Transmission of Areca Palm Velarivirus 1 by Mealybugs Causes Yellow Leaf Disease in Betel Palm (Areca catechu).

Yellow leaf disease (YLD) is the most destructive disease of betel palm (Areca catechu). A strong association between YLD and areca palm velarivirus 1 (APV1) has been observed. However, the causal relationship between APV1 and disease, and the transmission mode, warrant further investigation. This work showed that APV1 was transmitted by both Ferrisia virgata and Pseudococcus cryptus mealybugs and caused YLD symptoms in betel palm seedlings; therefore, we demonstrate that APV1 is a causal agent of YLD. APV1 was detected in the stylets, foreguts, midguts, and hindguts of the vectors via both immunocapture reverse transcription PCR and immunofluorescence assays. APV1 was not transmitted transovarially from viruliferous female F. virgata to their progeny. In summary, the transmission of APV1 by F. virgata may occur in a noncirculative, semipersistent manner. This study fills important gaps in our knowledge of velarivirus transmission, which is critical for developing YLD management practices.

Genomic diversity of Areca Palm Velarivirus 1 (APV1) in Areca palm (Areca catechu) plantations in Hainan, China.

BACKGROUND: Areca palm (Areca catechu L.) is an important commercial crop in southeast Asia, but its cultivation is threatened by yellowing leaf disease (YLD). Areca palm velarivirus 1 (APV1) was recently associated with YLD, but little is known regarding its population and genetic diversity. To assess the diversity of YLD, the APV1 genome was sequenced in YLD samples collected from different sites in Hainan. RESULTS: Twenty new and complete APV1 genomes were identified. The APV1 isolates had highly conserved sequences in seven open reading frames (ORFs; > 95% nucleotide [nt] identity) at the 3' terminal, but there was diversity (81-87% nt identity) in three ORFs at the 5' terminal. Phylogenetic analysis divided the APV1 isolates into three phylogroups, with 16 isolates (> 70%) in phylogroup A. Mixed infections with different genotypes in the same tree were identified; this was closely correlated with higher levels of genetic recombination. CONCLUSIONS: Phylogroup A is the most prevalent APV1 genotype in areca palm plantations in Hainan, China. Mixed infection with different genotypes can lead to genomic recombination of APV1. Our data provide a foundation for accurate diagnostics, characterization of etiology, and elucidation of the evolutionary relationships of APV1 populations.

Functional characterisation of Dof gene family and expression analysis under abiotic stresses and melatonin-mediated tolerance in pitaya (Selenicereus undatus).

DNA binding proteins with one finger (Dof ) transcription factors are essential for seed development and defence against various biotic and abiotic stresses in plants. Genomic analysis of Dof has not been determined yet in pitaya (Selenicereus undatus ). In this study, we have identified 26 Dof gene family members, renamed as HuDof-1 to HuDof-26 , and clustered them into seven subfamilies based on conserved motifs, domains, and phylogenetic analysis. The gene pairs of Dof family members were duplicated by segmental duplications that faced purifying selection, as indicated by the K a /K s ratio values. Promoter regions of HuDof genes contain many cis -acting elements related to phytohormones including abscisic acid, jasmonic acid, gibberellin, temperature, and light. We exposed pitaya plants to different environmental stresses and examined melatonin's influence on Dof gene expression levels. Signifcant expression of HuDof -2 and HuDof -6 were observed in different developmental stages of flower buds, flowers, pericarp, and pulp. Pitaya plants were subjected to abiotic stresses, and transcriptome analysis was carried out to identify the role of Dof gene family members. RNA-sequencing data and reverse transcription quantitative PCR-based expression analysis revealed three putative candidate genes (HuDof -1, HuDof -2, and HuDof -8), which might have diverse roles against the abiotic stresses. Our study provides a theoretical foundation for functional analysis through traditional and modern biotechnological tools for pitaya trait improvement.

