Deletion of a gene encoding an amino acid transporter in the midgut membrane causes resistance to a Bombyx parvo-like virus

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-05, Vol.105 (21), p.7523-7527
• Main Authors: Ito, Katsuhiko, Kidokoro, Kurako, Sezutsu, Hideki, Nohata, Junko, Yamamoto, Kimiko, Kobayashi, Isao, Uchino, Keiro, Kalyebi, Andrew, Eguchi, Ryokitsu, Hara, Wajiro, Tamura, Toshiki, Katsuma, Susumu, Shimada, Toru, Mita, Kazuei, Kadono-Okuda, Keiko
• Format: Article
• Language: English
• Subjects: Amino Acid Transport Systems - chemistry; Amino Acid Transport Systems - genetics; amino acid transporters; Amino acids; Animals; Base Sequence; Biological Sciences; Bombyx - genetics; Bombyx - virology; Bombyx mori; Bombyx mori densovirus; Chromosome Walking; Cloning; Densovirus - physiology; disease resistance; DNA; Gene Deletion; Gene expression; Genes; Genomes; Infections; Insect genetics; Insect Proteins - chemistry; Insect Proteins - genetics; Instars; Intestines - virology; Membranes - virology; Midgut; molecular cloning; Molecular Sequence Data; nsd-2 gene; Polymerase chain reaction; Protein Structure, Secondary; Proteins; receptors; Receptors, Virus - chemistry; Receptors, Virus - genetics; Resistance to control; Sequence Analysis, DNA; Silkworms; transgenes; transgenic insects; transmembrane proteins; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0711841105

Bombyx mori densovirus type 2 (BmDNV-2), a parvo-like virus, replicates only in midgut columnar cells and causes fatal disease. The resistance expressed in some silkworm strains against the virus is determined by a single gene, nsd-2, which is characterized as nonsusceptibility irrespective of the viral dose. However, the responsible gene has been unknown. We isolated the nsd-2 gene by positional cloning. The virus resistance is caused by a 6-kb deletion in the ORF of a gene encoding a 12-pass transmembrane protein, a member of an amino acid transporter family, and expressed only in midgut. Germ-line transformation with a wild-type transgene expressed in the midgut restores susceptibility, showing that the defective membrane protein is responsible for resistance. Cumulatively, our data show that the membrane protein is a functional receptor for BmDNV-2. This is a previously undescribed report of positional cloning of a mutant gene in Bombyx and isolation of an absolute virus resistance gene in insects.