Differential subgenome expression underlies biomass accumulation in allotetraploid Pennisetum giganteum.

BACKGROUND: Pennisetum giganteum (AABB, 2n = 4x = 28) is a C4 plant in the genus Pennisetum with origin in Africa but currently also grown in Asia and America. It is a crucial forage and potential energy grass with significant advantages in yield, stress resistance, and environmental adaptation. However, the mechanisms underlying these advantageous traits remain largely unexplored. Here, we present a high-quality genome assembly of the allotetraploid P. giganteum aiming at providing insights into biomass accumulation. RESULTS: Our assembly has a genome size 2.03 Gb and contig N50 of 88.47 Mb that was further divided into A and B subgenomes. Genome evolution analysis revealed the evolutionary relationships across the Panicoideae subfamily lineages and identified numerous genome rearrangements that had occurred in P. giganteum. Comparative genomic analysis showed functional differentiation between the subgenomes. Transcriptome analysis found no subgenome dominance at the overall gene expression level; however, differentially expressed homoeologous genes and homoeolog-specific expressed genes between the two subgenomes were identified, suggesting that complementary effects between the A and B subgenomes contributed to biomass accumulation of P. giganteum. Besides, C4 photosynthesis-related genes were significantly expanded in P. giganteum and their sequences and expression patterns were highly conserved between the two subgenomes, implying that both subgenomes contributed greatly and almost equally to the highly efficient C4 photosynthesis in P. giganteum. We also identified key candidate genes in the C4 photosynthesis pathway that showed sustained high expression across all developmental stages of P. giganteum. CONCLUSIONS: Our study provides important genomic resources for elucidating the genetic basis of advantageous traits in polyploid species, and facilitates further functional genomics research and genetic improvement of P. giganteum.

High-quality Fagopyrum esculentum genome provides insights into the flavonoid accumulation among different tissues and self-incompatibility.

Common buckwheat (Fagopyrum esculentum) and Tartary buckwheat (Fagopyrum tataricum), the two most widely cultivated buckwheat species, differ greatly in flavonoid content and reproductive mode. Here, we report the first high-quality and chromosome-level genome assembly of common buckwheat with 1.2 Gb. Comparative genomic analysis revealed that common buckwheat underwent a burst of long terminal repeat retrotransposons insertion accompanied by numerous large chromosome rearrangements after divergence from Tartary buckwheat. Moreover, multiple gene families involved in stress tolerance and flavonoid biosynthesis such as multidrug and toxic compound extrusion (MATE) and chalcone synthase (CHS) underwent significant expansion in buckwheat, especially in common buckwheat. Integrated multi-omics analysis identified high expression of catechin biosynthesis-related genes in flower and seed in common buckwheat and high expression of rutin biosynthesis-related genes in seed in Tartary buckwheat as being important for the differences in flavonoid type and content between these buckwheat species. We also identified a candidate key rutin-degrading enzyme gene (Ft8.2377) that was highly expressed in Tartary buckwheat seed. In addition, we identified a haplotype-resolved candidate locus containing many genes reportedly associated with the development of flower and pollen, which was potentially related to self-incompatibility in common buckwheat. Our study provides important resources facilitating future functional genomics-related research of flavonoid biosynthesis and self-incompatibility in buckwheat.

Emamectin benzoate induced enzymatic and transcriptional alternation in detoxification mechanism of predatory beetle Paederus fuscipes (Coleoptera: Staphylinidae) at the sublethal concentration.

