Identification and Expression Profiles of Sex Pheromone Biosynthesis and Transport Related Genes in Spodoptera litura

Abstract

Although the general pathway of sex pheromone synthesis in moth species has been established, the molecular mechanisms remain poorly understood. The common cutworm Spodoptera litura is an important agricultural pest worldwide and causes huge economic losses annually. The female sex pheromone of S. litura comprises Z9,E11-14:OAc, Z9,E12-14:OAc, Z9-14:OAc, and E11-14:OAc. By sequencing and analyzing the transcriptomic data of the sex pheromone glands, we identified 94 candidate genes related to pheromone biosynthesis (55 genes) or chemoreception (39 genes). Gene expression patterns and phylogenetic analysis revealed that two desaturase genes (SlitDes5 and SlitDes11) and one fatty acyl reductase gene (SlitFAR3) showed pheromone gland (PG) biased or specific expression, and clustered with genes known to be involved in pheromone synthesis in other moth species. Furthermore, 4 chemoreception related genes (SlitOBP6, SlitOBP11, SlitCSP3, and SlitCSP14) also showed higher expression in the PG, and could be additional candidate genes involved in sex pheromone transport. This study provides the first solid background information that should facilitate further elucidation of sex pheromone biosynthesis and transport, and indicates potential targets to disrupt sexual communication in S. litura for a novel pest management strategy.

Fig 1. Distribution of unigene size in the S. litura transcriptome assembly.

Fig 2. Gene ontology (GO) classification of the S. litura transcripts with Blast2GO program.

Fig 3. Top 20 most abundant transcripts in the S. litura transcriptome dataset.

The genes expression abundance is indicated as the Reads Per Kilobase per Million mapped reads (RPKM) values. The transcript annotation by homologous comparisons with Blastx is indicated in Tables 3 and 4 and S1 Table.

Fig 4. Expression patterns of sex pheromone biosynthesis related genes, using RT-PCR.

(A) Expression of Des genes. (B) Expression of FAR genes. (C) Expression of ACT genes. (D) Expression of ACBP, FATP and ACC genes. GAPDH gene was used as a positive control and NC (no cDNA template) as a negative control. PG, female pheromone glands; B, whole insect body without PGs.

Fig 5. Expression patterns of sex pheromone chemoreception related genes, using RT-PCR.

(A) Expression of OBP genes. (B) Expression of CSP genes. GAPDH gene was used as a positive control and NC (no cDNA template) as a negative control. PG, female pheromone glands; B, whole insect body without PGs.

Fig 6. Relative expression levels of 16 pheromone biosynthesis and chemoreception releated genes, using qPCR.

FA, female antennae; MA, male antennae; PG, female pheromone glands; Bo, whole insect body without PGs and antennae. The relative expression level is indicated as mean ± SE (N = 3). Different capital letters mean significant difference between tissues (P < 0.05, ANOVA, LSD); the “*” indicates significant difference between male and female (P < 0.05, Student t-test).

Fig 7. Phylogenetic tree of insect desaturase (Des).

The S. litura translated genes are shown in blue. Accession numbers are given in S2 Table. The tree was constructed with MEGA5.0, using the neighbour-joining method. Values at the nodes are results of bootstrap with 1000 replicates.

Fig 8. Phylogenetic tree of insect fatty acid redutase (FAR).

The S. litura translated genes are shown in blue. Accession numbers are given in S2 Table. The tree was constructed with MEGA5.0, using the neighbour-joining method. Values at the nodes are results of bootstrap with 1000 replicates.