Genome-Wide Investigation of Class III Peroxidase Genes in Brassica napus Reveals Their Responsiveness to Abiotic Stresses.

Brassica napus (B. napus) is susceptible to multiple abiotic stresses that can affect plant growth and development, ultimately reducing crop yields. In the past, many genes that provide tolerance to abiotic stresses have been identified and characterized. Peroxidase (POD) proteins, members of the oxidoreductase enzyme family, play a critical role in protecting plants against abiotic stresses. This study demonstrated a comprehensive investigation of the POD gene family in B. napus. As a result, a total of 109 POD genes were identified across the 19 chromosomes and classified into five distinct subgroups. Further, 44 duplicate events were identified; of these, two gene pairs were tandem and 42 were segmental. Synteny analysis revealed that segmental duplication was more prominent than tandem duplication among POD genes. Expression pattern analysis based on the RNA-seq data of B. napus indicated that BnPOD genes were expressed differently in various tissues; most of them were expressed in roots rather than in other tissues. To validate these findings, we performed RT-qPCR analysis on ten genes; these genes showed various expression levels under abiotic stresses. Our findings not only furnish valuable insights into the evolutionary dynamics of the BnPOD gene family but also serve as a foundation for subsequent investigations into the functional roles of POD genes in B. napus.

Effect of temperature on yellow leaf disease symptoms and its associated areca palm velarivirus 1 titer in areca palm (Areca catechu L.).

Yellow leaf disease (YLD) has been a major limiting factor threatening areca palm commonly known as betel palm (Areca catechu L.) plantations in Hainan, China. The YLD disease is closely associated with areca palm velarivirus 1 (APV1), which belongs to the family Closteroviridae. YLD-affected betel palms show more serious yellowing symptoms in winter than in summer based on anecdotal observations. In the present work, the underlying mechanism was investigated. We first observed that the severity of YLD symptoms was closely related with the APV1 viral titer determined by qRT-PCR and ELISA under natural conditions. To further investigate whether temperature plays a key role in APV1 accumulation, the areca palm seedlings were artificially inoculated with APV1-positive mealybugs (Ferrisia virgata) and then cultivated under controlled conditions. According to our results, the YLD symptoms severity in inoculated seedlings were closely associated with temperature, e.g., severest symptoms at low temperature (16/22 ± 2°C, night/day), severer symptoms at room temperature (24/26 ± 2°C, night/day), while moderate symptoms at high temperature (27/34 ± 2°C, night/day). The qRT-PCR and ELISA results showed that APV1 titer accumulates significantly abundant at low temperature as compared to high and room temperatures. In conclusion, this is the first report about the temperature effects on the symptoms severity of YLD and APV1 titer, which may have important implications for the epidemiology of YLD.

Silicon-mediated metabolic upregulation of ascorbate glutathione (AsA-GSH) and glyoxalase reduces the toxic effects of vanadium in rice.

Although beneficial metalloid silicon (Si) has been proven to reduce the toxicity of several heavy metals, there is a lack of understanding regarding Si potential function in mitigating phytotoxicity induced by vanadium (V). In this study, effect of Si (1.5 mM) on growth, biomass production, V uptake, reactive oxygen species (ROS), methylglyoxal (MG) formation, selected antioxidants enzymes activities, glyoxalase enzymes under V stress (35 mg L-1) was investigated in hydroponic experiment. The results showed that V stress reduced rice growth, caused V accumulation in rice. Addition of Si to the nutritional medium increased plant growth, biomass yield, root length, root diameter, chlorophyll parameters, photosynthetic assimilation, ion leakage, antioxidant enzymes activities under V stress. Notably, Si sustained V-homeostasis and alleviated V caused oxidative stress by boosting ascorbate (AsA) levels and the activity of antioxidant enzymes in V stressed rice plants. Furthermore, Si protected rice seedlings against the harmful effects of methylglyoxal by increasing the activity of glyoxalase enzymes. Additionally, Si increased the expression of numerous genes involved in the detoxification of reactive oxygen species (e.g., OsCuZnSOD1, OsCaTB, OsGPX1, OsAPX1, OsGR2, and OsGSTU37) and methylglyoxal (e.g., OsGLYI-1 and OsGLYII-2). The findings supported that Si can be applied to plants to minimize the V availability to plant, and also induced V stress tolerance.

