Saleh A. Aldosari

Antioxidant and Anti-inflammatory Assays Confirm Bioactive Compounds in Ajwa Date Fruit

Ajwa, a variety of date palm Phoenix dactylifera L., produces the most expensive date fruits. Percentages of seed, moisture, fructose, glucose, soluble protein, and fiber in Ajwa dates were 13.24, 6.21, 39.06, 26.35, 1.33, and 11.01, respectively. The ethyl acetate, methanolic, and water extracts of Ajwa dates, active at 250 μg/mL in the MTT assay, inhibited lipid peroxidation (LPO) by 88, 70, and 91% at 250 μg/mL and cyclooxygenase enzymes COX-1 by 30, 31, and 32% and COX-2 by 59, 48, and 45% at 100 μg/mL, respectively. Bioactivity-guided purifications afforded compounds 1-7, in addition to phthalates and fatty acids. Compounds 1-3 showed activity at 100 μg/mL in the MTT assay; inhibited COX-1 enzyme by 59, 48, amd 50% and COX-2 enzyme by 60, 40, amd 39% at 50 μg/mL; and inhibited LPO by 95, 58, amd 66% at 100 μg/mL, respectively. The soluble protein fraction was also very active in both antioxidant and anti-inflammatory assays.

Two fatty acyl reductases involved in moth pheromone biosynthesis.

Fatty acyl reductases (FARs) constitute an evolutionarily conserved gene family found in all kingdoms of life. Members of the FAR gene family play diverse roles, including seed oil synthesis, insect pheromone biosynthesis, and mammalian wax biosynthesis. In insects, FAR genes dedicated to sex pheromone biosynthesis (pheromone-gland-specific fatty acyl reductase, pgFAR) form a unique clade that exhibits substantial modifications in gene structure and possesses unique specificity and selectivity for fatty acyl substrates. Highly selective and semi-selective ‘single pgFARs’ produce single and multicomponent pheromone signals in bombycid, pyralid, yponomeutid and noctuid moths. An intriguing question is how a ‘single reductase’ can direct the synthesis of several fatty alcohols of various chain lengths and isomeric forms. Here, we report two active pgFARs in the pheromone gland of Spodoptera, namely a semi-selective, C14:acyl-specific pgFAR and a highly selective, C16:acyl-specific pgFAR, and demonstrate that these pgFARs play a pivotal role in the formation of species-specific signals, a finding that is strongly supported by functional gene expression data. The study envisages a new area of research for disclosing evolutionary changes associated with C14- and C16-specific FARs in moth pheromone biosynthesis.

Identification and expression profiling of novel plant cell wall degrading enzymes from a destructive pest of palm trees, Rhynchophorus ferrugineus

Plant cell wall degrading enzymes (PCWDEs) from insects were recently identified as a multigene family of proteins that consist primarily of glycoside hydrolases (GHs) and carbohydrate esterases (CEs) and play essential roles in the degradation of the cellulose/hemicellulose/pectin network in the invaded host plant. Here we applied transcriptomic and degenerate PCR approaches to identify the PCWDEs from a destructive pest of palm trees, Rhynchophorus ferrugineus, followed by a gut‐specific and stage‐specific differential expression analysis. We identified a total of 27 transcripts encoding GH family members and three transcripts of the CE family with cellulase, hemicellulase and pectinase activities. We also identified two GH9 candidates, which have not previously been reported from Curculionidae. The gut‐specific quantitative expression analysis identified key cellulases, hemicellulases and pectinases from R. ferrugineus. The expression analysis revealed a pectin methylesterase, RferCE8u02, and a cellulase, GH45c34485, which showed the highest gut enriched expression. Comparison of PCWDE expression patterns revealed that cellulases and pectinases are significantly upregulated in the adult stages, and we observed specific high expression of the hemicellulase RferGH16c4170. Overall, our study revealed the potential of PCWDEs from R. ferrugineus, which may be useful in biotechnological applications and may represent new tools in R. ferrugineus pest management strategies.

