Epigenetics in insects is the role that epigenetics (hertiable characteristics that do not involve changes in DNA sequence) plays in insects. Epigenetic mechanisms are regulatory mechanisms, which change expression levels of genes. Several mechanisms are considered

epigenetic In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Greek prefix '' epi-'' ( "over, outside of, around") in ''epigenetics'' implies features that are "o ...

, including

DNA methylation DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts t ...

histone modification In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn ar ...

s and non-coding RNAs. Epigenetic mechanisms play a role in processes like development, learning and memory formation,

aging Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In ...

diseases A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that ar ...

cell differentiation Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellula ...

and genome defence.

DNA methylation

DNA methylation is an epigenetic mechanism. It is a chemical modification of the DNA where a methyl group is attached to cytosine. This modification is set by DNA methyltransferases (Dnmts). There are three known types of DNA methyltransferases in mammals. Those DNA methyltransferases are present in insects as well, although it varies between different species which specific Dnmt types are present. It still is a matter of discussion what the specific role of DNA methylation in insects is, as some insects such as '' Drosophila melanogaster'' just have traces of DNA methylation in their genome and in general insect genomes are much less methylated compared to mammalian genomes (0.034% vs. 7.6% in ''Mus musculus''). In a comparison of different insect species and their respective methylation levels, there was a clear relationship between cell turn over and DNA methylation, but not between genome size or the number of repetitive sequences and DNA methylation.

In honeybees

Honeybees (''

Apis mellifera The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for "bee", and ''mellifera'' is the Latin for "honey-bearing" or "honey carrying", ...

'') possess homologs for all three DNA methyltransferases known in mammals. But unlike mammals they possess two DNA methyltransferases 1 and just one DNA methyltransferase 3. DNA methylation predominantly occurs in

coding regions The coding region of a gene, also known as the coding sequence (CDS), is the portion of a gene's DNA or RNA that codes for protein. Studying the length, composition, regulation, splicing, structures, and functions of coding regions compared to non ...

in honeybees. The function of the DNA methylation in honey bees is to regulate gene alternative splicing

Development

DNA methylation plays a major role in honeybee caste and subcaste development. In honeybees there are two different castes which are workers and queens. They are genetically the same, but show morphological, physiological and behavioral differences. Among the worker caste there are two subcastes, which are nurses and foragers. Which subcaste a worker bee belongs to depends on its age. The DNA methylation pattern in queens and workers, and between nurses and foragers is different. DNA methylation also increases in worker larvae with age, especially in coding regions and

CpG island The CpG sites or CG sites are regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction. CpG sites occur with high frequency in genomic regions called CpG isl ...

s. If DNA methyltransferase 3 is silenced in honeybee larvae they develop into queens, whereas they otherwise would develop into workers.

Associative learning

Using the DNA methyltransferase inhibitor zebularine, the role of DNA methyltransferases during

learning Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machine learning, machines ...

and memory formation has been studied. If DNA methyltransferases are inhibited during an associative learning paradigm, in which the bee is trained to associate an odour with a food reward, the odour specific associative long-term memory of bees is impaired, as well as their extinction memory.

Short-term memory Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recit ...

formation and acquisition are not affected by DNA methyltransferase inhibition.

In fruitflies

The fruitfly ''D. melanogaster'' possess just one DNA methyltransferase, which is Dnmt 2-like. Dnmt 2 is not known to methylate DNA in mammals. In Drosophila however a knock down of Dnmt 2-like protein is sufficient to deplete DNA methylation completely and an overexpression of Dnmt 2 causes hypermethylation of the DNA.

References

{{Reflist Insect morphology Epigenetics