Domain organization and phylogenetic analysis of the chitinase-like family of proteins in three species of insects

Abstract

A bioinformatics-based investigation of three insect species with completed genome sequences has revealed that insect chitinase-like proteins (glycosylhydrolase family 18) are encoded by a rather large and diverse group of genes. We identified 16, 16 and 13 putative chitinase-like genes in the genomic databases of the red flour beetle, Tribolium castaneum, the fruit fly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, respectively. Chitinase-like proteins encoded by this gene family were classified into five groups based on phylogenetic analyses. Group I chitinases are secreted proteins that are the most abundant such enzymes in molting fluid and/or integument, and represent the prototype enzyme of the family, with a single copy each of the catalytic domain and chitin-binding domain (ChBD) connected by an S/T-rich linker polypeptide. Group II chitinases are unusually larger-sized secreted proteins that contain multiple catalytic domains and ChBDs. Group III chitinases contain two catalytic domains and are predicted to be membrane-anchored proteins. Group IV chitinases are the most divergent. They usually lack a ChBD and/or an S/T-rich linker domain, and are known or predicted to be secreted proteins found in gut or fat body. Group V proteins include the putative chitinase-like imaginal disc growth factors (IDGFs). In each of the three insect genomes, multiple genes encode group IV and group V chitinase-like proteins. In contrast, groups I-III are each represented by only a singe gene in each species.

Functional specialization among insect chitinase family genes revealed by RNA interference

“…They differ in their developmental patterns and tissue specificities of expression. Phylogenetic analysis indicates that the appearance of these distinct groups of chitinases predates the separation of coleopteran and lepidopteran lineages of insects (8). Results from RNAi studies reported here support the hypothesis that genes in different groups have distinctly different biological functions.…”

“…Group II chitinases contain at least four catalytic domains and four putative chitin-binding domains, three of which are clustered between two catalytic domains (8). The domain organization of TcCHT10 is similar to that of the T. molitor ortholog, which contains five catalytic domains, of which the first and second were predicted to lack enzymatic activity (6).…”

“…7 and 8 and unpublished data). Based on amino acid sequence similarity and phylogenetic analysis, insect chitinase family proteins have been classified into five or possibly more groups (7,8). From currently available data on a large number of biochemically characterized insect chitinases, we have hypothesized that many and perhaps all group I insect chitinases are involved in chitinolysis associated with insect molting.…”

Obstructor A Organizes Matrix Assembly at the Apical Cell Surface to Promote Enzymatic Cuticle Maturation in Drosophila

“…Therefore mechanisms that coordinate assembly and maturation of all new cuticles are critical for barrier integrity. Even though production and degradation are well described in insects (1)(2)(3)(4)(5)(6), the regulatory processes of forming compact aECM barriers remain poorly understood.…”

Purification and Characterisation of a 31-kDa Chitinase from the Myzus Persicae Aphid: A Target for Hemiptera Biocontrol

“…In contrast, two insect chitinase inhibitors, allosamidin [26] and psammaplin A [29], and an oligosaccharide that mimics allosamidin [5] have been shown to induce high mortality rates and reduce fecundity of M. persicae when fed with artificial diet [5,24]. Among all insect chitinase proteins isolated from Lepidoptera [1,[16][17][18], Coleoptera [12,33] and Diptera [7,33,34], only 14 protein sequences are available [31]. Moreover, most investigated chitinases were from Lepidopteran species such as Manduca sexta and Bombyx mori [16], two important economic Lepidopteran pests.…”