時鐘基因在蜚蠊之表現

Abstract

時鐘基因是與日週律動調控有關的基因，其中週期基因 (period, per) 所產生的蛋白質 (PER) 是調控日週律動的核心蛋白質，而色素分散因子 (Pigment Dispersing Factor, PDF) 和黑化誘導神經肽 (Corazonin, CRZ) 是兩種日週律動輸出因子 (output factors)。本研究利用免疫染色法，染出兩種蜚蠊中樞神經系統中 PER、PDF 和 CRZ 的位置，從而建構出此二種蜚蠊中樞神經系統中調控日週律動的神經網路；此外，本文作者暨指導教授與捷克的 Dr. Ivo Sauman、Dr. František Sehnal、 Dr. Ivan Hrdý 和 Dr. Radka Závodská 合作，進行分屬現生等翅目七科中六個科（九個亞科）的十種白蟻腦部 PDF 和 CRZ 的免疫染色，已在期刊《節肢動物之構造與發育（Arthropod structure and development）》發表〈白蟻腦部黑化誘導神經肽與色素分散因子之分佈 （Distribution of Corazonin and Pigment-Dispersing Factor in the cephalic ganglia of termites）〉一文，在此作為附錄（appendix），一併收錄於本論文之末。 德國蜚蠊 Blattella germanica 和雙紋姬蠊 B. bisignata 是親緣關係極為接近的姊妹種，具有類似的per序列以及多項相似的生理和行為特徵，但具有不同活動行為。在此二蜚蠊的中樞神經系統中，PER 的分佈皆為在視葉每側具有三群主要時鐘細胞群，在前腦每側具有兩群與內分泌調控有關的細胞，在中腦、後腦、食道下神經球以及胸、腹神經球中僅具有少數細胞。PDF在視葉每側也具有三群細胞，並與 PER 的細胞位置完全重合。CRZ 在視葉每側具有兩個細胞，不與 PER/PDF 重合，但在空間位置上緊密相連，並有神經互相連接。因為此三種時鐘蛋白質在兩種蜚蠊中樞神經系統的分佈並無差異，其不同的活動行為可能由 per、pdf 和 crz 的下游基因調控。

The distributions of immunoreactivity (ir) cells against three clock-related proteins (Period, PER; Pigment Dispersing Factor, PDF; and Corazonin, CRZ) were compared between two species of cockroaches. The German cockroach, Blattella germanica, and the double-striped cockroach, B. bisignata, are sibling species with similar period sequence but distinctive circadian rhythm in locomotion. Three major groups of PER-ir cells are located in optic lobes (OLs), which are the sites of the major circadian clock. They are interconnected with PER-ir neural bundles. Interestingly, the potential output signal of the circadian clock, PDF, is co-localized with PER in all three groups of cells. However, only two CRZ-ir cells and their processes are found in the OLs and they are not co-localized with PER-ir or PDF-ir cells and processes. Since only one circadian rhythm is expressed in locomotion, the time signals from both major clocks in the OLs are coupled by connection with PDF-ir processes. A group of 3-4 PER-ir cells in the protocerebrum display typical characteristics of neurosecretary cells. In addition, there are numerous, small PER-ir and PDF-ir co-localized cells in the pars intercerebralis (PI) which have direct connections with the neurohemoorgan, corpora cardiaca (CC), through PER-ir and PDF-ir processes. Based on these findings, the cellular connection shows a circadian control through endocrine route. For the rest of central nervous system, only a few PER-ir and PDF-ir cells or processes are detected. This finding implies the circadian clock for locomotion is not located in subesophageal ganglion (SOG), thoracic or abdominal ganglia, but may use other neural messengers to pass on circadian signals. Since the overall distribution pattern of the clock cells are the same for B. germanica and B. bisignata, the possible explaination of the different expression of locomotion between the species depends on genes downstream of per, pdf and crz. The appendix at the end of the thesis is the the article “Distribution of Corazonin and Pigment-Dispersing Factor in the cephalic ganglia of termites”, which is accept by the journal “Arthropod structure and development”. We finished this work about termites by teamwork with our coauthors: Dr. Ivo Sauman, Dr. František Sehnal, Dr. Ivan Hrdý and Dr. Radka Závodská of Czech Republic.