Heme biosynthesis and oogenesis in the blood-sucking bug, Rhodnius prolixus

We have previously shown that the pathway of porphyrin synthesis operates i n the blood feeding triatomine bug Rhodnius prolixus but not in the cattle tick Boophilus microplus. In the present paper we studied the correlation b etween heme synthesis and egg development in Rhodnius. There is a sharp inc rease heme biosynthetic capability in the fat body (160%) and in the ovarie s (360%) in response to a blood meal, as evaluated from the activity of the enzyme delta -aminolevulinate dehydratase CEC 4.2.1.24). The in vivo inhib ition of ALA-D by succinyl acetone results in a dose dependent decrease of oviposition. Oviposition is recovered when porphobilinogen, the product of the impaired reaction, is added to the succinyl acetone enriched blood. Tak en together, these results show that heme biosynthesis is a fundamental eve nt to vitellogenic females. The demand for heme in this metabolic juncture cannot be supplied by the heme eventually absorbed during blood digestion a nd associated with Rhodnius heme binding protein (RHBP), which is then inco rporated into growing oocytes. Inhibition of heme biosynthesis results in l ower levels of RHBP in the hemolymph, suggesting that the synthesis of this protein is controlled by heme availability. (C) 2001 Elsevier Science Ltd. All rights reserved.