Callose is a plant polysaccharide. Its production is due to the glucan synthase-like gene (GLS) in various places within a plant. It is produced to act as a temporary cell wall in response to stimuli such as stress or damage. Callose is composed of

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

residues linked together through β-1,3-linkages, and is termed a

β-glucan Beta-glucans, β-glucans comprise a group of β-D-glucose polysaccharides (glucans) naturally occurring in the cell walls of cereals, bacteria, and fungi, with significantly differing physicochemical properties dependent on source. Typically, β ...

. It is thought to be manufactured at the cell wall by callose synthases and is degraded by β-1,3-

glucanase Glucanases are enzymes that break down large polysaccharides via hydrolysis. The product of the hydrolysis reaction is called a glucan, a linear polysaccharide made of up to 1200 glucose monomers, held together with glycosidic bonds. Glucans are ab ...

s. Callose is very important for the permeability of plasmodesmata (Pd) in plants; the plant's permeability is regulated by plasmodesmata callose (PDC). PDC is made by callose synthases and broken down by β-1,3-glucanases (BGs). The amount of callose that is built up at the plasmodesmatal neck, which is brought about by the interference of callose synthases (CalSs) and β-1,3-glucanases, determines the conductivity of the plasmodesmata.

Formation and function

Callose is laid down at

plasmodesmata Plasmodesmata (singular: plasmodesma) are microscopic channels which traverse the cell walls of plant cells and some algal cells, enabling transport and communication between them. Plasmodesmata evolved independently in several lineages, and spec ...

, at the cell plate during

cytokinesis Cytokinesis () is the part of the cell division process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and mei ...

, and during pollen development. Endothecium contains a substance callose, which makes it thicker. Callose is produced in response to wounding, infection by pathogens,

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

, and abscisic acid. When there is wounding in the plant tissue, it is fixed by the deposition of callose at the plasmodesmata and cell wall; this process happens within minutes after damage. Even though callose is not a constitutional component of the plant's cell wall, it is related to the plant's defense mechanism. Deposits often appear on the sieve plates at the end of the growing season. Callose also forms immediately around the developing meiocytes and tetrads of sexually reproducing angiosperms but is not found in related apomictic taxa. Callose deposition at the cell wall has been suggested as an early marker for direct somatic embryogenesis from cortical and epidermal cells of ''Cichorium'' hybrids. Temporary callose walls are also thought to be a barrier between a cell and its environment, while the cell is undergoing a genetic programming that allows it to differentiate. This is because, callose walls can be found around nucellar embryos during Nucellar embryony.

References

{{reflist Polysaccharides

Formation and function

See also

References