近日,，國際著名雜志Applied and Environmental Microbiology在線刊登了中科院水生生物研究所研究人員的最新研究成果“Molecular Basis and Phylogenetic Implications of Deoxycylindrospermopsin Biosynthesis in the Cyanobacterium Raphidiopsis curvata,，”,，在研究中，研究者在藍藻毒素合成基因研究上獲得了新的進展,。
隨著淡水水體富營養(yǎng)化的加劇,，藍藻水華尤其是微囊藻水華問題已經得到了廣泛關注和深入研究。目前,，國際上對擬柱胞藻水華以及該藻產生的擬柱胞藻毒素（Cylindrospermopsin,， CYN）的報道日益增多。但是,，我國對于此類擬柱胞藻引起的水華現象研究甚少,。CYN是一種兩性離子生物堿，能夠引起人體肝,、腎等多個器官的損傷和細胞壞死,。除擬柱胞藻外,，其它藍藻如尖頭藻,、束絲藻、魚腥藻,、顫藻等均有產生CYN的種類,。
由于CYN的產生對居民健康存在潛在的危害，中國科學院水生生物研究所博士研究生蔣永光在李仁輝研究員的指導下開展了相關研究，在CYN生物合成的分子機理方面取得了新進展,。
尖頭藻是擬柱胞藻的近緣種類,，兩者常共存于同一水體中。蔣永光等人利用從湖北蘄春赤東湖分離到一株含有脫氧擬柱胞藻毒素（deoxy-CYN）的尖頭藻,，克隆并測定了該藻株的CYN生物合成基因簇（cyr cluster）的全序列,。研究發(fā)現，在該藻株中,，cyrI基因內部含有92bp的插入序列,，閱讀框發(fā)生移碼突變。研究人員推測,，正是這一突變導致細胞內CYN合成終止在deoxy-CYN階段,。該發(fā)現為cyrI基因功能確認提供了證據。
該研究加深了對擬柱胞藻毒素生物合成的分子機理以及合成基因進化的了解,，為擬柱胞藻和尖頭藻的系統(tǒng)關系研究提供了新的證據,，并為開展擬柱胞藻毒素的分子檢測、監(jiān)測和預警奠定了基礎,。
該研究得到了國家基礎研究973計劃,、國家自然科學基金、國家重大科技水專項和中科院“百人計劃”項目的資助,。（生物谷Bioon.com）
doi:10.1128/AEM.07321-11
PMC:
PMID:
Molecular Basis and Phylogenetic Implications of Deoxycylindrospermopsin Biosynthesis in the Cyanobacterium Raphidiopsis curvata
Yongguang Jianga,b, Peng Xiaoa,b, Gongliang Yua, Tomoharu Sanoc, Qianqian Pana,b and Renhui Lia
New insights into the distribution and biochemistry of the cyanotoxin cylindrospermopsin (CYN) have been provided by the recent determination of its biosynthesis gene cluster (cyr) in several cyanobacterial species. Raphidiopsis curvata CHAB1150 isolated from China was analyzed for CYN analogues. Only 7-deoxy-CYN was detected in the cell extracts. The cyr gene cluster of R. curvata CHAB1150 was sequenced, and the cyr genes of this strain were found to have extremely high similarities (96% to 100%) to those from other nostocalean species. These species include Cylindrospermopsis raciborskii AWT205, Aphanizomenon sp. strain 10E6, and Aphanizomenon ovalisporum ILC-146. Insertion mutation was identified within the cyrI gene, and transcripts of cyrI and another functional gene cyrJ were detected in R. curvata CHAB1150. General congruence between the phylogenetic trees based on both cyr and 16S rrn was displayed. Neutral evolution was found on the whole sequences of the cyr genes, and 0 to 89 negative selected codons were detected in each gene. Therefore, the function of CyrI is to catalyze the oxygenation of 7-deoxy-CYN in CYN biosynthesis. The transcripts of the mutated cyrI gene may result from polycistronic transcription. The high conservation of the cyr genes may be ascribed to purifying selection and horizontal gene transfer.
