能够感染杀虫的真菌种类达数千种，广布于世界各地，在昆虫种群生态调控中发挥着重要的作用，代表性的金龟子绿僵菌（Metarhizium anisopliae）和蝗绿僵菌(M. acridum)等已经被发展成为环境友好的真菌杀虫剂，取得了良好的生态、经济及社会效益。
1月6日《PLoS遗传学》(PLoS Genetics)在线发表了中国科学院上海生命科学研究院植物生理生态研究所王成树课题组关于这两种杀虫真菌比较基因组的研究论文。该文章第一次测序、分析了寄主广谱的金龟子绿僵菌与蝗虫专化的蝗绿僵菌的基因组组成与结构的差异，推测绿僵菌由植物病原真菌进化而来。同植物病原真菌及其他丝状真菌相比，昆虫病原真菌基因组中的蛋白酶、几丁质酶及脂酶等用于昆虫体壁降解的基因家族存在显著的扩张现象。相比于蝗绿僵菌，除蛋白激酶外，广谱性的金龟子绿僵菌基因组编码有更多的不同蛋白基因，尤其是后者的基因组中含有大量的转座子基因以及丢失了重复引起点突变 (repeat-induced point mutation)的基因组防御功能，从而促进基因组进化而适应感染不同种类的昆虫宿主。
RNA-seq高通量转录组分析表明，金龟子绿僵菌与蝗绿僵菌在不同寄主体壁信号诱导下，表达不同信号识别蛋白，诱导下游的MAPK和PKA的信号强度不同，从而精确调控细胞分化，决定了绿僵菌的寄主范围。
绿僵菌基因组的测序为进一步推动真菌杀虫毒力基因鉴定、昆虫—真菌分子相互作用及遗传改造并提高真菌杀虫剂的应用效率等基础及应用研究提供了良好的平台，同时也有利于促进真菌进化与生态学的研究。
此项研究成果得到了科技部、国家自然科学基金及中科院项目的资助。（生物谷Bioon.com）
生物谷推荐原文出处：
PLoS Genet 7(1): e1001264. doi:10.1371/journal.pgen.1001264
Genome Sequencing and Comparative Transcriptomics of the Model Entomopathogenic Fungi Metarhizium anisopliae and M. acridum
Qiang Gao1#, Kai Jin2#, Sheng-Hua Ying3#, Yongjun Zhang4#, Guohua Xiao1#, Yanfang Shang1, Zhibing Duan1, Xiao Hu1, Xue-Qin Xie3, Gang Zhou3, Guoxiong Peng2, Zhibing Luo4, Wei Huang1, Bing Wang1, Weiguo Fang5, Sibao Wang5, Yi Zhong6, Li-Jun Ma7, Raymond J. St. Leger5, Guo-Ping Zhao6, Yan Pei4, Ming-Guang Feng3*, Yuxian Xia2*, Chengshu Wang1*
1 Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China, 2 College of Bioengineering, Chongqing University, Chongqing, China, 3 College of Life Sciences, Zhejiang University, Hangzhou, China, 4 Biotechnology Research Center, Southwest University, Chongqing, China, 5 Department of Entomology, University of Maryland, College Park, Maryland, United States of America, 6 Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China, 7 The Broad Institute, Cambridge, Massachusetts, United States of America
Abstract
Metarhizium spp. are being used as environmentally friendly alternatives to chemical insecticides, as model systems for studying insect-fungus interactions, and as a resource of genes for biotechnology. We present a comparative analysis of the genome sequences of the broad-spectrum insect pathogen Metarhizium anisopliae and the acridid-specific M. acridum. Whole-genome analyses indicate that the genome structures of these two species are highly syntenic and suggest that the genus Metarhizium evolved from plant endophytes or pathogens. Both M. anisopliae and M. acridum have a strikingly larger proportion of genes encoding secreted proteins than other fungi, while ~30% of these have no functionally characterized homologs, suggesting hitherto unsuspected interactions between fungal pathogens and insects. The analysis of transposase genes provided evidence of repeat-induced point mutations occurring in M. acridum but not in M. anisopliae. With the help of pathogen-host interaction gene database, ~16% of Metarhizium genes were identified that are similar to experimentally verified genes involved in pathogenicity in other fungi, particularly plant pathogens. However, relative to M. acridum, M. anisopliae has evolved with many expanded gene families of proteases, chitinases, cytochrome P450s, polyketide synthases, and nonribosomal peptide synthetases for cuticle-degradation, detoxification, and toxin biosynthesis that may facilitate its ability to adapt to heterogenous environments. Transcriptional analysis of both fungi during early infection processes provided further insights into the genes and pathways involved in infectivity and specificity. Of particular note, M. acridum transcribed distinct G-protein coupled receptors on cuticles from locusts (the natural hosts) and cockroaches, whereas M. anisopliae transcribed the same receptor on both hosts. This study will facilitate the identification of virulence genes and the development of improved biocontrol strains with customized properties.
