Dehydrin (DHN) is a multi-family of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s present in

plants Plants are the eukaryotes that form the kingdom Plantae; they are predominantly photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars f ...

that is produced in response to cold and drought stress. DHNs are

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...

, reliably thermostable, and disordered. They are stress proteins with a high number of charged

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

that belong to the Group II Late Embryogenesis Abundant ( LEA) family. DHNs are primarily found in the

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

and

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

but more recently, they have been found in other

organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to th ...

s, like mitochondria and chloroplasts. DHNs are characterized by the presence of

Glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (G ...

and other polar

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s. Many DHNs contain at least one copy of a consensus 15-amino acid sequence called the K-segment, . However, an inspection of a range of other reported dehydrin sequences shows that its conservation is not absolute.

Function

Dehydration-induced

s in plants were first observed in 1989, in a comparison of barley and corn

cDNA In genetics, complementary DNA (cDNA) is DNA that was reverse transcribed (via reverse transcriptase) from an RNA (e.g., messenger RNA or microRNA). cDNA exists in both single-stranded and double-stranded forms and in both natural and engin ...

from plants under

drought A drought is a period of drier-than-normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, ...

conditions. The protein has since been referred to as dehydrin and has been identified as the genetic basis of

drought tolerance In botany, drought tolerance is the ability by which a plant maintains its biomass production during arid or drought conditions. Some plants are naturally adapted to dry conditions'','' surviving with protection mechanisms such as desiccation tole ...

in plants. However, the first direct genetic evidence of dehydrin playing a role in cellular protection during

osmotic shock Osmotic shock or osmotic stress is physiologic dysfunction caused by a sudden change in the solute concentration around a cell, which causes a rapid change in the movement of water across its cell membrane. Under hypertonic conditions - conditio ...

was not observed until 2005, in the moss, ''

Physcomitrella patens ''Physcomitrella patens'' is a synonym of ''Physcomitrium patens'', the spreading earthmoss. It is a moss, a bryophyte used as a model organism for studies on plant evolution, development, and physiology. Distribution and ecology ''Physcomitr ...

''. In order to show a direct correlation between DHN and stress recovery, a knockout gene was created, which interfered with DHNA’s functionality. After being placed in an environment with salt and osmotic stress and then later being returned to a standard growth medium, the ''P. patens'' wildtype was able to recover to 94% of its fresh weight while the P. patens mutant only reached 39% of its fresh weight. This study also concludes that DHN production allows plants to function in high salt concentrations. Another study found evidence of DHN’s impact in drought-stress recovery by showing that transcription levels of a DHN increased in a drought-tolerant pine, ''Pinus pinaster'', when placed in a drought treatment. However, transcription levels of a DHN decreased in the same drought treatment in a drought-sensitive ''P. pinaster''. Drought-tolerance is a complex trait, thus that it cannot be genetically analyzed as a single gene trait. The exact mechanism of drought tolerance is yet to be determined and is still being researched. One chemical mechanism related to DHN production is the presence of the phytohormone ABA. One common response to environmental stresses is the process known as cellular dehydration. Cellular dehydration induces biosynthesis of abscisic acid ( ABA), which is known to react as a stress hormone because of its accumulation in the plant under water stress conditions. ABA also participates in stress signal transduction pathways ABA has been shown to increase the production of DHN, which provides more evidence of a link between DHN and drought tolerance.

Dehydrin-like proteins

There are other proteins in the cell that play a similar role in the recovery of drought treated plants. These proteins are considered dehydrin-like or dehydrin-related. They are poorly defined, in that these dehydrin-like proteins are similar to DHNs, but are unfit to be classified as DHNs for varying reasons. They are found to be similar in that they respond to some or all of the same environmental stresses that induce DHN production. In a particular study dehydrin-like proteins found in the

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

were upregulated in drought and cold treatments of cereals. Dehydrins have been reported to confer resistance against fungal infections and over-expression of dehydrins provide protection under abiotic and biotic stress conditions.

References

External links

Family: Dehydrin (PF00257) Wellcome Trust Sanger Institute
{Dead link, date=July 2019 , bot=InternetArchiveBot , fix-attempted=yes Plant proteins Protein families

Function

Dehydrin-like proteins

See also

References

External links