Control of oxidative phosphorylation during insect metamorphosis.

Area of Science:

• Biochemistry
• Cell Biology
• Developmental Biology

Background:

• The tobacco hornworm (Manduca sexta) midgut undergoes programmed cell death and replacement during metamorphosis.
• Understanding changes in cellular respiration is crucial for elucidating this developmental process.

Purpose of the Study:

• To investigate alterations in mitochondrial oxidative phosphorylation during the programmed death of larval midgut cells in Manduca sexta.
• To determine how substrate oxidation, proton leak, and phosphorylation are affected by developmental commitment to pupation.

Main Methods:

• Mitochondria were isolated from Manduca sexta larvae before and after commitment to pupation.
• Top-down control analysis was used to assess oxidative phosphorylation.
• Oxygen consumption and protonmotive force were monitored.

Main Results:

• Mitochondria from precommitment larvae exhibited higher respiration rates than postcommitment larvae.
• Proton leak increased in postcommitment larvae, suggesting altered mitochondrial membranes.
• The substrate oxidation system's control remained high, but its activity declined postcommitment, potentially due to cytochrome c loss.

Conclusions:

• Programmed cell death in Manduca sexta midgut involves significant alterations in mitochondrial function, including reduced respiration and increased proton leak.
• These changes are linked to developmental commitment and may involve modifications to mitochondrial membrane properties and protein content.