Silencing the Olfactory Co-Receptor RferOrco Reduces the Response to Pheromones in the Red Palm Weevil, Rhynchophorus ferrugineus.

The red palm weevil (RPW, Rhynchophorus ferrugineus), one of the most widespread of all invasive insect pest species, is a major cause of severe damage to economically important palm trees. RPW exhibits behaviors very similar to those of its sympatric species, the Asian palm weevil (R. vulneratus), which is restricted geographically to the southern part of Southeast Asia. Although efficient and sustainable control of these pests remains challenging, olfactory-system disruption has been proposed as a promising approach for controlling palm weevils. Here, we report the cloning and sequencing of an olfactory co-receptor (Orco) from R. ferrugineus (RferOrco) and R. vulneratus (RvulOrco) and examine the effects of RferOrco silencing (RNAi) on odorant detection. RferOrco and RvulOrco encoding 482 amino acids showing 99.58% identity. The injection of double-stranded RNA (dsRNA) from RferOrco into R. ferrugineus pupae significantly reduced RferOrco gene expression and led to the failure of odor-stimulus detection, as confirmed through olfactometer and electroantennography (EAG) assays. These results suggest that olfactory-system disruption leading to reduced pheromone detection holds great potential for RPW pest-control strategies.

Silencing the Odorant Binding Protein RferOBP1768 Reduces the Strong Preference of Palm Weevil for the Major Aggregation Pheromone Compound Ferrugineol

In insects, perception of the environment—food, mates, and prey—is mainly guided by chemical signals. The dynamic process of signal perception involves transport to odorant receptors (ORs) by soluble secretory proteins, odorant binding proteins (OBPs), which form the first stage in the process of olfactory recognition and are analogous to lipocalin family proteins in vertebrates. Although OBPs involved in the transport of pheromones to ORs have been functionally identified in insects, there is to date no report for Coleoptera. Furthermore, there is a lack of information on olfactory perception and the molecular mechanism by which OBPs participate in the transport of aggregation pheromones. We focus on the red palm weevil (RPW) Rhynchophorus ferrugineus, the most devastating quarantine pest of palm trees worldwide. In this work, we constructed libraries of all OBPs and selected antenna-specific and highly expressed OBPs for silencing through RNA interference. Aggregation pheromone compounds, 4-methyl-5-nonanol (ferrugineol) and 4-methyl-5-nonanone (ferruginone), and a kairomone, ethyl acetate, were then sequentially presented to individual RPWs. The results showed that antenna-specific RferOBP1768 aids in the capture and transport of ferrugineol to ORs. Silencing of RferOBP1768, which is responsible for pheromone binding, significantly disrupted pheromone communication. Study of odorant perception in palm weevil is important because the availability of literature regarding the nature and role of olfactory signaling in this insect may reveal likely candidates representative of animal olfaction and, more generally, of molecular recognition. Knowledge of OBPs recognizing the specific pheromone ferrugineol will allow for designing biosensors for the detection of this key compound in weevil monitoring in date palm fields.

Phylogeny of red palm weevil (Rhynchophorus ferrugineus) based on ITS1 and ITS2

Abstract Red palm weevil (Rhynchophorus ferrugineus Olivier) populations were collected from several regions in Saudi Arabia. Insects were graded based on different patterns of pronotum markings. The entire ITS1-5.8S-ITS2 region was cloned and sequenced for both R. ferrugineus and its related species R. vulneratus (Panzer). The novel ITS1 sequence form Rhynchophorus was found to be unique in the current Genbank database. Discrimination power of ITS1 region was shown to be much higher than ITS2 region. Penetrance of different pronotum markings varied from one region to another. The pronotum-based clustering diverged from that revealed by ribosomal sequence. Several Indels and nucleotide substitutions were detected along the ITS1-5.8S-ITS2 region between R. ferrugineus and R. vulneratus. The data support a two-species classification rather than considering them colour morphs of the same species.