Thermal regulation of phosphoenolpyruvate carboxylase and ribulose- 1,5-bisphosphate carboxylase in C3 and C4 plants native to hot and temperate climates
1989
Ghosh, S. | Gepstein, S. | Glick, B.R. | Heikkila, J.J. | Dumbroff, E.B.
Exposure of leaf sections from 2-week-old seedlings of sorghum (Sorghum bicolor L.) (C4 plant), corn (Zea mays L.) (C4), peanut (Arachis hypogaea L.) (C3 plant), and soybean (Glycine max L.) (C3) to 40 or 45 degrees C for up to 4 hours resulted in significant increases in the levels of 102 kilodalton (C4), 52 kilodalton (C3 and C4) and 15 kilodalton (C3 and C4) polypeptides. These proteins comigrated, repectively, with authentic phosphoenolypyruvate carboxylase (PEPC) and the large (RLSU) and small (RSSU) subunits of ribulose- 1,5-bisphophate carboxylase (Rubisco) during both one- and two-dimensional SDS-PAGE and reacted with antisera raised against these enzymes. After 4 hours at 50 degrees C, levels of the polypeptides either remained relatively stable (PEPC, RLSU) or increased in sorghum and peanut (plant native to hot climates). In corn and soybean (plant native to temperate climates), levels of the proteins either fell sharply (corn) or showed strong evidence of incomplete processing and/or aggregation (soybean). In addition to changes inlevels of the proteins, the activities of PEPC and Rubisco in extracts of leaves exposed to 50 degrees C fell by 84% and 11% of their respective control values in sorghum and by 54% each in peanut. In corn and soybean, the activities of both enzymes were depressed at 40 degrees C, with measured values at 50 degrees C not exceeding 5% of those from the nonstressed controls.
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