Expansion of Imaginal Disc Growth Factor Gene Family in Diptera Reflects the Evolution of Novel Functions

Abstract

Imaginal disc growth factors (IDGFs) are a small protein family found in insects. They are related to chitinases and implicated in multiple functions, including cell growth stimulation, antimicrobial activity, insect hemolymph clotting, and maintenance of the extracellular matrix. A number of new IDGFs have been found in several insect species and their detailed phylogenetic analysis provides a good basis for further functional studies. To achieve this goal, we sequenced Idgf cDNAs from several lepidopteran and trichopteran species and supplemented our data with sequences retrieved from public databases. A comparison of Idgf genes in different species showed that Diptera typically contain several Idgf paralogs with a simple exon-intron structure (2–3 exons), whereas lepidopteran Idgfs appear as a single copy per genome and contain a higher number of exons (around 9). Our results show that, while lepidopteran Idgfs, having single orthologs, are characterized by low divergence and stronger purifying selection over most of the molecule, the duplicated Idgf genes in Diptera, Idgf1 and Idgf4, exhibit signs of positive selection. This characterization of IDGF evolution provides, to our knowledge, the first information on the changes that formed these important molecules.

Gene Sequences of Potential Targets of Insecticidal PF2 Lectin Identified from the Larval De Novo Transcriptome of the Mexican Bean Weevil (Zabrotes Subfasciatus; Boheman 1833)

“…In this work, we report the presence of multiple IDGF genes expressed in Z. subfasciatus larvae. These data agree with observations in other insects such as T. castaneum, with a total of 22 genes encoding chitinases and chitinase-like proteins (IDGFs) and Drosophila with 16 genes encoding 10 chitinases and six IDGF [29]. All deduced amino acid sequences identified in this work for Z. subfasciatus IDGFs exhibited one potential N-glycosylation site; this supports the idea that IDGFs could play a role as a target receptor for PF2 lectin.…”

“…Unlike conventional chitinases class V chitinases have 24 additional amino acid residues and lack chitinase enzymatic activity. In insects, these proteins are important for regulating growth and proliferation [28,29]. IDGF4 genes are involved in the molting process and are essential for organizing the exoskeletal barrier in these organisms [30].…”

RNAi-Mediated Knockdown of Imaginal Disc Growth Factors (IDGFs) Genes Causes Developmental Malformation and Mortality in Melon Fly, Zeugodacus cucurbitae

“…dsRNA-mediated silencing of IDGF family genes resulted in deformed cuticles, larval, and adult molting defects in Drosophila . Individual IDGF3 knockdown via RNAi resulted in cuticle molting defects ( Zurovcova et al, 2019 ). In similar studies, Espinoza and Berg (2020) found that overexpressing IDGF3 leads to defects in the dorsal appendage with ∼50% frequency.…”

Imaginal disc growth factor maintains cuticle structure and controls melanization in the spot pattern formation of Bombyx mori

“…Drosophila has six IDGF genes that are involved in detoxification, innate immunity, and energy balance as well as in regulating temperature adaptation and development [ 27 – 29 ]. Intriguingly, a recent study of lepidopteran genome data revealed that lepidopteran insects have only one IDGF gene [ 30 ]. Some IDGF orthologues genes in Lepidoptera have been suggested to be involved in chitin matrix degradation during molting period [ 31 – 33 ].…”