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GROUP 1Subo, Ma. Phoebe T.

Velo, Jasmine C.

Penaflorida, Megan A.

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POTENTIAL OF PYRABACTIN AS AN

ABA AGONIST IN IMPROVINGDROUGHT TOLERANCE OF CROP

PLANTS.

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RESPONSE MECHANISMS

OF PLANTS TO DROUGHTSTRESS

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Role of Abscisic Acid (ABA )

Closure of stomata

Protecting cells from drought

Root growth

Bud dormancy

Seed maturation

Abscission

Seedling growth

Apical dominance

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Synthetic form of ABA

Costly

Difficult to synthesize

Relatively unstable under field conditions

AffordableStable

Environmentally friendly

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THESIS:

SPRAYING PYRABACTIN ON CROP

PLANTS CAN ENHANCE STRESS

TOLERANCE DURING DROUGHTSAND CAN THUS IMPROVE CROP

YIELDS.

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ROLE OF PYRABACTIN AS

SEED GERMINATION ANDHYPOCOTYL GROWTH

INHIBITOR

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PYRABACTIN

A synthetic plant growth inhibitor

that acts as a seed-selective

abscisic acid (ABA) agonist.

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PYRABACTIN MIMICS THEABA

PATHWAY

Binds to PYL/PYR proteins (except PYL

2 and PYL 4)

Inhibits expression of genes for

gibberellic acid (responsible for seed

germination)

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ROLE OF PYRABACTIN IN

STOMATAL CLOSURE

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THE MECHANISM OF STOMATAL

CLOSURE:

ABA binds to receptors at the surface of the plasma membrane of theguard cells.

The receptors activate several interconnecting pathways whichconverge to produce a rise in pH in the cytosol;

transfer of Ca2+from the vacuole to the cytosol.

These changes stimulate the loss of negatively-charged ions (anions), especially NO3

and Cl,from the cell and also

the loss of K+from the cell.

The loss of these solutes in the cytosol reduces the osmotic pressureof the cell and thus turgor.

The stomata close.

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Figure 1.1 Concentrations ofABA, pyrabactin, and apyrabactin required for maximum

stomatal closure (Puli and Raghavendra, 2011)

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The ABA-induced mechanism of stomatal closure

causes a rise in the guard cells cytoplasmic levels of

pH

Reactive oxygen species (ROS)

Nitric oxide

Pyrabactin-induced stomatal closure issimilar with that of ABA.

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The actions of ABA and pyrabactin are

additive.

Figure 1.2 Additive effect ofABA and pyrabactin during stomatal closure (Puli andRaghavendra, 2011)

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ADVANTAGES OF USING PYRABACTIN(VERSUS SYNTHETIC ABA)

Relatively inexpensive

Easier to make

Insensitive to light

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CONCLUSIONS

Pyrabactin can be used as a potential

chemical than can be sprayed to plants

crops to improve their drought-tolerance.

Pyrabactin is more efficient than

synthetic ABA.

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SIGNIFICANCE

Because of pyrabactinscost-efficiency, it can

help farmers improve and increase their cropyields.

Pyrabactin could be used in studying signal

transduction in guard cells and other plant

tissues.