Drought stress can induce programmed cell death (PCD) in plant roots, which may help plants survive drought by modifying root architecture. This study investigated the role of PCD in the drought response of Arabidopsis thaliana roots. PEG treatment was used to simulate drought stress. Results showed that PEG treatment inhibited primary root growth and induced root cell death over time. Expression analysis of ER and PCD marker genes suggested that PCD occurred in roots under PEG treatment, but not through an ER stress pathway. While a PCD inducer gene was overexpressed, it did not enhance the effects of PEG, as expected. Further study of additional PCD genes is needed to fully understand the molecular mechanisms of drought-induced PCD in plant roots.

1. The role of Programmed Cell Death in the
drought response of Arabidopsis roots
By: Mohammed Antar
MSc Plant Sciences student
Faculty of Life Sciences
Supervisor: Patrick Gallois
8/4/2015 1

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• Drought is a complex and hazardous condition which affect agricultural
productivity by decreasing crop yield.
• In crops, water stress/deficit is one of the most important elements affecting
plant roots by stopping their growth, changing their physiological and
morphological features, and eventually inducing programmed cell death (PCD).
Introduction

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• PCD is a genetically controlled cell death and active process.
• PCD can be activated by an intracellular programme during various environmental
stresses.

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• PCD may be important for plant survival when plants are under drought
condition.
• PCD may help plants to challenge drought more efficiently to enhance tolerance
by modifying root architecture (hypothesis).

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• To understand the importance of PCD for drought survival of the root system of
plants, Arabidopsis thaliana seedlings have been chosen for PCD induction studies
using polyethylene glycerol (PEG) treatment as an alternative to drought.
• This research is about:
1. The effect of drought on plant root growth.
2. Optimisation of PCD detection using Evans Blue staining.
3. Measure ER and PCD marker genes transcript level.
PEG 8000

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Method
Sterile Arabidopsis
seeds with 70%
Ethanol and germinate
on MS Agar medium.
Place plate in
Cold-dark room for
2 days.
Transfer plate to
growth chamber
(18hrs light+22ºC)
for 6 days.
Transfer the
seedlings to PEG-
infused medium.
Keeping the plate
in growth chamber
for 10 days.
Measuring root
length + Detect
dead roots.
Total RNA
extraction + QPCR.

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Results
Water deficit inhibit growth of the primary root in Arabidopsis.
10% PEGControl
Six-day-old Arabidopsis wild type (Col-0) seedlings were grown for 10 days on MS control and
MS media infused with various concentration of Polyethylene glycerol (PEG) for 48h.

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Root death of Arabidopsis following PEG treatment

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The time-course of root death induced by water stress.
Six-day-old Arabidopsis (Col-0) seedlings were transferred on MS agar control and MS media
infused with 10% Polyethylene glycerol (PEG) for 48h. At various time points after transfer,
the roots that showed from light to dark Evans Blue staining were considered dead.

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Expression analyses of Endoplasmic Reticulum (ER) stress
marker genes during 10% PEG treatment
• RT-QPCR
• Bip2: Binding Protein PDI: Protein Disulfide Isomerase
• CRT1: Calreticulins PGS: Galactic Synthase Protein

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• Dad1, Dad2 (Defender against death) and KOD (Kiss of Death) are PCD suppressors
(inhibitors)
• BAXI (Bax inhibitor) is a PCD inducer
Expression analyses of PCD marker genes during 10% PEG
treatment

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Severe water deficit inhibits growth of the primary root in
Arabidopsis (Col-0 and BAXI-OX) seedlings.
Six-day-old wild type Col-0 and 14-day-old BAXI seedlings were grown for 10 days on MS agar
media (control) and MS media infused with different concentrations of Polyethylene glycerol
(PEG) for 24h.

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• PEG treatment caused a water stress that induced PCD in the primary
roots of Arabidopsis.
• The expression data suggested that there was no ER stress induced PCD
in Arabidopsis roots under PEG treatment.
• BAXI overexpression did not reduce the effect of PEG treatment as
expected.
Conclusion

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• More PCD marker genes need to be tested to identify molecular and
physiological mechanisms of water stress induced PCD and test our
hypothesis.
• Test drought phenotypes of Arabidopsis lines with reduced PCD in real
(Field) conditions

15. Dr. Patrick Gallois
Dr. Giles Johnson
Galebotse Mathengwane
Mohamad Zulfazli Bin Mohd Sobri
Yao-Min Cai
ALL Plant Sciences members
HCDP Scholarship
(Human Capacity Developmental Programme
Kurdistan Regional Government - Iraq)
8/4/2015 15
Acknowledgements

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Any questions?
THANK YOU 