Vitellogenin
Encyclopedia
Vitellogenin (from latin
vitellus = yolk and gener = to produce) is a synonymous term for the gene and the expressed protein
. The protein molecule is classified as a glycolipoprotein, having properties of a sugar, fat and protein. It belongs to a family of several lipid transport proteins
.
Vitellogenin is an egg yolk
precursor protein expressed in the females of nearly all oviparous species including fish, amphibians, reptiles, birds, most invertebrates, and the platypus. Vitellogenin is the precursor of the lipoproteins and phosphoprotein
s that make up most of the protein content of yolk. In the presence of estrogenic endocrine disruptive chemical
s (EDCs), male fish can express the Vg gene in a dose dependent
manner. Vg gene expression
in male fish can be used as a molecular marker of exposure to estrogen
ic EDCs.
s deposit vitellogenin molecules in fat bodies in their abdomen and heads. The fat bodies apparently acts as a food storage reservoir. The glycolipoprotein vitellogenin has additional functionality as it acts as an antioxidant
to prolong Queen bee
and forager
lifespan as well as a hormone
that affects future foraging behavior.
The health of a honey bee colony is dependent upon the vitellogenin reserves of the nurse bees - the foragers having low levels of vitellogenin. As expendable laborers, the foragers are fed just enough protein to keep them working their risky task of collecting nectar and pollen. Vitellogenin levels are important during the nest stage and thus influence honey bee worker division of labor.
A nurse bee's vitellogenin titer that developed in the first four days after emergence, affects its subsequent age to begin foraging and whether it preferentially forages for nectar or pollen. If young workers are short on food their first days of life, they tend to begin foraging early and preferentially for nectar. If they are moderately fed, they forage at normal age preferentially for nectar. If they are abundantly fed, immediately after emergence, their vitellogenin titer is high and they begin foraging later in life, preferentially collecting pollen. Pollen is the only available protein source for honey bees.
The vitellogenin expression is part of a regulatory feedback loop that enables vitellogenin and juvenile hormone
to mutually suppress each other. Vitellogenin and juvenile hormone likely work antagonistically
in the honey bee to regulate the honey bees development and behavior. Suppression of one leads to high titer
s of the other.
It is likely that the balance between vitellogenin and juvenile hormone levels is also involved in swarming behavior.
Juvenile hormone levels drop in honey bee colonies pre-swarming and it is expected that vitellogenin levels would therefore rise. One may surmise, that swarming bees would want to pack along as much vitellogenin as possible to extend their lifespan and to be able to quickly build a new nest.
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
vitellus = yolk and gener = to produce) is a synonymous term for the gene and the expressed 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...
. The protein molecule is classified as a glycolipoprotein, having properties of a sugar, fat and protein. It belongs to a family of several lipid transport proteins
Vitellogenin lipid transport domain
This domain represents a conserved region found in several lipid transport proteins, including vitellogenin, microsomal triglyceride transfer protein and apolipoprotein B-100....
.
Vitellogenin is an egg yolk
Egg yolk
An egg yolk is a part of an egg which feeds the developing embryo. The egg yolk is suspended in the egg white by one or two spiral bands of tissue called the chalazae...
precursor protein expressed in the females of nearly all oviparous species including fish, amphibians, reptiles, birds, most invertebrates, and the platypus. Vitellogenin is the precursor of the lipoproteins and phosphoprotein
Phosphoprotein
Phosphoproteins are proteins that are physically bonded to a substance containing phosphoric acid . This category of organic molecules includes Fc receptors, Ulks, Calcineurins, K chips, and urocortins....
s that make up most of the protein content of yolk. In the presence of estrogenic endocrine disruptive chemical
Endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...
s (EDCs), male fish can express the Vg gene in a dose dependent
Effective dose
Effective dose may refer to:*Effective dose the dose of pharmacologic agent which will have a therapeutic effect in some fraction of the population receiving the drug...
manner. Vg gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
in male fish can be used as a molecular marker of exposure to estrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
ic EDCs.
Vitellogenin and honey bees
Honey beeHoney bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
s deposit vitellogenin molecules in fat bodies in their abdomen and heads. The fat bodies apparently acts as a food storage reservoir. The glycolipoprotein vitellogenin has additional functionality as it acts as an antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
to prolong Queen bee
Queen bee
The term queen bee is typically used to refer to an adult, mated female that lives in a honey bee colony or hive; she is usually the mother of most, if not all, the bees in the hive. The queens are developed from larvae selected by worker bees and specially fed in order to become sexually mature...
and forager
Worker bee
A Worker bee is any female eusocial bee that lacks the full reproductive capacity of the colony's queen bee; under most circumstances, this is correlated to an increase in certain non-reproductive activities relative to a queen, as well...
lifespan as well as a 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...
that affects future foraging behavior.
The health of a honey bee colony is dependent upon the vitellogenin reserves of the nurse bees - the foragers having low levels of vitellogenin. As expendable laborers, the foragers are fed just enough protein to keep them working their risky task of collecting nectar and pollen. Vitellogenin levels are important during the nest stage and thus influence honey bee worker division of labor.
A nurse bee's vitellogenin titer that developed in the first four days after emergence, affects its subsequent age to begin foraging and whether it preferentially forages for nectar or pollen. If young workers are short on food their first days of life, they tend to begin foraging early and preferentially for nectar. If they are moderately fed, they forage at normal age preferentially for nectar. If they are abundantly fed, immediately after emergence, their vitellogenin titer is high and they begin foraging later in life, preferentially collecting pollen. Pollen is the only available protein source for honey bees.
Vitellogenin and juvenile hormone feedback loop
For the majority of the investigated insect species it has been documented that juvenile hormone stimulates the transcription of the vitellogenin genes and the consequent control of vitellogenin production (cf. Engelmann, 1983; Wyatt and Davey, 1996).The vitellogenin expression is part of a regulatory feedback loop that enables vitellogenin and juvenile hormone
Juvenile hormone
Juvenile hormones are a group of acyclic sesquiterpenoids that regulate many aspects of insect physiology. JHs regulate development, reproduction, diapause, and polyphenisms....
to mutually suppress each other. Vitellogenin and juvenile hormone likely work antagonistically
Receptor antagonist
A receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses...
in the honey bee to regulate the honey bees development and behavior. Suppression of one leads to high titer
Titer
A titer is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positive or negative. The titer corresponds to the highest dilution factor that still yields a positive...
s of the other.
It is likely that the balance between vitellogenin and juvenile hormone levels is also involved in swarming behavior.
Juvenile hormone levels drop in honey bee colonies pre-swarming and it is expected that vitellogenin levels would therefore rise. One may surmise, that swarming bees would want to pack along as much vitellogenin as possible to extend their lifespan and to be able to quickly build a new nest.