TY - JOUR
T1 - On the mechanism of reinitiation of endogenous Crassulacean acid metabolism rhythm by temperature changes
AU - Grams, Thorsten Erhard Edgar
AU - Borland, Anne M.
AU - Roberts, Andrew
AU - Griffiths, Howard
AU - Beck, Friedrich
AU - Lüttge, Ulrich
PY - 1997/4
Y1 - 1997/4
N2 - Under continuous light the endogenous Crassulacean acid metabolism (CAM) rhythm of Kalanchoe daigremontiana Hamet et Perrier de la Bathie disappears at high (>29.0°C) or low (<8.0°C) temperatures. We investigated the reinitiation of rhythmicity when temperature was reduced from above the upper and increased from below the lower threshold level via measurements of (a) short-term changes in carbon-isotope discrimination to illustrate shifts between C3 and C4 carboxylation in vivo, and (b) the malate sensitivity of phosphoenolpyruvate carboxylase (PEPC) in vitro. When the net CO2-exchange rhythm disappears at both temperatures, the instantaneous discrimination indicates low PEPC activity. Leaf malate concentration and osmolarity attain high and low values at low and high temperatures, respectively. After small temperature increases or reductions from the low and high temperatures, respectively, the rhythm is reinitiated, with phases shifted by 180°relative to each other. This can be related to the contrasting low and high leaf malate concentrations due to direct inhibition of PEPC and possibly also of the phosphorylation of PEPC by malate. The experimental results were satisfactorily simulated by a mathematical CAM-cycle model, with temperature acting only on the passive efflux of malate from the vacuole. We stress the important role of the tonoplast in malate compartmentation and of malate itself for the reinitiation and generation of endogenous CAM rhythmicity.
AB - Under continuous light the endogenous Crassulacean acid metabolism (CAM) rhythm of Kalanchoe daigremontiana Hamet et Perrier de la Bathie disappears at high (>29.0°C) or low (<8.0°C) temperatures. We investigated the reinitiation of rhythmicity when temperature was reduced from above the upper and increased from below the lower threshold level via measurements of (a) short-term changes in carbon-isotope discrimination to illustrate shifts between C3 and C4 carboxylation in vivo, and (b) the malate sensitivity of phosphoenolpyruvate carboxylase (PEPC) in vitro. When the net CO2-exchange rhythm disappears at both temperatures, the instantaneous discrimination indicates low PEPC activity. Leaf malate concentration and osmolarity attain high and low values at low and high temperatures, respectively. After small temperature increases or reductions from the low and high temperatures, respectively, the rhythm is reinitiated, with phases shifted by 180°relative to each other. This can be related to the contrasting low and high leaf malate concentrations due to direct inhibition of PEPC and possibly also of the phosphorylation of PEPC by malate. The experimental results were satisfactorily simulated by a mathematical CAM-cycle model, with temperature acting only on the passive efflux of malate from the vacuole. We stress the important role of the tonoplast in malate compartmentation and of malate itself for the reinitiation and generation of endogenous CAM rhythmicity.
UR - http://www.scopus.com/inward/record.url?scp=0030953110&partnerID=8YFLogxK
U2 - 10.1104/pp.113.4.1309
DO - 10.1104/pp.113.4.1309
M3 - Article
AN - SCOPUS:0030953110
SN - 0032-0889
VL - 113
SP - 1309
EP - 1317
JO - Plant Physiology
JF - Plant Physiology
IS - 4
ER -