第一個(gè)完整的珊瑚基因組測(cè)序結(jié)果顯示,，珊瑚的起源時(shí)間比之前認(rèn)定的時(shí)間早了很多，并且至少有一個(gè)重要的物種比環(huán)保人士所擔(dān)心的更為脆弱,。
7月24日，日本沖繩縣科學(xué)與技術(shù)研究所的Chuya Shinzato和同事宣布,，他們已經(jīng)完成了鹿角珊瑚（Acropora digitifera）——占據(jù)了大部分印度洋—太平洋海域的一種構(gòu)成珊瑚礁的細(xì)長(zhǎng)珊瑚——的基因組測(cè)序工作,。
研究人員采集了珊瑚的精子，分析其中脫氧核糖核酸（DNA）的堿基序列,，確定了23688種編碼蛋白質(zhì)的基因,。
他們將珊瑚基因組與它的刺胞動(dòng)物表親水母、?？约八＿M(jìn)行了比較,，發(fā)現(xiàn)珊瑚最早出現(xiàn)在5億多年前，這比已知最早的化石記錄提前了2.5億年。
研究人員同時(shí)發(fā)現(xiàn),，鹿角珊瑚缺乏合成一種必需氨基酸——半胱氨酸——所需的酶,。這意味著珊瑚可能依賴(lài)被稱(chēng)為腰鞭毛蟲(chóng)的一種極小的共生生物體來(lái)生物合成半胱氨酸，從而使得珊瑚對(duì)于危及其小幫手的氣候變化顯得尤為敏感,。
日本科學(xué)家認(rèn)為,，本項(xiàng)研究不僅有助于理解珊瑚的進(jìn)化歷程，還能幫助人們研究珊瑚白化現(xiàn)象,。
日本科學(xué)家的這一發(fā)現(xiàn)已經(jīng)發(fā)表在最新一期英國(guó)《自然》雜志網(wǎng)絡(luò)版上,。
珊瑚蟲(chóng)是一種海生圓筒狀腔腸動(dòng)物，在白色幼蟲(chóng)階段便自動(dòng)固定在先輩珊瑚的石灰質(zhì)遺骨堆上,，珊瑚是珊瑚蟲(chóng)分泌出的外殼,，珊瑚的化學(xué)成分主要為CaCO3，以微晶方解石集合體形式存在,，成分中還有一定數(shù)量的有機(jī)質(zhì),，形態(tài)多呈樹(shù)枝狀，上面有縱條紋,，每個(gè)單體珊瑚橫斷面有同心圓狀和放射狀條紋,，顏色常呈白色，也有少量藍(lán)色和黑色,，珊瑚不僅形象像樹(shù)枝,，顏色鮮艷美麗，可以做裝飾品,，并且還有很高的藥用價(jià)值,。(生物谷 Bioon.com)
doi:10.1038/nature10249
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PMID:
Using the Acropora digitifera genome to understand coral responses to environmental change
Chuya Shinzato; Eiichi Shoguchi; Takeshi Kawashima; Mayuko Hamada; Kanako Hisata; Makiko Tanaka; Manabu Fujie; Mayuki Fujiwara; Ryo Koyanagi; Tetsuro Ikuta; Asao Fujiyama; David J. Miller; Nori Satoh
Despite the enormous ecological and economic importance of coral reefs, the keystone organisms in their establishment, the scleractinian corals, increasingly face a range of anthropogenic challenges including ocean acidification and seawater temperature rise1, 2, 3, 4. To understand better the molecular mechanisms underlying coral biology, here we decoded the approximately 420-megabase genome of Acropora digitifera using next-generation sequencing technology. This genome contains approximately 23,700 gene models. Molecular phylogenetics indicate that the coral and the sea anemone Nematostella vectensis diverged approximately 500 million years ago, considerably earlier than the time over which modern corals are represented in the fossil record (~240 million years ago)5. Despite the long evolutionary history of the endosymbiosis, no evidence was found for horizontal transfer of genes from symbiont to host. However, unlike several other corals, Acropora seems to lack an enzyme essential for cysteine biosynthesis, implying dependency of this coral on its symbionts for this amino acid. Corals inhabit environments where they are frequently exposed to high levels of solar radiation, and analysis of the Acropora genome data indicates that the coral host can independently carry out de novo synthesis of mycosporine-like amino acids, which are potent ultraviolet-protective compounds. In addition, the coral innate immunity repertoire is notably more complex than that of the sea anemone, indicating that some of these genes may have roles in symbiosis or coloniality. A number of genes with putative roles in calcification were identified, and several of these are restricted to corals. The coral genome provides a platform for understanding the molecular basis of symbiosis and responses to environmental changes.
