Harrison Robert L, Mowery Joseph D, Rowley Daniel L, Bauchan Gary R, Theilmann David A, Rohrmann George F, Erlandson Martin A
Invasive Insect Biocontrol and Behavior Laboratory, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, MD, 20705, USA.
Electron and Confocal Microscopy Unit, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, MD, 20705, USA.
Virus Genes. 2018 Apr;54(2):297-310. doi: 10.1007/s11262-017-1525-0. Epub 2017 Dec 4.
A baculovirus isolate from a USDA Forest Service collection was characterized by electron microscopy and analysis of its genome sequence. The isolate, formerly referred to as Pseudoletia (Mythimna) sp. nucleopolyhedrovirus #7 (MyspNPV#7), was determined by barcoding PCR to derive from the host species Mythimna unipuncta (true armyworm) and was renamed Mythimna unipuncta nucleopolyhedrovirus #7 (MyunNPV#7). The occlusion bodies (OBs) and virions exhibited a size and morphology typical for OBs produced by the species of genus Alphabaculovirus, with occlusion-derived virions consisting of 2-5 nucleocapsids within a single envelope. The MyunNPV#7 genome was determined to be 148,482 bp with a 48.58% G+C nucleotide distribution. A total of 159 ORFs of 150 bp or larger were annotated in the genome sequence, including the 38 core genes of family Baculoviridae. The genome contained six homologous repeat regions (hrs) consisting of multiple copies of a 34-bp imperfect palindrome. Phylogenetic inference from concatenated baculovirus core gene amino acid sequence alignments placed MyunNPV#7 with group II alphabaculoviruses isolated from other armyworm and cutworm host species of lepidopteran family Noctuidae. MyunNPV#7 could be distinguished from other viruses in this group on the basis of differences in gene content and order. Pairwise nucleotide distances suggested that MyunNPV#7 represents a distinct species in Alphabaculovirus. The MyunNPV#7 genome was found to contain two copies of the late expression factor-7 (lef-7) gene, a feature not reported for any other baculovirus genome to date. Both copies of lef-7 encoded an F-box domain, which is required for the function of LEF-7 in baculovirus DNA replication.
对从美国农业部林业局收集的一种杆状病毒分离株进行了电子显微镜观察及其基因组序列分析。该分离株以前称为伪粘虫（Mythimna）属核多角体病毒#7（MyspNPV#7），通过条形码PCR确定其来源于宿主物种粘虫（Mythimna unipuncta）（真夜蛾），并重新命名为粘虫核多角体病毒#7（MyunNPV#7）。包涵体（OBs）和病毒粒子呈现出甲型杆状病毒属物种产生的OBs典型的大小和形态，从包涵体衍生的病毒粒子在单个包膜内由2 - 5个核衣壳组成。MyunNPV#7基因组被确定为148,482 bp，G + C核苷酸分布为48.58%。在基因组序列中总共注释了159个150 bp或更大的开放阅读框（ORF），包括杆状病毒科的38个核心基因。基因组包含六个同源重复区域（hrs），由一个34 bp不完全回文的多个拷贝组成。基于串联的杆状病毒核心基因氨基酸序列比对的系统发育推断将MyunNPV#7与从鳞翅目夜蛾科的其他夜蛾和地老虎宿主物种分离的II组甲型杆状病毒归为一类。MyunNPV#7可根据基因含量和顺序的差异与该组中的其他病毒区分开来。成对核苷酸距离表明MyunNPV#7代表甲型杆状病毒属中的一个独特物种。发现MyunNPV#7基因组包含晚期表达因子-7（lef-7）基因的两个拷贝，这是迄今为止任何其他杆状病毒基因组都未报道的特征。lef-7的两个拷贝都编码一个F-box结构域，这是lef-7在杆状病毒DNA复制中发挥功能所必需的。