In this study, the detoxification enzyme activity and the transcriptional profile changes in the second instar through RNA-sequencing technology due to emamectin benzoate (EB) were assessed. The cytochrome P450 monooxygenases (P450) enzyme activity was not altered by EB due to the change in concentration and exposure time in all treatments. The glutathione S-transferase (GST) enzyme was not considerably varying in all treatments, while exposure time significantly changed the enzyme activity. Results showed that the esterase (Ests) activity was elevated with the increasing concentrations and exposure time. Two libraries were generated, containing 107,767,542 and 108,142,289 clean reads for the samples treated with LC30 of EB and control. These reads were grouped into 218,070 transcripts and 38,097 unigenes. A total of 2257 differentially expressed genes (DEGs) were identified from these unigenes, of which 599 up-regulated and 1658 were down-regulated. The majority of these DEGs related to pesticides resistance were identified in numerous Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, e.g., steroid hormone biosynthesis, glutathione metabolism, drug metabolism-other enzymes, chemical carcinogenesis, pathways of cancer, metabolism of xenobiotics by cytochrome P450, drug metabolism of cytochrome P450, linoleic acid metabolism, retinol metabolism, and insect hormone biosynthesis. These pathways also shared the same genes as cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs), Esterase (Ests), UDP-glucosyltransferases (UGTs), and ATP-binding cassettes (ABCs). A heatmap analysis also showed that regulation of genes in a pathway causes a series of gene expression regulation in subsequent pathways. Our quantitative reverse transcription-PCR (qRT-PCR) results were consistent with the DEG's data of transcriptome analysis. The comprehensive transcriptome sequence resource attained through this study evidence that the EB induces significant modification in enzyme activity and transcriptome profile of Paederus fuscipes, which may enable more significant molecular underpinnings behind the insecticide-resistance mechanism for further investigations.

Heavy metals transported through a multi-trophic food chain influence the energy metabolism and immune responses of Cryptolaemus montrouzieri.

Contamination of environment with heavy metals is increasingly becoming an issue of major concern across the globe. Heavy metals are highly toxic to humans as well as other organisms of the ecosystem. The translocation of heavy metals from soil to predatory insects via multi-tophic food chains can influence the growth, reproduction, metabolism and innate immune systems of the predators. This study was performed to observe the changes in energy metabolism and immune responses of Cryptolaemus montrouzieri feeding on heavy metal (Cd, Pb, Ni and Zn) contaminated pink hibiscus mealybug (Dysmicoccus neobrevipes). The average concentrations of Cd, Pb, Ni and Zn in mealybugs used for feeding assays were 30.57, 32.64, 31.47 and 33.19 mg/kg, respectively. The results showed a significant increase in total protein, glycogen, cholesterol and triglycerides content of C. montrouzieri feeding on heavy metals contaminated mealybugs compared with control groups. The activities of endogenous enzymes (acid phosphatase and alkaline phosphatase) as well as antioxidant enzymes (SOD, POD and CAT) were significantly higher in beetles feeding on heavy metals contaminated mealybugs. Our results provide basic insight into the influences of heavy metals (Cd, Pb and Ni) on energy metabolism and the innate immune system of the insect predator (C. montrouzieri) in a multi-trophic food chain. Further research on genetic processes involved in the regulation of metabolism and innate immune system of C. montrouzieri is still needed.

The genome of okra (Abelmoschus esculentus) provides insights into its genome evolution and high nutrient content.

Okra (Abelmoschus esculentus) is an important vegetable crop with high nutritional value. However, the mechanism underlying its high nutrient content remains poorly understood. Here, we present a chromosome-scale genome of okra with a size of 1.19 Gb. Comparative genomics analysis revealed the phylogenetic status of A. esculentus, as well as whole-genome duplication (WGD) events that have occurred widely across the Malvaceae species. We found that okra has experienced three additional WGDs compared with the diploid cotton Gossypium raimondii, resulting in a large chromosome number (2n = 130). After three WGDs, okra has undergone extensive genomic deletions and retained substantial numbers of genes related to secondary metabolite biosynthesis and environmental adaptation, resulting in significant differences between okra and G. raimondii in the gene families related to cellulose synthesis. Combining transcriptomic and metabolomic analysis, we revealed the relationship between gene expression and metabolite content change across different okra developmental stages. Furthermore, the sinapic acid/S-lignin biosynthesis-related gene families have experienced remarkable expansion in okra, and the expression of key enzymes involved in the sinapic acid/S-lignin biosynthesis pathway vary greatly across developmental periods, which partially explains the differences in metabolite content across the different stages. Our study gains insights into the comprehensive evolutionary history of Malvaceae species and the genetic basis that underlies the nutrient content changes in okra, which will facilitate the functional study and genetic improvement of okra varieties.

