Transcriptomics supports that pleuropodia of insect embryos function in degradation of the serosal cuticle to enable hatching

Abstract

18 19 Pleuropodia are limb-derived vesicular organs that transiently appear on the first 20 abdominal segment of embryos from the majority of insect "orders". They are 21 missing in the model Drosophila and little is known about them. Experiments

Lepidopteran prolegs are novel traits, not leg homologs

“…Previous research demonstrated that Hox genes regulate the number and type of abdominal larval appendages in several insect lineages. For instance, Ultrabithorax ( Ubx ), which is normally expressed in abdominal segments 1 and 2 (A1 and A2) ( 25 ), modifies the appendage primordia of A1 of several insects into a transient embryonic glandular organ, the pleuropodium ( 26 , 27 , 28 ), that secretes a chitinase to facilitate embryonic hatching ( 29 ). When Ubx was down-regulated in Tribolium , pleuropodia were transformed into a partial thoracic leg, suggesting that the pleuropodium is a leg homolog ( 26 ).…”

Lepidopteran prolegs are novel traits, not leg homologs

“…Previous research demonstrated that Hox genes regulate the number and type of abdominal larval appendages in some insect lineages. For instance, Ultrabithorax (Ubx ) modifies the appendage primordia of the first abdominal segment (A1) of several insects into a transient embryonic glandular organ, the pleuropodium ( 3, 4, 5 ), that secretes a chitinase to facilitate embryonic hatching ( 6 ); and abd-A acts as a limb repressor in more posterior segments, in both Tribolium and Drosophila flies, partially via the repression of Distal-less ( Dll ) ( 3, 7 ). In Lepidoptera, however, a novel type of abdominal limb has evolved (Fig.…”

Comparative gene expression to study the developmental basis of organ diversification.

“…Surprisingly, our GO-term enrichment analysis of differentially expressed genes points towards a role of pleuropodia in insect embryonic immunity, a function that is usually conferred by the extraembryonic serosa (Jacobs et al, 2014). It remains to be shown functionally if the pleuropodia take over immune protection of the embryo after degeneration of the serosa upon dorsal closure (Konopová et al, 2019;Panfilio, 2008). Overall, we demonstrate that the combination of thorough phenotyping of developing structures with the analysis of differential expression levels as an intermediate phenotype allows to gain major insights into function and developmental processes of embryonic structures.…”

“…gregaria). Pleuropodia and the third leg pair (in blue) were dissected to generate a comparative transcriptomic dataset (adapted from (Konopová et al, 2019)). B. Schematic representation of an insect embryo (germband stage).…”