Effects Of Endosymbionts Wolbachia On The Reproduction Of Laodelphax Striatellus And The Correlation Between Wolbachia And Bacteriophage WO

Laodelphax striatellus, Sogatella furcifera and Nilaparvata lugens belong to Insecta, Hemiptera, Delphacidae and they are very important pests distributed broadly in many regions. They do damages to the rice by sucking and spreading virus. Wolbachia pipientis (often referred to simply as Wolbachia), a Rickettsia-like a-proteobacterium, is a ubiquitous, maternally transmitted intracellular endosymbiotic bacterium in invertebrates. Infections of Wolbachia have been associated with various abnormalities of host reproduction:cytoplasmic incompatibility (CI), feminization, parthenogenesis induction (PI) and male-killing. It exists and spreads in different populations by regulating host reproduction.Bacteriophages are the viruses which infect bacteria, they are highly specific in hosts and make a significant force in bacterial genome evolution. In 2000, Shinjit and Masui firstly found and reported the WO phage from the Wolbachia genome in Teleogryllus taiwanemma. Bacteriophage WO can be either lysogenicly intergrated into the Wolbachia chromosome, or lytic and free in the cytopoasm. It may take important genes into the Wolbachia genome and participate in the process of Wolbachia regulating the host's reproductive mode. We investigated the reproduction abnormalities in L. striatellus of two populations. Also, we surveyed the infection of WO phage and the correlation between Wolbachia and WO phage in three planthopper species.To understand the effect of Wolbachia on the L. striatellus, two populations of L. striatellus in China. the Nanning (NN) and Ning'er (NE), were investigated. Our results showed that Wolbachia induced strong CI in these two populations, and CI is expressed as a reduction in eggs numbers and hatchability. We firstly reported WO phage infection in Wolbachia from three planthoppers by PCR amplification of orf7 gene encoding WO phage' capsid protein. The types of WO phage were also investigated by analyzing the orf7sequences. Our results indicated WO phage was widely infected in Wolbachia of planthoppers species. There were three types of WO phage and the accession numbers were recorded in Genbank.After sequencing the orf7 gene of WO phage and the wsp gene of Wolbachia in planthoppers from 20 populations and analyzing the phylogeny between WO phage and Wolbachia, we found that the topological structure of WO phage and Wolbachia is different. That showed the correlation between WO phage and Wolbachia wasn't evident. In the phylogenetic analysis of WO phage, the orf7 sequence in Ephestia kuehniella and L. striatellus were classified into the same clade. This raises the possibility that horizontal transmission of WO phage occurs between some Wolbachia strains. If this reference is right, WO phage probably took part in the process of promoting the evolution of Wolbachia. This is the first discovery of WO phage in planthoppers.We enumerated the copy numbers of Wolbachia and WO phage by real-time quantitative PCR (RTQ-PCR) in 20 populations of three planthopper species, L. striatellus, S.furcifera and N.lugens. To understand the relationship between WO phage and Wolbachia. the copy numbers of them were estimated in males of L. striatellus at different ages. The findings showed that the numbers of Wolbachia varied according to the developmental stage. So was the WO phage. This is the first time to quantity WO phage in L.striatellus with RTQ-PCR method.