A reference gene set for sex pheromone biosynthesis and degradation genes from the diamondback moth, Plutella xylostella, based on genome and transcriptome digital gene expression analyses

Abstract

Background: Female moths synthesize species-specific sex pheromone components and release them to attract male moths, which depend on precise sex pheromone chemosensory system to locate females. Two types of genes involved in the sex pheromone biosynthesis and degradation pathways play essential roles in this important moth behavior. To understand the function of genes in the sex pheromone pathway, this study investigated the genome-wide and digital gene expression of sex pheromone biosynthesis and degradation genes in various adult tissues in the diamondback moth (DBM), Plutella xylostella, which is a notorious vegetable pest worldwide.

Results: A massive transcriptome data (at least 39.04 Gb) was generated by sequencing 6 adult tissues including male antennae, female antennae, heads, legs, abdomen and female pheromone glands from DBM by using Illumina 4000 next-generation sequencing and mapping to a published DBM genome. Bioinformatics analysis yielded a total of 89,332 unigenes among which 87 transcripts were putatively related to seven gene families in the sex pheromone biosynthesis pathway. Among these, seven [two desaturases (DES), three fatty acyl-CoA reductases (FAR) one acetyltransferase (ACT) and one alcohol dehydrogenase (AD)] were mainly expressed in the pheromone glands with likely function in the three essential sex pheromone biosynthesis steps: desaturation, reduction, and esterification. We also identified 210 odorant-degradation related genes (including sex pheromone-degradation related genes) from seven major enzyme groups. Among these genes, 100 genes are new identified and two aldehyde oxidases (AOXs), one aldehyde dehydrogenase (ALDH), five carboxyl/cholinesterases (CCEs), five UDP-glycosyltransferases (UGTs), eight cytochrome P450 (CYP) and three glutathione S-transferases (GSTs) displayed more robust expression in the antennae, and thus are proposed to participate in the degradation of sex pheromone components and plant volatiles.

Conclusions: To date, this is the most comprehensive gene data set of sex pheromone biosynthesis and degradation enzyme related genes in DBM created by genome- and transcriptome-wide identification, characterization and expression profiling. Our findings provide a basis to better understand the function of genes with tissue enriched expression. The results also provide information on the genes involved in sex pheromone biosynthesis and degradation, and may be useful to identify potential gene targets for pest control strategies by disrupting the insect-insect communication using pheromone-based behavioral antagonists.

Keywords: Aldehyde oxidase; Carboxyl/Cholinesterase; Desaturase; Detoxification; Fatty acyl reductase; Pheromone-biosynthesis enzymes; Pheromone-degrading enzymes.

Fig. 1

Dissection of P. xylostella female sex pheromone glands. The pheromone glands from female P. xylostella were squeezed out from the abdomen using forceps (the gland is similarly inflated when the female calls). The abdomen of P. xylostella was cut at the sclerotized cuticle from the 8^th abdominal segment, and the sclerotized cuticle was removed before immersing the glands in liquid nitrogen. 1: Sclerotized ovipositor valves; 2: Pheromone gland; 3: Sclerotized cuticle that was removed

Fig. 2

Proposed biosynthetic pathway of sex pheromone production in female DBM moths (adapted from [2, 16, 77])

Fig. 3

Heat map illustration of the tissue expression profile of sex pheromone biosynthesis and degradation genes based on FPKM values. m_Ant, male antennae; f_Ant, female antennae; H, Head; L, Leg; AB, Abdomen; PG, female pheromone gland. Gene names are indicated on the left. Scale Bar on bottom right indicates the degree of expression

Fig. 4

Relative expression levels of sex pheromone biosynthesis and degradation gene transcripts with antennae or pheromone gland-biased expression in different adult tissues. m_Ant, male antennae; f_Ant, female antennae; H, Head; L, Leg; AB, Abdomen; PG, female pheromone gland

