星野黑皮海綿轉錄體之分析

Abstract

近年來台灣綠島地區的珊瑚大量地由平鋪狀星野黑皮海綿（以下簡稱黑皮海綿）覆蓋而死亡，稱為“珊瑚黑病”。野外觀察發現黑皮海綿的前、後端於外觀上有差異，而這些差異是前人研究中沒有被探討。因此，本研究針對綠島的黑皮海綿，採取前端、後端樣本分別進行電子顯微鏡的觀察及轉錄體的定序分析。另外建立一組與珊瑚隔離生長的解剖盒樣本，比較三個不同生長位置的黑皮海綿，討論他們在生理生化與外觀上差異之間的關係。電子顯微鏡觀察結果發現，黑皮海綿樣本體內含有大量的球狀藍綠菌及骨針，前端樣本的骨針呈隨機排列，而解剖盒海綿樣本則常呈束狀排列。此外，前端樣本的細胞狀況較後端樣本完整且良好。轉錄體的分析結果顯示，前端樣本較後端及解剖盒樣本表現較多與能量相關的基因，這些能量可能是黑皮海綿覆蓋珊瑚後掠食得到的，可以用來增殖與擴張生長空間。後端樣本則表現較多與細胞凋亡相關反應及DNA修復的基因，說明此部分的黑皮海綿正處於生理狀況較差或逆境的狀態。解剖盒樣本所表現的基因大多與細胞移動有關，與其絲狀結構及束狀排列的骨針相呼應。由於黑皮海綿細胞內含有大量的原核生物，待原核生物的轉錄體定序完成之後，將能經由互相比較黑皮海綿及內含的原核生物轉錄體的表現，期望能找出黑皮海綿與體內原核生物之間的相關的生理代謝途徑並推測黑皮海綿與內含的原核生物之間的關係，和黑皮海綿與珊瑚之間的交互作用。

Recently, the corals in Lyudao, Taiwan, are prevalently suffered from the attack of “Black Disease”, caused by the overlaying of an encrusting sponge T. hoshinota. To understand the insights underlying T. hoshinota’s behavior, we sampled different parts of the sponge in Lyudao, including front-end, middle-site, and an isolated culture in mesh box as a control, for comparative purpose. The morphology of T. hoshinota was studied using electron microscopes, and the transcriptome profile was analyzed for validating possible associations between gene expression and appearance. The electron microscopes observation indicated that there were many coccus-like cyanobacteria, and tylostyle spicules were arranged regularly in the mesh box sample but disorderly in the front-end sample. Also, the front-end sample was in a healthier condition as being more intact compared to other samples. According to the transcriptomic analysis, the front-end sample had higher expression of the energy-related genes, suggesting that the front T. hoshinota might acquire energy by using coral as “food resource” for proliferation and territory expansion. The middle-site sample expressed more transcripts related to apoptosis and DNA repair, saying that this part of the sponge might be under stress. The preferred expression on cell motility genes in the mesh box sample revealed possible purpose of its silk-like appearance and might lead T. hoshinota to move. This transcriptomic study is just a start uncovering physiological and biochemical features of T. hoshinota. Further understandings about the interactions between coral, sponge, and associated bacteria can be obtained when the microbial gene expression data were incorporated.