Rolletschek Hardy, Hajirezaei Mohammad-Reza, Wobus Ulrich, Weber Hans
Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), 06466 Gatersleben, Germany.
Planta. 2002 Apr;214(6):954-64. doi: 10.1007/s00425-001-0710-4. Epub 2002 Jan 23.
We previously reported on Vicia narbonensis seeds with largely decreased alpha- D-glucose-1-phosphate adenyltransferase (AGP; EC 2.7.7.27) due to antisense inhibition [H. Weber et al. (2000) Plant J 24:33-43]. In an extended biochemical analysis we show here that in transgenic seeds both AGP activity and ADP-glucose levels were strongly decreased but starch was only moderately reduced and contained less amylose. The flux control coefficient of AGP to starch accumulation was as low as 0.08, i.e. AGP exerts low control on starch biosynthesis in Vicia seeds. Mature cotyledons of antisense seeds had increased contents of lipids, nitrogen and sulfur. The protein content was higher due, in particular, to increased sulfur-rich albumins. Globulin fractions of storage proteins had a lower ratio of legumin to vicilin. Isolated cotyledons partitioned less [14C]sucrose into starch and more into soluble sugars with no change in the protein fraction. Respiration of isolated cotyledons and activities of the major glycolytic and carbohydrate-metabolizing enzymes were not affected. Sucrose and the hexose-phosphate pool were increased but UDP-glucose, 3-phosphoglyceric acid, phospho enolpyruvate, pyruvate, ATP and ADP were unchanged or even lower, indicating that carbon partitioning changed from starch to sucrose without affecting the glycolytic and respiratory pathways. Soluble compounds were increased but osmolality remained unchanged, indicating compensatory water influx resulting in higher water contents. Developmental patterns of water and nitrogen accumulation suggest a coupled uptake of amino acids and water into cotyledons. We conclude that, due to higher water uptake, transgenic cotyledons take up more amino acids, which become available for protein biosynthesis leading to a higher protein content. Obviously, a substantial part of amino acid uptake into Vicia seeds occurs passively and is osmotically controlled and driven by water influx.
我们之前报道过，由于反义抑制作用，窄叶野豌豆种子中的α-D-葡萄糖-1-磷酸腺苷转移酶（AGP；EC 2.7.7.27）大幅减少[H. Weber等人（2000年），《植物杂志》24:33 - 43]。在此，我们通过进一步的生化分析表明，在转基因种子中，AGP活性和ADP-葡萄糖水平均大幅降低，但淀粉仅适度减少且直链淀粉含量降低。AGP对淀粉积累的流量控制系数低至0.08，即AGP对野豌豆种子中淀粉生物合成的控制作用较弱。反义种子的成熟子叶中脂质、氮和硫的含量增加。蛋白质含量较高，特别是由于富含硫的白蛋白增加。贮藏蛋白的球蛋白组分中豆球蛋白与豌豆球蛋白的比例较低。分离的子叶将较少的[14C]蔗糖分配到淀粉中，而更多地分配到可溶性糖中，蛋白质组分没有变化。分离的子叶的呼吸作用以及主要糖酵解和碳水化合物代谢酶的活性不受影响。蔗糖和己糖磷酸池增加，但UDP-葡萄糖、3-磷酸甘油酸、磷酸烯醇丙酮酸、丙酮酸、ATP和ADP没有变化甚至更低，这表明碳分配从淀粉转向蔗糖，而不影响糖酵解和呼吸途径。可溶性化合物增加，但渗透压不变，表明有补偿性的水分流入，导致含水量更高。水和氮积累的发育模式表明氨基酸和水协同进入子叶。我们得出结论，由于水分吸收增加，转基因子叶吸收了更多的氨基酸，这些氨基酸可用于蛋白质生物合成，从而导致蛋白质含量更高。显然，野豌豆种子吸收的氨基酸有很大一部分是被动吸收的，受渗透压控制，并由水分流入驱动。