Synthesis of Metarhizium anisopliae-Chitosan Nanoparticles and Their Pathogenicity against Plutella xylostella (Linnaeus).

Nanotechnology is increasingly being used in areas of pesticide production and pest management. This study reports the isolation and virulence of a new Metarhizium anisopliae isolate SM036, along with the synthesis and characterization of M. anisopliae-chitosan nanoparticles followed by studies on the efficacy of nanoparticles against Plutella xylostella. The newly identified strain proved pathogenic to P. xylostella under laboratory conditions. The characterization of M. anisopliae-chitosan nanoparticles through different analytical techniques showed the successful synthesis of nanoparticles. SEM and HRTEM images confirmed the synthesis of spherical-shaped nanoparticles; X-ray diffractogram showed strong peaks between 2θ values of 16-30°; and atomic force microscopy (AFM) analysis revealed a particle size of 75.83 nm for M. anisopliae-chitosan nanoparticles, respectively. The bioassay studies demonstrated that different concentrations of M. anisopliae-chitosan nanoparticles were highly effective against second instar P. xylostella under laboratory and semi-field conditions. These findings suggest that M. anisopliae-chitosan nanoparticles can potentially be used in biorational P. xylostella management programs.

Endophytic Isolates of Cordyceps fumosorosea to Enhance the Growth of Solanum melongena and Reduce the Survival of Whitefly (Bemisia tabaci).

This study reports the effects of seed treatment with Cordyceps fumosorosea on seed germination, growth, colonization of eggplant (Solanum melongena), and growth of Bemisia tabaci (feeding on fungal colonized eggplant leaves). Germination rates of eggplant seeds were similar among different treatments. The growth parameters such as root length, shoot length, and number of leaves) differed significantly after 15, 30, and 60 days of seed treatment. The total dry weight of eggplant in response to treatment with C. fumosorosea isolates increased significantly when compared with the control. Both isolates of C. fumosorosea colonized different plant tissues, although the extent of colonization decreased during the experimental period. The colonization of eggplants by both C. fumosorosea isolates resulted in a significant reduction of B. tabaci incidence. This study possibly provides the first report of increased plant growth and increased insect mortality in eggplants inoculated with C. fumosorosea isolates.

Toxicity and Biological Effects of Beauveria brongniartii Fe0 Nanoparticles against Spodoptera litura (Fabricius).

Nanotechnology has clear potential in the development of innovative insecticidal products for the biorational management of major insect pests. Metal-based nanoparticles of different microbial pest control agents have been effective against several pests. Synthesis of Beauveria brongniartii based Fe0 nanoparticles (Fe0NPs) and their bio-efficacy against Spodoptera litura was observed during this study. Beauveria brongniartii conidia were coated with Fe0NPs and characterized by applying a selection of different analytical techniques. Ultraviolet (UV) spectroscopy showed the characteristic band of surface plasmon at 430 nm; Scanning electron microscopy (SEM) images showed spherical shaped nanoparticles with a size ranging between 0.41 to 0.80 µm; Energy-dispersive X-ray (EDX) spectral analysis revealed characteristic Fe peaks at 6.5 and 7.1 Kev; the X-ray diffractogram showed three strong peaks at 2θ values of 45.72°, 64.47°, and 84.05°. The bioassay studies demonstrated that mortality of 2nd instar S. litura larvae following Fe0NPs treatment increased with increasing concentrations of Fe0NPs at different time intervals. The median lethal concentration (LC50) values of Fe0NPs against S. litura after seven days of fungal treatment was 59 ppm, whereas median survival time (LT50) values for 200 and 500 ppm concentrations of Fe0NPs against S. litura seven days post-treatment were 5.1 and 2.29 days, respectively. Beauveria brongniartii-Fe0NPs caused significant reductions in feeding and growth parameters (relative growth rate, relative consumption rate, and efficiency of conversion of ingested food) of S. litura. Beauveria brongniartii Fe0NPs induced reduction in glutathione-S-transferase activities throughout the infection period whereas activities of antioxidant enzymes decreased during later periods of infection. These findings suggest that B. brongniartii Fe0NPs can potentially be used in biorational S. litura management programs.

