Monday, December 11, 2006

Upregulation of two actin genes and redistribution of actin during diapause and cold stress in the northern house mosquito, Culex pipiens

Mijung Kim, kim.1851@osu.edu1, Rebecca M. Robich2, Joseph P. Rinehart3, and David L. Denlinger1. (1) Ohio State University, Entomology, 318 West 12th Avenue, Columbus, OH, (2) Harvard School of Public Health, Immunology and Infectious Disease, 665 Huntington Avenue, Boston, MA, (3) USDA-ARS, 1605 Albrecht Boulevard, Fargo, ND

Two actin genes cloned from Culex pipiens (L) are upregulated during adult diapause. Though actins 1 and 2 were expressed throughout diapause, both genes were most highly expressed early in diapause. These changes in gene expression were accompanied by a conspicuous redistribution of polymerized actin that was most pronounced in the midguts of diapausing mosquitoes that were exposed to low temperature. In nondiapausing mosquitoes reared at 25C and in diapausing mosquitoes reared at 18C, polymerized actin was clustered at high concentrations at the intersections of the muscle fibers that form the midgut musculature. When 7-10 day-old mosquitoes were exposed to low temperature (-5C for 12h), the polymerized actin was evenly distributed along the muscle fibers in both nondiapausing and diapausing mosquitoes. Exposure to low temperature (-5C for 12h) in 1month-old mosquitoes elicited an even greater distribution of polymerized actin, an effect that was especially pronounced in diapausing mosquitoes. These changes in gene expression and actin distribution suggest a role for actins in enhancing survival of diapausing adults during the low temperatures of winter by fortification of the cytoskeleton.

Species 1: Diptera Culicidae Culex pipiens (northern house mosquito)