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Insect Biochem Mol Biol. 2015 Jul;62:75-85. doi: 10.1016/j.ibmb.2014.12.006. Epub 2014 Dec 29.

Structural features, evolutionary relationships, and transcriptional regulation of C-type lectin-domain proteins in Manduca sexta.

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School of Plant Protection, Anhui Agricultural University, Hefei, Anhui 230036, PR China.
Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
Boyce Thompson Institute, Cornell University, Ithaca, NY 14853, USA.
Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA. Electronic address:


C-type lectins (CTLs) are a large family of Ca(2+)-dependent carbohydrate-binding proteins recognizing various glycoconjugates and functioning primarily in immunity and cell adhesion. We have identified 34 CTLDP (for CTL-domain protein) genes in the Manduca sexta genome, which encode proteins with one to three CTL domains. CTL-S1 through S9 (S for simple) have one or three CTL domains; immulectin-1 through 19 have two CTL domains; CTL-X1 through X6 (X for complex) have one or two CTL domains along with other structural modules. Nine simple CTLs and seventeen immulectins have a signal peptide and are likely extracellular. Five complex CTLs have both an N-terminal signal peptide and a C-terminal transmembrane region, indicating that they are membrane anchored. Immulectins exist broadly in Lepidoptera and lineage-specific gene duplications have generated three clusters of fourteen genes in the M. sexta genome, thirteen of which have similar expression patterns. In contrast to the family expansion, CTL-S1∼S6, S8, and X1∼X6 have 1:1 orthologs in at least four lepidopteran/dipteran/coleopteran species, suggestive of conserved functions in a wide range of holometabolous insects. Structural modeling suggests the key residues for Ca(2+)-dependent or independent binding of certain carbohydrates by CTL domains. Promoter analysis identified putative κB motifs in eighteen of the CTL genes, which did not have a strong correlation with immune inducibility in the mRNA or protein levels. Together, the gene identification, sequence comparisons, structure modeling, phylogenetic analysis, and expression profiling establish a solid foundation for future studies of M. sexta CTL-domain proteins.


Carbohydrate recognition domain; Comparative genomics; Expression profiling; Insect immunity; Pattern recognition

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