The Genome Sequencing Of Sogatella Furcifera And The Transcriptome Analysis In Response To Southern Rice Black-streaked Dwarf Virus Infection

The white-backed planthopper(WBPH),Sogatella furcifera,is one of the most destructive agriculture pests.WBPH has become one of the most destructive pests in rice production owing to its plant sap-sucking behavior and efficient transmission of Southern rice black-streaked dwarf virus(SRBSDV)in a circulative,propagative and persistent manner.Due to the lack of well-assembled and annotated genome sequences,critical aspects of the insect’s biology,including the interaction between WBPH and SRBSDV,are hampered.Therefore,the genome sequencing of WBPH was performed,the immune related genes were identified,and transcriptome analysis was carried out in WBPH in response to SRBSDV infection.The main results were listed below:A sibling inbred line of WBPH was developed in our laboratory.The heterozygosity of each generation was evaluated and the sixth generation WBPH was used for the whole genome sequencing.A series of genomic libraries with distinct insert sizes ranging from 180 bp to 40 kb were constructed and sequenced by next generation sequencer.In total,241.3 gigabase reads were obtained,which covered the genome 330 times.These reads were assembled into a～720 Mb genome assembly with a contig N50 of 70.7 kb and scaffold N50 of 1.18 Mb.The genome was annotated with 21,254 protein-coding genes.In addition,2,386 genetic markers were developed using RAD-seq datasets generated from F1 parents and 62 offsprings.15 genetic linkage groups were constructed based on these genetic markers,which covered 529 longest scaffolds(71%)and 13,626 genes(64%).In this study,based on a homology-based genome-wide analysis,348 immune-related genes belonging to 28 families were identified in WBPH.A transcriptome analysis of non-viruliferous(NVF)and viruliferous groups with high viral titers(HVT)and median viral titers(MVT)revealed that feeding on SRBSDV-infected rice plants has a significant impact on gene expression,regardless of viral titers in insects.The normalized abundance ratio of the SRBSDV S9-2 segment to RP49 transcripts was six orders of magnitude different among viruliferous individuals.We identified 278 up-regulated and 406 down-regulated genes shared among the NVF,MVT,and HVT groups and detected significant down-regulation of primary metabolism-related genes and oxidoreductase.In viruliferous WBPH with viral titer-specific transcriptome changes,1,906 and 1,467 genes exhibited strict monotonically increasing and decreasing expression,respectively.The RNAi pathway was the major antiviral response to increasing viral titers among diverse immune responses.Small RNA analysis also confirmed that the RNAi pathway of WBPH was involved in the immune response to SRBSDV in cell level as well as the adult level.In summary,these results obtained in this study improved our knowledge of SRBSDV-WBPH interaction,including the 720-Mb draft WBPH genome with 21,254 protein-coding genes,348 immune-related genes belonging to 28 families and the gene profiles of the insect in response to SRBSDV infection.Most importantly,these results provided an important foundation for studying the mechanism of SRBSDV-WBPH-rice plant interaction.