Molecular analysis of acetylcholinesterase gene in field-collected populations of Musca domestica (Diptera: Muscidae) in Northwestern Iran

Nowadays, pyrethroid (Py) insecticides are commonly used against household insect pests and housefly. The combination of Py and organophosphates (OP) are also utilized to combat these insects. The resistance status of Iranian housefly populations to them and carbamate (CB) insecticides is uncertain. This study investigates the presence of acetylcholinesterase (AChE) mutations related to the resistance of Musca domestica to OP and/or CB insecticides in Northwestern Iran. Nucleotides 1041-1776, based on their positions in the ACE gene of aabys strain, were amplified and sequenced in houseflies collected from West Azerbaijan, Gilan, and Ardebil Provinces, Iran. Among 12 single-nucleotide polymorphisms detected, 3 mismatches were found at nucleotides 1174 (T/A, G), 1473 (G/T, C), and 1668 (T/A), leading to amino acid substitutions in V260L, G342A/V, and F407Y positions with various combinations. Genotyping results showed that 85% of specimens had at least one of these substitutions. In addition, the Iranian housefly population was composed of 5 insensitive and sensitive alleles. For the first time, the current study reports the presence of V260L, G342A, G342V, and F407Y substitutions in M. domestica specimens collected from Northwestern Iran. The selection of multiple alleles in field populations might be due to the application of various pesticides/insecticides during extended periods in the region. These molecular levels signify the presence of control problems in the area and the need for developing effective control strategies for such populations.

Purification and Partial Characterization of Agglutinin Lectin from Heamolymph of German Cockroach, Blattella germanica

Background:

Lectin molecules have crucial biological role in insects’ immune system. The aim of present study was to find the agglutinin activities in haemolymph of German cockroach, Belatella germanica with appropriate screening and purification.

Methods:

The heamolymph of cockroach was collected and agglutinin test performed against different animal and human red blood cells (RBC). Then sugar inhibition assay was carried out to find carbohydrate specific binding lectin. The proteins of haemolymph was purified using ion-exchange chromatography (HPLC) and each fraction was tested for agglutinin activity. Finally the molecular weight of the agglutinin protein was determined using SDS-page.

Results:

The most agglutinin activity of haemolymph was found against RBC of mouse at titer 1/128ml/L dilution and sugar inhibition assay showed that fucos, N-acetyglucoseamine and galactose reduced titer of agglutinin to ½ml/L. Only one fraction of heamolymph at rotation time of 36 minute showed agglutinin activity. The molecular weight of this lectin was measured as 120Kds.

Conclusion:

The range of agglutinin activities against different RBC indicates that the isolated lectin is not specific for a particular carbohydrate. In addition, the isolated lectin at low concentration present in heamolymph should be an innate lactin not secreted, because we found it without any trigger immunity of the insect.

Antibacterial/Antifungal Activity of Extracted Chitosan From American Cockroach (Dictyoptera: Blattidae) and German Cockroach (Blattodea: Blattellidae)

We investigated bactericidal and fungicidal properties of chitosan extracted from adults and nymphs from both German cockroach, Blattella germanica (Blattodea: Blattellidae) and American cockroach, Periplaneta americana (Dictyoptera: Blattidae). The cuticle of adults and nymphs extracted from both cockroaches were dried and ground. The powders were demineralized and deproteinized followed by deacetylation using NaOH. Finally, the chitosan yields were examined for antibacterial and antifungal activities. The degree of deacetylation (DD) was different between adults and nymph stages. The antimicrobial effect of American cockroach chitosan (ACC) and German cockroach chitosan (GCC) was tested against four bacteria and four fungi. The extracted chitosans from American cockroach, Periplaneta americana and German Cockroach, Blattella germanica suppressed the growth of Gram-negative/positive bacteria except Micrococcus luteus. The growth of Aspergillus flavus and Aspergillus niger were notability inhibited by the extracted chitosans. The antimicrobial effect of the chitosan depended on the cockroach species, with chitosan of the American cockroach showing more inhibitory effect. This difference may be due to differences in the structure of chitin between the two cockroach species.

Ribosomal DNA internal transcribed spacer 2 sequence analysis and phylogenetic comparison of seven cockroach species in northwestern Iran

Objectives

The current study was conducted to identify cockroach species (Blattodea) of northwestern Iran in public places using morphological characteristics and ribosomal DNA internal transcribed spacer 2 (rDNA-ITS2). Sequences were analyzed with Basic Local Alignment Search Tool (BLAST) searches, Neighbor-Joining methods based on and Tamura-Nei phylogenetic analyses. In addition, eight cockroach rDNA-ITS2 sequences from China, India, Iran and the United States obtained from GenBank were compared to those obtained in this study.

Results

Specimens collected in Iran were identified as Periplaneta americana (L.), Shelfordella lateralis (Walker), Blatta orientalis (L.) (Blattodea: Blattidae), Blattella germanica (L.), Supella longipalpa (F.) (Blattodea: Ectobiidae), Polyphaga aegyptiaca (L.), and Polyphaga saussurei (Dohrn) (Blattodea: Corydiidae). rDNA-ITS2 nucleotide sequence analysis showed 100% similarity between P. aegyptiaca and P. saussurei species collected from Iran despite morphological differences. However, ITS2 sequence of P. americana submitted from China showed 30.49–31.71% difference to P. americana sequences from Iran and the United States. The results highlight the importance of morphological identification of cockroach species before conducting molecular techniques.

Age-dependance of pteridines in the malaria vector, Anopheles stephensi

Determining the accurate age of malaria vectors is crucial to measure the risk of malaria transmission. A group of fluorescent chemicals derived from a pyrimidine-pyrazine ring structure known as pteridines from the head, thorax and whole body of adult female Anopheles stephensi were identified and evaluated as a tool for chronological and physiological age determination of malaria vectors. The female mosquitoes were collected from an insectary colony at an interval of every 5 days, up to 30 days, and the pteridines of head, thorax and whole body were detected fluorometrically by high-pressure liquid chromatography (HPLC) using excitation and emission wavelengths of 365 and 455 nm, respectively. In addition, alteration of the pteridines compounds was compared between blood and sugar fed mosquito groups. Although four pteridines including pterin-6-carboxylic acid, biopterin, xanthopterin and isoxanthopterin were detected, some of them were absent in the head or thorax of mosquitoes. Levels of all four pteridines were similarly decreased in a linear manner throughout 30 days. No significant difference in alteration of pteridine compounds was observed between the two groups of blood or sugar fed mosquitoes. This result indicates that diet has a little effect on pteridines alteration. Age determination based on pteridines, as an age-grading technique, could be used for field collected mosquitoes, which have either sugar or blood meal. In addition, analyzing total pteridine fluorescence from only whole body could be a convenient method to estimate the age.

Mosquito genomics. Highly evolvable malaria vectors: the genomes of 16 Anopheles mosquitoes

Variation in vectorial capacity for human malaria among Anopheles mosquito species is determined by many factors, including behavior, immunity, and life history. To investigate the genomic basis of vectorial capacity and explore new avenues for vector control, we sequenced the genomes of 16 anopheline mosquito species from diverse locations spanning ~100 million years of evolution. Comparative analyses show faster rates of gene gain and loss, elevated gene shuffling on the X chromosome, and more intron losses, relative to Drosophila. Some determinants of vectorial capacity, such as chemosensory genes, do not show elevated turnover but instead diversify through protein-sequence changes. This dynamism of anopheline genes and genomes may contribute to their flexible capacity to take advantage of new ecological niches, including adapting to humans as primary hosts.