Chemical Architecture of Arthropod Neuromuscular Junctions as Phylogenetic Characters

今天的生物体通过蛋白质的氨基酸序列和核酸的组成来保留它们过去的信息。因此，现代分类学现在主要是基于DNA序列分析和比较。然而，严重缺乏其他具有系统发育意义的非分子特征，这些特征可用于确认或调整基于分子的系统发育，并有助于澄清任何不一致之处。由于细胞通讯对生物体的功能很重要，对信息分子分布的系统发育分析可以提供这样一组独立的特征，这可能有助于对进化史有更多的了解。在整个动物界，许多不同的物种在骨骼肌的神经肌肉连接处使用乙酰胆碱作为神经递质。相反，谷氨酸似乎是某些节肢动物神经肌肉突触的兴奋性递质。该项目将检验节肢动物门骨骼肌的兴奋性运动神经元完全是谷氨酸能的假设。利用电生理学、细胞化学和免疫染色技术，我们将研究这一特征是真节肢动物还是潜在的全节肢动物（真节肢动物、爪足动物、缓步动物）的突触形态。gaba能运动神经元的外周抑制在无脊椎动物中广泛存在，但在一些群体中似乎缺失。为了检验细胞特异性化学标记是否可以作为表征系统类群的特征，该项目将把胆碱能、氨基丁酸能和谷氨酸能标记与节肢动物和选定的外类群物种的神经肌肉连接处的电生理学标记结合起来。因此，该项目旨在提供一套神经肌肉连接处的神经递质，可作为系统发育分析的独特特征。

Organisms today retain information about their past in terms of amino acid sequences of their proteins and in the composition of nucleic acids. Thus, modern systematics is now based largely on DNA sequence analysis and comparisons. There is however a severe shortage of other, non-molecular characters with phylogenetic significance that can be used to confirm or adjust molecular-based phylogenetics and help to clarify any inconsistencies. Since cellular communication is important to organismic functioning, a phylogenetic analysis of the distribution of informational molecules could provide such a set of independent characters that may be helpful to gain additional insights into the evolutionary history. Throughout the animal kingdom, many diverse species use acetylcholine as a neurotransmitter at the neuromuscular junction of skeletal muscles. In contrast, glutamate appears to be the excitatory transmitter at neuromuscular synapses in some arthropod species. The project will test the hypothesis that in the arthropod phylum excitatory motoneurons of skeletal muscles are exclusively glutamatergic. Using electrophysiology as well as cytochemical and immuostaining techniques, we will examine whether this feature is a synapomorphy of the Euarthropoda or potentially of the Panarthropoda (Euarthropoda, Onychophora, Tardigrada). Peripheral inhibition by GABAergic motoneurons is widely distributed within the invertebrates, but it appears to be missing in several groups. To examine whether cell-specific chemical markers can be used as features to characterize systematic groups, the project will combine labelling for cholinergic, GABAergic, and glutamatergic markers with electrophysiology of the neuromuscular junction in arthropods and selected outgroup species. As a result, the project aims at providing a set of neurotransmitters at the neuromuscular junction that can be used as distinct characters for phylogenetic analysis.