Sulfur nutrition and partitioning in rice under different stress conditions

Student: Viviana Cavallaro Supervisor: Gian Attilio Sacchi

September 24th, 2019

Cycle: XXXIV° - First Year Academic Year: 2018-2019

Foreground of the Project

SULTR gene family H+/SO4

2- co-transporters

Group 1: high affinity – root

expression

Group 2: low affinity – translocation

Group 3: most diffuse – plastid

membranes

Group 4: vacuolar sulfate transport

Expression finely regulated by environmental condition

Aim of the project

Build a model describing S systemic fluxes in rice, in order to obtain

information about the contribute of S nutrition in determining plant

tolerance under different environmental conditions

STABLE ISOTOPES

The abundances in our planet were determined long ago, at the start of

the universe...

However isotopes are not uniformly distributed: changing during the cycle of elements

Sometimes the extra neutron make a difference

During evaporation the residual water gets enriched with the heavy isotope of oxygen

(18O): the water molecules containing lighter isotopes (16O) diffuse relatively faster than

those with heavy oxygen isotope.

THIS PHENOMENON IS CALLED FRACTIONATION

δ34S =𝑅𝑠𝑎𝑚𝑝𝑙𝑒

𝑅𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑

− 1 ∗ 1000R = ratio 34S/32S

Mass 64 (32S16O2)

Mass 66 (34S16O2 or 32S16O18O)SO2

VCDT (0.0441626‰)

δ < 0‰Sample is more enriched in light

isotopes than the standard

δ = 0‰Sample has the same isotope

composition of the standard

δ > 0‰Sample is more

enriched in heavy isotopes than the

standard

EA-IRMS

Shoot δ34S-SO42-: 7.28 ± 0.12‰

Root δ34S-SO42-: 4.34 ± 0.13‰

Sourceδ34S-SO4

2- : 4.49 ± 0.04‰Stot measured on the whole plant

δ34S-Stot : 3.24 ± 0.02‰≠

We generally think that isotope composition of the biomass reflects

that of the SO42- in solution

Preliminary Experiment

Set-up of the Experiment

-10,00

-5,00

0,00

5,00

10,00

15,00

20,00

00,10,20,30,40,50,60,70,80,91

HX

(‰

)

f

Substrate

Product

Istantaneous Product

f → fraction of substrate remaining in the system

e → isotope effect

e

SubstrateSO4

2- in solution

Producttotal S in rice

Our closed system is a hydroponic culture

• cv. Vialone Nano• [SO4

2-] = 100 µM

f

Main Results

e2: 0.16 ‰

e1: 1.02 ‰

e1

e2

The isotope effect is ten time less

*f < 0.3[SO4

2-] < 50 µM*

f

*

*f < 0.3[SO4

2-] < 50 µM

Perspectives

1. Isotope effect that occurs during translocation root

to shoot and vice versa → fractionation mediated

also by other OsSULTR?

2. Build an S systemic flux model that we can use

under different stress environmental condition

(salt stress, heavy metal stress)

Thanks for your attention!