caa a22 4500 47710200X CHVBK 20180405111545.0 cr unu---uuuuu 170330e19960601xx s 000 0 eng 10.1007/BF00196567 doi (NATIONALLICENCE)springer-10.1007/BF00196567 The roles of malate and aspartate in C4 photosynthetic metabolism of Flaveria bidentis (L.) [Elektronische Daten] [Michaela Meister, Anthony Agostino, Marshall Hatch] In C4 grasses belonging to the NADP-malic enzyme-type subgroup, malate is considered to be the predominant C4 acid metabolized during C4 photosynthesis, and the bundle sheath cell chloroplasts contain very little photosystem-II (PSII) activity. The present studies showed that Flaveria bidentis (L.), an NADP-malic enzyme-type C4 dicotyledon, had substantial PSII activity in bundle sheath cells and that malate and aspartate apparently contributed about equally to the transfer of CO2 to bundle sheath cells. Preparations of bundle sheath cells and chloroplasts isolated from these cells evolved O2 at rates between 1.5 and 2 μmol · min−1 · mg−1 chlorophyll (Chl) in the light in response to adding either 3-phosphoglycerate plus HCO 3 − or aspartate plus 2-oxoglutarate. Rates of more than 2 μmol O2 · min−1 · mg−1 Chl were recorded for cells provided with both sets of these substrates. With bundle sheath cell preparations the maximum rates of light-dependent CO2 fixation and malate decarboxylation to pyruvate recorded were about 1.7 μmol · min−1 · mg−1 Chl. Compared with NADP-malic enzyme-type grass species, F. bidentis bundle sheath cells contained much higher activities of NADP-malate dehydrogenase and of aspartate and alanine aminotransferases. Time-course and pulse-chase studies following the kinetics of radiolabelling of the C-4 carboxyl of C4 acids from 14CO2 indicated that the photosynthetically active pool of malate was about twice the size of the aspartate pool. However, there was strong evidence for a rapid flux of carbon through both these pools. Possible routes of aspartate metabolism and the relationship between this metabolism and PSII activity in bundle sheath cells are considered. Springer-Verlag, 1996 Aspartate decarboxylation nationallicence Bundle sheath nationallicence C4 photosynthesis nationallicence Flaveria (C4 photosynthesis) nationallicence Malate decarboxylation nationallicence DHAP : dihydroxyacetone phosphate nationallicence NADP-ME(-type) : NADP-malic enzyme (type) nationallicence NADP-MDH : NADP-malate dehydrogenase nationallicence OAA : oxaloacetic acid nationallicence 2-OG : 2-oxoglutarate nationallicence PEP : phosphoenolpyruvate nationallicence PGA : 3-phosphoglycerate nationallicence Pi : orthophosphate nationallicence Ru5P : ribulose 5-phosphate nationallicence Meister Michaela Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia aut Agostino Anthony Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia aut Hatch Marshall Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia aut Planta Springer-Verlag 199/2(1996-06-01), 262-269 0032-0935 199:2<262 1996 199 425 https://doi.org/10.1007/BF00196567 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00196567 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Meister Michaela Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia aut NATIONALLICENCE 700 1- Agostino Anthony Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia aut NATIONALLICENCE 700 1- Hatch Marshall Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/2(1996-06-01), 262-269 0032-0935 199:2<262 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer