第一个珊瑚基因组测序完成
第一个珊瑚基因组测序完成
2011/08/18 23:34:58
第一个完整的珊瑚基因组测序结果显示，珊瑚的起源时间比之前认定的时间早了很多，并且至少有一个重要的物种比环保人士所担心的更为脆弱。
7月24日，日本冲绳县科学与技术研究所的Chuya Shinzato和同事宣布，他们已经完成了鹿角珊瑚（Acropora digitifera）——占据了大部分印度洋—太平洋海域的一种构成珊瑚礁的细长珊瑚——的基因组测序工作。
研究人员采集了珊瑚的精子，分析其中脱氧核糖核酸（DNA）的碱基序列，确定了23688种编码蛋白质的基因。
他们将珊瑚基因组与它的刺胞动物表亲水母、海葵以及水螅进行了比较，发现珊瑚最早出现在5亿多年前，这比已知最早的化石记录提前了2.5亿年。
研究人员同时发现，鹿角珊瑚缺乏合成一种必需氨基酸——半胱氨酸——所需的酶。这意味着珊瑚可能依赖被称为腰鞭毛虫的一种极小的共生生物体来生物合成半胱氨酸，从而使得珊瑚对于危及其小帮手的气候变化显得尤为敏感。
日本科学家认为，本项研究不仅有助于理解珊瑚的进化历程，还能帮助人们研究珊瑚白化现象。
日本科学家的这一发现已经发表在最新一期英国《自然》杂志网络版上。
珊瑚虫是一种海生圆筒状腔肠动物，在白色幼虫阶段便自动固定在先辈珊瑚的石灰质遗骨堆上，珊瑚是珊瑚虫分泌出的外壳，珊瑚的化学成分主要为CaCO3，以微晶方解石集合体形式存在，成分中还有一定数量的有机质，形态多呈树枝状，上面有纵条纹，每个单体珊瑚横断面有同心圆状和放射状条纹，颜色常呈白色，也有少量蓝色和黑色，珊瑚不仅形象像树枝，颜色鲜艳美丽，可以做装饰品，并且还有很高的药用价值。
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.