Geigenberger P, Stamme C, Tjaden J, Schulz A, Quick P W, Betsche T, Kersting H J, Neuhaus H E
Botanisches Institut der Universität Heidelberg, Im Neuenheimer Feld 360, D-69120 Heidelberg, Germany.
Plant Physiol. 2001 Apr;125(4):1667-78. doi: 10.1104/pp.125.4.1667.
We showed recently that antisense plants with decreased activity of the plastidic ATP/ADP-transporter protein exhibit drastically reduced levels of starch and a decreased amylose/amylopectin ratio, whereas sense plants with increased activity of the transporter possessed more starch than wild-type plants and an increased amylose/amylopectin ratio. In this paper we investigate the effect of altered plastidic ATP/ADP-transporter protein expression on primary metabolism and granule morphology in more detail. Tuber tissues from antisense and sense plants exhibited substantially increased respiratory activity compared with the wild type. Tubers from antisense plants contained markedly increased levels of free sugars, UDP-Glc, and hexose phosphates, whereas phosphoenolpyruvate, isocitrate, ATP, ADP, AMP, UTP, UDP, and inorganic pyrophosphate levels were slightly decreased. In contrast, tubers from sense plants revealed a slight increase in adenine and uridine nucleotides and in the levels of inorganic pyrophosphate, whereas no significant changes in the levels of soluble sugars and metabolites were observed. Antisense tubers contained 50% reduced levels of ADP-Glc, whereas sense tubers contained up to 2-fold increased levels of this sole precursor for starch biosynthesis. Microscopic examination of starch grain morphology revealed that the size of starch grains from antisense tubers was substantially smaller (50%) compared with the wild type. The large starch grains from sense tubers appeared of a more angular morphology, which differed to the more ellipsoid shape of wild type grains. The results suggest a close interaction between plastidial adenylate transport and starch biosynthesis, indicating that ADP-Glc pyrophosphorylase is ATP-limited in vivo and that changes in ADP-Glc concentration determine starch yield, as well as granule morphology. Possible factors linking starch synthesis and respiration are discussed.
我们最近发现，质体ATP/ADP转运蛋白活性降低的反义植株淀粉水平大幅降低，直链淀粉/支链淀粉比例下降，而该转运蛋白活性增加的正义植株比野生型植株含有更多淀粉，直链淀粉/支链淀粉比例升高。在本文中，我们更详细地研究了质体ATP/ADP转运蛋白表达改变对初级代谢和颗粒形态的影响。与野生型相比，反义植株和正义植株的块茎组织呼吸活性显著增加。反义植株的块茎中游离糖、UDP-葡萄糖和己糖磷酸水平明显升高，而磷酸烯醇丙酮酸、异柠檬酸、ATP、ADP、AMP、UTP、UDP和无机焦磷酸水平略有下降。相反，正义植株的块茎中腺嘌呤和尿苷核苷酸以及无机焦磷酸水平略有增加，而可溶性糖和代谢物水平未观察到显著变化。反义块茎中ADP-葡萄糖水平降低50%，而正义块茎中这种淀粉生物合成唯一前体的水平增加了2倍。淀粉粒形态的显微镜检查显示，反义块茎淀粉粒的大小比野生型小得多（50%）。正义块茎的大淀粉粒呈现出更有棱角的形态，与野生型颗粒更椭圆的形状不同。结果表明质体腺苷酸转运与淀粉生物合成之间存在密切相互作用，表明ADP-葡萄糖焦磷酸化酶在体内受ATP限制，并且ADP-葡萄糖浓度的变化决定淀粉产量以及颗粒形态。讨论了连接淀粉合成与呼吸的可能因素。
