Characterization of the Adult Head Transcriptome and Identification of Migration and Olfaction Genes in the Oriental Armyworm Mythimna separate

Abstract

The oriental armyworm Mythimna separate is an economically important insect with a wide distribution and strong migratory activity. However, knowledge about the molecular mechanisms regulating the physiological and behavioural responses of the oriental armyworm is scarce. In the present study, we took a transcriptomic approach to characterize the gene network in the adult head of M. separate. The sequencing and de novo assembly yielded 63,499 transcripts, which were further assembled into 46,459 unigenes with an N50 of 1,153 bp. In the head transcriptome data, unigenes involved in the 'signal transduction mechanism' are the most abundant. In total, 937 signal transduction unigenes were assigned to 22 signalling pathways. The circadian clock, melanin synthesis, and non-receptor protein of olfactory gene families were then identified, and phylogenetic analyses were performed with these M. separate genes, the model insect Bombyx mori and other insects. Furthermore, 1,372 simple sequence repeats of 2-6 bp in unit length were identified. The transcriptome data represent a comprehensive molecular resource for the adult head of M. separate, and these identified genes can be valid targets for further gene function research to address the molecular mechanisms regulating the migratory and olfaction genes of the oriental armyworm.

Figure 1

GO classification (a) and KOG categories (b) for the M. separate head transcriptome. The number of unigenes is shown on the right column for KOG categories.

Figure 2

KEGG Orthology (KO) classification (a) and third-tier KEGG pathways in the signal transduction category (b) for M. separate head transcriptome. The number of unigenes is shown in the column. P13K-Akt exhibits the highest number of assigned unigenes in the signal transduction category.

Figure 3

Neighbour-joining tree based on the amino acid sequences of the clock genes. CYC, cycle; MET, methoprene-tolerant; CLK, clock; VRI, vrille; PDP1, PAR-domain protein 1; CRY, cryptochrome; TIM, timeless; SLMB, slimb; PER, period; CK2b, casein kinase 2 beta; DBT, double time; SGG, shaggy; CK2a, casein kinase 2 alpha.

Figure 4

Neighbour-joining tree based on the amino acid sequences of melanin synthesis/related genes (a,b) and a schematic representation of the melanin synthesis pathway (c) found in M. separate. PPO, prophenoloxidase; tan, NBAD hydrolase; aaNAT, arylalkylamine N-acetyl transferase; DDC, DOPA decarboxylase; LAC, laccase; TH, tyrosine hydroxylase; ebony, NBAD synthase; GTPCH, GTP cyclohydrolase.

Figure 5

Neighbour-joining tree of candidate SNMP proteins (a) and CSP proteins (b). Five CSP orthologues (1:1:1:1) among four species are marked.

Figure 6

Neighbour-joining tree (a) and gene number comparison (b) of candidate OBP proteins among four lepidopteran species. Six groups, including PBP-GOBP, CRLBP, ABP-I, ABP-II, Plus-C and Minus-C, are marked on the dendrogram. Twelve orthologues (1:1:1:1) among four lepidopteran species are also marked.