PLANT PHYSIOLOGY , Vol 107, Issue 2 585-591, Copyright © 1995 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
The Effects of Chilling in the Light on Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Activation in Tomato (Lycopersicon esculentum Mill.)
G. T. Byrd, D. R. Ort and W. L. Ogren
Photosynthesis Research Unit, Agricultural Research Service, United States Department of Agriculture (G.T.B., D.R.O., W.L.O.)
Photosynthesis rate, ribulsoe-1,5-bisphosphate carboxylase/oxygenase
(Rubisco) activation state, and ribulose bisphosphate concentration were
reduced after exposing tomato (Lycopersicon esculentum Mill.) plants to
light at 4[deg]C for 6 h. Analysis of lysed and reconsituted chloroplasts
showed that activity of the thylakoid membrane was inhibited and that
Rubisco, Rubisco activase, and other soluble factors were not affected.
Leaf photosynthesis rates and the ability of chilled thylakoid membranes to
promote Rubisco activation recovered after 24 h at 25[deg]C. Thylakoid
membranes from control tomato plants were as effective as spinach
thylakoids in activating spinach Rubisco in the presence of spinach Rubisco
activase. This observation is in sharp contrast to the poor ability of
spinach Rubisco activase to activate tomato Rubisco (Z.-Y. Wang, G.W.
Snyder, B.D. Esau, A.R. Portis, and W.L. Ogren [1992] Plant Physiol 100:
1858-1862). The ability of thylakoids from chilled tomato plants to
activate Rubisco in the assay system was greatly inhibited compared to
control plants. These experiments indicate that chilling tomato plants at
4[deg]C interferes with photosynthetic carbon metabolism at two sites,
thioredoxin/ferredoxin reduction (G.F. Sassenrath, D.R. Ort, and A.R.
Portis, Jr. [1990] Arch Biochem Biophys 282: 302-308), which limits
bisphosphatase activity, and Rubisco activase, which reduces Rubisco
activation state.
