Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Activase Deficiency Delays Senescence of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase but Progressively Impairs Its Catalysis during Tobacco Leaf Development
| Autor: | S. von Caemmerer, T J Andrews, Zhili He, Graham S. Hudson, G. D. Price, Murray R. Badger |
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| Rok vydání: | 1997 |
| Předmět: |
DNA
Bacterial Oxygenase Carboxy-lyases Physiology Ribulose-Bisphosphate Carboxylase Nicotiana tabacum DNA Single-Stranded Plant Science Photosynthesis DNA Antisense chemistry.chemical_compound Tobacco Genetics RNA Messenger Plant Proteins Ribulose 1 5-bisphosphate biology fungi RuBisCO food and beverages Carbon Dioxide Plants Genetically Modified biology.organism_classification Pyruvate carboxylase Plant Leaves Plants Toxic Biochemistry chemistry Chlorophyll biology.protein Research Article |
| Zdroj: | Scopus-Elsevier |
| ISSN: | 1532-2548 0032-0889 |
| Popis: | Transgenic tobacco (Nicotiana tabacum L. cv W38) plants with an antisense gene directed against the mRNA of ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) activase grew more slowly than wild-type plants in a CO2-enriched atmosphere, but eventually attained the same height and number of leaves. Compared with the wild type, the anti-activase plants had reduced CO2 assimilation rates, normal contents of chlorophyll and soluble leaf protein, and much higher Rubisco contents, particularly in older leaves. Activase deficiency greatly delayed the usual developmental decline in Rubisco content seen in wild-type leaves. This effect was much less obvious in another transgenic tobacco with an antisense gene directed against chloroplast-located glyceraldehyde-3-phosphate dehydrogenase, which also had reduced photosynthetic rates and delayed development. Although Rubisco carbamylation was reduced in the anti-activase plants, the reduction was not sufficient to explain the reduced photosynthetic rate of older anti-activase leaves. Instead, up to a 10-fold reduction in the catalytic turnover rate of carbamylated Rubisco in vivo appeared to be the main cause. Slower catalytic turnover by carbamylated Rubisco was particularly obvious in high-CO2-grown leaves but was also detectable in air-grown leaves. Rubisco activity measured immediately after rapid extraction of anti-activase leaves was not much less than that predicted from its degree of carbamylation, ruling out slow release of an inhibitor from carbamylated sites as a major cause of the phenomenon. Nor could substrate scarcity or product inhibition account for the impairment. We conclude that activase must have a role in vivo, direct or indirect, in promoting the activity of carbamylated Rubisco in addition to its role in promoting carbamylation. |
| Databáze: | OpenAIRE |
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