Genome-Wide Identification and Expression Pattern of the GRAS Gene Family in Pitaya (Selenicereus undatus L.).

The GRAS gene family is one of the most important families of transcriptional factors that have diverse functions in plant growth and developmental processes including axillary meristem patterning, signal-transduction, cell maintenance, phytohormone and light signaling. Despite their importance, the function of GRAS genes in pitaya fruit (Selenicereus undatus L.) remains unknown. Here, 45 members of the HuGRAS gene family were identified in the pitaya genome, which was distributed on 11 chromosomes. All 45 members of HuGRAS were grouped into nine subfamilies using phylogenetic analysis with six other species: maize, rice, soybeans, tomatoes, Medicago truncatula and Arabidopsis. Among the 45 genes, 12 genes were selected from RNA-Seq data due to their higher expression in different plant tissues of pitaya. In order to verify the RNA-Seq data, these 12 HuGRAS genes were subjected for qRT-PCR validation. Nine HuGRAS genes exhibited higher relative expression in different tissues of the plant. These nine genes which were categorized into six subfamilies inlcuding DELLA (HuGRAS-1), SCL-3 (HuGRAS-7), PAT1 (HuGRAS-34, HuGRAS-35, HuGRAS-41), HAM (HuGRAS-37), SCR (HuGRAS-12) and LISCL (HuGRAS-18, HuGRAS-25) might regulate growth and development in the pitaya plant. The results of the present study provide valuable information to improve tropical pitaya through a molecular and conventional breeding program.

Wide visible-range activatable fluorescence ZnSe:Eu3+/Mn2+@ZnS quantum dots: local atomic structure order and application as a nanoprobe for bioimaging.

The development of QDs-based fluorescent bionanoprobe for cellular imaging fundamentally relies upon the precise knowledge of particle-cell interaction, optical properties of QDs inside and outside of the cell, movement of a particle in and out of the cell, and the fate of particle. We reported engineering and physicochemical characterization of water-dispersible Eu3+/Mn2+ co-doped ZnSe@ZnS core/shell QDs and studied their potential as a bionanoprobe for biomedical applications, evaluating their biocompatibility, fluorescence behaviour by CytoViva dual mode fluorescence imaging, time-dependent uptake, endocytosis and exocytosis in RAW 264.7 macrophages. The oxidation state and local atomic structure of the Eu dopant studied by X-ray absorption fine structure (XAFS) analysis manifested that the Eu3+ ions occupied sites in both ZnSe and ZnS lattices for the core/shell QDs. A novel approach was developed to relieve the excitation constraint of wide bandgap ZnSe by co-incorporation of Eu3+/Mn2+ codopants, enabling the QDs to be excited at a wide UV-visible range. The QDs displayed tunable emission colors by a gradual increase in Eu3+ concentration at a fixed amount of Mn2+, systematically enhancing the Mn2+ emission intensity via energy transfer from the Eu3+ to Mn2+ ion. The ZnSe:Eu3+/Mn2+@ZnS QDs presented high cell viability above 85% and induced no cell activation. The detailed analyses of QDs-treated cells by dual mode fluorescence CytoViva microscopy confirmed the systematic color-tunable fluorescence and its intensity enhances as a function of incubation time. The QDs were internalized by the cells predominantly via macropinocytosis and other lipid raft-mediated endocytic pathways, retaining an efficient amount for 24 h. The unique color tunability and consistent high intensity emission make these QDs useful for developing a multiplex fluorescent bionanoprobe, activatable in wide-visible region.

