This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Ohsugi, R. Articles by Huber, S. C. Search for Related Content PubMed PubMed Citation Articles by Ohsugi, R. Articles by Huber, S. C. Agricola Articles by Ohsugi, R. Articles by Huber, S. C.

Metabolism and Enzymology

Light Modulation and Localization of Sucrose Phosphate Synthase Activity between Mesophyll Cells and Bundle Sheath Cells in C₄ Species ¹

United States Department of Agriculture, Agricultural Research Service, North Carolina State University, Raleigh, North Carolina 27695-7631, Department of Crop Science and Botany, North Carolina State University, Raleigh, North Carolina 27695-7631

Experiments were conducted with several Panicum species (representing the different C₄ subtypes) to examine the light modulation of sucrose phosphate synthase (SPS) activity and the effect of illumination on the distribution of SPS activity between mesophyll cells (MC) and bundle sheath cells (BSC). Activity of SPS in the light decreased in the order: C₄ > C₃-C₄ intermediate > C₃. In illuminated leaves, SPS activities were similar among the three C₄ subtypes, but SPS activity was higher for NAD-malic enzyme (NAD-ME) species with centripetal chloroplasts in BSC (NAD-ME(P) species) than for NAD-ME species with centrifugal chloroplasts in BSC (NAD-ME(F) species). Transfer of plants into darkness for 30 minutes resulted in decreased SPS activity for all species tested except Panicum bisulcatum (C₃ species) and Panicum virgatum (NAD-ME(P) species) which showed little or no change. All C₄ subtypes had some SPS activity both in MC and BSC. In the light, SPS activity was mainly in the MC for NADP-ME, NAD-ME(F) and phosphoenolpyruvate carboxykinase species, while it was mainly in the BSC for NAD-ME(P) species. In the dark, for all C₄ subtypes, SPS activity in the MC was decreased to a greater extent than that in the BSC. It is intriguing that NAD-ME(F) and NAD-ME(P) species differed in the activity and distribution of SPS activity between MC and BSC, although they are otherwise identical in the photosynthetic carbon assimilation pathway. Diurnal changes in SPS activity in the MC and BSC were also examined in maize leaves. SPS activity in the MC in maize leaves was high and relatively constant throughout the middle of the light period, dropped rapidly after sunset and increased again prior to the light period. On the other hand, SPS activity in the BSC was lower and changed more coincidently with light intensity than that in the MC. The results suggested that light activation of SPS activity located in the BSC may require higher irradiance for saturation than the SPS in the MC. We conclude that SPS may function in both MC and BSC for sucrose synthesis in the light, particularly at high light intensity, while in the dark, the major function may be in the BSC during starch degradation.

¹ Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. Paper No. 10994 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601.

This article has been cited by other articles:

				P. Sowinski, J. Szczepanik, and P. E. H. Minchin On the mechanism of C4 photosynthesis intermediate exchange between Kranz mesophyll and bundle sheath cells in grasses J. Exp. Bot., April 1, 2008; 59(6): 1137 - 1147. [Abstract] [Full Text] [PDF]

				B. Grodzinski, J. Jiao, and E. D. Leonardos Estimating Photosynthesis and Concurrent Export Rates in C3 and C4 Species at Ambient and Elevated CO21,2 Plant Physiology, May 1, 1998; 117(1): 207 - 215. [Abstract] [Full Text]