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

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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.

PCD

Biotic Stresses

Bacteria

Virus

fungi

Abiotic Stresses

Ozone

Salinity

Drought

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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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ResultsWater 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

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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)

Acknowledgements

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Any questions?

THANK YOU