7月3日,，《美國國家科學(xué)院院刊》（PNAS）在線發(fā)表了由中國科學(xué)院微生物研究所劉杏忠研究員和University of Texas的安志強(qiáng)教授共同領(lǐng)導(dǎo)的研究團(tuán)隊(duì)在捕食性子囊菌起源與進(jìn)化方面所取得的新進(jìn)展,。
捕食性真菌是通過營養(yǎng)菌絲形成的特化捕食結(jié)構(gòu)來捕獲線蟲、變形蟲等微小生物作為營養(yǎng)源的一類特殊來群,。由于其獨(dú)特的生態(tài)特性，捕食性真菌的起源與進(jìn)化引起了科學(xué)界的廣泛興趣,。在2007年,，由劉杏忠研究員和安志強(qiáng)教授共同領(lǐng)導(dǎo)的研究團(tuán)隊(duì)對(duì)捕食性子囊菌（占捕食性真菌的90%以上）捕食結(jié)構(gòu)的進(jìn)化歷程作出較為詳細(xì)的論證，發(fā)現(xiàn)原始捕食結(jié)構(gòu)由于捕食機(jī)制的不同,，分別形成了主動(dòng)類的收縮環(huán)捕食結(jié)構(gòu)和被動(dòng)類的粘性捕食結(jié)構(gòu)（PNAS 104：8379）,。隨后，SCIENCE（318：1743,， 2010）報(bào)道了一種已滅絕捕食結(jié)構(gòu)的真菌化石,。Duke University的Heitman教授認(rèn)為這兩項(xiàng)研究為研究捕食性真菌的系統(tǒng)發(fā)育鋪平了道路（ Faculty of 1000：1098524）。
在前期工作的基礎(chǔ)上,，劉杏忠研究員和安志強(qiáng)教授領(lǐng)導(dǎo)的研究團(tuán)隊(duì)通過對(duì)精心選擇的,、代表6種捕食結(jié)構(gòu)的 16種捕食性子囊菌的5個(gè)蛋白質(zhì)編碼基因片段進(jìn)行分析，結(jié)合相關(guān)的化石證據(jù)和分子鐘計(jì)算,，推測(cè)捕食性子囊菌的祖先可能起源于4.19億年前,；在2.46億年前，主動(dòng)類的收縮環(huán)捕食結(jié)構(gòu)和被動(dòng)類的粘性捕食結(jié)構(gòu)發(fā)生分化,；而粘性捕食結(jié)構(gòu)在1.98-2.08億年之間快速分化并形成現(xiàn)存捕食結(jié)構(gòu)的主要分支,。而基于捕食結(jié)構(gòu)為收縮環(huán)的Drechslerella stenobrocha基因組數(shù)據(jù)，通過獨(dú)立的時(shí)間校正點(diǎn)對(duì)1069個(gè)同源蛋白序列分析,，推測(cè)主動(dòng)類的收縮環(huán)捕食結(jié)構(gòu)和被動(dòng)類的粘性捕食結(jié)構(gòu)的分化事件在2.60億年前,，與上述分析結(jié)果高度接近。
由于捕食性子囊菌兩次重大分化事件的發(fā)生事件接近于2.51億年前的二疊紀(jì)-三疊紀(jì)物種大滅絕事件和2.01億年前的三疊紀(jì)-侏羅紀(jì)物種大滅絕事件,，研究團(tuán)隊(duì)進(jìn)而推測(cè)物種大滅絕所導(dǎo)致的大量有機(jī)物,，促使線蟲大量繁衍，而真菌為了獲取氮源以及在惡劣環(huán)境壓力脅迫下,，可能驅(qū)動(dòng)了子囊菌捕食能力的進(jìn)化,。該研究為真菌在極端環(huán)境下的適應(yīng)性進(jìn)化提供了新的理論。（生物谷Bioon.com）
doi:10.1073/pnas.1120915109
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Origin and evolution of carnivorism in the Ascomycota (fungi)
Ence Yanga,1, Lingling Xua,b,1, Ying Yanga, Xinyu Zhanga, Meichun Xianga, Chengshu Wangc, Zhiqiang And,2, and Xingzhong Liua,2
Carnivorism is one of the basic life strategies of fungi. Carnivorous fungi possess the ability to trap and digest their preys by sophisticated trapping devices. However, the origin and development of fungal carnivorism remains a gap in evolution biology. In this study, five protein-encoding genes were used to construct the phylogeny of the carnivorous fungi in the phylum Ascomycota; these fungi prey on nematodes by means of specialized trapping structures such as constricting rings and adhesive traps. Our analysis revealed a definitive pattern of evolutionary development for these trapping structures. Molecular clock calibration based on two fossil records revealed that fungal carnivorism diverged from saprophytism about 419 Mya, which was after the origin of nematodes about 550–600 Mya. Active carnivorism (fungi with constricting rings) and passive carnivorism (fungi with adhesive traps) diverged from each other around 246 Mya, shortly after the occurrence of the Permian–Triassic extinction event about 251.4 Mya. The major adhesive traps evolved around 198–208 Mya, which was within the time frame of the Triassic–Jurassic extinction event about 201.4 Mya. However, no major carnivorous ascomycetes divergence was correlated to the Cretaceous–Tertiary extinction event, which occurred more recently (about 65.5 Mya). Therefore, a causal relationship between mass extinction events and fungal carnivorism evolution is not validated in this study. More evidence including additional fossil records is needed to establish if fungal carnivorism evolution was a response to mass extinction events.
