Condensed lignins are synthesized in poplar leaves exposed to ozone
Condensed lignins are synthesized in poplar leaves exposed to ozone
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DOI：
10.1104/pp.103.031765
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发表时间：
2004-02-01
期刊：
影响因子：
7.4
通讯作者：
Lapierre, C
中科院分区：
文献类型：
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作者：
Cabané, M;Pireaux, JC;Lapierre, C
以杨树（Populus tremula X alba）无性株INRA 717-1-B4为研究对象，在60和120 nL -1臭氧浓度条件下培养1个月。以对照水平为对照，比较了莽草酸脱氢酶（EC 1.1.1.25）、苯丙氨酸解氨酶（EC 4.3.1.5）和肉桂醇脱氢酶（CAD, EC 1.1.1.195）的叶片活性。此外，我们还研究了对照和臭氧熏蒸叶片的木质素含量和结构。在臭氧暴露条件下，无论叶片发育的哪个阶段，CAD活性和CAD RNA水平都迅速而强烈地增加。相反，莽草酸脱氢酶和苯丙氨酸解氨酶活性在老叶和中年叶中有所增加，而在年轻叶中没有增加。这些参与木质素代谢途径的后期或早期步骤的酶的活性增加与无提取物叶片中较高的克拉森木质素含量有关。此外，与本构木质素相比，在臭氧条件下合成的应力木质素具有不同的结构。它们富含碳-碳单元间键和对羟基苯基丙烷单元，这让人想起在早期发育阶段形成的木质素，在压缩木材中，或对真菌激发剂的反应。最高臭氧剂量（120 nL -1）时木质素化和酶活性变化最大。这些结果表明，臭氧诱导的木质素可能因其对活性氧的屏障或抗氧化作用而有助于杨树对臭氧的耐受性。
Poplar (Populus tremula X alba) trees (clone INRA 717-1-B4) were cultivated for 1 month in phytotronic chambers with two different levels of ozone (60 and 120 nL L-1). Foliar activities of shikimate dehydrogenase (EC 1.1.1.25), phenylalanine ammonia lyase (EC 4.3.1.5), and cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) were compared with control levels. In addition, we examined lignin content and structure in control and ozone-fumigated leaves. Under ozone exposure, CAD activity and CAD RNA levels were found to be rapidly and strongly increased whatever the foliar developmental stage. In contrast, shikimate dehydrogenase and phenylalanine ammonia lyase activities were increased in old and midaged leaves but not in the youngest ones. The increased activities of these enzymes involved in the late or early steps of the metabolic pathway leading to lignins were associated with a higher Klason lignin content in extract-free leaves. In addition, stress lignins synthesized in response to ozone displayed a distinct structure, relative to constitutive lignins. They were found substantially enriched in carbon-carbon interunit bonds and in p-hydroxyphenylpropane units, which is reminiscent of lignins formed at early developmental stages, in compression wood, or in response to fungal elicitor. The highest changes in lignification and in enzyme activities were obtained with the highest ozone dose (120 nL L-1). These results suggest that ozone-induced lignins might contribute to the poplar tolerance to ozone because of their barrier or antioxidant effect toward reactive oxygen species.