Bursicon
Encyclopedia
Bursicon is an insect
hormone
which mediates tanning in the cuticle
of adult flies
.
heterodimeric
protein
which is encoded by CG13419 gene and made of two cysteine knot subunits, Burs-α and Burs-β. It is nondialyzable
and loses its activity in alcohol, acetone, some protease
s and trichloroacetate
, renaturates after adding ammonium sulfate
.
: maturation
of the wing. At this time, the newly emerged adult removes dead cells of larva
l tissues. In Drosophila
and Lucilia cuprina
fly, the epidermis of wing is detached by extensive cell death apoptosis
, at the time of wing spreading.
The cells that undergo death are removed from the wing cuticle and are absorbed into the thoracic cavity
through wing veins
. Subsequent wing maturation is disrupted if the process of cell death is inhibited or delayed somehow.
Bursicon is released just after eclosion
and induces epidermis cell death. At the same time it hastens the tanning reaction, and hardens the newly expanded cuticle
of the wing.
.
The structure of the protein has been investigated well in fruit fly (Drosophila melanogaster
), and in some insect species bursicon gene has been sequenced, including the mosquito (Anopheles gambiae
), cricket (Gryllus bimaculatus
), locust (Locusta migratoria), and mealworm (Tenebrio molitor).
The hormone is also present in the silkworm (Bombyx mori
), blow fly (Calliphora erythrocephala), and cockroach (Periplaneta americana).
.
Using hybridization and immunocytochemistry
it has been shown that bursicon is colocalized with Crustacean Cardioactive Peptide
(CCAP
). CCAP is responsible for activation of the ecdysis
motor program. Mutant flies that had a defect in CCAP neurons also didn’t express bursicon.
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
which mediates tanning in the cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
of adult flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
.
Structure
The molecular structure of the hormone has been characterized rather recently. Bursicon is a 30 kDa neurohormoneNeurohormone
A neurohormone is any hormone produced and released by neurons.Examples include:*Thyrotropin-releasing hormone *Gonadotropin-releasing hormone *Adrenocorticotropin-releasing hormone*Oxytocin*Antidiuretic hormone *Epinephrine...
heterodimeric
Protein dimer
In biochemistry, a dimer is a macromolecular complex formed by two, usually non-covalently bound, macromolecules like proteins or nucleic acids...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
which is encoded by CG13419 gene and made of two cysteine knot subunits, Burs-α and Burs-β. It is nondialyzable
Dialysis
In medicine, dialysis is a process for removing waste and excess water from the blood, and is primarily used to provide an artificial replacement for lost kidney function in people with renal failure...
and loses its activity in alcohol, acetone, some protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
s and trichloroacetate
Trichloroacetic acid
Trichloroacetic acid is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms....
, renaturates after adding ammonium sulfate
Ammonium sulfate
Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...
.
Function
Bursicon plays a very important role in insect wing expansion during the last step of metamorphosisMetamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
: maturation
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
of the wing. At this time, the newly emerged adult removes dead cells of larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l tissues. In Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...
and Lucilia cuprina
Blow-fly
Calliphoridae are insects in the Order Diptera, family Calliphoridae...
fly, the epidermis of wing is detached by extensive cell death apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
, at the time of wing spreading.
The cells that undergo death are removed from the wing cuticle and are absorbed into the thoracic cavity
Thoracic cavity
The thoracic cavity is the chamber of the human body that is protected by the thoracic wall ....
through wing veins
Insect wing
Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...
. Subsequent wing maturation is disrupted if the process of cell death is inhibited or delayed somehow.
Bursicon is released just after eclosion
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
and induces epidermis cell death. At the same time it hastens the tanning reaction, and hardens the newly expanded cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
of the wing.
Where the peptide is found
Bursicon is found in different insects and considered to be unspecific. It is produced by median neurosecretory cells in the brain, circulates in blood and stored in corpora cardiacaInsect diuretic hormones
Insect diuretic hormones are hormones that regulate water balance through diuretic action.The insect excretory system, responsible for regulating water balance in the insect, comprises the Malpighian tubules and the hindgut...
.
The structure of the protein has been investigated well in fruit fly (Drosophila melanogaster
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
), and in some insect species bursicon gene has been sequenced, including the mosquito (Anopheles gambiae
Anopheles gambiae
Anopheles gambiae is a complex of at least seven morphologically distinguishable species of mosquitoes in the genus Anopheles. This complex was recognised in the 1960s and includes the most important vectors of malaria in sub-Saharan Africa and the most efficient malaria vectors known.This species...
), cricket (Gryllus bimaculatus
Gryllus bimaculatus
Gryllus bimaculatus is one of many cricket species known as the Field cricket. Also known as the African or Mediterranean field cricket or as the two-spotted cricket, it can be discriminated from other Gryllus species by the two dot-like marks on the base of its wings.This species of cricket is...
), locust (Locusta migratoria), and mealworm (Tenebrio molitor).
The hormone is also present in the silkworm (Bombyx mori
Bombyx mori
The silkworm is the larva or caterpillar of the domesticated silkmoth, Bombyx mori . It is an economically important insect, being a primary producer of silk...
), blow fly (Calliphora erythrocephala), and cockroach (Periplaneta americana).
Effect of absence
Firstly, mutants of Drosophila melanogaster that lack bursicon gene do not spread their wings after eclosion. Secondly, the elongated abdomen shape of a newly eclosed fly remains for a much longer period of time. In addition, the abdomen of a fly is less melanizedMelanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
.
Using hybridization and immunocytochemistry
Immunocytochemistry
Immunocytochemistry is a common laboratory technique that uses antibodies that target specific peptides or protein antigens in the cell via specific epitopes. These bound antibodies can then be detected using several different methods. ICC allows researchers to evaluate whether or not cells in a...
it has been shown that bursicon is colocalized with Crustacean Cardioactive Peptide
Crustacean Cardioactive Peptide
Crustacean cardioactive peptide is a highly conserved, amidated cyclic nonapeptide with the primary structure PFCNAFTGC-NH2 and a disulfide bridge between Cys3 and Cys9. It is found in crustaceans and insects where it behaves as a cardioaccelerator, neuropeptide transmitter for other areas of the...
(CCAP
Crustacean Cardioactive Peptide
Crustacean cardioactive peptide is a highly conserved, amidated cyclic nonapeptide with the primary structure PFCNAFTGC-NH2 and a disulfide bridge between Cys3 and Cys9. It is found in crustaceans and insects where it behaves as a cardioaccelerator, neuropeptide transmitter for other areas of the...
). CCAP is responsible for activation of the ecdysis
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
motor program. Mutant flies that had a defect in CCAP neurons also didn’t express bursicon.