Modulation of larval nutrition affects midgut neutral lipid storage and temporal pattern of transcription factor expression during mosquito metamorphosis.
During holometabolous insect development the critical weight marks a physiological transition after which juvenile hormone (JH) concentration decreases to such a level that a subsequent increase in ecdysone titer will initiate metamorphosis. Starvation experiments indicate that the Aedes aegypti critical weight is achieved by 24 h after the last larval-larval molt. When grown at 24 degrees C with excess food, the time between the critical weight and maximum weight (interval to cessation of growth) is about 24 h and pupation occurs about 24 h after the maximum weight is achieved. Oil Red O staining of 3rd and early 4th instars indicates that the midgut is a neutral lipid storage organ during this period. Coincident with the attainment of the critical weight is the depletion of stored midgut neutral lipid. Application of methoprene to 24 h post-molt 4th instars results in renewed midgut storage of neutral lipid suggesting that midgut neutral lipid storage is a JH dependent process. Starvation of 4th instars during the 24 h post-molt period suspends development in a fraction of the larvae, and with the resumption of feeding, development resumes. A regimen of starvation and resumption of feeding of 4th instars suggests that JH concentration decreased over a 40 h period after the resumption of feeding and maximum weight is attained about 48 h after the resumption of feeding. We hypothesize that this results in a shortening of the interval to cessation of growth. Real-time PCR experiments indicate that shortening the interval to cessation of growth compresses the time period during which increases in AHR3, AaEcR-B and AaUSP-a expression occur.
Nishiura
James T
JT
Biology Department, Brooklyn College, 2900 Bedford Ave. Brooklyn, NY 11210, USA. jamesn@brooklyn.cuny.edu
Burgos
Cynthia
C
Aya
Samuel
S
Goryacheva
Yekaterina
Y
Lo
Wingyin
W
D000330:Aedes / Q000502:physiology*; D000818:Animals; D005508:Food Deprivation; D041981:Gastrointestinal Tract / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D007814:Larva / Q000502:physiology; D008055:Lipids / Q000502:physiology*; D008675:Metamorphosis, Biological / Q000502:physiology*; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*
D008055:Lipids; D014157:Transcription Factors