''Zerknüllt'' (zen,

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...

for "crumpled") is a

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

in the

Antennapedia ''Antennapedia'' (abbreviated ''Antp'') is a Hox gene first discovered in ''Drosophila'' which controls the formation of insect leg, legs during development. Loss-of-function mutations in the regulatory region of this gene result in the devel ...

complex of ''

Drosophila ''Drosophila'' () is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species ...

'' (fruit flies) and other insects, where it operates very differently from the canonical

Hox gene Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the cor ...

s in the same gene cluster. Comparison of

s between species showed that the ''Zerknüllt'' gene evolved from one of the standard

s (the 'paralogy group 3' Hox gene) in insects through accumulating many amino acid changes, changing expression pattern, losing ancestral function and gaining a new function. ''Zerknüllt''

codes In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication c ...

for a homeoprotein regulates aspects of early

embryogenesis An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

in insects. Unlike the canonical

s which are expressed in precise zones along the anteroposterior (head to tail) body axis, ''zerknüllt'' expression is restricted along the dorsoventral (back to belly) body axis. Expression of ''Zerknüllt'' is repressed in the ventral part of the embryo by a protein called Dorsal, and activated in the dorsal part of the embryo by the

TGF beta signaling pathway The transforming growth factor beta (TGFB) signaling pathway is involved in many cellular processes in both the adult organism and the developing embryo including cell growth, cell differentiation, cell migration, apoptosis, cellular homeostasis an ...

. The cells which activate the ''Zerknüllt'' develop into extraembryonic tissues which surround the developing insect embryo. ''Zerknüllt'' has been found to undergo a number of gene duplications in certain insect lineages. For example, in the beetle ''Tribolium castaneum'' ''zen'' duplicated to yield ''zen'' and ''zen2;'' in many flies, including ''

,'' zen duplicated to give ''zen, zen2'' and the even more divergent ''

Bicoid Homeotic protein bicoid is encoded by the ''bcd'' maternal effect gene in ''Drosophilia''. Homeotic protein bicoid concentration gradient patterns the anterior-posterior (A-P) axis during ''Drosophila'' embryogenesis. Bicoid was the first prot ...

'' gene. Large expansions of ''zen'' through

gene duplication Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. ...

have also been observed within

Lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

. In this group, ''zen'' has duplicated at least four times resulting in the emergence of the additional divergent 'Special homeobox' (''Shx'') genes, named ''ShxA'', ''ShxB'', ''ShxC'' and ''ShxD''. The original zen gene is still present. In some

lepidopteran Lepidoptera ( ) is an order of insects that includes butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described specie ...

species, such as the Domesticated Silkmoth ''

Bombyx mori The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...

,'' even greater numbers of duplications of ''zen'' occurred, with 12 ''Shx'' loci annotated along with ''zen''.

References

Developmental genes and proteins Drosophila melanogaster genes {{Gene-stub

See also

References