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Figures
- Fig. 1.
Changes in RNA and protein levels in response to an instantaneous doubling of mRNA synthesis. The rate of change in RNA level (dR/dt) was calculated from the rate of RNA synthesis (θ) minus the rate of RNA degradation, which is the product of the RNA level (R) and the RNA decay rate (–mR). An RNA half-life of 4 h results in an RNA decay rate (mR) of 4.1 day–1. The change in protein levels (dP/dt) was calculated from the rate of protein synthesis (the product of RNA level, R, and a constant reflecting translation, ϵ) minus the rate of protein degradation (the product of the protein level, P, and the protein decay rate, –mR). A protein half-life of 4 days results in a decay rate of 0.17 day–1. The exact values of θ and ϵ are not critical when expressing values relative to an initial steady-state value of 1 for levels of both RNA and protein. The time course is for an instantaneous doubling of RNA synthesis at day 0, with the inset focusing on changes over the first 2 days.
- Fig. 2.
Multi-level regulation of fluxes related to energy metabolism in air-breathing vertebrates. At basal metabolic rate (BMR), biosynthesis and transport dominate as the main energy-expending processes in various organs. Under these conditions, O2 and CO2 fluxes as well as fuel oxidation rates are low. During high-intensity exercise, locomotory muscles account for increasing fractions of whole-body O2 consumption and CO2 production rates. At maximal metabolic rates (MMR or V̇O2,max), actomyosin-ATPase is the main ATP-utilizing process and fluxes through fuel oxidation pathways increase to a maximum. Taken from Weibel (Weibel, 2002) with kind permission from the author and publisher.
- Fig. 3.
Relationship between enzyme Vmax and glycolytic flux (both ln-transformed) at eight reactions in energy metabolism in the flight muscles of 14 Panamanian orchid bee species belonging to four genera. Each point represents data from a single species. Linear regression yields slopes that represent hierarchical regulation coefficients, ρh, that are significant for cytochrome c oxidase (COX; 0.46), hexokinase (HK; 0.98) and glycogen phosphorylase (GP; 0.36). ρh=0 at all other reactions [glycerol 3-phosphate dehydrogenase (GPDH), citrate synthase (CS), phosphoglucoisomerase (PGI), phosphofructokinase (PFK) and trehalase (TR)], indicating that metabolic regulation accounts for interspecific variation in flux at these steps. Phylogenetically independent contrast analysis resulted in support for hierarchical regulation only at HK, providing an explanation for the interspecific variation in flux at this step. Therefore, in addition to morphological and physiological factors resulting in allometric variation in metabolic rates during flight, the allometric variation in metabolic fluxes in muscles during flight is the consequence of both hierarchical and metabolic regulation. Taken from Suarez et al. (Suarez et al., 2005).
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