Plants have developed signaling systems to adapt environmental changes

1. Israr Khan
Soil science lab
Gyeongsang National
University
South Korea

2. Introduction

3. • Plants respond to stresses as individual cells and as whole
organisms
• stress induced signals can be transmitted throughout the plant,
making other parts more ready to withstand the stress.
• Plants must adapt
to stresses because
of their sedentary
lifestyle

4. Stresses are abiotic or biotic
ABIOTIC STRESSES
Environmental, non-biological
• Temperature (high / low)
•Water (high / low)
• Salt
• Radiation
• Chemical
BIOTIC STRESSES
Caused by living
organisms
• Fungi
• Bacteria
• Insects
• Herbivores
• Other
plants/competition
• Stresses cause responses in
metabolism and development
• Injuries occur in susceptible
plants, can lead to impeding
flowering, death

5. Research background
• Plants have developed signaling systems to adapt environmental
changes
• ATP an important signaling molecule used by plants in various
processes including growth, development and stress responses.
• DORN1 was identified as the first plant purinoceptor essential for
plant response to ATP.
• To study the possible role of DORN1 for the research of role of
ATP in plants

6. Adenosine triphosphate (ATP)
• Small hydrophilic molecule
that consist of an adenine
base, a pentose sugar and
three phosphates.
• Energy currency in all
organisms
• Building block of genetic
material
• Extracellular signaling
molecule

7. DORN1?
• Also called as purinergic receptor found in
green plants
• DORN1 is a lectin receptor kinas (LecRK).
Functions
• Along with ATP acting as a DAMP
• Mediating wound-induced inflammatory
responses in green plants
• In response to cell lysis, ATP is discharged
and binds onto the extracellular lectin domain
of the DORN1 receptor.
• Intracellular DORN1 kinase domain is subsequently activated
• Activating mitogen-activated protein kinases
• increased cytosolic calcium concentration, and the induction of gene expression

8. Introduction
• ATP as a universal energy source for all organisms
• Cells have maintained high concentration of ATP inside
• Wounding, certain stimuli cause the release of ATP in to the
extracellular matrix which is recognized by PM based
purinoceptors.
• Animals have two purinoceptors
① P2X-ligand gated ion channels
② P2Y G protein coupled receptors

9. Introduction
Function of ATP in animals
• Muscle contraction, inflammation, neurotransmission, cell growth
and death
Extracellular ATP as a signal in plants
• Identification of the first plant purinoceptor (DORN1) have
stimulated greater interest in the role of extracellular signaling in
plants

11. Extracellular ATP and environmental plant responses
• Exogenous application of ATP can trigger elevation of
• Cellular Ca2+ concentration
• Production of nitric oxide (NO)
• Reactive oxygen species (ROS)
• Phosphatidic acid
• Activation of (MPK) phosphorylation
• These responses ultimately lead to the induction of gene
expression.
• About 600 genes in Arabidopsis responded to the addition of ATP
• A total of 322 genes were upregulated by ATP addition
• They hypothesized that ATP released from plants acts as an
intermediate signal to activate stress-responsive pathways.

12. Role of Extracellular ATP in plant responses to wounding
• Many stimuli including chemical, heat, pathogen attack, and other
stresses can trigger ATP release from cells, but the levels of ATP
released are usually very low
• In contrast, ATP levels released in response to wounding can
reach nearly 40 μM
• These data suggest that extracellular ATP released during
wounding as a damage associated molecular pattern (DAMP)
signal, which is then recognized by the DORN1 receptor
• ATP is well known as a DAMP signal in animals where it
contributes to the wound-induced inflammatory response which is
an important defense against short-term pathogen infection

13. Role of Extracellular ATP signaling in plant innate immunity
• ATP play an important role in plant innate immune responses
• It depends upon on
① Dose dependent
② Time dependent
• Short term treatment with ATP induced defense related gene
expression
• Exposure to high level of ATP was shown to trigger programmed
cell death in in populus euphratica
• Such treatments also leads to stomatal closure in Arabidopsis
• ATP addition was reported to trigger Ca increase in endoplasmic
reticulum and mitochondrion, which might link to apotosis.

14. A model for ATP action
• The role of an ATP is of great importance as a signal in plants
• Cytosolic ATP is released by physical wounding or other stresses.
• The released ATP directly binds to DORN1 which causes
intracellular signaling by activating DORN1’s kinase activity.
• Subsequently the signaling steps would lead to the induction of
calcium influx, ROS and NO production, MPK phosphorylation,
and gene expression.
• This pathway will activate those plant processes necessary to
protect the plant against environmental changes.

15. Figure:1. Functional categorization of ATP-upregulated genes using GO term enrichment test
based on Biological Processes. A list of GO terms was generated for 322 ATP-upregulated gen
es by AgriGO (<ce:inter-ref id="intr0005" href="http://bioinfo.cau.edu.cn/a...

16. Figure:2. An overview of ATP signaling pathway in plants. Cytosolic ATP is discharged outside the cell
via cell lysis (i.e. wounding), exocytosis, or active transport. The released ATP binds to
the extracellular lectin domain of the DORN1 receptor, which in turn activates the intracellular DORN1
kinase domain. Receptor activation ultimately leads to a variety f cellular responses, including increase
d cytosolic Ca2+, MAPK activation, and gene expression.

17. Conclusions
• These results strongly supports the existence of extracellular ATP
in plants and its role as a vital extra-cellular signal
• The identification of the DORN1 purinoceptor and studies of
plants lacking this receptor indicate that extracellular ATP is a
central signal involved in the plant response to a variety of
stresses.

18. Thanks for listening