Aleurone
Aleurone (from
Description
The aleurone layer surrounds the
The aleurone layer is important for both the developing seed and the mature plant. The aleurone tissue accumulates large quantities of oils and lipids that are useful during seed development. It is also a site of mineral storage and in some species, functions in seed dormancy. The aleurone may also express several pathogen-protective proteins including PR-4. Aleurone also serves as the most dietarily beneficial fraction in many brans.[7] In addition, the aleurone tissue contains many protein-storing vacuoles known as protein bodies. In cereals with starchy endosperm, the aleurone contains about 30% of the kernel's proteins. In multicolored corn, anthocyanin pigments in the aleurone layer give the kernels a dark, bluish-black color.
Aleurone proteins can have two different morphological features, homogenous and heterogeneous. The homogenous aleurone consists of similar protein bodies (e.g.
Development
The development of the aleurone layer involves several
Mutants of the dek1 gene block the formation of aleurone and cause the cells to develop as starchy endosperm cells instead of aleurone cells.
Similar to the dek1 mutation, genes with a mutation in the cr4 gene also cause a switch in the fate of aleurone cells. The cr4 gene codes for a receptor kinase and so is involved in signal transduction pathways involving the fate of aleurone cells. Plants with a mutated cr4 gene are shorter than normal and produce crinkled leaves.[12]
In addition, several hormones influence the development of the aleurone layer, including auxin, cytokinin, abscisic acid (ABA), and gibberellin (GA). Auxin and cytokinin play a role in the earlier stages of aleurone development. The maturation of aleurone is promoted by ABA while germination is promoted by GA.
Function
The aleurone layer performs a variety of functions to help maintain proper development of the seed. One example of this is maintaining a low pH in the apoplast. In cereals, the aleurone layer releases organic and phosphoric acids in order to keep the pH of the endosperm between a pH of 3.5 and 4. In barley, the aleurone layer also releases nitrite into the starchy endosperm and apoplast under anaerobic conditions.[13] In addition, although the function is unclear, a certain class of hemoglobins is present in the outer layer of living cells including the aleurone tissue in barley and rice seeds.[14]
During seed
Experiments conducted in the 1960s confirmed that in order for the aleurone layer to secrete starch-degrading enzymes, the embryo must be present. Following removal of the embryo, starch-degrading enzymes were not released and no degradation of the starch tissue occurred.[16]
The gibberellin effect on the aleurone is used in brewing, specifically in the production of barley malt where treatment ensures that a batch of barley seeds will germinate evenly.
References
- ^ Taiz, L., & Zeiger, E. (2002). Plant physiology. (3 ed., p. 484). Sunderland, MA: Sinauer Associates, Inc., Publishers.
- ^ (2007). K.. Bradford & H. Nonogaki (Eds.), Seed Development, Dormancy and Germination (Vol. 27, p. 28). Oxford, UK: Blackwell Publishing.
- ^ Becraft, P., & Yi, G. (2011). Regulation of aleurone development in cereal grains. Journal of Experimental Botany, 62(5), 1669-1675.
- ^ A.L. Winton & K.B. Winton: The Structure and Composition of Foods. Volume I: Cereals, Starch, Oil Seeds, Nuts, Oils, Forage Plants, 1. John Wiley & Sons, New York, 1932: 710 pp.
- ^ H. Hahn & I. Michaelsen: Mikroskopische Diagnostik pflanzlicher Nahrungs-, Genuß- und Futtermittel, einschließlich Gewürze. Springer, Berlin/Heidelberg/New York, 1996, 174 pp.
- ^ Taiz, L., & Zeiger, E. (2002). Plant physiology. (3 ed., p. 484). Sunderland, MA: Sinauer Associates, Inc., Publishers.
- ^ Becraft, P., & Yi, G. (2011). Regulation of aleurone development in cereal grains. Journal of Experimental Botany, 62(5), 1669-1675.
- ^ Becraft, P., & Yi, G. (2011). Regulation of aleurone development in cereal grains. Journal of Experimental Botany, 62(5), 1669-1675.
- ^ Endosperm development. (n.d.). Retrieved from http://www.public.iastate.edu/~becraft/Endosperm.htm Archived 2018-07-07 at the Wayback Machine.
- ^ Becraft, P., & Asuncion-Crabb, Y. (2000). Positional cues specify and maintain aleurone cell fate in maize endosperm development. Development, 127, 4039-4048.
- ^ Becraft, P., & Asuncion-Crabb, Y. (2000). Positional cues specify and maintain aleurone cell fate in maize endosperm development. Development, 127, 4039-4048.
- ^ Endosperm development. (n.d.). Retrieved from http://www.public.iastate.edu/~becraft/Endosperm.htm Archived 2018-07-07 at the Wayback Machine
- ^ (2007). K. Bradford & H. Nonogaki (Eds.), Seed Development, Dormancy and Germination (Vol. 27, p. 164). Oxford, UK: Blackwell Publishing.
- ^ (2007). K. Bradford & H. Nonogaki (Eds.), Seed Development, Dormancy and Germination (Vol. 27, p. 165). Oxford, UK: Blackwell Publishing.
- ^ Taiz, L., & Zeiger, E. (2002). Plant physiology. (3 ed., p. 487). Sunderland, MA: Sinauer Associates, Inc., Publishers.
- ^ Taiz, L., & Zeiger, E. (2002). Plant physiology. (3 ed., p. 484). Sunderland, MA: Sinauer Associates, Inc., Publishers.
External links
- New International Encyclopedia. 1905. .