Enzymic properties and capacities of developing tomato (Lycopersicon esculentum L.) fruit plastids
Enzymic properties and capacities of developing tomato (Lycopersicon esculentum L.) fruit plastids
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DOI：
10.1093/jexbot/49.321.681
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发表时间：
1998-04-01
影响因子：
6.9
通讯作者：
Borchert, S
中科院分区：
文献类型：
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作者：
Büker, M;Schünemann, D;Borchert, S
为表征番茄果实发育阶段，测定了番茄果皮叶片叶绿素含量、光合作用O-2进化和CO2固定。在发育初期，磷酸三糖转运子的表达水平较高。运输测量显示，磷酸己糖和磷酸三糖转运体在这个时候都很可能是活跃的。在绿色果皮中，塑性和胞质形式的果糖-1,6-二磷酸酶是活跃的，而在红色果皮中，只有胞质形式的果糖-1,6-二磷酸酶存在。番茄果实叶绿体能够从Glc6P合成淀粉，淀粉的合成强烈依赖于3PGA和AIP的添加以及质体的光照。果实叶绿体的CO2固定率非常低，因此研究了绿色果皮切片的能力。就叶绿素含量而言，果皮片显示出与菠菜或马铃薯叶片相同的淀粉合成能力。为了研究消耗光合电子传递产物的进一步反应的存在，测量了GOGAT活性。在光照下，谷氨酸依赖于谷氨酰胺/2-氧戊二酸盐的形成以高活性发生。在Glc6P存在下，仅获得18%的光活性。由于glc6p依赖性活性相当低，我们还测量了标记的[1-C-14]-Glc6P释放的(CO2)-C-14。在黑暗中，谷氨酸的形成和Glc6P的氧化在水果叶绿体中是紧密耦合的。
To characterize the developmental stage of tomato fruits, chlorophyll content, photosynthetic O-2 evolution and CO2 fixation of pericarp slices were determined. During the first developmental stages a higher expression level of the triose phosphate translocator was detected. Transport measurements revealed that both the hexose phosphate and the triose phosphate translocator are very likely to be active at this time. Plastidic and cytosolic fructose-1,6-bisphosphatase are active in green fruit pericarp, whereas in red pericarp only the cytosolic form is present. Tomato fruit chloroplasts are able to synthesize starch from Glc6P, Starch synthesis is strongly dependent on the addition of 3PGA and AIP and on plastid illumination. Fruit chloroplasts exhibit very low CO2 fixation rates and so the capacities of green pericarp slices were investigated. In relation to chlorophyll content, pericarp slices show the same capacity of starch synthesis as spinach or potato leaves. To investigate the presence of further reactions consuming the products of photosynthetic electron transport, the GOGAT activity was measured. In the light, glutamine/2-oxoglutarate-dependent formation of glutamate occurred with a high activity. In the presence of Glc6P only 18% of the light activity was obtained. Since the Glc6P-dependent activity is rather low,, the release of (CO2)-C-14 from labelled [1-C-14]-Glc6P was also measured. In the dark, the formation of glutamate and oxidation of Glc6P are very tightly coupled to each other in fruit chloroplasts.