Metabolism of phenolic natural compounds at the threshold to life on land

从水生生活方式转变为陆生生活方式的植物会遇到各种生物（病原体、食草动物）和非生物（紫外线照射、失水）胁迫，这些胁迫可以在具有威慑或抗生素以及紫外线吸收特性或被纳入亲脂性屏障的酚类化合物的帮助下克服。酚类化合物生物合成的基础是类苯丙素途径，其通过三种酶的作用从L-苯丙氨酸或L-酪氨酸形成活化的羟基肉桂酸：苯丙氨酸解氨酶（PAL）、肉桂酸4-羟化酶（C4 H）和4-香豆酸CoA-连接酶（4CL）。4-香豆酰-CoA然后在羟基肉桂酰转移酶（HCT）、细胞色素P450单加氧酶（CYP 98）和咖啡酰莽草酸酯酶（CSE）的参与下进一步代谢为单木酚和羟基肉桂酸酯/酰胺。所有这些酶在种子植物中是众所周知的，但我们对早期分化的陆地植物或藻类中的酶的了解要有限得多。在第一个资助期内，我们的主要重点是在最早的陆地植物的现存成员中的上述基因和酶，使用bratetes Anthoceros agrestis，地钱和立碗藓作为模式生物。布朗轮藻作为轮藻科的绿色轮藻也有一定的研究。从这些植物中选择感兴趣的酶的基因序列，异源表达并进行生物化学表征。一般来说，我们的研究结果表明，在brandiete数据库中的注释大多是正确的，生化特性是相似的种子植物的相应酶。这是不同的轮藻braunii。在这里，首先，不能很容易地确定基因使用种子植物序列作为诱饵，其次，注释往往是不正确的或混乱的。这向我们表明，重要的是要集中在藻类模型系统，以遵循苯丙烷途径的基因/酶的进化，因为这种进化可能发生在生物体中。除了Chara braunii，因此，我们将集中在另一个藻类模式生物，中带藻endlicherianum（Zygnematophyceae），寻找酚代谢的基因/酶的存在和编码的酶的特征。首次检查轮藻braunii和中带藻endlicherianum基因组数据库表明，我们的目标基因的识别是更加繁琐，必须考虑替代的生物合成途径。

Plants changing from an aquatic to a terrestrial lifestyle encounter various biotic (pathogens, herbivores) and abiotic (UV irradiation, loss of water) stresses which can be overcome with help of phenolic compounds that have deterring or antibiotic as well as UV-absorbing properties or are incorporated into lipophilic barriers. The basis for the biosynthesis of phenolic compounds is the phenylpropanoid pathway which forms an activated hydroxycinnamic acid from L-phenylalanine or L-tyrosine by the action of three enzymes: phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H) and 4-coumarate CoA-ligase (4CL). 4-Coumaroyl-CoA then is further metabolized to monolignols and hydroxycinnamic acid esters/amides under participation of hydroxycinnamoyltransferases (HCT), cytochrome P450 monooxygenases (CYP98) and caffeoylshikimate esterases (CSE). All these enzymes are well known in seed plants, but our knowledge on them in early diverged land plants or algae is much more limited. In the first funding period, our main focus was on the above-mentioned genes and enzymes in extant members of the earliest land plants using the bryophytes Anthoceros agrestis, Marchantia polymorpha and Physcomitrium patens as model organisms. Chara braunii as green alga of the Characeae was also investigated to some extent. Gene sequences from these plants for the enzymes of interest were selected, heterologously expressed and biochemically characterized. Generally, our results showed that annotations in the bryophyte databases are mostly correct and the biochemical characteristics are similar to those of the respective enzymes from seed plants. This was different for Chara braunii. Here, firstly genes can not be identified as easily using seed plant sequences as baits, and secondly, the annotations often are not correct or confusing. This shows us, that it is important to concentrate on the algal model systems to follow the evolution of genes/enzymes of the phenylpropanoid pathway as organisms where this evolution might have occurred. Besides Chara braunii, we will therefore concentrate on another algal model organism, Mesotaenium endlicherianum (Zygnematophyceae), to look there for the presence of genes/enzymes of phenolic metabolism and to characterize the encoded enzymes. First inspections of Chara braunii and Mesotaenium endlicherianum genome databases have shown that the identification of our target genes is more tedious and alternative biosynthetic pathways must be taken into consideration.