Melatonin Improves Drought Stress Tolerance of Tomato by Modulating Plant Growth, Root Architecture, Photosynthesis, and Antioxidant Defense System.

Tomato is an important vegetable that is highly sensitive to drought (DR) stress which impairs the development of tomato seedlings. Recently, melatonin (ME) has emerged as a nontoxic, regulatory biomolecule that regulates plant growth and enhances the DR tolerance mechanism in plants. The present study was conducted to examine the defensive role of ME in photosynthesis, root architecture, and the antioxidant enzymes' activities of tomato seedlings subjected to DR stress. Our results indicated that DR stress strongly suppressed growth and biomass production, inhibited photosynthesis, negatively affected root morphology, and reduced photosynthetic pigments in tomato seedlings. Per contra, soluble sugars, proline, and ROS (reactive oxygen species) were suggested to be improved in seedlings under DR stress. Conversely, ME (100 µM) pretreatment improved the detrimental-effect of DR by restoring chlorophyll content, root architecture, gas exchange parameters and plant growth attributes compared with DR-group only. Moreover, ME supplementation also mitigated the antioxidant enzymes [APX (ascorbate peroxidase), CAT (catalase), DHAR (dehydroascorbate reductase), GST (glutathione S-transferase), GR (glutathione reductase), MDHAR (monodehydroascorbate reductase), POD (peroxidase), and SOD (superoxide dismutase)], non-enzymatic antioxidant [AsA (ascorbate), DHA (dehydroascorbic acid), GSH (glutathione), and GSSG, (oxidized glutathione)] activities, reduced oxidative damage [EL (electrolyte leakage), H2O2 (hydrogen peroxide), MDA (malondialdehyde), and O2•- (superoxide ion)] and osmoregulation (soluble sugars and proline) of tomato seedlings, by regulating gene expression for SOD, CAT, APX, GR, POD, GST, DHAR, and MDHAR. These findings determine that ME pretreatment could efficiently improve the seedlings growth, root characteristics, leaf photosynthesis and antioxidant machinery under DR stress and thereby increasing the seedlings' adaptability to DR stress.

Hybrid magneto-luminescent iron oxide nanocubes functionalized with europium complexes: synthesis, hemolytic properties and protein corona formation.

The use of hybrid nanostructures based on magneto-luminescent properties is a promising strategy for nano-bio applications and theranostics platforms. In this work, we carried out the synthesis and functionalization of iron oxide nanocubes (IONCs) to obtain multifunctional hybrid nanostructures towards biomedical applications. The IONCs were functionalized with tetraethylorthosilicate, thenoyltrifluoroacetone-propyl-triethoxysilane and europium(iii)-dibenzoylmethane complexes to obtain the materials termed as IOCNCs@SiO2, IONCs@SiO2TTA, IONCs@SiO2TTA-Eu and IONCs@SiO2-TTA-Eu-DBM, respectively. Then, the biological interactions of these nanostructures with red blood cells - RBCs (hemolysis) and human blood plasma (protein corona formation) were evaluated. The XPS spectrocopy and EDS chemical mapping analysis showed that each domain is homogeneously occupied in the hybrid material, with the magnetic core at the center and the luminescent domain on the surface of the hybrid nanomaterial with a core@shell like structure. Futhermore, after each functionalization step, the nanomaterial surface charge drastically changed, with critical impact on RBC lysis and corona formation. While IONCs@SiO2 and IONCs@SiO2-TTA-Eu-DBM showed hemolytic properties in a dose-dependent manner, the IONCs@SiO2TTA-Eu did not present any hemolytic effect up to 300 µg mL-1. Protein corona results showed a pattern of selective adsorption of proteins with each surface of the synthesized hybrid materials. However, as a general result, a suppression of hemolysis after protein corona formation in all tests was verified. Finally, this study provides a solid background for further applications of these hybrid magneto-luminescent materials containing new surface functionalities in the emerging field of medical nanobiotechnology.