Download Abscisic acid

6/5/2014
Abscisic Acid
(ABA)
ABA basics
● ABA is reported in all kingdoms of life with the
exception of Archea.
● Almost all plant cells have the ability to synthesize
ABA, and its presence has been detected in every
major organ and living tissue.
● It may be transported in the phloem or xylem, it can
also be translocated through paranchyma cells.
● It accumulates in plant cells under water stress; water
deficit also stimulates increased synthesis and release
of abscisic acid in the leaves.
ABA biosynthetic pathway
ABA is
predominantly
biosynthesized
and metabolized
in vascular tissue
plastids.
Seed Dormancy
● During seed maturation, ABA
levels increase dramatically
o Inhibits germination by
inhibiting growth hormones
o Induces production of
proteins to withstand
dehydration
● Seeds germinate upon
inactivation of ABA
o Heavy rains wash ABA out of
the seeds
o Light and prolonged cold
inactivates ABA
C15H20O4
Seed Dormancy
● Seed Dormancy
o Increases likelihood that seeds germinate when there is sufficient
light, temperature, and moisture
● ABA prevents seeds from germinating immediately after
dispersal or while they are still in the interior of fruit
o ABA inhibits actions of growth hormones
o Ratio of ABA to growth hormones determines outcome
Drought Prevention
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When plants detect dry conditions, they synthesize ABA, which
causes changes from root tips to leaves and flowers.
Plants under the influence of this hormone begin to conserve water.
o
Their seeds lie dormant in the ground.
o
Their leaves close microscopic pores to stop water loss.
o
They slow their own growth and reprogram themselves for
survival by signaling numerous genetic changes.
Scientists discovered a cluster of genes is associated with the
hormone and mutations in these genes can lead to a greatly
impaired ABA response and reduced drought resistance.
They found two copies of PYR1 fit snugly together in plant cells,
and they are receptors for ABA. Each copy of the PYR1 molecule
has an internal open space like the inside of a tin can, and when a
ABA molecule comes along, it fits into one of the two spaces. This
induces part of the PYR1 protein that serves as the "lid" to close.
One possible way to translate this research to agricultural products
is to design chemicals to mimic the action of abscisic acid. Such
chemicals would then be sprayed on crops to protect them in the
drought.
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6/5/2014
Sources
1. Campbell, N. A., & Reece, J. B. (2011). Biology (9th ed.). Boston: Benjamin Cummings.
2. The National Center for Biotechnology Information. (2014). Chemicals & Bioassays, PubChem
Compound. Retrieved from:
http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5375199&loc=ec_rcs
3. Umezawa, T., et al. Molecular basis of the core regulatory network in ABA responses: sensing,
signaling and transport. Plant Cell Physiol.. 2010; 51: 1821–1839.
4. Baier, M., Dietz, K.J. Chloroplasts as source and target of cellular redox regulation. J. Exp. Bot.
(June 2005) 56 (416): 1449-1462.
5. Danquah A, et al, The role of ABA and MAPK signaling pathways in plant abiotic stress
responses, Biotechnol Adv (2013), http://dx.doi.org/10.1016/j.biotechadv.2013.09.006.
6. Scientists Reveal Secrets of Drought Resistance (2009). Plants and Animals, Phys.Org.
Retrieved from: http://phys.org/news175440942.html#jCp
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