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The biochemical basis for thermoregulation in heat-producing flowers.

Umekawa Y, Seymour RS, Ito K - Sci Rep (2016)

Bottom Line: Here, we show that respiratory control in homeothermic spadices of skunk cabbage (Symplocarpus renifolius) is achieved by rate-determining biochemical reactions in which the overall thermodynamic activation energy exhibits a negative value.Moreover, NADPH production, catalyzed by mitochondrial isocitrate dehydrogenase in a chemically endothermic reaction, plays a role in the pre-equilibrium reaction.We propose that a law of chemical equilibrium known as Le Châtelier's principle governs the homeothermic control in skunk cabbage.

View Article: PubMed Central - PubMed

Affiliation: United Graduate School of Agricultural Science, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan.

ABSTRACT
Thermoregulation (homeothermy) in animals involves a complex mechanism involving thermal receptors throughout the body and integration in the hypothalamus that controls shivering and non-shivering thermogenesis. The flowers of some ancient families of seed plants show a similar degree of physiological thermoregulation, but by a different mechanism. Here, we show that respiratory control in homeothermic spadices of skunk cabbage (Symplocarpus renifolius) is achieved by rate-determining biochemical reactions in which the overall thermodynamic activation energy exhibits a negative value. Moreover, NADPH production, catalyzed by mitochondrial isocitrate dehydrogenase in a chemically endothermic reaction, plays a role in the pre-equilibrium reaction. We propose that a law of chemical equilibrium known as Le Châtelier's principle governs the homeothermic control in skunk cabbage.

No MeSH data available.


Comparison of the dynamic temperature response (δ) of Eo in mitochondrial respiration mediated by the AOX- and COX- pathways.Values for δ of AOX-and COX-mediated oxygen consumptions were analysed (n = 3). n.s.: not significant.
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f4: Comparison of the dynamic temperature response (δ) of Eo in mitochondrial respiration mediated by the AOX- and COX- pathways.Values for δ of AOX-and COX-mediated oxygen consumptions were analysed (n = 3). n.s.: not significant.

Mentions: It should be noted here that the value of in equation 2 is always identical at any temperature condition, because it shares the same activation energy in the reversible steps of the pre-equilibrium reaction (Fig. 2). Therefore, we attempted to ascertain whether AOX- or COX-mediated pathways contribute equally to setting of the switching temperature. Towards this end, we performed the same in vitro mitochondrial respiration assay and measured NADPH-NDA/ICDH-mediated oxygen consumption in the presence of specific inhibitors (KCN for the AOX-pathway and n-propyl gallate for the COX-pathway) (Supplementary Fig. 5). Data from both experiments again fit well to the modified Arrhenius model (Supplementary Fig. 5a), which calculated an Eo of zero for AOX and COX-pathways at 16.1 °C and 24.9 °C, respectively (Supplementary Fig. 5b). These results prompt us to suggest that the AOX-mediated respiration pathway has the greatest influence on the switching temperature in the intact spadices. Further analysis of the dynamic response of Eo to temperature (δ) showed no statistically significant difference between the AOX- and COX-mediated respiratory pathways, which is caused by a larger variation in the data of AOX-mediated respiration (Fig. 4).


The biochemical basis for thermoregulation in heat-producing flowers.

Umekawa Y, Seymour RS, Ito K - Sci Rep (2016)

Comparison of the dynamic temperature response (δ) of Eo in mitochondrial respiration mediated by the AOX- and COX- pathways.Values for δ of AOX-and COX-mediated oxygen consumptions were analysed (n = 3). n.s.: not significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837406&req=5

f4: Comparison of the dynamic temperature response (δ) of Eo in mitochondrial respiration mediated by the AOX- and COX- pathways.Values for δ of AOX-and COX-mediated oxygen consumptions were analysed (n = 3). n.s.: not significant.
Mentions: It should be noted here that the value of in equation 2 is always identical at any temperature condition, because it shares the same activation energy in the reversible steps of the pre-equilibrium reaction (Fig. 2). Therefore, we attempted to ascertain whether AOX- or COX-mediated pathways contribute equally to setting of the switching temperature. Towards this end, we performed the same in vitro mitochondrial respiration assay and measured NADPH-NDA/ICDH-mediated oxygen consumption in the presence of specific inhibitors (KCN for the AOX-pathway and n-propyl gallate for the COX-pathway) (Supplementary Fig. 5). Data from both experiments again fit well to the modified Arrhenius model (Supplementary Fig. 5a), which calculated an Eo of zero for AOX and COX-pathways at 16.1 °C and 24.9 °C, respectively (Supplementary Fig. 5b). These results prompt us to suggest that the AOX-mediated respiration pathway has the greatest influence on the switching temperature in the intact spadices. Further analysis of the dynamic response of Eo to temperature (δ) showed no statistically significant difference between the AOX- and COX-mediated respiratory pathways, which is caused by a larger variation in the data of AOX-mediated respiration (Fig. 4).

Bottom Line: Here, we show that respiratory control in homeothermic spadices of skunk cabbage (Symplocarpus renifolius) is achieved by rate-determining biochemical reactions in which the overall thermodynamic activation energy exhibits a negative value.Moreover, NADPH production, catalyzed by mitochondrial isocitrate dehydrogenase in a chemically endothermic reaction, plays a role in the pre-equilibrium reaction.We propose that a law of chemical equilibrium known as Le Châtelier's principle governs the homeothermic control in skunk cabbage.

View Article: PubMed Central - PubMed

Affiliation: United Graduate School of Agricultural Science, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan.

ABSTRACT
Thermoregulation (homeothermy) in animals involves a complex mechanism involving thermal receptors throughout the body and integration in the hypothalamus that controls shivering and non-shivering thermogenesis. The flowers of some ancient families of seed plants show a similar degree of physiological thermoregulation, but by a different mechanism. Here, we show that respiratory control in homeothermic spadices of skunk cabbage (Symplocarpus renifolius) is achieved by rate-determining biochemical reactions in which the overall thermodynamic activation energy exhibits a negative value. Moreover, NADPH production, catalyzed by mitochondrial isocitrate dehydrogenase in a chemically endothermic reaction, plays a role in the pre-equilibrium reaction. We propose that a law of chemical equilibrium known as Le Châtelier's principle governs the homeothermic control in skunk cabbage.

No MeSH data available.