High light inhibits chlorophyll biosynthesis at the level of 5-aminolevulinate synthesis during de-etiolation in cucumber (Cucumis sativus) cotyledons
High light inhibits chlorophyll biosynthesis at the level of 5-aminolevulinate synthesis during de-etiolation in cucumber (Cucumis sativus) cotyledons
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DOI：
10.1562/2006-03-06-ra-835
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发表时间：
2007-01-01
影响因子：
3.3
通讯作者：
Tanaka, A.
中科院分区：
文献类型：
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作者：
Aarti, D.;Tanaka, R.;Tanaka, A.
以维管植物黄瓜（Cucumis sativus）为模型，研究了强光（强光和过量光）对黄瓜脱黄化过程中叶绿素生物合成的影响。在强光（1500-1600 μ E/m（2）/s）下，黄瓜子叶不能完全合成叶绿素。然而，转移到低光条件（40-45 μ E/m（2）/S），叶绿素生物合成和随后的积累恢复后，最初的2-12小时的延迟。强光处理持续时间与叶绿素生物合成活性呈负相关。具体来说，我们发现，强光严重抑制5-氨基乙酰丙酸（ALA）的合成。这种效应部分可能是由于观察到的谷氨酰-tRNA还原酶（GluTR）的蛋白质水平降低。谷氨酸-1-半醛（GSA-AT）的蛋白水平保持不变。还发现，强光不抑制HEMA I表达。因此，我们推测，这种对ALA合成的显著抑制可能主要是因为伴随的GluTR失活和/或GluTR和GSA-AT之间复合物形成的抑制。我们进一步观察到甲基紫精和玫瑰红在低光条件下同样抑制ALA合成，这表明活性氧（ROS）可能是导致暴露于强光条件下的子叶中ALA合成抑制的原因。
Using the vascular plant Cucumis sativus (cucumber) as a model, we studied the effects of high (intense and excess) light upon chlorophyll biosynthesis during de-etiolation. When illuminated with high light (1500-1600 mu E/m(2)/s), ctiolated cucumber cotyledons failed to synthesize chlorophyll entirely. However, upon transfer to low light conditions (40-45 mu E/m(2)/S), chlorophyll biosynthesis and subsequent accumulation resumed following an initial 2-12 h delay. Duration of high light treatment negatively correlated with chlorophyll biosynthetic activity. Specifically, we found that high light severely inhibited 5-aminolevulinic acid (ALA) synthesis. This effect partly could be because of the decrease in protein level of glutamyl-tRNA reductase (GluTR) observed. Protein level of glutamate-1-semialdehyde (GSA-AT) remained unchanged. It was also found that high light did not suppress HEMA I expression. Therefore, we speculated that this significant inhibition of ALA, synthesis might have occurred mainly because of concomitant inactivation of GluTR and/or inhibition of complex formation between GluTR and GSA-AT. Our further observation that both methyl viologen and rose bengal similarly inhibit ALA synthesis under low light conditions suggested that reactive oxygen species (ROS) could be responsible for the inhibition of ALA synthesis in cotyledons exposed to high light conditions.