Gene expression in Plasmodium: from gametocytes to sporozoites

Completion of the complex developmental program of Plasmodium in the mosquito is essential for parasite transmission, yet this part of its life cycle is still poorly understood. In recent years, considerable progress has been made in the identification and characterization of genes expressed during parasite development in the mosquito. This line of investigation was greatly facilitated by the availability of the genome sequence of several Plasmodium, and by the application of approaches such as proteomics, microarrays, gene disruption by homologous recombination (gene knockout) and by use of subtraction libraries. Here, we review what is presently known about genes expressed in gametocytes and during the Plasmodium life cycle in the mosquito.

The Musca domestica larval hexamerin is composed of multiple, similar polypeptides

The Musca domestica larval hexamerin (MdHex-L) is a hexameric glycoprotein with an apparent native molecular weight of 500 kDa. Seven different cDNAs that encode MdHex-L subunits were cloned and sequenced. Furthermore, amino acid sequences of isolated subunits were determined by the Edman degradation method and compared to the conceptual translation products derived from the cloned cDNAs. The obtained data indicate the existence of multiple forms of MdHex-L subunits and that these multiple forms may be grouped into three categories according to their percentages of nucleotide sequence identity.

Analysis of salivary gland proteins of the mosquito Anopheles darlingi (Diptera: Culicidae)

The salivary proteins of Anopheles darlingi Root, the principal vector of malaria in the Amazon Region, Brazil, were analyzed. Comparison of the protein profiles between adult males and females revealed that most of the polypeptides are present in both sexes, but female-specific polypeptides also were observed. SDS-PAGE analysis of sugar-fed female mosquitoes with ages varying from 1 to 10 d after adult emergence indicated that the proteins start to be accumulated in the first day of life and are present throughout the period analyzed. Analysis of blood-fed mosquitoes showed no differences in salivary proteins when compared with sugar fed ones, suggesting that there is no specific protein induced by blood. The protein profiles of the salivary glands dissected from wild-caught female mosquitoes from different geographical regions of Brazil were compared and some differences were observed.

Apyrase and alpha-glucosidase in the salivary glands of Aedes albopictus

An apyrase and an alpha-glucosidase were detected in the salivary glands extracts of adult Aedes albopictus. The apyrase is a 61,000 Da secreted protein that hydrolyses ATP and ADP. This protein is synthe-sized in adults and is preferentially accumulated in the distal lateral lobes of the female salivary glands. The alpha-glucosidase is a secreted 67,000 Da protein. This enzyme is synthesized during adult life and accumulated in the proximal-lateral lobes of both males and females. The results are discussed and compared with data previously obtained with Aedes aegypti salivary glands.