Identification and Virulence Characterization of Two Akanthomyces attenuatus Isolates Against Megalurothrips usitatus (Thysanoptera: Thripidae).

Megalurothrips usitatus (Bagnall) is one of the most harmful pests of leguminous plants. In order to expand our knowledge on the infection of M. usitatus by entomopathogenic fungi, two newly identified isolates of Akanthomyces attenuatus (Zare & Gams) were tested for their pathogenicity against M. usitatus. Both isolates of A. attenuatus (SCAUDCL-38 and SCAUDCL-56) were isolated from soil and were identified by morphological and molecular analyses. The adult females of M. usitatus were treated with five different concentrations (1 × 104, 1 × 105, 1 × 106, 1 × 107, and 1 × 108 conidia/mL) of the isolates. Our results revealed 76.25% and 57.5% mortality of M. usitatus after five days of treatment with 1 × 108 conidia/mL of SCAUDCL-38 and SCAUDCL-56, respectively. The median lethal concentrations (LC50) of SCAUDCL-38 and SCAUDCL-56 calculated through linear regression analysis after five days of fungal treatment of M. usitatus were 1.9 × 106 and 1.5 × 107 conidia/mL, respectively, whereas the median lethal time (LT50) observed for 1 × 108 conidia/mL of SCAUDCL-38 and SCAUDCL-56 were 3.52 days and 4.9 days, respectively. A. attenuatus isolates SCAUDCL-38 and SCAUDCL-56 are highly pathogenic strains of M. usitatus. These findings offer valuable information on the development and commercialization of alternative control measures against M. usitatus.

Isaria fumosorosea-based zero-valent iron nanoparticles affect the growth and survival of sweet potato whitefly, Bemisia tabaci (Gennadius).

BACKGROUND: Nanoparticles can be used for effective pest management as a combined formulation of metal and some other material that has proven efficacy against a given pest. This study reports the synthesis, characterization and efficacy of Isaria fumosorosea-based zero-valent iron (ZVI) nanoparticles against sweet potato whitefly Bemisia tabaci (Gennadius). RESULTS: The I. fumosorosea-ZVI nanoparticles showed a characteristic surface plasmon absorption band at 470 nm during UV-visible spectroscopy. The scanning electron micrographs of nanoparticles showed spherical shaped nanoparticles with sizes ranging between 1.71 and 3.0 µm. The EDX analysis showed the characteristic peak of iron at 0.6 and 6.8 KeV. The XRD analysis showed characteristic peaks at 44.72°, 65.070°, 82.339° and 82.65°. The bioassay results indicated that the percentage of larval mortality of B. tabaci challenged with I. fumosorosea ZVI nanoparticles was both concentration and age dependent. Isaria fumosorosea ZVI nanoparticles showed high pathogenicity against second and third instar nymphs, and pupae with LC50 values of 19.17, 26.10 and 37.71 ppm, respectively. The LT50 was lowest for second instar nymphs (3.15 days) and highest for pupae (4.22 days) when inoculated with a concentration of 50 ppm. CONCLUSION: Isaria fumosorosea ZVI nanoparticles can be an eco-friendly tool for effective B. tabaci management. © 2019 Society of Chemical Industry.