Exploration of the Use of Plant Biosensors for Environmental - - PowerPoint PPT Presentation

Exploration of the Use of Plant Biosensors for Environmental Surveillance

NIE02 Jerlyn Chua T an Ning Vivienne

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RATIONALE

• Many residents consume

vegetables grown in their community gardens without consideration of potential health risks involved.

• Singapore hosts numerous

petrochemical industries at Jurong Island, putting us in the risk of pollution

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HYPER- ACCUMULATORS

• Capable of growing in soils

with very high concentrations

• f metals, sequestering large

quantities of heavy metals in their leaves.

• Dietary intake of these heavy

metals through the consumption of plants have long term detrimental effects

• n human health

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PLANTS AS BIOSENSORS

• Performing holistic

environmental surveillance is costly and time consuming

• A cheaper and more

convenient alternative is to use plants as on site biosensors to monitor environmental quality

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TO INVESTIGATE THE ADDITIVE EFFECT OF HEAVY METALS ON A.THAILANA

AIM

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WHY ARABIDOPSIS THALIANA?

SIMPLE GENOME

• Relatively small genome of

approximately 135 megabase pairs (Mbp)

• Has its entire genome

sequenced

NON-HYPERACCUMULATOR

• Responds rapidly to

environmental stresses with highly noticeable responses

• Possible to identify potential

hazard sites that are unsuitable for the growth of food plants

• A. thaliana seeds were sown
• n the MS Mediums

prepared for 7 days PLANTIN ING G OF SEEDL DLIN INGS GS

METHODOLOGY

• A. thaliana seedlings were

transferred to MS Mediums supplemented with varying concentration of heavy metal (As, Pb, Cd) respectively TRE REATME TMENT T WITH TH HEAVY VY METALS After 7 days, the percentage of dead A.thaliana seedlings was calculated and plotted on a graph to determine the 𝑀𝐸50 concentration DETERM TERMIN INTATI TION N OF LETHA THAL DOSE , 50% OF HEAVY VY METAL 𝑀𝐸50 concentration of the 3 heavy metals were mixed to investigate the additive effect MIXIN ING G OF HEAVY VY METALS The fold difference (2ΔCt) was obtained, which shows the number of times the gene of interest expressed relative to the housekeeping gene QUANTI TITATIV IVE POL OLYM YMERASE SE CHAIN IN REACT CTION ION (qPCR CR)

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ANALYSIS OF RESULTS

P H E N OT Y P I C C H A N G E S

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OVERALL PHENOTYPIC CHANGES

• Steep decrease in height
• Whitening of leaves
• shows plant death due to

inability to photosynthesize

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ANALYSIS

• A.thaliana has different

sensitivities to different heavy metals as shown by the different 𝑀𝐸50 concentrations

• Highest susceptibility towards

As among the three heavy metals studied, followed by Cd and Pb HEAVY METAL 𝑀𝐸50 CONCENTRATION/uM As 36 Cd 503 Pb 2400

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RESULTS

50 52 54 72 50 86 10 20 30 40 50 60 70 80 90 100 As Cd Pb As + Cd As + Pb Cd + Pb

Percentage Dead/%

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ANALYSIS

• For seedlings treated with

As, Pb and Cd respectively, percentage of seedling which died ≈ 50%

• Generally, those with 2

heavy metals show a higher number of percentage dead

HEAVY METAL(s) PERCENTAGE DEAD/% As 50 Cd 52 Pb 54 As + Cd 72 As + Pb 50 Cd + Pb 86

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ANALYSIS OF RESULTS

G E N OT Y P I C C H A N G E S

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Phytochelatin

PCS1 RESULTS

• Upregulation of PCS1 gene for seedlings treated

with Cd and Pb

• Downregulation of PCS1 gene for seedlings

treated with As

• Plants is more susceptible to low concentrations
• f As, as compared to Cd and Pb
• 25
• 20
• 15
• 10
• 5

5 10 2ΔCt Ct

PCS1

GLUTATHIONE

RESULTS

• Overall downregulation of GSH1 gene in all

samples.

• Mutation in the GSH1 gene, which resulted in

reduced level of expression of the gene,

• Cbf1 proteins bound to the promoter of GSH1,

preventing transcription

• 20
• 18
• 16
• 14
• 12
• 10
• 8
• 6
• 4
• 2

2ΔCt Ct

GSH1

RESULTS

• Overall upregulation of GSH2
• Glutathione synthetase (GS) catalyzes the

synthesis of glutathione

• Glutathione protects plants from environmental

stresses, oxidative stress, xenobiotics and heavy metals

• 15
• 10
• 5

5 10 15 2ΔCt Ct

GSH2

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CONCLUSION

• A.thaliana has different sensitivities

to different heavy metals as shown by the different 𝑀𝐸50 concentrations

• Highest susceptibility towards As

among the three heavy metals studied, followed by Cd and Pb

• The additive effect of heavy metals

differ from the effects of individual metals

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FUTURE WORK

• To accurately and fully evaluate

Arabidopsis heavy-metal stress tolerance, more standard phenotypic parameters can be measured.

• Other more commonly found

plants with hypersensitivity to heavy metals can be considered as biosensors in community gardens.

• e.g. Spinach (Spinacia
• leracea),

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THANK YOU