Guan L M, Scandalios J G
Department of Genetics, North Carolina State University, Raleigh 27695-7614, USA.
Redox Rep. 2000;5(6):377-83. doi: 10.1179/135100000101535951.
The effect of osmotic stress and dehydration on maize catalase transcript accumulation was examined in leaves of abscisic acid (ABA)-deficient and ABA-insensitive mutants. We have found that the response of Cat1 to osmotic stress and dehydration is not via an ABA-mediated pathway in young leaves, suggesting that there are two different mechanisms by which Cat1 responds to osmotic stress in embryos and in leaves. The Cat2 transcript increased in response to osmotic stress, but was repressed by dehydration. On the other hand, the Cat3 transcript is up-regulated by dehydration and osmotic stress only in ABA-deficient mutant leaves, implying that ABA may act as a repressor for Cat3 expression in response to dehydration and high osmoticum. We also found that the VP1 trans-acting factor is not required for the induction of Cat1 by ABA in leaves, but may play a role in stabilizing the Cat1 transcript after an initial induction. The exact nature of the signals triggering Cat responses to osmotic stress and dehydration is not clear. We speculate that oxygen free radicals may play a role in this response. Osmotic stress and dehydration may indirectly induce production of oxygen free radicals in leaves, thus triggering the antioxidant response.
在脱落酸（ABA）缺陷型和ABA不敏感型突变体的叶片中，研究了渗透胁迫和脱水对玉米过氧化氢酶转录物积累的影响。我们发现，在幼叶中，Cat1对渗透胁迫和脱水的响应并非通过ABA介导的途径，这表明Cat1在胚和叶片中对渗透胁迫的响应存在两种不同机制。Cat2转录物在渗透胁迫下增加，但在脱水时受到抑制。另一方面，Cat3转录物仅在ABA缺陷型突变体叶片中被脱水和渗透胁迫上调，这意味着ABA可能作为脱水和高渗条件下Cat3表达的抑制因子。我们还发现，VP1反式作用因子并非叶片中ABA诱导Cat1所必需，但可能在初始诱导后对稳定Cat1转录物起作用。触发Cat对渗透胁迫和脱水响应的信号的确切性质尚不清楚。我们推测氧自由基可能在此响应中起作用。渗透胁迫和脱水可能间接诱导叶片中氧自由基的产生，从而触发抗氧化反应。
