A LYSOZYME IN THE SALIVARY-GLANDS OF THE MALARIA VECTOR ANOPHELES DARLINGI

A cDNA encoding a lysozyme expressed specifically in the salivary glan ds of the malaria vector mosquito, Anopheles darlingi, was isolated by differential screening an adult female salivary gland library with ab domen and salivary gland cDNAs. The primary nucleic acid sequence of t he cDNA contains a deduced coding region of 429 nucleotides and 5'- an d 3'-end non-transcribed regions. A signal peptide of twenty-three ami no acids and a mature protein of 120 amino acids are evident in the co nceptual translation product. The results of RT-PCR experiments indica ted that in adult mosquitoes this gene is expressed specifically in th e salivary glands. Lysozyme enzymatic activity was detected in the sal ivary glands and abdomens of adult mosquitoes, but the pH optimum diff ered for each tissue and this was interpreted to indicate the presence of more than one enzyme, each being expressed in a different tissue. The salivary gland lysozyme may be involved in protection against bact erial infection in the anterior portion of the mosquito digestive trac t.