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Insect Biochem Mol Biol. 2017 Mar;82:74-82. doi: 10.1016/j.ibmb.2017.02.001. Epub 2017 Feb 7.

Expression map of a complete set of gustatory receptor genes in chemosensory organs of Bombyx mori.

Author information

1
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, PR China.
2
National Institute of Agrobiological Sciences, 1-2 Owashi, Tsukuba 305-8634, Ibaraki, Japan.
3
Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India.
4
Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
5
Ministry of Education Key Laboratory of Diagnostic Medicine, College of Laboratory Medicine, Chongqing Medical University, Chongqing 400016, PR China.
6
Department of Zoology, University of Delhi, Delhi 110007, India.
7
Indian Institute of Science, Bangalore, India.
8
Sorbonne Universités, UPMC Univ Paris 06, Institute of Ecology and Environmental Sciences IEES-Paris, 4 Place Jussieu, Paris F-75005, France.
9
INRA, Institute of Ecology and Environmental Sciences IEES-Paris, Route de Saint-Cyr, Versailles F-78000, France. Electronic address: emmanuelle.joly@inra.fr.
10
Department of Biological Sciences, University of Rhode Island, Kingston 02881, RI, USA. Electronic address: mki101@uri.edu.
11
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, PR China. Electronic address: mitakazuei@gmail.com.

Abstract

Most lepidopteran species are herbivores, and interaction with host plants affects their gene expression and behavior as well as their genome evolution. Gustatory receptors (Grs) are expected to mediate host plant selection, feeding, oviposition and courtship behavior. However, due to their high diversity, sequence divergence and extremely low level of expression it has been difficult to identify precisely a complete set of Grs in Lepidoptera. By manual annotation and BAC sequencing, we improved annotation of 43 gene sequences compared with previously reported Grs in the most studied lepidopteran model, the silkworm, Bombyx mori, and identified 7 new tandem copies of BmGr30 on chromosome 7, bringing the total number of BmGrs to 76. Among these, we mapped 68 genes to chromosomes in a newly constructed chromosome distribution map and 8 genes to scaffolds; we also found new evidence for large clusters of BmGrs, especially from the bitter receptor family. RNA-seq analysis of diverse BmGr expression patterns in chemosensory organs of larvae and adults enabled us to draw a precise organ specific map of BmGr expression. Interestingly, most of the clustered genes were expressed in the same tissues and more than half of the genes were expressed in larval maxillae, larval thoracic legs and adult legs. For example, BmGr63 showed high expression levels in all organs in both larval and adult stages. By contrast, some genes showed expression limited to specific developmental stages or organs and tissues. BmGr19 was highly expressed in larval chemosensory organs (especially antennae and thoracic legs), the single exon genes BmGr53 and BmGr67 were expressed exclusively in larval tissues, the BmGr27-BmGr31 gene cluster on chr7 displayed a high expression level limited to adult legs and the candidate CO2 receptor BmGr2 was highly expressed in adult antennae, where few other Grs were expressed. Transcriptional analysis of the Grs in B. mori provides a valuable new reference for finding genes involved in plant-insect interactions in Lepidoptera and establishing correlations between these genes and vital insect behaviors like host plant selection and courtship for mating.

KEYWORDS:

Annotation; Bombyx mori; Gustatory receptor; Insect-plant interactions; RNA-seq; Taste

PMID:
28185941
DOI:
10.1016/j.ibmb.2017.02.001
[Indexed for MEDLINE]
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