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The effects of Rubisco activase on C4 photosynthesis and metabolism at high temperature

机译：Rubisco活化酶对高温下C 4 光合作用和代谢的影响

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The activation of Rubisco in vivo requires the presence of the regulatory protein Rubisco activase. This enzyme facilitates the release of sugar phosphate inhibitors from Rubisco catalytic sites thereby influencing carbamylation. T1 progeny of transgenic Flaveria bidentis (a C4 dicot) containing genetically reduced levels of Rubisco activase were used to explore the role of the enzyme in C4 photosynthesis at high temperature. A range of T1 progeny was screened at 25 °C and 40 °C for Rubisco activase content, photosynthetic rate, Rubisco carbamylation, and photosynthetic metabolite pools. The small isoform of F. bidentis activase was expressed and purified from E. coli and used to quantify leaf activase content. In wild-type F. bidentis, the activase monomer content was 10.6±0.8 μmol m−2 (447±36 mg m−2) compared to a Rubisco site content of 14.2±0.8 μmol m−2. CO2 assimilation rates and Rubisco carbamylation declined at both 25 °C and 40 °C when the Rubisco activase content dropped below 3 μmol m−2 (125 mg m−2), with the status of Rubisco carbamylation at an activase content greater than this threshold value being 44±5% at 40 °C compared to 81±2% at 25 °C. When the CO2 assimilation rate was reduced, ribulose-1,5-bisphosphate and aspartate pools increased whereas 3-phosphoglycerate and phosphoenol pyruvate levels decreased, demonstrating an interconnectivity of the C3 and C4 metabolites pools. It is concluded that during short-term treatment at 40 °C, Rubisco activase content is not the only factor modulating Rubisco carbamylation during C4 photosynthesis.
机译：体内Rubisco的活化需要调节蛋白Rubisco活化酶的存在。该酶有助于从Rubisco催化位点释放糖磷酸酯抑制剂，从而影响氨基甲酰化作用。使用含有降低的Rubisco活化酶水平的转基因黄花苜蓿（C 4 双子叶植物）的T 1 后代来研究该酶在C 4 < / sub>高温下的光合作用。在25°C和40°C下筛选一系列T 1 后代的Rubisco活化酶含量，光合速率，Rubisco氨基甲酸酯化和光合代谢产物库。从大肠杆菌中表达并纯化了牛双歧杆菌活化酶的小同工型，并用于定量叶片活化酶的含量。在野生型牛鞭草中，活化酶单体含量为10.6±0.8μmolm -2 （447±36 mg m -2 ），而Rubisco位点为14.2±0.8μmolm -2 。当Rubisco活化酶含量降至3μmolm -2 （125 mg m ）以下时，CO 2 同化率和Rubisco氨甲酰化在25°C和40°C均下降。 -2 ），活化酶含量大于此阈值的Rubisco氨甲酰化状态在40°C为44±5％，而在25°C为81±2％。当CO 2 同化率降低时，核糖-1,5-双磷酸和天冬氨酸池增加，而3-磷酸甘油酸和磷酸烯醇丙酮酸水平降低，表明C 3 和C 4 代谢物库。结论：在40°C短期处理下，C 4 光合作用中Rubisco活化酶的含量不是调节Rubisco氨基甲酸酯化的唯一因素。

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    《Journal of Experimental Botany》 |2008年第7期|p.1789-1798|共10页
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    L. Hendrickson12 R. Sharwood2 M. Ludwig3 S. M. Whitney2 M. R. Badger12 and S. von Caemmerer2*;

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    1ARC Centre for Excellence in Plant Energy Biology, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia 2Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, PO Box 475, Canberra, ACT 2601, Australia 3School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009, Australia;

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