indicating that the ovate gene family plays an important role in regulating the process of tea leaf development. In addition, we identified a key structural variation with a length of 184 bp, and the population genotyping showed that it was closely related to the area of tea leaves. Our research provides an important clue for further exploring the function of ovate gene family in tea plants and the development mechanism of tea leaves.

Effects of Boric Acid Gel on Vaginal Candida albicans Infections and the Local Immune System in Mice.

The objective was to determine the effect of 5% boric acid gel on vaginal Candida albicans (CA) infections in mice and its effect on the local immune system (i.e., Th1, Th2, and Th17). Female mice were divided into four groups, with 10 mice in each group. Mycelial suspensions were administered into the vaginal lumen close to the cervix in groups B, F, and M. Mice in group B were given boric acid gel, and group F was treated with fluconazole gel for 30 min every 12 h. Group M was treated with sterile water, and group N was not given treatment. After the seventh day of treatment, each group was observed with the naked eye, and vaginal lavage fluid and vaginal tissue were collected. Expression levels of cytokines were measured using enzyme-linked immunosorbent assays (ELISA) and immunohistochemistry. Periodic acid Schiff (PAS) staining was used to measure the fungi in vaginal tissues. There were no significant changes in group M. In groups B and F, there was less vaginal injury and less exudate, with group B doing better than group F. The numbers of CA colonies were higher in groups B, F, and M than in group N (P < 0.01). There was less vaginal colonization of CA in group B than in group F (P < 0.01). After the seventh day of treatment, levels of IFN-γ, IL-17, IL-6, TGF-ß, IL-4, and IL-10 were significantly greater in groups B, F, and M than in group N (P < 0.001); levels of IFN-γ, IL-17, IL-6, and TGF-ß in groups B and F were higher than those of group M (P < 0.01), while IL-4 and IL-10 levels were significantly lower (P < 0.001). The trends of cytokine increases and decreases were more significant in group B than in group F (P < 0.05). Immunohistochemical results were similar to ELISA results. PAS staining revealed that boric acid inhibited hyphal reproduction. The boric acid significantly reduced the symptoms associated with CA vaginal infection. It inhibited the CA growth, prevented vaginal lesions, promoted the secretion of Th1 and Th17 cytokines, and reduced Th2 cytokines.

The epigenetic regulator ULTRAPETALA1 suppresses de novo root regeneration from Arabidopsis leaf explants.

Plants have the potency to regenerate adventitious roots from aerial organs after detachment. In Arabidopsis thaliana, de novo root regeneration (DNRR) from leaf explants is triggered by wounding signaling that rapidly induces the expression of the ETHYLENE RESPONSE FACTOR (ERF) transcription factors ERF109 and ABR1 (ERF111). In turn, the ERFs promote the expression of ASA1, an essential enzyme of auxin biosynthesis, which contributes to rooting by providing high levels of auxin near the wounding side of the leaf. Here, we show that the loss of the epigenetic regulator ULTRAPETALA1 (ULT1), which interacts with Polycomb and Trithorax Group proteins, accelerates and reinforces adventitious root formation. Expression of ERF109 and ASA1 was increased in ult1 mutants, whereas ABR1 was not significantly changed. Cultivation of explants on media with exogenous auxin equates adventitious root formation in wild-type with ult1 mutants, suggesting that ULT1 negatively regulates DNRR by suppressing auxin biosynthesis. Based on these findings, we propose that ULT1 is involved in a novel mechanism that prevents overproliferation of adventitious roots during DNRR.

Polycomb proteins control floral determinacy by H3K27me3-mediated repression of pluripotency genes in Arabidopsis thaliana.

