Sequence Analysis And Biological Characteristics Of Hypovirus FgHV2-JS16from Fusarium Graminearum

Fungal viruses (mycoviruses) occur in all four phyla of the true fungi. Fusariumgraminearum isolates from China were screened for dsRNA mycoviruses. Adouble-stranded (ds) RNA element, sized at approximately13kilobase pairs, was purifiedfrom a field isolate, JS16of Fusarium graminearum. Sequence alignments indicated thedsRNA represent the genome of a nove mycovirus. Phylogenetic analysis showed that thevirus existed in strain JS16belongs to the hypoviridae and was designated FgHV2/JS16.We also exploe the influence of the virus on biological properties of host strain JS16. Thispaper will lay foundation for the study of mycoviruses of Fusarium. spp isolated fromChina and provide resources for the clarification of phylogenetic relationships amongviruses in the family hypoviridae.1. Totally,1,862strains of Fusarium.spp were isolated from infected wheat headgrowen on the major wheat producing proviences. Through CF-11dsRNA purification, wedetected16(23%) out of70isolates collected. The dsRNA fragment size ranged from1700bp to13000bp. And several fragments could be detected from some strains. A dsRNAfragment sized at more than10kb was purified from strain JS16. Result of blast for thesequence of EF-1suggest that strain JS16was Fusarium graminearum.2. Through sequence assembling of clones got with random primers, sequencespecific primers and RACE, a stand of12,841bp tailed with polyA was obtained.3. The coding strand of the dsRNA was12,800nucleotides (nt) long (excluding the3′poly-A tail) and was predicted to contain one open reading frames (ORF). The ORFencoded a protein of3944amino acids (aa), and a nucleottide BLAST search showed it tobe similar to none genome sequence. The protein BALST search showed that to be similarto the putative papain-like protease domains encoded by Cryphonectria hypovirus1(CHV1)(51%identity), Cryphonectria hypovirus2(CHV2)(57%identity), Fusariumgraminearum hypovirus1(FgHV1)(48%identity) and Sclerotinia sclerotiorum hypovirus2(SsHV2)(44%identity). The ORF encoded a large polyprotein with two conserveddomains, including RNA-dependent RNA polymerase and RNA helicase domains. Boththe genome organization and phylogenetic analysis suggested that the characterized RNArepresented a novel hypovirus, designated “Fusarium graminearum hypovirus2(FgHV2)”, which was closely related to CHV1and CHV2in the Hypoviridae family.4. FgHV2/JS16infection had reductions in mycelial growth rate and conidiationproduction while the virus had effects on fungal phenotypes including morphology, sexual reproduction, virulence or toxin production.