Transcriptional complexity of the Anopheles stephensi nitric oxide synthase gene

Anopheles stephensi nitric oxide synthase (AsNOS) is a single copy gene tha t shares significant structural homology with the three human NOS genes and is inducibly expressed in Plasmodium-infected mosquitoes. Exon-specific No rthern analyses and exon-spanning polymerase chain reaction amplification w ere used to further characterize transcription from this gene. A total of 1 8-22 AsNOS transcripts, ranging in size from 1.0 to 7.5 kb, were detected i n replicated Northern blots from three separate cohorts of mosquitoes. Thre e transcripts (1604, 2330, and 2585 bp) were significantly induced in Plasm odium-infected mosquitoes (p<0.05), while others showed varying patterns of induction or downregulation. Five splice variants contained deletions of 1 -7 exons. All but one deletion pattern was predicted to introduce in-frame stop codons or alter the translational reading frame. A novel insertion der ived from intron sequence was predicted to introduce in-frame stop codons f ollowing exon 11. Two truncated novel exon 1 variants were identified that are homologous to a previously published 5' sequence for this exon. The lar ge number of AsNOS transcripts and diversity in AsNOS splicing and exon 1 s equences indicate that transcriptional complexity is a hallmark of both inv ertebrate and vertebrate NOS genes. (C) 2001 Elsevier Science Ltd. All righ ts reserved.