Polycomb group (PcG) protein-mediated histone methylation (H3K27me3) controls the correct spatiotemporal expression of numerous developmental regulators in Arabidopsis. Epigenetic silencing of the stem cell factor gene WUSCHEL (WUS) in floral meristems (FMs) depends on H3K27me3 deposition by PcG proteins. However, the role of H3K27me3 in silencing of other meristematic regulator and pluripotency genes during FM determinacy has not yet been studied. To this end, we report the genome-wide dynamics of H3K27me3 levels during FM arrest and the consequences of strongly depleted PcG activity on early flower morphogenesis including enlarged and indeterminate FMs. Strong depletion of H3K27me3 levels results in misexpression of the FM identity gene AGL24, which partially causes floral reversion leading to ap1-like flowers and indeterminate FMs ectopically expressing WUS and SHOOT MERISTEMLESS (STM). Loss of STM can rescue supernumerary floral organs and FM indeterminacy in H3K27me3-deficient flowers, indicating that the hyperactivity of the FMs is at least partially a result of ectopic STM expression. Nonetheless, WUS remained essential for the FM activity. Our results demonstrate that PcG proteins promote FM determinacy at multiple levels of the floral gene regulatory network, silencing initially floral regulators such as AGL24 that promotes FM indeterminacy and, subsequently, meristematic pluripotency genes such as WUS and STM during FM arrest.

Eugenol functions as a signal mediating cold and drought tolerance via UGT71A59-mediated glucosylation in tea plants.

Cold and drought stress are the most critical stresses encountered by crops and occur simultaneously under field conditions. However, it is unclear whether volatiles contribute to both cold and drought tolerance, and if so, by what mechanisms they act. Here, we show that airborne eugenol can be taken up by the tea (Camellia sinensis) plant and metabolized into glycosides, thus enhancing cold and drought tolerance of tea plants. A uridine diphosphate (UDP)-glucosyltransferase, UGT71A59, was discovered, whose expression is strongly induced by multiple abiotic stresses. UGT71A59 specifically catalyzes glucosylation of eugenol glucoside in vitro and in vivo. Suppression of UGT71A59 expression in tea reduced the accumulation of eugenol glucoside, lowered reactive oxygen species (ROS) scavenging capacity, and ultimately impaired cold and drought stress tolerance. Exposure to airborne eugenol triggered a marked increase in UGT71A59 expression, eugenol glucoside accumulation, and cold tolerance by modulating ROS accumulation and CBF1 expression. It also promoted drought tolerance by altering abscisic acid homeostasis and stomatal closure. CBF1 and CBF3 play positive roles in eugenol-induced cold tolerance and CBF2 may be a negative regulator of eugenol-induced cold tolerance in tea plants. These results provide evidence that eugenol functions as a signal in cold and drought tolerance regulation and shed new light on the biological functions of volatiles in the response to multiple abiotic stresses in plants.

Salicylic acid carboxyl glucosyltransferase UGT87E7 regulates disease resistance in Camellia sinensis.

Plant immune response following pathogenic infection is regulated by plant hormones, and salicylic acid (SA) and its sugar conjugates play important roles in establishing basal resistance. Here, the important pathogen Pseudopestalotiopsis camelliae-sinensis (Pcs) was isolated from tea gray blight, one of the most destructive diseases in tea plantations. Transcriptomic analysis led to the discovery of the putative Camellia sinensis UDP-glucosyltransferase CsUGT87E7 whose expression was significantly induced by SA application and Pcs infection. Recombinant CsUGT87E7 glucosylates SA with a Km value of 12 µM to form SA glucose ester (SGE). Downregulation reduced the accumulation of SGE, and CsUGT87E7-silenced tea plants exhibited greater susceptibility to pathogen infection than control plants. Similarly, CsUGT87E7-silenced tea leaves accumulated significantly less SA after infection and showed reduced expression of pathogenesis-related genes. These results suggest that CsUGT87E7 is an SA carboxyl glucosyltransferase that plays a positive role in plant disease resistance by modulating SA homeostasis through a mechanism distinct from that described in Arabidopsis (Arabidopsis thaliana). This study provides insight into the mechanisms of SA metabolism and highlights the role of SGE in the modulation of plant disease resistance.