Identification of immunity-related genes in Ostrinia furnacalis against entomopathogenic fungi by RNA-seq analysis.
BACKGROUND
The Asian corn borer (Ostrinia furnacalis (Guenée)) is one of the most serious corn pests in Asia. Control of this pest with entomopathogenic fungus Beauveria bassiana has been proposed. However, the molecular mechanisms involved in the interactions between O. furnacalis and B. bassiana are unclear, especially under the conditions that the genomic information of O. furnacalis is currently unavailable. So we sequenced and characterized the transcriptome of O. furnacalis larvae infected by B. bassiana with special emphasis on immunity-related genes.


RESULTS
Illumina Hiseq2000 was used to sequence 4.64 and 4.72 Gb of the transcriptome from water-injected and B. bassiana-injected O. furnacalis larvae, respectively. De novo assembly generated 62,382 unigenes with mean length of 729 nt. All unigenes were searched against Nt, Nr, Swiss-Prot, COG, and KEGG databases for annotations using BLASTN or BLASTX algorithm with an E-value cut-off of 10(-5). A total of 35,700 (57.2%) unigenes were annotated to at least one database. Pairwise comparisons resulted in 13,890 differentially expressed genes, with 5,843 up-regulated and 8,047 down-regulated. Based on sequence similarity to homologs known to participate in immune responses, we totally identified 190 potential immunity-related unigenes. They encode 45 pattern recognition proteins, 33 modulation proteins involved in the prophenoloxidase activation cascade, 46 signal transduction molecules, and 66 immune responsive effectors, respectively. The obtained transcriptome contains putative orthologs for nearly all components of the Toll, Imd, and JAK/STAT pathways. We randomly selected 24 immunity-related unigenes and investigated their expression profiles using quantitative RT-PCR assay. The results revealed variant expression patterns in response to the infection of B. bassiana.


CONCLUSIONS
This study provides the comprehensive sequence resource and expression profiles of the immunity-related genes of O. furnacalis. The obtained data gives an insight into better understanding the molecular mechanisms of innate immune processes in O. furnacalis larvae against B. bassiana.
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
Yang
Y
Liu
Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
Dongxu
D
Shen
Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
Fan
F
Zhou
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
Guirong
G
Wang
Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
Chunju
C
An
D000595:Amino Acid Sequence; D000818:Animals; D052982:Beauveria / Q000502:physiology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D063990:Gene Ontology; D017344:Genes, Insect / Q000235:genetics*; D007109:Immunity / Q000235:genetics*; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics; D007915:Lepidoptera / Q000235:genetics* / Q000276:immunology* / Q000382:microbiology; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000378:metabolism; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017423:Sequence Analysis, RNA / Q000379:methods*; D059467:Transcriptome
D019476:Insect Proteins; D010457:Peptidoglycan