PPOs: Prophenoloxidases
Summary

Jianyong Li 

Biochemistry, Virginia Tech, Blacksburg, USA 

We have assessed the transcription of 6 individual Aa PPO sequences. Most of them are transcribed during larval and pupal stages. Among them, AaPPO1 seems to be transcribed in the entire stages (larvae, pupae and adults), AaPPO2 and AaPPO3 are transcribed during early larval stages, and AaPPO4 and AaPPO6 are transcribed during both larval and pupal stages, but AaPPO5 seems expressed only in adults 12 hours after a blood meal. Individual PPOs are actually translated in the Aa. For example, AaPPO1, AaPPO2, AaPPO3, AaPPO4 and AaPPO6 are translated in mosquito larvae and AaPPO5 is translated in adults following blood feeding. Transcriptional profiles of individual PPOs do not seem to be closely correlated to the level of their gene products. For example, transcripts of AaPPO2 and AaPPO3 were not detected in later stage larvae, but their proteins were isolated from 6-day old larvae. Some PPOs might be proteolytically processed at their carboxyl end, resulting in the cleavage of the last 120 some residues. Because an absence of these carboxyl side residues does not affect their catalytic function, the carboxyl end fragment in PPOs might be somewhat related to their tissue specific localization. The phylogenetic tree shows expansions with duplications in each of the mosquitoes with AgPPO1 and AaPPO6 being most closely related to the Dm PPOs. 

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