Fig. 5

Phylogenetic tree of typical insect DES genes. PxylDES are highlighted in red. Species abbreviations: Bmor. B. mori; Slit. Spodoptera litura; Sinf. Sesamia inferens; Tni. T. ni; Ofur. O. furnacalis; Onub. O. nubilalis; Osca. O. scapulalis; Hass. H. assulta; Lcap. L. capitella; Cpar. C. parallela; Dpun. D. punctatus; Cros. C. rosaceana; Obru. O. brumata; Aper. A. pernyi; Msex. M. sexta; Tpit. T. pityocampa; Hzea. H. zea; Mbra. M. brassicae; Ypad. Y. padellus; Poct. P. octo; Epos. E. postvittana; Avel. A. velutinana; and Asel. A. selenaria cretacea

Fig. 6

Phylogenetic tree of typical insect FAR genes. PxFARs are highlighted in red. Species abbreviations: Bmor. B. mori; Cqui. C.ulex quinquefasciatus; Yevo. Y. evonymellus; Ypad. Y. padellus; Yror. Y. rorrellus; Hass. H. assulta; Harm. H. armigera; Hsub. H. subflexa; Hvir. H. virescens; Nvit. N. vitripennis; Amel. A. mellifera; Sinv. S. invicta; Hsal. H. saltator; Cflo. C. floridanus; Osca. O. scapulalis; Aaeg. Aedes aegypti; Dmoj. D. mojavensis; Dvir. D. virilis; Dgri. D. grimshawi; Dwii. D. willistoni; Dper. D. persimilis; Dpse. D. pseudoobscura; Dana. D. ananassae; Dsec. D. sechellia; Dere. D. erecta; Dyak. D. yakuba; Dpul. D. pulex; Dmel. D. melanogaster and Apis. A. pisum

Fig. 7

Phylogenetic tree of typical insect AOX genes. PxylAOXs are highlighted in red. Species abbreviations: Dmel, D. melanogaster; Bmor, B. mori; Cqui, C quinquefasciatus; Agam, A. gambiae; Aaeg, A. aegypti; Ofur, Ostrinia. furnacalis; Sinf, S. inferens; Atra, A. transitella and Mbra. Mamestra. brassicae. Scale bar on top left indicates the color code for bootstrap values in the phylogenetic tree

Fig. 8

Phylogenetic tree of typical insect CCE genes. PxCCEs are highlighted in red. Species abbreviations: Dmel. D. melanogaster; Bmor. B. mori; Agos. Aphis gossypii; Hirr. Haematobia irritans; Lcup. Lucilia cuprina; Mdom. Musca domestica; Cqui. Culex quinquefasciatus; Ctar. Culex tarsalis; Ctri. Culex tritaeniorhynchus; Ha. H. armigera; Sexi. Spodoptera exigua; Sl. S. littoralis; Slit. Spodoptera litura; Ep. Epiphyas postvittana; Apol. Antheraea polyphemus; Amel. Apis mellifera; Pjap. Popillia japonica; Nlug. Nilaparvata lugens; Mper. Myzus persicae; Aaeg. Aedes aegypti; Gass. Gryllus assimilis; Phil. Psacothea hilaris; Tmol. Tenebrio molitor; Apis. Acyrthosiphon pisum; Tcas. Tribolium castaneum; Hass. Heliothis assulta; Nvit. Nasonia vitripennis; Cfum. Choristoneura fumiferana; Hvir. Heliothis virescens; Mbra. M. brassicae and Msex. Manduca sexta

Fig. 9

Phylogenetic tree and intron positions of PxCCE genes. The nomenclatures of clades are based on previously published data. The intron positions in sequences are shown as (|) for a phase 0 intron, ([) for a phase 1 intron and (]) for a phase 2 intron. Arrows indicate the most conserved intron insertion site in PxCCEs. Same color brackets indicate the same intron insertion site among different genes

Fig. 10

Phylogenetic tree of typical insect UGT genes. PxUGTs are highlighted in red. Species abbreviations: Bm. B. mori; Sl. S. littoralis; Ha. H. armigera