Barbora Konopova

Since February 2017 I am based at the University of Göttingen (Department of Developmental Biology, Gregor Bucher’s research group), where I continue as a Postdoc working on my own research. I also work with Kristen Panfilio (University of Cologne) on her electron microscopy project on the serosa of the model beetle Tribolium.

Pleuropodia are appendicular organs that develop on the first abdominal segment of insect embryos.Perhaps because the pleuropodia degenerate before hatching (larvae do not have them) and were completely lost in such models like Drosophila, moths and bees, the pleuropodia have recently escaped attention and not much is known about them. Electron microscopic studies in 1970s revealed that the pleuropodia harbor a peculiar epithelium of highly specialized cells, but what exactly is the function of this epithelium is unclear.

Special appendicular organs on the first abdominal segment develop also in the more basal relatives of the insects. They are especially well known in springtails (Collembola) where the two appendages fuse together to form a single organ called the collophore (ventral tube). The collophore remains present during whole life of the animals and is involved in water uptake and ion movement. Research on springtails had been hampered by that there had been no species established as a genetic developmental model.

In collaboration with Dick Roelofs and Nico van Straalen (VU University, Amsterdam) I introduced Orchesella cincta, as a suitable model springtail. I have shown that the Hox gene Ultrabihorax, that specifies the pleuropodia, also specifies the collophore in springtails, thus supporting the homology between these organs (Konopova and Akam, 2014).

I combine morphology, genetics and physiology (using the genetic model beetle Tribolium, locusts and springtails) to decipher the genetic control of the development of the pleuropodia and the collophore and their function

Metamorphosis in insects is a sudden morphological and physiological change that happens at the transition between the larva and the adult. Insects with holometabolous development (such as beetles, butterflies and flies) metamorphose through the pupal stage. In insects with hemimetabolous development (majority of the non-holometabolous metamorphosing insects) the pupal stage is missing.

There had been two major enigmas associated with the insect metamorphosis:

In 1930’s V.B. Wigglesworth discovered, using the true bug Rhodnius, that metamorphosis is regulated by the juvenile hormone. High levels of the juvenile hormone in larvae prevent them from

metamorphosing to adults and keep them in their juvenile stage. When secretion of the juvenile hormone ceases in the final larval instar, metamorphosis starts. How juvenile hormone signals to the cells had been poorly understood and the receptor for the juvenile hormone had remained an enigma

for decades.

My discovery that silencing of the gene Methoprene tolerant (Met) in larvae of the beetle Tribolium causes premature entry into metamorphosis (Konopova and Jindra, 2007) was key for the identification that the Met gene encodes the receptor for juvenile hormone. I found that the juvenile hormone regulated gene BR-C is a target of Met (Konopova and Jindra, 2008). In a study finished by a colleague in our lab we showed that both hemimetabolous and holometabolous insects use the same genetic core to regulate entry into metamorphosis (Konopova et al., 2011). In the same study I genetically reproduced the phenotypes of premature metamorphosis in Rhodnius, a species where the anti-metamorphic function of the juvenile hormone was discovered.

The holometabolous type of metamorphosis evolved from hemimetaboly, but how this happened had been disputed for centuries. Either the holometabolous pupa evolved from the final larva of the hemimetabolous ancestor, or holometaboly arose by a major ontogenetic shift: the embryos of the hemimetabolous ancestor of holometabolans started to hatch prematurely and these “outside egg-living embryos” are now the holometabolous larvae; the pupa then originated by compressing all hemimetabolous juveniles into one instar.

In support of the hypothesis that holometabolous larvae are prematurely hatched embryos it was claimed that holometabolous embryos secrete one embryonic cuticle less compared to the embryos of hemimetabolous insects.

My comparative embryological study by transmission and scanning electron microscopy has shown that both hemimetabolous and holometabolous insects deposit the same number of embryonic

cuticles, and at similar developmental stages. This supported the hypothesis that larvae of holometabolous and hemimetabolous insects hatch at equal ontogenetic stages (Konopova and Zrzavy, 2005). These data together with my genetic studies thus support the idea that larvae of hemimetabolous and holometabolous insects are homologous and holometabolous metamorphosis arose by modification of hemimetabolous postembryonic instars rather than by “des-embryonisation”.

I talk about insect metamorphosis and our findings in a radio interview “Receptor pro juvenilni hormon nalezen!” (Receptor for juvenile hormone found!) for “Český Rozhlas Leonardo”, the Czech Radio Program on Science. In Czech.

Konopova B, Akam M. 2014. The Hox genes Ultrabithorax and abdominal-A specify three different

types of abdominal appendage in the springtail Orchesella cincta (Collembola). EvoDevo 5 :2.

Konopova B, Smykal V, Jindra M. 2011. Common and distinct roles of juvenile hormone signaling

genes in metamorphosis of holometabolous and hemimetabolous insects. PLoS One

6(12):e28728.

Posnien N, Schinko J, Grossmann D, Shippy TD, Konopova B, Bucher G. 2009. RNAi in the red flour

beetle (Tribolium). Cold Spring Harb Protoc 2009(8):pdb.prot5256.

Konopova B, Jindra M. 2008. Broad-Complex acts downstream of Met in juvenile hormone signaling

to coordinate primitive holometabolan metamorphosis. Development 135:559-568.

Konopova B, Jindra M. 2007. Juvenile hormone resistance gene Methoprene-tolerant controls entry

into metamorphosis in the beetle Tribolium castaneum. Proc Natl Acad Sci USA 104:10488-

10493.

Konopova B, Zrzavy J. 2005. Ultrastructure, development and homology of insect embryonic cuticles.

J Morphol 264:339-362.