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首页> 美国卫生研究院文献>Biochemical Journal >Sugars and light/dark exposure trigger differential regulation of ADP-glucose pyrophosphorylase genes in Arabidopsis thaliana (thale cress).
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Sugars and light/dark exposure trigger differential regulation of ADP-glucose pyrophosphorylase genes in Arabidopsis thaliana (thale cress).

机译：糖和光/暗暴露触发了拟南芥（拟南芥）中ADP-葡萄糖焦磷酸化酶基因的差异调节。

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Expression of four Arabidopsis (thale cress) genes corresponding to the small (ApS) and large subunits (ApL1, ApL2, ApL3) of ADP-glucose pyrophosphorylase (AGPase), a key enzyme of starch biosynthesis, was found to be profoundly and differentially regulated by sugar and light/dark exposures. Transcript levels of both ApL2 and ApL3, and to a lesser extent ApS, increased severalfold upon feeding sucrose or glucose to the detached leaves in the dark, whereas the mRNA content for ApL1 decreased under the same conditions. Glucose was, in general, less effective than sucrose in inducing regulation of AGPase genes, possibly due to observed limitations in its uptake when compared with sucrose uptake by detached leaves. Osmotic agents [sorbitol, poly(ethylene glycol)] had no effect on ApS, ApL2 and ApL3 transcript level, but they did mimic the effect of sucrose on ApL1 gene, suggesting that the latter is regulated by osmotic pressure rather than any particular sugar. For all the genes the sugar effect was closely mimicked by an exposure of the dark-pre-adapted leaves to the light. Under both dark and light conditions, sucrose fed to the detached leaves was found to be rapidly metabolized to hexoses and, to some extent, starch. Starch production reflected most probably an increase in substrate availability for AGPase reaction rather than being due to changes in AGPase protein content, since both the sugar feeding and light exposure had little or no effect on the activity of AGPase or on the levels of its small and large subunit proteins in leaf extracts. The data suggest tight translational or post-translational control, but they may also reflect spatial control of AGPase gene expression within a leaf. The sugar/light-dependent regulation of AGPase gene expression may represent a part of a general cellular response to the availability/allocation of carbohydrates during photosynthesis.
机译：发现与淀粉生物合成关键酶ADP-葡萄糖焦磷酸化酶（AGPase）的小的（ApS）和大的亚基（ApL1，ApL2，ApL3）相对应的四个拟南芥（拟南芥）基因的表达受到深远的差异调节。糖和光/暗暴露。在黑暗中将蔗糖或葡萄糖喂入离体的叶片中后，ApL2和ApL3的转录水平以及少量的ApS升高了几倍，而在相同条件下，ApL1的mRNA含量却下降了。通常，葡萄糖在诱导AGPase基因调控方面不如蔗糖有效，这可能是由于观察到其与离体叶片摄取蔗糖相比，其摄取受到限制。渗透剂[山梨糖醇，聚乙二醇]对ApS，ApL2和ApL3转录水平没有影响，但它们确实模仿了蔗糖对ApL1基因的作用，表明后者受渗透压而不是任何特定糖的调节。对于所有基因，通过将暗适应的叶子暴露在光线下，糖的作用被紧密模仿。在黑暗和明亮的条件下，发现喂入离体叶片的蔗糖会迅速代谢为己糖，并在一定程度上代谢为淀粉。淀粉的产生很可能反映了AGPase反应的底物利用率增加，而不是由于AGPase蛋白含量的变化所致，因为糖的摄取和光照都对AGPase的活性或其小，低水平的影响很小或没有影响。叶提取物中的大亚基蛋白。数据表明严格的翻译或翻译后控制，但它们也可能反映了叶内AGPase基因表达的空间控制。 AGPase基因表达的糖/光依赖性调节可能代表了光合作用过程中对碳水化合物的有效性/分配的一般细胞反应的一部分。

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