Juvenile hormone affects the splicing of Culex quinquefasciatus early trypsin messenger RNA

Authors: BOROVSKY, DOV - Oak Ridge Institute For Science And Education (ORISE); HANCOCK, ROBERT - Metropolitan State University; ROUGE, PIERRE - University Of Toulouse; POWELL, CHARLES - University Of Florida; Shatters, Robert - Bob

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2018
Publication Date: 10/20/2018
Citation: Borovsky, D., Hancock, R.G., Rouge, P., Powell, C.A., Shatters, R.G. 2018. Juvenile hormone affects the splicing of Culex quinquefasciatus early trypsin messenger RNA. Archives of Insect Biochemistry and Physiology. 99(3), e21506. https://doi.org/10.1002/arch.21506.
DOI: https://doi.org/10.1002/arch.21506

Interpretive Summary: Inhibition of digestive processes has been demonstrated as a good interdiction point to develop new insect control strategies for a number of insect pests to humans and to agriculture. Developing basic science information on how insects control digestive processes provide information on novel interdiction strategies. In this paper, it was demonstrated that mosquitos regulate a specific subset of protease digestive enzymes (Trypsin proteases) through the activity of juvenile hormone III (JHIII). The JHIII hormone controls the synthesis of these enzymes through specific Ribonucleic acid (RNA) splicing events that control the ability of these RNAs to produce the trypsin proteins. This novel mechanism of RNA splicing control is presented as a new potential interdiction point for the development of control strategies for mosquitos and potentially other pest insects that utilize similar RNA splicing regulatory processes.

Technical Abstract: The full length of Culex quiquefasciatus early trypsin has been cloned and sequenced and a three-dimensional (3D) model of the enzyme was built showing that the enzyme has the canonical trypsin’s active pocket containing H78, D123, S129, and D128. The biosynthesis of juvenile hormone (JH) III by the corpora allata (CA) in female Cx. quiquefasciatus is sugar-dependent. Females that were maintained on water after emergence synthesize very little JH III, JH III bisepoxide, and methyl farnesoate (MF) (3.8, 1.1, and 0.8'fmol/4'hr/CA, respectively). One hour after sugar feeding, the synthesis of JH III and JH III bisepoxide reached a maximum (11.3 and 5.9'fmol/4'hr/CA, respectively) whereas MF biosynthesis reached a maximum at 24'hours (5.2'fmol/4'hr/CA). The early trypsin is transcribed with a short intron (51'nt) is spliced when JH III biosynthesis is high in sugar fed and at 1'hour after the blood meal (22 and 15' fmol/4'hr/CA, respectively). We investigated the transcriptional and posttranscriptional regulation of the early trypsin gene showing that JH III concentrations influence splicing. In the absence JH III the unspliced transcript is linked by a phosphoamide bond at the 5'-end to Ribonucleic acid (RNA) ribonuleoprotein (RNP). The biosynthesis of the early trypsin was followed in ligated abdomens (without CA) of newly emerged females that fed blood by enema. Our results show that the early trypsin biosynthesis depends on sugar and blood feeding, whereas the late trypsin biosynthesis does not depend on sugar feeding, or JH III biosynthesis. Downregulating the early trypsin transcript does not affect the late trypsin.